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- @chapter Filtering Introduction
- @c man begin FILTERING INTRODUCTION
- Filtering in FFmpeg is enabled through the libavfilter library.
- In libavfilter, a filter can have multiple inputs and multiple
- outputs.
- To illustrate the sorts of things that are possible, we consider the
- following filtergraph.
- @example
- input --> split ---------------------> overlay --> output
- | ^
- | |
- +-----> crop --> vflip -------+
- @end example
- This filtergraph splits the input stream in two streams, sends one
- stream through the crop filter and the vflip filter before merging it
- back with the other stream by overlaying it on top. You can use the
- following command to achieve this:
- @example
- ffmpeg -i INPUT -vf "split [main][tmp]; [tmp] crop=iw:ih/2:0:0, vflip [flip]; [main][flip] overlay=0:H/2" OUTPUT
- @end example
- The result will be that in output the top half of the video is mirrored
- onto the bottom half.
- Filters in the same linear chain are separated by commas, and distinct
- linear chains of filters are separated by semicolons. In our example,
- @var{crop,vflip} are in one linear chain, @var{split} and
- @var{overlay} are separately in another. The points where the linear
- chains join are labelled by names enclosed in square brackets. In the
- example, the split filter generates two outputs that are associated to
- the labels @var{[main]} and @var{[tmp]}.
- The stream sent to the second output of @var{split}, labelled as
- @var{[tmp]}, is processed through the @var{crop} filter, which crops
- away the lower half part of the video, and then vertically flipped. The
- @var{overlay} filter takes in input the first unchanged output of the
- split filter (which was labelled as @var{[main]}), and overlay on its
- lower half the output generated by the @var{crop,vflip} filterchain.
- Some filters take in input a list of parameters: they are specified
- after the filter name and an equal sign, and are separated from each other
- by a colon.
- There exist so-called @var{source filters} that do not have an
- audio/video input, and @var{sink filters} that will not have audio/video
- output.
- @c man end FILTERING INTRODUCTION
- @chapter graph2dot
- @c man begin GRAPH2DOT
- The @file{graph2dot} program included in the FFmpeg @file{tools}
- directory can be used to parse a filter graph description and issue a
- corresponding textual representation in the dot language.
- Invoke the command:
- @example
- graph2dot -h
- @end example
- to see how to use @file{graph2dot}.
- You can then pass the dot description to the @file{dot} program (from
- the graphviz suite of programs) and obtain a graphical representation
- of the filter graph.
- For example the sequence of commands:
- @example
- echo @var{GRAPH_DESCRIPTION} | \
- tools/graph2dot -o graph.tmp && \
- dot -Tpng graph.tmp -o graph.png && \
- display graph.png
- @end example
- can be used to create and display an image representing the graph
- described by the @var{GRAPH_DESCRIPTION} string. Note that this string must be
- a complete self-contained graph, with its inputs and outputs explicitly defined.
- For example if your command line is of the form:
- @example
- ffmpeg -i infile -vf scale=640:360 outfile
- @end example
- your @var{GRAPH_DESCRIPTION} string will need to be of the form:
- @example
- nullsrc,scale=640:360,nullsink
- @end example
- you may also need to set the @var{nullsrc} parameters and add a @var{format}
- filter in order to simulate a specific input file.
- @c man end GRAPH2DOT
- @chapter Filtergraph description
- @c man begin FILTERGRAPH DESCRIPTION
- A filtergraph is a directed graph of connected filters. It can contain
- cycles, and there can be multiple links between a pair of
- filters. Each link has one input pad on one side connecting it to one
- filter from which it takes its input, and one output pad on the other
- side connecting it to the one filter accepting its output.
- Each filter in a filtergraph is an instance of a filter class
- registered in the application, which defines the features and the
- number of input and output pads of the filter.
- A filter with no input pads is called a "source", a filter with no
- output pads is called a "sink".
- @anchor{Filtergraph syntax}
- @section Filtergraph syntax
- A filtergraph can be represented using a textual representation, which is
- recognized by the @option{-filter}/@option{-vf} and @option{-filter_complex}
- options in @command{ffmpeg} and @option{-vf} in @command{ffplay}, and by the
- @code{avfilter_graph_parse()}/@code{avfilter_graph_parse2()} function defined in
- @file{libavfilter/avfiltergraph.h}.
- A filterchain consists of a sequence of connected filters, each one
- connected to the previous one in the sequence. A filterchain is
- represented by a list of ","-separated filter descriptions.
- A filtergraph consists of a sequence of filterchains. A sequence of
- filterchains is represented by a list of ";"-separated filterchain
- descriptions.
- A filter is represented by a string of the form:
- [@var{in_link_1}]...[@var{in_link_N}]@var{filter_name}=@var{arguments}[@var{out_link_1}]...[@var{out_link_M}]
- @var{filter_name} is the name of the filter class of which the
- described filter is an instance of, and has to be the name of one of
- the filter classes registered in the program.
- The name of the filter class is optionally followed by a string
- "=@var{arguments}".
- @var{arguments} is a string which contains the parameters used to
- initialize the filter instance, and are described in the filter
- descriptions below.
- The list of arguments can be quoted using the character "'" as initial
- and ending mark, and the character '\' for escaping the characters
- within the quoted text; otherwise the argument string is considered
- terminated when the next special character (belonging to the set
- "[]=;,") is encountered.
- The name and arguments of the filter are optionally preceded and
- followed by a list of link labels.
- A link label allows to name a link and associate it to a filter output
- or input pad. The preceding labels @var{in_link_1}
- ... @var{in_link_N}, are associated to the filter input pads,
- the following labels @var{out_link_1} ... @var{out_link_M}, are
- associated to the output pads.
- When two link labels with the same name are found in the
- filtergraph, a link between the corresponding input and output pad is
- created.
- If an output pad is not labelled, it is linked by default to the first
- unlabelled input pad of the next filter in the filterchain.
- For example in the filterchain:
- @example
- nullsrc, split[L1], [L2]overlay, nullsink
- @end example
- the split filter instance has two output pads, and the overlay filter
- instance two input pads. The first output pad of split is labelled
- "L1", the first input pad of overlay is labelled "L2", and the second
- output pad of split is linked to the second input pad of overlay,
- which are both unlabelled.
- In a complete filterchain all the unlabelled filter input and output
- pads must be connected. A filtergraph is considered valid if all the
- filter input and output pads of all the filterchains are connected.
- Libavfilter will automatically insert scale filters where format
- conversion is required. It is possible to specify swscale flags
- for those automatically inserted scalers by prepending
- @code{sws_flags=@var{flags};}
- to the filtergraph description.
- Follows a BNF description for the filtergraph syntax:
- @example
- @var{NAME} ::= sequence of alphanumeric characters and '_'
- @var{LINKLABEL} ::= "[" @var{NAME} "]"
- @var{LINKLABELS} ::= @var{LINKLABEL} [@var{LINKLABELS}]
- @var{FILTER_ARGUMENTS} ::= sequence of chars (eventually quoted)
- @var{FILTER} ::= [@var{LINKLABELS}] @var{NAME} ["=" @var{FILTER_ARGUMENTS}] [@var{LINKLABELS}]
- @var{FILTERCHAIN} ::= @var{FILTER} [,@var{FILTERCHAIN}]
- @var{FILTERGRAPH} ::= [sws_flags=@var{flags};] @var{FILTERCHAIN} [;@var{FILTERGRAPH}]
- @end example
- @section Notes on filtergraph escaping
- Some filter arguments require the use of special characters, typically
- @code{:} to separate key=value pairs in a named options list. In this
- case the user should perform a first level escaping when specifying
- the filter arguments. For example, consider the following literal
- string to be embedded in the @ref{drawtext} filter arguments:
- @example
- this is a 'string': may contain one, or more, special characters
- @end example
- Since @code{:} is special for the filter arguments syntax, it needs to
- be escaped, so you get:
- @example
- text=this is a \'string\'\: may contain one, or more, special characters
- @end example
- A second level of escaping is required when embedding the filter
- arguments in a filtergraph description, in order to escape all the
- filtergraph special characters. Thus the example above becomes:
- @example
- drawtext=text=this is a \\\'string\\\'\\: may contain one\, or more\, special characters
- @end example
- Finally an additional level of escaping may be needed when writing the
- filtergraph description in a shell command, which depends on the
- escaping rules of the adopted shell. For example, assuming that
- @code{\} is special and needs to be escaped with another @code{\}, the
- previous string will finally result in:
- @example
- -vf "drawtext=text=this is a \\\\\\'string\\\\\\'\\\\: may contain one\\, or more\\, special characters"
- @end example
- Sometimes, it might be more convenient to employ quoting in place of
- escaping. For example the string:
- @example
- Caesar: tu quoque, Brute, fili mi
- @end example
- Can be quoted in the filter arguments as:
- @example
- text='Caesar: tu quoque, Brute, fili mi'
- @end example
- And finally inserted in a filtergraph like:
- @example
- drawtext=text=\'Caesar: tu quoque\, Brute\, fili mi\'
- @end example
- See the ``Quoting and escaping'' section in the ffmpeg-utils manual
- for more information about the escaping and quoting rules adopted by
- FFmpeg.
- @c man end FILTERGRAPH DESCRIPTION
- @chapter Audio Filters
- @c man begin AUDIO FILTERS
- When you configure your FFmpeg build, you can disable any of the
- existing filters using @code{--disable-filters}.
- The configure output will show the audio filters included in your
- build.
- Below is a description of the currently available audio filters.
- @section aconvert
- Convert the input audio format to the specified formats.
- The filter accepts a string of the form:
- "@var{sample_format}:@var{channel_layout}".
- @var{sample_format} specifies the sample format, and can be a string or the
- corresponding numeric value defined in @file{libavutil/samplefmt.h}. Use 'p'
- suffix for a planar sample format.
- @var{channel_layout} specifies the channel layout, and can be a string
- or the corresponding number value defined in @file{libavutil/channel_layout.h}.
- The special parameter "auto", signifies that the filter will
- automatically select the output format depending on the output filter.
- Some examples follow.
- @itemize
- @item
- Convert input to float, planar, stereo:
- @example
- aconvert=fltp:stereo
- @end example
- @item
- Convert input to unsigned 8-bit, automatically select out channel layout:
- @example
- aconvert=u8:auto
- @end example
- @end itemize
- @section aformat
- Set output format constraints for the input audio. The framework will
- negotiate the most appropriate format to minimize conversions.
- The filter accepts the following named parameters:
- @table @option
- @item sample_fmts
- A comma-separated list of requested sample formats.
- @item sample_rates
- A comma-separated list of requested sample rates.
- @item channel_layouts
- A comma-separated list of requested channel layouts.
- @end table
- If a parameter is omitted, all values are allowed.
- For example to force the output to either unsigned 8-bit or signed 16-bit stereo:
- @example
- aformat='sample_fmts=u8,s16:channel_layouts=stereo'
- @end example
- @section amerge
- Merge two or more audio streams into a single multi-channel stream.
- The filter accepts the following named options:
- @table @option
- @item inputs
- Set the number of inputs. Default is 2.
- @end table
- If the channel layouts of the inputs are disjoint, and therefore compatible,
- the channel layout of the output will be set accordingly and the channels
- will be reordered as necessary. If the channel layouts of the inputs are not
- disjoint, the output will have all the channels of the first input then all
- the channels of the second input, in that order, and the channel layout of
- the output will be the default value corresponding to the total number of
- channels.
- For example, if the first input is in 2.1 (FL+FR+LF) and the second input
- is FC+BL+BR, then the output will be in 5.1, with the channels in the
- following order: a1, a2, b1, a3, b2, b3 (a1 is the first channel of the
- first input, b1 is the first channel of the second input).
- On the other hand, if both input are in stereo, the output channels will be
- in the default order: a1, a2, b1, b2, and the channel layout will be
- arbitrarily set to 4.0, which may or may not be the expected value.
- All inputs must have the same sample rate, and format.
- If inputs do not have the same duration, the output will stop with the
- shortest.
- Example: merge two mono files into a stereo stream:
- @example
- amovie=left.wav [l] ; amovie=right.mp3 [r] ; [l] [r] amerge
- @end example
- Example: multiple merges:
- @example
- ffmpeg -f lavfi -i "
- amovie=input.mkv:si=0 [a0];
- amovie=input.mkv:si=1 [a1];
- amovie=input.mkv:si=2 [a2];
- amovie=input.mkv:si=3 [a3];
- amovie=input.mkv:si=4 [a4];
- amovie=input.mkv:si=5 [a5];
- [a0][a1][a2][a3][a4][a5] amerge=inputs=6" -c:a pcm_s16le output.mkv
- @end example
- @section amix
- Mixes multiple audio inputs into a single output.
- For example
- @example
- ffmpeg -i INPUT1 -i INPUT2 -i INPUT3 -filter_complex amix=inputs=3:duration=first:dropout_transition=3 OUTPUT
- @end example
- will mix 3 input audio streams to a single output with the same duration as the
- first input and a dropout transition time of 3 seconds.
- The filter accepts the following named parameters:
- @table @option
- @item inputs
- Number of inputs. If unspecified, it defaults to 2.
- @item duration
- How to determine the end-of-stream.
- @table @option
- @item longest
- Duration of longest input. (default)
- @item shortest
- Duration of shortest input.
- @item first
- Duration of first input.
- @end table
- @item dropout_transition
- Transition time, in seconds, for volume renormalization when an input
- stream ends. The default value is 2 seconds.
- @end table
- @section anull
- Pass the audio source unchanged to the output.
- @section apad
- Pad the end of a audio stream with silence, this can be used together with
- -shortest to extend audio streams to the same length as the video stream.
- @anchor{aresample}
- @section aresample
- Resample the input audio to the specified parameters, using the
- libswresample library. If none are specified then the filter will
- automatically convert between its input and output.
- This filter is also able to stretch/squeeze the audio data to make it match
- the timestamps or to inject silence / cut out audio to make it match the
- timestamps, do a combination of both or do neither.
- The filter accepts the syntax
- [@var{sample_rate}:]@var{resampler_options}, where @var{sample_rate}
- expresses a sample rate and @var{resampler_options} is a list of
- @var{key}=@var{value} pairs, separated by ":". See the
- ffmpeg-resampler manual for the complete list of supported options.
- For example, to resample the input audio to 44100Hz:
- @example
- aresample=44100
- @end example
- To stretch/squeeze samples to the given timestamps, with a maximum of 1000
- samples per second compensation:
- @example
- aresample=async=1000
- @end example
- @section asetnsamples
- Set the number of samples per each output audio frame.
- The last output packet may contain a different number of samples, as
- the filter will flush all the remaining samples when the input audio
- signal its end.
- The filter accepts parameters as a list of @var{key}=@var{value} pairs,
- separated by ":".
- @table @option
- @item nb_out_samples, n
- Set the number of frames per each output audio frame. The number is
- intended as the number of samples @emph{per each channel}.
- Default value is 1024.
- @item pad, p
- If set to 1, the filter will pad the last audio frame with zeroes, so
- that the last frame will contain the same number of samples as the
- previous ones. Default value is 1.
- @end table
- For example, to set the number of per-frame samples to 1234 and
- disable padding for the last frame, use:
- @example
- asetnsamples=n=1234:p=0
- @end example
- @section ashowinfo
- Show a line containing various information for each input audio frame.
- The input audio is not modified.
- The shown line contains a sequence of key/value pairs of the form
- @var{key}:@var{value}.
- A description of each shown parameter follows:
- @table @option
- @item n
- sequential number of the input frame, starting from 0
- @item pts
- Presentation timestamp of the input frame, in time base units; the time base
- depends on the filter input pad, and is usually 1/@var{sample_rate}.
- @item pts_time
- presentation timestamp of the input frame in seconds
- @item pos
- position of the frame in the input stream, -1 if this information in
- unavailable and/or meaningless (for example in case of synthetic audio)
- @item fmt
- sample format
- @item chlayout
- channel layout
- @item rate
- sample rate for the audio frame
- @item nb_samples
- number of samples (per channel) in the frame
- @item checksum
- Adler-32 checksum (printed in hexadecimal) of the audio data. For planar audio
- the data is treated as if all the planes were concatenated.
- @item plane_checksums
- A list of Adler-32 checksums for each data plane.
- @end table
- @section asplit
- Split input audio into several identical outputs.
- The filter accepts a single parameter which specifies the number of outputs. If
- unspecified, it defaults to 2.
- For example:
- @example
- [in] asplit [out0][out1]
- @end example
- will create two separate outputs from the same input.
- To create 3 or more outputs, you need to specify the number of
- outputs, like in:
- @example
- [in] asplit=3 [out0][out1][out2]
- @end example
- @example
- ffmpeg -i INPUT -filter_complex asplit=5 OUTPUT
- @end example
- will create 5 copies of the input audio.
- @section astreamsync
- Forward two audio streams and control the order the buffers are forwarded.
- The argument to the filter is an expression deciding which stream should be
- forwarded next: if the result is negative, the first stream is forwarded; if
- the result is positive or zero, the second stream is forwarded. It can use
- the following variables:
- @table @var
- @item b1 b2
- number of buffers forwarded so far on each stream
- @item s1 s2
- number of samples forwarded so far on each stream
- @item t1 t2
- current timestamp of each stream
- @end table
- The default value is @code{t1-t2}, which means to always forward the stream
- that has a smaller timestamp.
- Example: stress-test @code{amerge} by randomly sending buffers on the wrong
- input, while avoiding too much of a desynchronization:
- @example
- amovie=file.ogg [a] ; amovie=file.mp3 [b] ;
- [a] [b] astreamsync=(2*random(1))-1+tanh(5*(t1-t2)) [a2] [b2] ;
- [a2] [b2] amerge
- @end example
- @section atempo
- Adjust audio tempo.
- The filter accepts exactly one parameter, the audio tempo. If not
- specified then the filter will assume nominal 1.0 tempo. Tempo must
- be in the [0.5, 2.0] range.
- For example, to slow down audio to 80% tempo:
- @example
- atempo=0.8
- @end example
- For example, to speed up audio to 125% tempo:
- @example
- atempo=1.25
- @end example
- @section earwax
- Make audio easier to listen to on headphones.
- This filter adds `cues' to 44.1kHz stereo (i.e. audio CD format) audio
- so that when listened to on headphones the stereo image is moved from
- inside your head (standard for headphones) to outside and in front of
- the listener (standard for speakers).
- Ported from SoX.
- @section pan
- Mix channels with specific gain levels. The filter accepts the output
- channel layout followed by a set of channels definitions.
- This filter is also designed to remap efficiently the channels of an audio
- stream.
- The filter accepts parameters of the form:
- "@var{l}:@var{outdef}:@var{outdef}:..."
- @table @option
- @item l
- output channel layout or number of channels
- @item outdef
- output channel specification, of the form:
- "@var{out_name}=[@var{gain}*]@var{in_name}[+[@var{gain}*]@var{in_name}...]"
- @item out_name
- output channel to define, either a channel name (FL, FR, etc.) or a channel
- number (c0, c1, etc.)
- @item gain
- multiplicative coefficient for the channel, 1 leaving the volume unchanged
- @item in_name
- input channel to use, see out_name for details; it is not possible to mix
- named and numbered input channels
- @end table
- If the `=' in a channel specification is replaced by `<', then the gains for
- that specification will be renormalized so that the total is 1, thus
- avoiding clipping noise.
- @subsection Mixing examples
- For example, if you want to down-mix from stereo to mono, but with a bigger
- factor for the left channel:
- @example
- pan=1:c0=0.9*c0+0.1*c1
- @end example
- A customized down-mix to stereo that works automatically for 3-, 4-, 5- and
- 7-channels surround:
- @example
- pan=stereo: FL < FL + 0.5*FC + 0.6*BL + 0.6*SL : FR < FR + 0.5*FC + 0.6*BR + 0.6*SR
- @end example
- Note that @command{ffmpeg} integrates a default down-mix (and up-mix) system
- that should be preferred (see "-ac" option) unless you have very specific
- needs.
- @subsection Remapping examples
- The channel remapping will be effective if, and only if:
- @itemize
- @item gain coefficients are zeroes or ones,
- @item only one input per channel output,
- @end itemize
- If all these conditions are satisfied, the filter will notify the user ("Pure
- channel mapping detected"), and use an optimized and lossless method to do the
- remapping.
- For example, if you have a 5.1 source and want a stereo audio stream by
- dropping the extra channels:
- @example
- pan="stereo: c0=FL : c1=FR"
- @end example
- Given the same source, you can also switch front left and front right channels
- and keep the input channel layout:
- @example
- pan="5.1: c0=c1 : c1=c0 : c2=c2 : c3=c3 : c4=c4 : c5=c5"
- @end example
- If the input is a stereo audio stream, you can mute the front left channel (and
- still keep the stereo channel layout) with:
- @example
- pan="stereo:c1=c1"
- @end example
- Still with a stereo audio stream input, you can copy the right channel in both
- front left and right:
- @example
- pan="stereo: c0=FR : c1=FR"
- @end example
- @section silencedetect
- Detect silence in an audio stream.
- This filter logs a message when it detects that the input audio volume is less
- or equal to a noise tolerance value for a duration greater or equal to the
- minimum detected noise duration.
- The printed times and duration are expressed in seconds.
- @table @option
- @item duration, d
- Set silence duration until notification (default is 2 seconds).
- @item noise, n
- Set noise tolerance. Can be specified in dB (in case "dB" is appended to the
- specified value) or amplitude ratio. Default is -60dB, or 0.001.
- @end table
- Detect 5 seconds of silence with -50dB noise tolerance:
- @example
- silencedetect=n=-50dB:d=5
- @end example
- Complete example with @command{ffmpeg} to detect silence with 0.0001 noise
- tolerance in @file{silence.mp3}:
- @example
- ffmpeg -f lavfi -i amovie=silence.mp3,silencedetect=noise=0.0001 -f null -
- @end example
- @section asyncts
- Synchronize audio data with timestamps by squeezing/stretching it and/or
- dropping samples/adding silence when needed.
- As an alternative, you can use @ref{aresample} to do squeezing/stretching.
- The filter accepts the following named parameters:
- @table @option
- @item compensate
- Enable stretching/squeezing the data to make it match the timestamps. Disabled
- by default. When disabled, time gaps are covered with silence.
- @item min_delta
- Minimum difference between timestamps and audio data (in seconds) to trigger
- adding/dropping samples. Default value is 0.1. If you get non-perfect sync with
- this filter, try setting this parameter to 0.
- @item max_comp
- Maximum compensation in samples per second. Relevant only with compensate=1.
- Default value 500.
- @item first_pts
- Assume the first pts should be this value. The time base is 1 / sample rate.
- This allows for padding/trimming at the start of stream. By default, no
- assumption is made about the first frame's expected pts, so no padding or
- trimming is done. For example, this could be set to 0 to pad the beginning with
- silence if an audio stream starts after the video stream or to trim any samples
- with a negative pts due to encoder delay.
- @end table
- @section channelsplit
- Split each channel in input audio stream into a separate output stream.
- This filter accepts the following named parameters:
- @table @option
- @item channel_layout
- Channel layout of the input stream. Default is "stereo".
- @end table
- For example, assuming a stereo input MP3 file
- @example
- ffmpeg -i in.mp3 -filter_complex channelsplit out.mkv
- @end example
- will create an output Matroska file with two audio streams, one containing only
- the left channel and the other the right channel.
- To split a 5.1 WAV file into per-channel files
- @example
- ffmpeg -i in.wav -filter_complex
- 'channelsplit=channel_layout=5.1[FL][FR][FC][LFE][SL][SR]'
- -map '[FL]' front_left.wav -map '[FR]' front_right.wav -map '[FC]'
- front_center.wav -map '[LFE]' lfe.wav -map '[SL]' side_left.wav -map '[SR]'
- side_right.wav
- @end example
- @section channelmap
- Remap input channels to new locations.
- This filter accepts the following named parameters:
- @table @option
- @item channel_layout
- Channel layout of the output stream.
- @item map
- Map channels from input to output. The argument is a comma-separated list of
- mappings, each in the @code{@var{in_channel}-@var{out_channel}} or
- @var{in_channel} form. @var{in_channel} can be either the name of the input
- channel (e.g. FL for front left) or its index in the input channel layout.
- @var{out_channel} is the name of the output channel or its index in the output
- channel layout. If @var{out_channel} is not given then it is implicitly an
- index, starting with zero and increasing by one for each mapping.
- @end table
- If no mapping is present, the filter will implicitly map input channels to
- output channels preserving index.
- For example, assuming a 5.1+downmix input MOV file
- @example
- ffmpeg -i in.mov -filter 'channelmap=map=DL-FL\,DR-FR' out.wav
- @end example
- will create an output WAV file tagged as stereo from the downmix channels of
- the input.
- To fix a 5.1 WAV improperly encoded in AAC's native channel order
- @example
- ffmpeg -i in.wav -filter 'channelmap=1\,2\,0\,5\,3\,4:channel_layout=5.1' out.wav
- @end example
- @section join
- Join multiple input streams into one multi-channel stream.
- The filter accepts the following named parameters:
- @table @option
- @item inputs
- Number of input streams. Defaults to 2.
- @item channel_layout
- Desired output channel layout. Defaults to stereo.
- @item map
- Map channels from inputs to output. The argument is a comma-separated list of
- mappings, each in the @code{@var{input_idx}.@var{in_channel}-@var{out_channel}}
- form. @var{input_idx} is the 0-based index of the input stream. @var{in_channel}
- can be either the name of the input channel (e.g. FL for front left) or its
- index in the specified input stream. @var{out_channel} is the name of the output
- channel.
- @end table
- The filter will attempt to guess the mappings when those are not specified
- explicitly. It does so by first trying to find an unused matching input channel
- and if that fails it picks the first unused input channel.
- E.g. to join 3 inputs (with properly set channel layouts)
- @example
- ffmpeg -i INPUT1 -i INPUT2 -i INPUT3 -filter_complex join=inputs=3 OUTPUT
- @end example
- To build a 5.1 output from 6 single-channel streams:
- @example
- ffmpeg -i fl -i fr -i fc -i sl -i sr -i lfe -filter_complex
- 'join=inputs=6:channel_layout=5.1:map=0.0-FL\,1.0-FR\,2.0-FC\,3.0-SL\,4.0-SR\,5.0-LFE'
- out
- @end example
- @section resample
- Convert the audio sample format, sample rate and channel layout. This filter is
- not meant to be used directly.
- @section volume
- Adjust the input audio volume.
- The filter accepts the following named parameters. If the key of the
- first options is omitted, the arguments are interpreted according to
- the following syntax:
- @example
- volume=@var{volume}:@var{precision}
- @end example
- @table @option
- @item volume
- Expresses how the audio volume will be increased or decreased.
- Output values are clipped to the maximum value.
- The output audio volume is given by the relation:
- @example
- @var{output_volume} = @var{volume} * @var{input_volume}
- @end example
- Default value for @var{volume} is 1.0.
- @item precision
- Set the mathematical precision.
- This determines which input sample formats will be allowed, which affects the
- precision of the volume scaling.
- @table @option
- @item fixed
- 8-bit fixed-point; limits input sample format to U8, S16, and S32.
- @item float
- 32-bit floating-point; limits input sample format to FLT. (default)
- @item double
- 64-bit floating-point; limits input sample format to DBL.
- @end table
- @end table
- @subsection Examples
- @itemize
- @item
- Halve the input audio volume:
- @example
- volume=volume=0.5
- volume=volume=1/2
- volume=volume=-6.0206dB
- @end example
- In all the above example the named key for @option{volume} can be
- omitted, for example like in:
- @example
- volume=0.5
- @end example
- @item
- Increase input audio power by 6 decibels using fixed-point precision:
- @example
- volume=volume=6dB:precision=fixed
- @end example
- @end itemize
- @section volumedetect
- Detect the volume of the input video.
- The filter has no parameters. The input is not modified. Statistics about
- the volume will be printed in the log when the input stream end is reached.
- In particular it will show the mean volume (root mean square), maximum
- volume (on a per-sample basis), and the beginning of an histogram of the
- registered volume values (from the maximum value to a cumulated 1/1000 of
- the samples).
- All volumes are in decibels relative to the maximum PCM value.
- Here is an excerpt of the output:
- @example
- [Parsed_volumedetect_0 @ 0xa23120] mean_volume: -27 dB
- [Parsed_volumedetect_0 @ 0xa23120] max_volume: -4 dB
- [Parsed_volumedetect_0 @ 0xa23120] histogram_4db: 6
- [Parsed_volumedetect_0 @ 0xa23120] histogram_5db: 62
- [Parsed_volumedetect_0 @ 0xa23120] histogram_6db: 286
- [Parsed_volumedetect_0 @ 0xa23120] histogram_7db: 1042
- [Parsed_volumedetect_0 @ 0xa23120] histogram_8db: 2551
- [Parsed_volumedetect_0 @ 0xa23120] histogram_9db: 4609
- [Parsed_volumedetect_0 @ 0xa23120] histogram_10db: 8409
- @end example
- It means that:
- @itemize
- @item
- The mean square energy is approximately -27 dB, or 10^-2.7.
- @item
- The largest sample is at -4 dB, or more precisely between -4 dB and -5 dB.
- @item
- There are 6 samples at -4 dB, 62 at -5 dB, 286 at -6 dB, etc.
- @end itemize
- In other words, raising the volume by +4 dB does not cause any clipping,
- raising it by +5 dB causes clipping for 6 samples, etc.
- @c man end AUDIO FILTERS
- @chapter Audio Sources
- @c man begin AUDIO SOURCES
- Below is a description of the currently available audio sources.
- @section abuffer
- Buffer audio frames, and make them available to the filter chain.
- This source is mainly intended for a programmatic use, in particular
- through the interface defined in @file{libavfilter/asrc_abuffer.h}.
- It accepts the following mandatory parameters:
- @var{sample_rate}:@var{sample_fmt}:@var{channel_layout}
- @table @option
- @item sample_rate
- The sample rate of the incoming audio buffers.
- @item sample_fmt
- The sample format of the incoming audio buffers.
- Either a sample format name or its corresponging integer representation from
- the enum AVSampleFormat in @file{libavutil/samplefmt.h}
- @item channel_layout
- The channel layout of the incoming audio buffers.
- Either a channel layout name from channel_layout_map in
- @file{libavutil/channel_layout.c} or its corresponding integer representation
- from the AV_CH_LAYOUT_* macros in @file{libavutil/channel_layout.h}
- @end table
- For example:
- @example
- abuffer=44100:s16p:stereo
- @end example
- will instruct the source to accept planar 16bit signed stereo at 44100Hz.
- Since the sample format with name "s16p" corresponds to the number
- 6 and the "stereo" channel layout corresponds to the value 0x3, this is
- equivalent to:
- @example
- abuffer=44100:6:0x3
- @end example
- @section aevalsrc
- Generate an audio signal specified by an expression.
- This source accepts in input one or more expressions (one for each
- channel), which are evaluated and used to generate a corresponding
- audio signal.
- It accepts the syntax: @var{exprs}[::@var{options}].
- @var{exprs} is a list of expressions separated by ":", one for each
- separate channel. In case the @var{channel_layout} is not
- specified, the selected channel layout depends on the number of
- provided expressions.
- @var{options} is an optional sequence of @var{key}=@var{value} pairs,
- separated by ":".
- The description of the accepted options follows.
- @table @option
- @item channel_layout, c
- Set the channel layout. The number of channels in the specified layout
- must be equal to the number of specified expressions.
- @item duration, d
- Set the minimum duration of the sourced audio. See the function
- @code{av_parse_time()} for the accepted format.
- Note that the resulting duration may be greater than the specified
- duration, as the generated audio is always cut at the end of a
- complete frame.
- If not specified, or the expressed duration is negative, the audio is
- supposed to be generated forever.
- @item nb_samples, n
- Set the number of samples per channel per each output frame,
- default to 1024.
- @item sample_rate, s
- Specify the sample rate, default to 44100.
- @end table
- Each expression in @var{exprs} can contain the following constants:
- @table @option
- @item n
- number of the evaluated sample, starting from 0
- @item t
- time of the evaluated sample expressed in seconds, starting from 0
- @item s
- sample rate
- @end table
- @subsection Examples
- @itemize
- @item
- Generate silence:
- @example
- aevalsrc=0
- @end example
- @item
- Generate a sin signal with frequency of 440 Hz, set sample rate to
- 8000 Hz:
- @example
- aevalsrc="sin(440*2*PI*t)::s=8000"
- @end example
- @item
- Generate a two channels signal, specify the channel layout (Front
- Center + Back Center) explicitly:
- @example
- aevalsrc="sin(420*2*PI*t):cos(430*2*PI*t)::c=FC|BC"
- @end example
- @item
- Generate white noise:
- @example
- aevalsrc="-2+random(0)"
- @end example
- @item
- Generate an amplitude modulated signal:
- @example
- aevalsrc="sin(10*2*PI*t)*sin(880*2*PI*t)"
- @end example
- @item
- Generate 2.5 Hz binaural beats on a 360 Hz carrier:
- @example
- aevalsrc="0.1*sin(2*PI*(360-2.5/2)*t) : 0.1*sin(2*PI*(360+2.5/2)*t)"
- @end example
- @end itemize
- @section anullsrc
- Null audio source, return unprocessed audio frames. It is mainly useful
- as a template and to be employed in analysis / debugging tools, or as
- the source for filters which ignore the input data (for example the sox
- synth filter).
- It accepts an optional sequence of @var{key}=@var{value} pairs,
- separated by ":".
- The description of the accepted options follows.
- @table @option
- @item sample_rate, s
- Specify the sample rate, and defaults to 44100.
- @item channel_layout, cl
- Specify the channel layout, and can be either an integer or a string
- representing a channel layout. The default value of @var{channel_layout}
- is "stereo".
- Check the channel_layout_map definition in
- @file{libavutil/channel_layout.c} for the mapping between strings and
- channel layout values.
- @item nb_samples, n
- Set the number of samples per requested frames.
- @end table
- Follow some examples:
- @example
- # set the sample rate to 48000 Hz and the channel layout to AV_CH_LAYOUT_MONO.
- anullsrc=r=48000:cl=4
- # same as
- anullsrc=r=48000:cl=mono
- @end example
- @section abuffer
- Buffer audio frames, and make them available to the filter chain.
- This source is not intended to be part of user-supplied graph descriptions but
- for insertion by calling programs through the interface defined in
- @file{libavfilter/buffersrc.h}.
- It accepts the following named parameters:
- @table @option
- @item time_base
- Timebase which will be used for timestamps of submitted frames. It must be
- either a floating-point number or in @var{numerator}/@var{denominator} form.
- @item sample_rate
- Audio sample rate.
- @item sample_fmt
- Name of the sample format, as returned by @code{av_get_sample_fmt_name()}.
- @item channel_layout
- Channel layout of the audio data, in the form that can be accepted by
- @code{av_get_channel_layout()}.
- @end table
- All the parameters need to be explicitly defined.
- @section flite
- Synthesize a voice utterance using the libflite library.
- To enable compilation of this filter you need to configure FFmpeg with
- @code{--enable-libflite}.
- Note that the flite library is not thread-safe.
- The source accepts parameters as a list of @var{key}=@var{value} pairs,
- separated by ":".
- The description of the accepted parameters follows.
- @table @option
- @item list_voices
- If set to 1, list the names of the available voices and exit
- immediately. Default value is 0.
- @item nb_samples, n
- Set the maximum number of samples per frame. Default value is 512.
- @item textfile
- Set the filename containing the text to speak.
- @item text
- Set the text to speak.
- @item voice, v
- Set the voice to use for the speech synthesis. Default value is
- @code{kal}. See also the @var{list_voices} option.
- @end table
- @subsection Examples
- @itemize
- @item
- Read from file @file{speech.txt}, and synthetize the text using the
- standard flite voice:
- @example
- flite=textfile=speech.txt
- @end example
- @item
- Read the specified text selecting the @code{slt} voice:
- @example
- flite=text='So fare thee well, poor devil of a Sub-Sub, whose commentator I am':voice=slt
- @end example
- @item
- Input text to ffmpeg:
- @example
- ffmpeg -f lavfi -i flite=text='So fare thee well, poor devil of a Sub-Sub, whose commentator I am':voice=slt
- @end example
- @item
- Make @file{ffplay} speak the specified text, using @code{flite} and
- the @code{lavfi} device:
- @example
- ffplay -f lavfi flite=text='No more be grieved for which that thou hast done.'
- @end example
- @end itemize
- For more information about libflite, check:
- @url{http://www.speech.cs.cmu.edu/flite/}
- @c man end AUDIO SOURCES
- @chapter Audio Sinks
- @c man begin AUDIO SINKS
- Below is a description of the currently available audio sinks.
- @section abuffersink
- Buffer audio frames, and make them available to the end of filter chain.
- This sink is mainly intended for programmatic use, in particular
- through the interface defined in @file{libavfilter/buffersink.h}.
- It requires a pointer to an AVABufferSinkContext structure, which
- defines the incoming buffers' formats, to be passed as the opaque
- parameter to @code{avfilter_init_filter} for initialization.
- @section anullsink
- Null audio sink, do absolutely nothing with the input audio. It is
- mainly useful as a template and to be employed in analysis / debugging
- tools.
- @section abuffersink
- This sink is intended for programmatic use. Frames that arrive on this sink can
- be retrieved by the calling program using the interface defined in
- @file{libavfilter/buffersink.h}.
- This filter accepts no parameters.
- @c man end AUDIO SINKS
- @chapter Video Filters
- @c man begin VIDEO FILTERS
- When you configure your FFmpeg build, you can disable any of the
- existing filters using @code{--disable-filters}.
- The configure output will show the video filters included in your
- build.
- Below is a description of the currently available video filters.
- @section alphaextract
- Extract the alpha component from the input as a grayscale video. This
- is especially useful with the @var{alphamerge} filter.
- @section alphamerge
- Add or replace the alpha component of the primary input with the
- grayscale value of a second input. This is intended for use with
- @var{alphaextract} to allow the transmission or storage of frame
- sequences that have alpha in a format that doesn't support an alpha
- channel.
- For example, to reconstruct full frames from a normal YUV-encoded video
- and a separate video created with @var{alphaextract}, you might use:
- @example
- movie=in_alpha.mkv [alpha]; [in][alpha] alphamerge [out]
- @end example
- Since this filter is designed for reconstruction, it operates on frame
- sequences without considering timestamps, and terminates when either
- input reaches end of stream. This will cause problems if your encoding
- pipeline drops frames. If you're trying to apply an image as an
- overlay to a video stream, consider the @var{overlay} filter instead.
- @section ass
- Same as the @ref{subtitles} filter, except that it doesn't require libavcodec
- and libavformat to work. On the other hand, it is limited to ASS (Advanced
- Substation Alpha) subtitles files.
- @section bbox
- Compute the bounding box for the non-black pixels in the input frame
- luminance plane.
- This filter computes the bounding box containing all the pixels with a
- luminance value greater than the minimum allowed value.
- The parameters describing the bounding box are printed on the filter
- log.
- @section blackdetect
- Detect video intervals that are (almost) completely black. Can be
- useful to detect chapter transitions, commercials, or invalid
- recordings. Output lines contains the time for the start, end and
- duration of the detected black interval expressed in seconds.
- In order to display the output lines, you need to set the loglevel at
- least to the AV_LOG_INFO value.
- This filter accepts a list of options in the form of
- @var{key}=@var{value} pairs separated by ":". A description of the
- accepted options follows.
- @table @option
- @item black_min_duration, d
- Set the minimum detected black duration expressed in seconds. It must
- be a non-negative floating point number.
- Default value is 2.0.
- @item picture_black_ratio_th, pic_th
- Set the threshold for considering a picture "black".
- Express the minimum value for the ratio:
- @example
- @var{nb_black_pixels} / @var{nb_pixels}
- @end example
- for which a picture is considered black.
- Default value is 0.98.
- @item pixel_black_th, pix_th
- Set the threshold for considering a pixel "black".
- The threshold expresses the maximum pixel luminance value for which a
- pixel is considered "black". The provided value is scaled according to
- the following equation:
- @example
- @var{absolute_threshold} = @var{luminance_minimum_value} + @var{pixel_black_th} * @var{luminance_range_size}
- @end example
- @var{luminance_range_size} and @var{luminance_minimum_value} depend on
- the input video format, the range is [0-255] for YUV full-range
- formats and [16-235] for YUV non full-range formats.
- Default value is 0.10.
- @end table
- The following example sets the maximum pixel threshold to the minimum
- value, and detects only black intervals of 2 or more seconds:
- @example
- blackdetect=d=2:pix_th=0.00
- @end example
- @section blackframe
- Detect frames that are (almost) completely black. Can be useful to
- detect chapter transitions or commercials. Output lines consist of
- the frame number of the detected frame, the percentage of blackness,
- the position in the file if known or -1 and the timestamp in seconds.
- In order to display the output lines, you need to set the loglevel at
- least to the AV_LOG_INFO value.
- The filter accepts the syntax:
- @example
- blackframe[=@var{amount}:[@var{threshold}]]
- @end example
- @var{amount} is the percentage of the pixels that have to be below the
- threshold, and defaults to 98.
- @var{threshold} is the threshold below which a pixel value is
- considered black, and defaults to 32.
- @section boxblur
- Apply boxblur algorithm to the input video.
- This filter accepts the parameters:
- @var{luma_radius}:@var{luma_power}:@var{chroma_radius}:@var{chroma_power}:@var{alpha_radius}:@var{alpha_power}
- Chroma and alpha parameters are optional, if not specified they default
- to the corresponding values set for @var{luma_radius} and
- @var{luma_power}.
- @var{luma_radius}, @var{chroma_radius}, and @var{alpha_radius} represent
- the radius in pixels of the box used for blurring the corresponding
- input plane. They are expressions, and can contain the following
- constants:
- @table @option
- @item w, h
- the input width and height in pixels
- @item cw, ch
- the input chroma image width and height in pixels
- @item hsub, vsub
- horizontal and vertical chroma subsample values. For example for the
- pixel format "yuv422p" @var{hsub} is 2 and @var{vsub} is 1.
- @end table
- The radius must be a non-negative number, and must not be greater than
- the value of the expression @code{min(w,h)/2} for the luma and alpha planes,
- and of @code{min(cw,ch)/2} for the chroma planes.
- @var{luma_power}, @var{chroma_power}, and @var{alpha_power} represent
- how many times the boxblur filter is applied to the corresponding
- plane.
- Some examples follow:
- @itemize
- @item
- Apply a boxblur filter with luma, chroma, and alpha radius
- set to 2:
- @example
- boxblur=2:1
- @end example
- @item
- Set luma radius to 2, alpha and chroma radius to 0
- @example
- boxblur=2:1:0:0:0:0
- @end example
- @item
- Set luma and chroma radius to a fraction of the video dimension
- @example
- boxblur=min(h\,w)/10:1:min(cw\,ch)/10:1
- @end example
- @end itemize
- @section colormatrix
- The colormatrix filter allows conversion between any of the following color
- space: BT.709 (@var{bt709}), BT.601 (@var{bt601}), SMPTE-240M (@var{smpte240m})
- and FCC (@var{fcc}).
- The syntax of the parameters is @var{source}:@var{destination}:
- @example
- colormatrix=bt601:smpte240m
- @end example
- @section copy
- Copy the input source unchanged to the output. Mainly useful for
- testing purposes.
- @section crop
- Crop the input video.
- This filter accepts a list of @var{key}=@var{value} pairs as argument,
- separated by ':'. If the key of the first options is omitted, the
- arguments are interpreted according to the syntax
- @var{out_w}:@var{out_h}:@var{x}:@var{y}:@var{keep_aspect}.
- A description of the accepted options follows:
- @table @option
- @item w, out_w
- Set the crop area width. It defaults to @code{iw}.
- This expression is evaluated only once during the filter
- configuration.
- @item h, out_h
- Set the crop area width. It defaults to @code{ih}.
- This expression is evaluated only once during the filter
- configuration.
- @item x
- Set the expression for the x top-left coordinate of the cropped area.
- It defaults to @code{(in_w-out_w)/2}.
- This expression is evaluated per-frame.
- @item y
- Set the expression for the y top-left coordinate of the cropped area.
- It defaults to @code{(in_h-out_h)/2}.
- This expression is evaluated per-frame.
- @item keep_aspect
- If set to 1 will force the output display aspect ratio
- to be the same of the input, by changing the output sample aspect
- ratio. It defaults to 0.
- @end table
- The @var{out_w}, @var{out_h}, @var{x}, @var{y} parameters are
- expressions containing the following constants:
- @table @option
- @item x, y
- the computed values for @var{x} and @var{y}. They are evaluated for
- each new frame.
- @item in_w, in_h
- the input width and height
- @item iw, ih
- same as @var{in_w} and @var{in_h}
- @item out_w, out_h
- the output (cropped) width and height
- @item ow, oh
- same as @var{out_w} and @var{out_h}
- @item a
- same as @var{iw} / @var{ih}
- @item sar
- input sample aspect ratio
- @item dar
- input display aspect ratio, it is the same as (@var{iw} / @var{ih}) * @var{sar}
- @item hsub, vsub
- horizontal and vertical chroma subsample values. For example for the
- pixel format "yuv422p" @var{hsub} is 2 and @var{vsub} is 1.
- @item n
- the number of input frame, starting from 0
- @item pos
- the position in the file of the input frame, NAN if unknown
- @item t
- timestamp expressed in seconds, NAN if the input timestamp is unknown
- @end table
- The expression for @var{out_w} may depend on the value of @var{out_h},
- and the expression for @var{out_h} may depend on @var{out_w}, but they
- cannot depend on @var{x} and @var{y}, as @var{x} and @var{y} are
- evaluated after @var{out_w} and @var{out_h}.
- The @var{x} and @var{y} parameters specify the expressions for the
- position of the top-left corner of the output (non-cropped) area. They
- are evaluated for each frame. If the evaluated value is not valid, it
- is approximated to the nearest valid value.
- The expression for @var{x} may depend on @var{y}, and the expression
- for @var{y} may depend on @var{x}.
- @subsection Examples
- @itemize
- @item
- Crop area with size 100x100 at position (12,34).
- @example
- crop=100:100:12:34
- @end example
- Using named options, the example above becomes:
- @example
- crop=w=100:h=100:x=12:y=34
- @end example
- @item
- Crop the central input area with size 100x100:
- @example
- crop=100:100
- @end example
- @item
- Crop the central input area with size 2/3 of the input video:
- @example
- crop=2/3*in_w:2/3*in_h
- @end example
- @item
- Crop the input video central square:
- @example
- crop=in_h
- @end example
- @item
- Delimit the rectangle with the top-left corner placed at position
- 100:100 and the right-bottom corner corresponding to the right-bottom
- corner of the input image:
- @example
- crop=in_w-100:in_h-100:100:100
- @end example
- @item
- Crop 10 pixels from the left and right borders, and 20 pixels from
- the top and bottom borders
- @example
- crop=in_w-2*10:in_h-2*20
- @end example
- @item
- Keep only the bottom right quarter of the input image:
- @example
- crop=in_w/2:in_h/2:in_w/2:in_h/2
- @end example
- @item
- Crop height for getting Greek harmony:
- @example
- crop=in_w:1/PHI*in_w
- @end example
- @item
- Appply trembling effect:
- @example
- crop=in_w/2:in_h/2:(in_w-out_w)/2+((in_w-out_w)/2)*sin(n/10):(in_h-out_h)/2 +((in_h-out_h)/2)*sin(n/7)
- @end example
- @item
- Apply erratic camera effect depending on timestamp:
- @example
- crop=in_w/2:in_h/2:(in_w-out_w)/2+((in_w-out_w)/2)*sin(t*10):(in_h-out_h)/2 +((in_h-out_h)/2)*sin(t*13)"
- @end example
- @item
- Set x depending on the value of y:
- @example
- crop=in_w/2:in_h/2:y:10+10*sin(n/10)
- @end example
- @end itemize
- @section cropdetect
- Auto-detect crop size.
- Calculate necessary cropping parameters and prints the recommended
- parameters through the logging system. The detected dimensions
- correspond to the non-black area of the input video.
- It accepts the syntax:
- @example
- cropdetect[=@var{limit}[:@var{round}[:@var{reset}]]]
- @end example
- @table @option
- @item limit
- Threshold, which can be optionally specified from nothing (0) to
- everything (255), defaults to 24.
- @item round
- Value which the width/height should be divisible by, defaults to
- 16. The offset is automatically adjusted to center the video. Use 2 to
- get only even dimensions (needed for 4:2:2 video). 16 is best when
- encoding to most video codecs.
- @item reset
- Counter that determines after how many frames cropdetect will reset
- the previously detected largest video area and start over to detect
- the current optimal crop area. Defaults to 0.
- This can be useful when channel logos distort the video area. 0
- indicates never reset and return the largest area encountered during
- playback.
- @end table
- @section decimate
- This filter drops frames that do not differ greatly from the previous
- frame in order to reduce framerate. The main use of this filter is
- for very-low-bitrate encoding (e.g. streaming over dialup modem), but
- it could in theory be used for fixing movies that were
- inverse-telecined incorrectly.
- It accepts the following parameters:
- @var{max}:@var{hi}:@var{lo}:@var{frac}.
- @table @option
- @item max
- Set the maximum number of consecutive frames which can be dropped (if
- positive), or the minimum interval between dropped frames (if
- negative). If the value is 0, the frame is dropped unregarding the
- number of previous sequentially dropped frames.
- Default value is 0.
- @item hi, lo, frac
- Set the dropping threshold values.
- Values for @var{hi} and @var{lo} are for 8x8 pixel blocks and
- represent actual pixel value differences, so a threshold of 64
- corresponds to 1 unit of difference for each pixel, or the same spread
- out differently over the block.
- A frame is a candidate for dropping if no 8x8 blocks differ by more
- than a threshold of @var{hi}, and if no more than @var{frac} blocks (1
- meaning the whole image) differ by more than a threshold of @var{lo}.
- Default value for @var{hi} is 64*12, default value for @var{lo} is
- 64*5, and default value for @var{frac} is 0.33.
- @end table
- @section delogo
- Suppress a TV station logo by a simple interpolation of the surrounding
- pixels. Just set a rectangle covering the logo and watch it disappear
- (and sometimes something even uglier appear - your mileage may vary).
- The filter accepts parameters as a string of the form
- "@var{x}:@var{y}:@var{w}:@var{h}:@var{band}", or as a list of
- @var{key}=@var{value} pairs, separated by ":".
- The description of the accepted parameters follows.
- @table @option
- @item x, y
- Specify the top left corner coordinates of the logo. They must be
- specified.
- @item w, h
- Specify the width and height of the logo to clear. They must be
- specified.
- @item band, t
- Specify the thickness of the fuzzy edge of the rectangle (added to
- @var{w} and @var{h}). The default value is 4.
- @item show
- When set to 1, a green rectangle is drawn on the screen to simplify
- finding the right @var{x}, @var{y}, @var{w}, @var{h} parameters, and
- @var{band} is set to 4. The default value is 0.
- @end table
- Some examples follow.
- @itemize
- @item
- Set a rectangle covering the area with top left corner coordinates 0,0
- and size 100x77, setting a band of size 10:
- @example
- delogo=0:0:100:77:10
- @end example
- @item
- As the previous example, but use named options:
- @example
- delogo=x=0:y=0:w=100:h=77:band=10
- @end example
- @end itemize
- @section deshake
- Attempt to fix small changes in horizontal and/or vertical shift. This
- filter helps remove camera shake from hand-holding a camera, bumping a
- tripod, moving on a vehicle, etc.
- The filter accepts parameters as a string of the form
- "@var{x}:@var{y}:@var{w}:@var{h}:@var{rx}:@var{ry}:@var{edge}:@var{blocksize}:@var{contrast}:@var{search}:@var{filename}"
- A description of the accepted parameters follows.
- @table @option
- @item x, y, w, h
- Specify a rectangular area where to limit the search for motion
- vectors.
- If desired the search for motion vectors can be limited to a
- rectangular area of the frame defined by its top left corner, width
- and height. These parameters have the same meaning as the drawbox
- filter which can be used to visualise the position of the bounding
- box.
- This is useful when simultaneous movement of subjects within the frame
- might be confused for camera motion by the motion vector search.
- If any or all of @var{x}, @var{y}, @var{w} and @var{h} are set to -1
- then the full frame is used. This allows later options to be set
- without specifying the bounding box for the motion vector search.
- Default - search the whole frame.
- @item rx, ry
- Specify the maximum extent of movement in x and y directions in the
- range 0-64 pixels. Default 16.
- @item edge
- Specify how to generate pixels to fill blanks at the edge of the
- frame. An integer from 0 to 3 as follows:
- @table @option
- @item 0
- Fill zeroes at blank locations
- @item 1
- Original image at blank locations
- @item 2
- Extruded edge value at blank locations
- @item 3
- Mirrored edge at blank locations
- @end table
- The default setting is mirror edge at blank locations.
- @item blocksize
- Specify the blocksize to use for motion search. Range 4-128 pixels,
- default 8.
- @item contrast
- Specify the contrast threshold for blocks. Only blocks with more than
- the specified contrast (difference between darkest and lightest
- pixels) will be considered. Range 1-255, default 125.
- @item search
- Specify the search strategy 0 = exhaustive search, 1 = less exhaustive
- search. Default - exhaustive search.
- @item filename
- If set then a detailed log of the motion search is written to the
- specified file.
- @end table
- @section drawbox
- Draw a colored box on the input image.
- The filter accepts parameters as a list of @var{key}=@var{value} pairs,
- separated by ":".
- The description of the accepted parameters follows.
- @table @option
- @item x, y
- Specify the top left corner coordinates of the box. Default to 0.
- @item width, w
- @item height, h
- Specify the width and height of the box, if 0 they are interpreted as
- the input width and height. Default to 0.
- @item color, c
- Specify the color of the box to write, it can be the name of a color
- (case insensitive match) or a 0xRRGGBB[AA] sequence. If the special
- value @code{invert} is used, the box edge color is the same as the
- video with inverted luma.
- @item thickness, t
- Set the thickness of the box edge. Default value is @code{4}.
- @end table
- If the key of the first options is omitted, the arguments are
- interpreted according to the following syntax:
- @example
- drawbox=@var{x}:@var{y}:@var{width}:@var{height}:@var{color}:@var{thickness}
- @end example
- Some examples follow:
- @itemize
- @item
- Draw a black box around the edge of the input image:
- @example
- drawbox
- @end example
- @item
- Draw a box with color red and an opacity of 50%:
- @example
- drawbox=10:20:200:60:red@@0.5
- @end example
- The previous example can be specified as:
- @example
- drawbox=x=10:y=20:w=200:h=60:color=red@@0.5
- @end example
- @item
- Fill the box with pink color:
- @example
- drawbox=x=10:y=10:w=100:h=100:color=pink@@0.5:t=max
- @end example
- @end itemize
- @anchor{drawtext}
- @section drawtext
- Draw text string or text from specified file on top of video using the
- libfreetype library.
- To enable compilation of this filter you need to configure FFmpeg with
- @code{--enable-libfreetype}.
- @subsection Syntax
- The filter accepts parameters as a list of @var{key}=@var{value} pairs,
- separated by ":".
- The description of the accepted parameters follows.
- @table @option
- @item box
- Used to draw a box around text using background color.
- Value should be either 1 (enable) or 0 (disable).
- The default value of @var{box} is 0.
- @item boxcolor
- The color to be used for drawing box around text.
- Either a string (e.g. "yellow") or in 0xRRGGBB[AA] format
- (e.g. "0xff00ff"), possibly followed by an alpha specifier.
- The default value of @var{boxcolor} is "white".
- @item draw
- Set an expression which specifies if the text should be drawn. If the
- expression evaluates to 0, the text is not drawn. This is useful for
- specifying that the text should be drawn only when specific conditions
- are met.
- Default value is "1".
- See below for the list of accepted constants and functions.
- @item expansion
- Select how the @var{text} is expanded. Can be either @code{none},
- @code{strftime} (default for compatibity reasons but deprecated) or
- @code{normal}. See the @ref{drawtext_expansion, Text expansion} section
- below for details.
- @item fix_bounds
- If true, check and fix text coords to avoid clipping.
- @item fontcolor
- The color to be used for drawing fonts.
- Either a string (e.g. "red") or in 0xRRGGBB[AA] format
- (e.g. "0xff000033"), possibly followed by an alpha specifier.
- The default value of @var{fontcolor} is "black".
- @item fontfile
- The font file to be used for drawing text. Path must be included.
- This parameter is mandatory.
- @item fontsize
- The font size to be used for drawing text.
- The default value of @var{fontsize} is 16.
- @item ft_load_flags
- Flags to be used for loading the fonts.
- The flags map the corresponding flags supported by libfreetype, and are
- a combination of the following values:
- @table @var
- @item default
- @item no_scale
- @item no_hinting
- @item render
- @item no_bitmap
- @item vertical_layout
- @item force_autohint
- @item crop_bitmap
- @item pedantic
- @item ignore_global_advance_width
- @item no_recurse
- @item ignore_transform
- @item monochrome
- @item linear_design
- @item no_autohint
- @item end table
- @end table
- Default value is "render".
- For more information consult the documentation for the FT_LOAD_*
- libfreetype flags.
- @item shadowcolor
- The color to be used for drawing a shadow behind the drawn text. It
- can be a color name (e.g. "yellow") or a string in the 0xRRGGBB[AA]
- form (e.g. "0xff00ff"), possibly followed by an alpha specifier.
- The default value of @var{shadowcolor} is "black".
- @item shadowx, shadowy
- The x and y offsets for the text shadow position with respect to the
- position of the text. They can be either positive or negative
- values. Default value for both is "0".
- @item tabsize
- The size in number of spaces to use for rendering the tab.
- Default value is 4.
- @item timecode
- Set the initial timecode representation in "hh:mm:ss[:;.]ff"
- format. It can be used with or without text parameter. @var{timecode_rate}
- option must be specified.
- @item timecode_rate, rate, r
- Set the timecode frame rate (timecode only).
- @item text
- The text string to be drawn. The text must be a sequence of UTF-8
- encoded characters.
- This parameter is mandatory if no file is specified with the parameter
- @var{textfile}.
- @item textfile
- A text file containing text to be drawn. The text must be a sequence
- of UTF-8 encoded characters.
- This parameter is mandatory if no text string is specified with the
- parameter @var{text}.
- If both @var{text} and @var{textfile} are specified, an error is thrown.
- @item reload
- If set to 1, the @var{textfile} will be reloaded before each frame.
- Be sure to update it atomically, or it may be read partially, or even fail.
- @item x, y
- The expressions which specify the offsets where text will be drawn
- within the video frame. They are relative to the top/left border of the
- output image.
- The default value of @var{x} and @var{y} is "0".
- See below for the list of accepted constants and functions.
- @end table
- The parameters for @var{x} and @var{y} are expressions containing the
- following constants and functions:
- @table @option
- @item dar
- input display aspect ratio, it is the same as (@var{w} / @var{h}) * @var{sar}
- @item hsub, vsub
- horizontal and vertical chroma subsample values. For example for the
- pixel format "yuv422p" @var{hsub} is 2 and @var{vsub} is 1.
- @item line_h, lh
- the height of each text line
- @item main_h, h, H
- the input height
- @item main_w, w, W
- the input width
- @item max_glyph_a, ascent
- the maximum distance from the baseline to the highest/upper grid
- coordinate used to place a glyph outline point, for all the rendered
- glyphs.
- It is a positive value, due to the grid's orientation with the Y axis
- upwards.
- @item max_glyph_d, descent
- the maximum distance from the baseline to the lowest grid coordinate
- used to place a glyph outline point, for all the rendered glyphs.
- This is a negative value, due to the grid's orientation, with the Y axis
- upwards.
- @item max_glyph_h
- maximum glyph height, that is the maximum height for all the glyphs
- contained in the rendered text, it is equivalent to @var{ascent} -
- @var{descent}.
- @item max_glyph_w
- maximum glyph width, that is the maximum width for all the glyphs
- contained in the rendered text
- @item n
- the number of input frame, starting from 0
- @item rand(min, max)
- return a random number included between @var{min} and @var{max}
- @item sar
- input sample aspect ratio
- @item t
- timestamp expressed in seconds, NAN if the input timestamp is unknown
- @item text_h, th
- the height of the rendered text
- @item text_w, tw
- the width of the rendered text
- @item x, y
- the x and y offset coordinates where the text is drawn.
- These parameters allow the @var{x} and @var{y} expressions to refer
- each other, so you can for example specify @code{y=x/dar}.
- @end table
- If libavfilter was built with @code{--enable-fontconfig}, then
- @option{fontfile} can be a fontconfig pattern or omitted.
- @anchor{drawtext_expansion}
- @subsection Text expansion
- If @option{expansion} is set to @code{strftime} (which is the default for
- now), the filter recognizes strftime() sequences in the provided text and
- expands them accordingly. Check the documentation of strftime(). This
- feature is deprecated.
- If @option{expansion} is set to @code{none}, the text is printed verbatim.
- If @option{expansion} is set to @code{normal} (which will be the default),
- the following expansion mechanism is used.
- The backslash character '\', followed by any character, always expands to
- the second character.
- Sequence of the form @code{%@{...@}} are expanded. The text between the
- braces is a function name, possibly followed by arguments separated by ':'.
- If the arguments contain special characters or delimiters (':' or '@}'),
- they should be escaped.
- Note that they probably must also be escaped as the value for the
- @option{text} option in the filter argument string and as the filter
- argument in the filter graph description, and possibly also for the shell,
- that makes up to four levels of escaping; using a text file avoids these
- problems.
- The following functions are available:
- @table @command
- @item expr, e
- The expression evaluation result.
- It must take one argument specifying the expression to be evaluated,
- which accepts the same constants and functions as the @var{x} and
- @var{y} values. Note that not all constants should be used, for
- example the text size is not known when evaluating the expression, so
- the constants @var{text_w} and @var{text_h} will have an undefined
- value.
- @item gmtime
- The time at which the filter is running, expressed in UTC.
- It can accept an argument: a strftime() format string.
- @item localtime
- The time at which the filter is running, expressed in the local time zone.
- It can accept an argument: a strftime() format string.
- @item n, frame_num
- The frame number, starting from 0.
- @item pts
- The timestamp of the current frame, in seconds, with microsecond accuracy.
- @end table
- @subsection Examples
- Some examples follow.
- @itemize
- @item
- Draw "Test Text" with font FreeSerif, using the default values for the
- optional parameters.
- @example
- drawtext="fontfile=/usr/share/fonts/truetype/freefont/FreeSerif.ttf: text='Test Text'"
- @end example
- @item
- Draw 'Test Text' with font FreeSerif of size 24 at position x=100
- and y=50 (counting from the top-left corner of the screen), text is
- yellow with a red box around it. Both the text and the box have an
- opacity of 20%.
- @example
- drawtext="fontfile=/usr/share/fonts/truetype/freefont/FreeSerif.ttf: text='Test Text':\
- x=100: y=50: fontsize=24: fontcolor=yellow@@0.2: box=1: boxcolor=red@@0.2"
- @end example
- Note that the double quotes are not necessary if spaces are not used
- within the parameter list.
- @item
- Show the text at the center of the video frame:
- @example
- drawtext="fontsize=30:fontfile=FreeSerif.ttf:text='hello world':x=(w-text_w)/2:y=(h-text_h-line_h)/2"
- @end example
- @item
- Show a text line sliding from right to left in the last row of the video
- frame. The file @file{LONG_LINE} is assumed to contain a single line
- with no newlines.
- @example
- drawtext="fontsize=15:fontfile=FreeSerif.ttf:text=LONG_LINE:y=h-line_h:x=-50*t"
- @end example
- @item
- Show the content of file @file{CREDITS} off the bottom of the frame and scroll up.
- @example
- drawtext="fontsize=20:fontfile=FreeSerif.ttf:textfile=CREDITS:y=h-20*t"
- @end example
- @item
- Draw a single green letter "g", at the center of the input video.
- The glyph baseline is placed at half screen height.
- @example
- drawtext="fontsize=60:fontfile=FreeSerif.ttf:fontcolor=green:text=g:x=(w-max_glyph_w)/2:y=h/2-ascent"
- @end example
- @item
- Show text for 1 second every 3 seconds:
- @example
- drawtext="fontfile=FreeSerif.ttf:fontcolor=white:x=100:y=x/dar:draw=lt(mod(t\,3)\,1):text='blink'"
- @end example
- @item
- Use fontconfig to set the font. Note that the colons need to be escaped.
- @example
- drawtext='fontfile=Linux Libertine O-40\:style=Semibold:text=FFmpeg'
- @end example
- @item
- Print the date of a real-time encoding (see strftime(3)):
- @example
- drawtext='fontfile=FreeSans.ttf:expansion=normal:text=%@{localtime:%a %b %d %Y@}'
- @end example
- @end itemize
- For more information about libfreetype, check:
- @url{http://www.freetype.org/}.
- For more information about fontconfig, check:
- @url{http://freedesktop.org/software/fontconfig/fontconfig-user.html}.
- @section edgedetect
- Detect and draw edges. The filter uses the Canny Edge Detection algorithm.
- This filter accepts the following optional named parameters:
- @table @option
- @item low, high
- Set low and high threshold values used by the Canny thresholding
- algorithm.
- The high threshold selects the "strong" edge pixels, which are then
- connected through 8-connectivity with the "weak" edge pixels selected
- by the low threshold.
- @var{low} and @var{high} threshold values must be choosen in the range
- [0,1], and @var{low} should be lesser or equal to @var{high}.
- Default value for @var{low} is @code{20/255}, and default value for @var{high}
- is @code{50/255}.
- @end table
- Example:
- @example
- edgedetect=low=0.1:high=0.4
- @end example
- @section fade
- Apply fade-in/out effect to input video.
- It accepts the parameters:
- @var{type}:@var{start_frame}:@var{nb_frames}[:@var{options}]
- @var{type} specifies if the effect type, can be either "in" for
- fade-in, or "out" for a fade-out effect.
- @var{start_frame} specifies the number of the start frame for starting
- to apply the fade effect.
- @var{nb_frames} specifies the number of frames for which the fade
- effect has to last. At the end of the fade-in effect the output video
- will have the same intensity as the input video, at the end of the
- fade-out transition the output video will be completely black.
- @var{options} is an optional sequence of @var{key}=@var{value} pairs,
- separated by ":". The description of the accepted options follows.
- @table @option
- @item type, t
- See @var{type}.
- @item start_frame, s
- See @var{start_frame}.
- @item nb_frames, n
- See @var{nb_frames}.
- @item alpha
- If set to 1, fade only alpha channel, if one exists on the input.
- Default value is 0.
- @end table
- A few usage examples follow, usable too as test scenarios.
- @example
- # fade in first 30 frames of video
- fade=in:0:30
- # fade out last 45 frames of a 200-frame video
- fade=out:155:45
- # fade in first 25 frames and fade out last 25 frames of a 1000-frame video
- fade=in:0:25, fade=out:975:25
- # make first 5 frames black, then fade in from frame 5-24
- fade=in:5:20
- # fade in alpha over first 25 frames of video
- fade=in:0:25:alpha=1
- @end example
- @section field
- Extract a single field from an interlaced image using stride
- arithmetic to avoid wasting CPU time. The output frames are marked as
- non-interlaced.
- This filter accepts the following named options:
- @table @option
- @item type
- Specify whether to extract the top (if the value is @code{0} or
- @code{top}) or the bottom field (if the value is @code{1} or
- @code{bottom}).
- @end table
- If the option key is not specified, the first value sets the @var{type}
- option. For example:
- @example
- field=bottom
- @end example
- is equivalent to:
- @example
- field=type=bottom
- @end example
- @section fieldorder
- Transform the field order of the input video.
- It accepts one parameter which specifies the required field order that
- the input interlaced video will be transformed to. The parameter can
- assume one of the following values:
- @table @option
- @item 0 or bff
- output bottom field first
- @item 1 or tff
- output top field first
- @end table
- Default value is "tff".
- Transformation is achieved by shifting the picture content up or down
- by one line, and filling the remaining line with appropriate picture content.
- This method is consistent with most broadcast field order converters.
- If the input video is not flagged as being interlaced, or it is already
- flagged as being of the required output field order then this filter does
- not alter the incoming video.
- This filter is very useful when converting to or from PAL DV material,
- which is bottom field first.
- For example:
- @example
- ffmpeg -i in.vob -vf "fieldorder=bff" out.dv
- @end example
- @section fifo
- Buffer input images and send them when they are requested.
- This filter is mainly useful when auto-inserted by the libavfilter
- framework.
- The filter does not take parameters.
- @section format
- Convert the input video to one of the specified pixel formats.
- Libavfilter will try to pick one that is supported for the input to
- the next filter.
- The filter accepts a list of pixel format names, separated by ":",
- for example "yuv420p:monow:rgb24".
- Some examples follow:
- @example
- # convert the input video to the format "yuv420p"
- format=yuv420p
- # convert the input video to any of the formats in the list
- format=yuv420p:yuv444p:yuv410p
- @end example
- @section fps
- Convert the video to specified constant framerate by duplicating or dropping
- frames as necessary.
- This filter accepts the following named parameters:
- @table @option
- @item fps
- Desired output framerate. The default is @code{25}.
- @item round
- Rounding method.
- Possible values are:
- @table @option
- @item zero
- zero round towards 0
- @item inf
- round away from 0
- @item down
- round towards -infinity
- @item up
- round towards +infinity
- @item near
- round to nearest
- @end table
- The default is @code{near}.
- @end table
- Alternatively, the options can be specified as a flat string:
- @var{fps}[:@var{round}].
- See also the @ref{setpts} filter.
- @section framestep
- Select one frame every N.
- This filter accepts in input a string representing a positive
- integer. Default argument is @code{1}.
- @anchor{frei0r}
- @section frei0r
- Apply a frei0r effect to the input video.
- To enable compilation of this filter you need to install the frei0r
- header and configure FFmpeg with @code{--enable-frei0r}.
- The filter supports the syntax:
- @example
- @var{filter_name}[@{:|=@}@var{param1}:@var{param2}:...:@var{paramN}]
- @end example
- @var{filter_name} is the name of the frei0r effect to load. If the
- environment variable @env{FREI0R_PATH} is defined, the frei0r effect
- is searched in each one of the directories specified by the colon (or
- semicolon on Windows platforms) separated list in @env{FREIOR_PATH},
- otherwise in the standard frei0r paths, which are in this order:
- @file{HOME/.frei0r-1/lib/}, @file{/usr/local/lib/frei0r-1/},
- @file{/usr/lib/frei0r-1/}.
- @var{param1}, @var{param2}, ... , @var{paramN} specify the parameters
- for the frei0r effect.
- A frei0r effect parameter can be a boolean (whose values are specified
- with "y" and "n"), a double, a color (specified by the syntax
- @var{R}/@var{G}/@var{B}, @var{R}, @var{G}, and @var{B} being float
- numbers from 0.0 to 1.0) or by an @code{av_parse_color()} color
- description), a position (specified by the syntax @var{X}/@var{Y},
- @var{X} and @var{Y} being float numbers) and a string.
- The number and kind of parameters depend on the loaded effect. If an
- effect parameter is not specified the default value is set.
- Some examples follow:
- @itemize
- @item
- Apply the distort0r effect, set the first two double parameters:
- @example
- frei0r=distort0r:0.5:0.01
- @end example
- @item
- Apply the colordistance effect, take a color as first parameter:
- @example
- frei0r=colordistance:0.2/0.3/0.4
- frei0r=colordistance:violet
- frei0r=colordistance:0x112233
- @end example
- @item
- Apply the perspective effect, specify the top left and top right image
- positions:
- @example
- frei0r=perspective:0.2/0.2:0.8/0.2
- @end example
- @end itemize
- For more information see:
- @url{http://frei0r.dyne.org}
- @section geq
- The filter takes one, two or three equations as parameter, separated by ':'.
- The first equation is mandatory and applies to the luma plane. The two
- following are respectively for chroma blue and chroma red planes.
- The filter syntax allows named parameters:
- @table @option
- @item lum_expr
- the luminance expression
- @item cb_expr
- the chrominance blue expression
- @item cr_expr
- the chrominance red expression
- @end table
- If one of the chrominance expression is not defined, it falls back on the other
- one. If none of them are specified, they will evaluate the luminance
- expression.
- The expressions can use the following variables and functions:
- @table @option
- @item N
- The sequential number of the filtered frame, starting from @code{0}.
- @item X, Y
- The coordinates of the current sample.
- @item W, H
- The width and height of the image.
- @item SW, SH
- Width and height scale depending on the currently filtered plane. It is the
- ratio between the corresponding luma plane number of pixels and the current
- plane ones. E.g. for YUV4:2:0 the values are @code{1,1} for the luma plane, and
- @code{0.5,0.5} for chroma planes.
- @item T
- Time of the current frame, expressed in seconds.
- @item p(x, y)
- Return the value of the pixel at location (@var{x},@var{y}) of the current
- plane.
- @item lum(x, y)
- Return the value of the pixel at location (@var{x},@var{y}) of the luminance
- plane.
- @item cb(x, y)
- Return the value of the pixel at location (@var{x},@var{y}) of the
- blue-difference chroma plane.
- @item cr(x, y)
- Return the value of the pixel at location (@var{x},@var{y}) of the
- red-difference chroma plane.
- @end table
- For functions, if @var{x} and @var{y} are outside the area, the value will be
- automatically clipped to the closer edge.
- Some examples follow:
- @itemize
- @item
- Flip the image horizontally:
- @example
- geq=p(W-X\,Y)
- @end example
- @item
- Generate a bidimensional sine wave, with angle @code{PI/3} and a
- wavelength of 100 pixels:
- @example
- geq=128 + 100*sin(2*(PI/100)*(cos(PI/3)*(X-50*T) + sin(PI/3)*Y)):128:128
- @end example
- @item
- Generate a fancy enigmatic moving light:
- @example
- nullsrc=s=256x256,geq=random(1)/hypot(X-cos(N*0.07)*W/2-W/2\,Y-sin(N*0.09)*H/2-H/2)^2*1000000*sin(N*0.02):128:128
- @end example
- @end itemize
- @section gradfun
- Fix the banding artifacts that are sometimes introduced into nearly flat
- regions by truncation to 8bit color depth.
- Interpolate the gradients that should go where the bands are, and
- dither them.
- This filter is designed for playback only. Do not use it prior to
- lossy compression, because compression tends to lose the dither and
- bring back the bands.
- The filter accepts a list of options in the form of @var{key}=@var{value} pairs
- separated by ":". A description of the accepted options follows.
- @table @option
- @item strength
- The maximum amount by which the filter will change
- any one pixel. Also the threshold for detecting nearly flat
- regions. Acceptable values range from @code{0.51} to @code{64}, default value
- is @code{1.2}.
- @item radius
- The neighborhood to fit the gradient to. A larger
- radius makes for smoother gradients, but also prevents the filter from
- modifying the pixels near detailed regions. Acceptable values are
- @code{8-32}, default value is @code{16}.
- @end table
- Alternatively, the options can be specified as a flat string:
- @var{strength}[:@var{radius}]
- @subsection Examples
- @itemize
- @item
- Apply the filter with a @code{3.5} strength and radius of @code{8}:
- @example
- gradfun=3.5:8
- @end example
- @item
- Specify radius, omitting the strength (which will fall-back to the default
- value):
- @example
- gradfun=radius=8
- @end example
- @end itemize
- @section hflip
- Flip the input video horizontally.
- For example to horizontally flip the input video with @command{ffmpeg}:
- @example
- ffmpeg -i in.avi -vf "hflip" out.avi
- @end example
- @section histeq
- This filter applies a global color histogram equalization on a
- per-frame basis.
- It can be used to correct video that has a compressed range of pixel
- intensities. The filter redistributes the pixel intensities to
- equalize their distribution across the intensity range. It may be
- viewed as an "automatically adjusting contrast filter". This filter is
- useful only for correcting degraded or poorly captured source
- video.
- The filter accepts parameters as a list of @var{key}=@var{value}
- pairs, separated by ":". If the key of the first options is omitted,
- the arguments are interpreted according to syntax
- @var{strength}:@var{intensity}:@var{antibanding}.
- This filter accepts the following named options:
- @table @option
- @item strength
- Determine the amount of equalization to be applied. As the strength
- is reduced, the distribution of pixel intensities more-and-more
- approaches that of the input frame. The value must be a float number
- in the range [0,1] and defaults to 0.200.
- @item intensity
- Set the maximum intensity that can generated and scale the output
- values appropriately. The strength should be set as desired and then
- the intensity can be limited if needed to avoid washing-out. The value
- must be a float number in the range [0,1] and defaults to 0.210.
- @item antibanding
- Set the antibanding level. If enabled the filter will randomly vary
- the luminance of output pixels by a small amount to avoid banding of
- the histogram. Possible values are @code{none}, @code{weak} or
- @code{strong}. It defaults to @code{none}.
- @end table
- @section hqdn3d
- High precision/quality 3d denoise filter. This filter aims to reduce
- image noise producing smooth images and making still images really
- still. It should enhance compressibility.
- It accepts the following optional parameters:
- @var{luma_spatial}:@var{chroma_spatial}:@var{luma_tmp}:@var{chroma_tmp}
- @table @option
- @item luma_spatial
- a non-negative float number which specifies spatial luma strength,
- defaults to 4.0
- @item chroma_spatial
- a non-negative float number which specifies spatial chroma strength,
- defaults to 3.0*@var{luma_spatial}/4.0
- @item luma_tmp
- a float number which specifies luma temporal strength, defaults to
- 6.0*@var{luma_spatial}/4.0
- @item chroma_tmp
- a float number which specifies chroma temporal strength, defaults to
- @var{luma_tmp}*@var{chroma_spatial}/@var{luma_spatial}
- @end table
- @section hue
- Modify the hue and/or the saturation of the input.
- This filter accepts the following optional named options:
- @table @option
- @item h
- Specify the hue angle as a number of degrees. It accepts a float
- number or an expression, and defaults to 0.0.
- @item H
- Specify the hue angle as a number of degrees. It accepts a float
- number or an expression, and defaults to 0.0.
- @item s
- Specify the saturation in the [-10,10] range. It accepts a float number and
- defaults to 1.0.
- @end table
- The @var{h}, @var{H} and @var{s} parameters are expressions containing the
- following constants:
- @table @option
- @item n
- frame count of the input frame starting from 0
- @item pts
- presentation timestamp of the input frame expressed in time base units
- @item r
- frame rate of the input video, NAN if the input frame rate is unknown
- @item t
- timestamp expressed in seconds, NAN if the input timestamp is unknown
- @item tb
- time base of the input video
- @end table
- The options can also be set using the syntax: @var{hue}:@var{saturation}
- In this case @var{hue} is expressed in degrees.
- Some examples follow:
- @itemize
- @item
- Set the hue to 90 degrees and the saturation to 1.0:
- @example
- hue=h=90:s=1
- @end example
- @item
- Same command but expressing the hue in radians:
- @example
- hue=H=PI/2:s=1
- @end example
- @item
- Same command without named options, hue must be expressed in degrees:
- @example
- hue=90:1
- @end example
- @item
- Note that "h:s" syntax does not support expressions for the values of
- h and s, so the following example will issue an error:
- @example
- hue=PI/2:1
- @end example
- @item
- Rotate hue and make the saturation swing between 0
- and 2 over a period of 1 second:
- @example
- hue="H=2*PI*t: s=sin(2*PI*t)+1"
- @end example
- @item
- Apply a 3 seconds saturation fade-in effect starting at 0:
- @example
- hue="s=min(t/3\,1)"
- @end example
- The general fade-in expression can be written as:
- @example
- hue="s=min(0\, max((t-START)/DURATION\, 1))"
- @end example
- @item
- Apply a 3 seconds saturation fade-out effect starting at 5 seconds:
- @example
- hue="s=max(0\, min(1\, (8-t)/3))"
- @end example
- The general fade-out expression can be written as:
- @example
- hue="s=max(0\, min(1\, (START+DURATION-t)/DURATION))"
- @end example
- @end itemize
- @subsection Commands
- This filter supports the following command:
- @table @option
- @item reinit
- Modify the hue and/or the saturation of the input video.
- The command accepts the same named options and syntax than when calling the
- filter from the command-line.
- If a parameter is omitted, it is kept at its current value.
- @end table
- @section idet
- Interlaceing detect filter. This filter tries to detect if the input is
- interlaced or progressive. Top or bottom field first.
- @section kerndeint
- Deinterlace input video by applying Donald Graft's adaptive kernel
- deinterling. Work on interlaced parts of a video to produce
- progressive frames.
- This filter accepts parameters as a list of @var{key}=@var{value}
- pairs, separated by ":". If the key of the first options is omitted,
- the arguments are interpreted according to the following syntax:
- @var{thresh}:@var{map}:@var{order}:@var{sharp}:@var{twoway}.
- The description of the accepted parameters follows.
- @table @option
- @item thresh
- Set the threshold which affects the filter's tolerance when
- determining if a pixel line must be processed. It must be an integer
- in the range [0,255] and defaults to 10. A value of 0 will result in
- applying the process on every pixels.
- @item map
- Paint pixels exceeding the threshold value to white if set to 1.
- Default is 0.
- @item order
- Set the fields order. Swap fields if set to 1, leave fields alone if
- 0. Default is 0.
- @item sharp
- Enable additional sharpening if set to 1. Default is 0.
- @item twoway
- Enable twoway sharpening if set to 1. Default is 0.
- @end table
- @subsection Examples
- @itemize
- @item
- Apply default values:
- @example
- kerndeint=thresh=10:map=0:order=0:sharp=0:twoway=0
- @end example
- @item
- Enable additional sharpening:
- @example
- kerndeint=sharp=1
- @end example
- @item
- Paint processed pixels in white:
- @example
- kerndeint=map=1
- @end example
- @end itemize
- @section lut, lutrgb, lutyuv
- Compute a look-up table for binding each pixel component input value
- to an output value, and apply it to input video.
- @var{lutyuv} applies a lookup table to a YUV input video, @var{lutrgb}
- to an RGB input video.
- These filters accept in input a ":"-separated list of options, which
- specify the expressions used for computing the lookup table for the
- corresponding pixel component values.
- The @var{lut} filter requires either YUV or RGB pixel formats in
- input, and accepts the options:
- @table @option
- @item @var{c0} (first pixel component)
- @item @var{c1} (second pixel component)
- @item @var{c2} (third pixel component)
- @item @var{c3} (fourth pixel component, corresponds to the alpha component)
- @end table
- The exact component associated to each option depends on the format in
- input.
- The @var{lutrgb} filter requires RGB pixel formats in input, and
- accepts the options:
- @table @option
- @item @var{r} (red component)
- @item @var{g} (green component)
- @item @var{b} (blue component)
- @item @var{a} (alpha component)
- @end table
- The @var{lutyuv} filter requires YUV pixel formats in input, and
- accepts the options:
- @table @option
- @item @var{y} (Y/luminance component)
- @item @var{u} (U/Cb component)
- @item @var{v} (V/Cr component)
- @item @var{a} (alpha component)
- @end table
- The expressions can contain the following constants and functions:
- @table @option
- @item w, h
- the input width and height
- @item val
- input value for the pixel component
- @item clipval
- the input value clipped in the @var{minval}-@var{maxval} range
- @item maxval
- maximum value for the pixel component
- @item minval
- minimum value for the pixel component
- @item negval
- the negated value for the pixel component value clipped in the
- @var{minval}-@var{maxval} range , it corresponds to the expression
- "maxval-clipval+minval"
- @item clip(val)
- the computed value in @var{val} clipped in the
- @var{minval}-@var{maxval} range
- @item gammaval(gamma)
- the computed gamma correction value of the pixel component value
- clipped in the @var{minval}-@var{maxval} range, corresponds to the
- expression
- "pow((clipval-minval)/(maxval-minval)\,@var{gamma})*(maxval-minval)+minval"
- @end table
- All expressions default to "val".
- Some examples follow:
- @example
- # negate input video
- lutrgb="r=maxval+minval-val:g=maxval+minval-val:b=maxval+minval-val"
- lutyuv="y=maxval+minval-val:u=maxval+minval-val:v=maxval+minval-val"
- # the above is the same as
- lutrgb="r=negval:g=negval:b=negval"
- lutyuv="y=negval:u=negval:v=negval"
- # negate luminance
- lutyuv=y=negval
- # remove chroma components, turns the video into a graytone image
- lutyuv="u=128:v=128"
- # apply a luma burning effect
- lutyuv="y=2*val"
- # remove green and blue components
- lutrgb="g=0:b=0"
- # set a constant alpha channel value on input
- format=rgba,lutrgb=a="maxval-minval/2"
- # correct luminance gamma by a 0.5 factor
- lutyuv=y=gammaval(0.5)
- @end example
- @section mp
- Apply an MPlayer filter to the input video.
- This filter provides a wrapper around most of the filters of
- MPlayer/MEncoder.
- This wrapper is considered experimental. Some of the wrapped filters
- may not work properly and we may drop support for them, as they will
- be implemented natively into FFmpeg. Thus you should avoid
- depending on them when writing portable scripts.
- The filters accepts the parameters:
- @var{filter_name}[:=]@var{filter_params}
- @var{filter_name} is the name of a supported MPlayer filter,
- @var{filter_params} is a string containing the parameters accepted by
- the named filter.
- The list of the currently supported filters follows:
- @table @var
- @item detc
- @item dint
- @item divtc
- @item down3dright
- @item dsize
- @item eq2
- @item eq
- @item fil
- @item fspp
- @item harddup
- @item il
- @item ilpack
- @item ivtc
- @item kerndeint
- @item mcdeint
- @item noise
- @item ow
- @item perspective
- @item phase
- @item pp7
- @item pullup
- @item qp
- @item sab
- @item softpulldown
- @item softskip
- @item spp
- @item telecine
- @item tinterlace
- @item unsharp
- @item uspp
- @end table
- The parameter syntax and behavior for the listed filters are the same
- of the corresponding MPlayer filters. For detailed instructions check
- the "VIDEO FILTERS" section in the MPlayer manual.
- Some examples follow:
- @itemize
- @item
- Adjust gamma, brightness, contrast:
- @example
- mp=eq2=1.0:2:0.5
- @end example
- @item
- Add temporal noise to input video:
- @example
- mp=noise=20t
- @end example
- @end itemize
- See also mplayer(1), @url{http://www.mplayerhq.hu/}.
- @section negate
- Negate input video.
- This filter accepts an integer in input, if non-zero it negates the
- alpha component (if available). The default value in input is 0.
- @section noformat
- Force libavfilter not to use any of the specified pixel formats for the
- input to the next filter.
- The filter accepts a list of pixel format names, separated by ":",
- for example "yuv420p:monow:rgb24".
- Some examples follow:
- @example
- # force libavfilter to use a format different from "yuv420p" for the
- # input to the vflip filter
- noformat=yuv420p,vflip
- # convert the input video to any of the formats not contained in the list
- noformat=yuv420p:yuv444p:yuv410p
- @end example
- @section null
- Pass the video source unchanged to the output.
- @section ocv
- Apply video transform using libopencv.
- To enable this filter install libopencv library and headers and
- configure FFmpeg with @code{--enable-libopencv}.
- The filter takes the parameters: @var{filter_name}@{:=@}@var{filter_params}.
- @var{filter_name} is the name of the libopencv filter to apply.
- @var{filter_params} specifies the parameters to pass to the libopencv
- filter. If not specified the default values are assumed.
- Refer to the official libopencv documentation for more precise
- information:
- @url{http://opencv.willowgarage.com/documentation/c/image_filtering.html}
- Follows the list of supported libopencv filters.
- @anchor{dilate}
- @subsection dilate
- Dilate an image by using a specific structuring element.
- This filter corresponds to the libopencv function @code{cvDilate}.
- It accepts the parameters: @var{struct_el}:@var{nb_iterations}.
- @var{struct_el} represents a structuring element, and has the syntax:
- @var{cols}x@var{rows}+@var{anchor_x}x@var{anchor_y}/@var{shape}
- @var{cols} and @var{rows} represent the number of columns and rows of
- the structuring element, @var{anchor_x} and @var{anchor_y} the anchor
- point, and @var{shape} the shape for the structuring element, and
- can be one of the values "rect", "cross", "ellipse", "custom".
- If the value for @var{shape} is "custom", it must be followed by a
- string of the form "=@var{filename}". The file with name
- @var{filename} is assumed to represent a binary image, with each
- printable character corresponding to a bright pixel. When a custom
- @var{shape} is used, @var{cols} and @var{rows} are ignored, the number
- or columns and rows of the read file are assumed instead.
- The default value for @var{struct_el} is "3x3+0x0/rect".
- @var{nb_iterations} specifies the number of times the transform is
- applied to the image, and defaults to 1.
- Follow some example:
- @example
- # use the default values
- ocv=dilate
- # dilate using a structuring element with a 5x5 cross, iterate two times
- ocv=dilate=5x5+2x2/cross:2
- # read the shape from the file diamond.shape, iterate two times
- # the file diamond.shape may contain a pattern of characters like this:
- # *
- # ***
- # *****
- # ***
- # *
- # the specified cols and rows are ignored (but not the anchor point coordinates)
- ocv=0x0+2x2/custom=diamond.shape:2
- @end example
- @subsection erode
- Erode an image by using a specific structuring element.
- This filter corresponds to the libopencv function @code{cvErode}.
- The filter accepts the parameters: @var{struct_el}:@var{nb_iterations},
- with the same syntax and semantics as the @ref{dilate} filter.
- @subsection smooth
- Smooth the input video.
- The filter takes the following parameters:
- @var{type}:@var{param1}:@var{param2}:@var{param3}:@var{param4}.
- @var{type} is the type of smooth filter to apply, and can be one of
- the following values: "blur", "blur_no_scale", "median", "gaussian",
- "bilateral". The default value is "gaussian".
- @var{param1}, @var{param2}, @var{param3}, and @var{param4} are
- parameters whose meanings depend on smooth type. @var{param1} and
- @var{param2} accept integer positive values or 0, @var{param3} and
- @var{param4} accept float values.
- The default value for @var{param1} is 3, the default value for the
- other parameters is 0.
- These parameters correspond to the parameters assigned to the
- libopencv function @code{cvSmooth}.
- @anchor{overlay}
- @section overlay
- Overlay one video on top of another.
- It takes two inputs and one output, the first input is the "main"
- video on which the second input is overlayed.
- This filter accepts a list of @var{key}=@var{value} pairs as argument,
- separated by ":". If the key of the first options is omitted, the
- arguments are interpreted according to the syntax @var{x}:@var{y}.
- A description of the accepted options follows.
- @table @option
- @item x, y
- Set the expression for the x and y coordinates of the overlayed video
- on the main video. Default value is 0.
- The @var{x} and @var{y} expressions can contain the following
- parameters:
- @table @option
- @item main_w, main_h
- main input width and height
- @item W, H
- same as @var{main_w} and @var{main_h}
- @item overlay_w, overlay_h
- overlay input width and height
- @item w, h
- same as @var{overlay_w} and @var{overlay_h}
- @end table
- @item rgb
- If set to 1, force the filter to accept inputs in the RGB
- color space. Default value is 0.
- @end table
- Be aware that frames are taken from each input video in timestamp
- order, hence, if their initial timestamps differ, it is a a good idea
- to pass the two inputs through a @var{setpts=PTS-STARTPTS} filter to
- have them begin in the same zero timestamp, as it does the example for
- the @var{movie} filter.
- You can chain together more overlays but you should test the
- efficiency of such approach.
- @subsection Examples
- @itemize
- @item
- Draw the overlay at 10 pixels from the bottom right corner of the main
- video:
- @example
- overlay=main_w-overlay_w-10:main_h-overlay_h-10
- @end example
- Using named options the example above becomes:
- @example
- overlay=x=main_w-overlay_w-10:y=main_h-overlay_h-10
- @end example
- @item
- Insert a transparent PNG logo in the bottom left corner of the input,
- using the @command{ffmpeg} tool with the @code{-filter_complex} option:
- @example
- ffmpeg -i input -i logo -filter_complex 'overlay=10:main_h-overlay_h-10' output
- @end example
- @item
- Insert 2 different transparent PNG logos (second logo on bottom
- right corner) using the @command{ffmpeg} tool:
- @example
- ffmpeg -i input -i logo1 -i logo2 -filter_complex 'overlay=10:H-h-10,overlay=W-w-10:H-h-10' output
- @end example
- @item
- Add a transparent color layer on top of the main video, WxH specifies
- the size of the main input to the overlay filter:
- @example
- color=red@@.3:WxH [over]; [in][over] overlay [out]
- @end example
- @item
- Play an original video and a filtered version (here with the deshake
- filter) side by side using the @command{ffplay} tool:
- @example
- ffplay input.avi -vf 'split[a][b]; [a]pad=iw*2:ih[src]; [b]deshake[filt]; [src][filt]overlay=w'
- @end example
- The above command is the same as:
- @example
- ffplay input.avi -vf 'split[b], pad=iw*2[src], [b]deshake, [src]overlay=w'
- @end example
- @item
- Chain several overlays in cascade:
- @example
- nullsrc=s=200x200 [bg];
- testsrc=s=100x100, split=4 [in0][in1][in2][in3];
- [in0] lutrgb=r=0, [bg] overlay=0:0 [mid0];
- [in1] lutrgb=g=0, [mid0] overlay=100:0 [mid1];
- [in2] lutrgb=b=0, [mid1] overlay=0:100 [mid2];
- [in3] null, [mid2] overlay=100:100 [out0]
- @end example
- @end itemize
- @section pad
- Add paddings to the input image, and places the original input at the
- given coordinates @var{x}, @var{y}.
- It accepts the following parameters:
- @var{width}:@var{height}:@var{x}:@var{y}:@var{color}.
- The parameters @var{width}, @var{height}, @var{x}, and @var{y} are
- expressions containing the following constants:
- @table @option
- @item in_w, in_h
- the input video width and height
- @item iw, ih
- same as @var{in_w} and @var{in_h}
- @item out_w, out_h
- the output width and height, that is the size of the padded area as
- specified by the @var{width} and @var{height} expressions
- @item ow, oh
- same as @var{out_w} and @var{out_h}
- @item x, y
- x and y offsets as specified by the @var{x} and @var{y}
- expressions, or NAN if not yet specified
- @item a
- same as @var{iw} / @var{ih}
- @item sar
- input sample aspect ratio
- @item dar
- input display aspect ratio, it is the same as (@var{iw} / @var{ih}) * @var{sar}
- @item hsub, vsub
- horizontal and vertical chroma subsample values. For example for the
- pixel format "yuv422p" @var{hsub} is 2 and @var{vsub} is 1.
- @end table
- Follows the description of the accepted parameters.
- @table @option
- @item width, height
- Specify the size of the output image with the paddings added. If the
- value for @var{width} or @var{height} is 0, the corresponding input size
- is used for the output.
- The @var{width} expression can reference the value set by the
- @var{height} expression, and vice versa.
- The default value of @var{width} and @var{height} is 0.
- @item x, y
- Specify the offsets where to place the input image in the padded area
- with respect to the top/left border of the output image.
- The @var{x} expression can reference the value set by the @var{y}
- expression, and vice versa.
- The default value of @var{x} and @var{y} is 0.
- @item color
- Specify the color of the padded area, it can be the name of a color
- (case insensitive match) or a 0xRRGGBB[AA] sequence.
- The default value of @var{color} is "black".
- @end table
- @subsection Examples
- @itemize
- @item
- Add paddings with color "violet" to the input video. Output video
- size is 640x480, the top-left corner of the input video is placed at
- column 0, row 40:
- @example
- pad=640:480:0:40:violet
- @end example
- @item
- Pad the input to get an output with dimensions increased by 3/2,
- and put the input video at the center of the padded area:
- @example
- pad="3/2*iw:3/2*ih:(ow-iw)/2:(oh-ih)/2"
- @end example
- @item
- Pad the input to get a squared output with size equal to the maximum
- value between the input width and height, and put the input video at
- the center of the padded area:
- @example
- pad="max(iw\,ih):ow:(ow-iw)/2:(oh-ih)/2"
- @end example
- @item
- Pad the input to get a final w/h ratio of 16:9:
- @example
- pad="ih*16/9:ih:(ow-iw)/2:(oh-ih)/2"
- @end example
- @item
- In case of anamorphic video, in order to set the output display aspect
- correctly, it is necessary to use @var{sar} in the expression,
- according to the relation:
- @example
- (ih * X / ih) * sar = output_dar
- X = output_dar / sar
- @end example
- Thus the previous example needs to be modified to:
- @example
- pad="ih*16/9/sar:ih:(ow-iw)/2:(oh-ih)/2"
- @end example
- @item
- Double output size and put the input video in the bottom-right
- corner of the output padded area:
- @example
- pad="2*iw:2*ih:ow-iw:oh-ih"
- @end example
- @end itemize
- @section pixdesctest
- Pixel format descriptor test filter, mainly useful for internal
- testing. The output video should be equal to the input video.
- For example:
- @example
- format=monow, pixdesctest
- @end example
- can be used to test the monowhite pixel format descriptor definition.
- @section pp
- Enable the specified chain of postprocessing subfilters using libpostproc. This
- library should be automatically selected with a GPL build (@code{--enable-gpl}).
- Subfilters must be separated by '/' and can be disabled by prepending a '-'.
- Each subfilter and some options have a short and a long name that can be used
- interchangeably, i.e. dr/dering are the same.
- All subfilters share common options to determine their scope:
- @table @option
- @item a/autoq
- Honor the quality commands for this subfilter.
- @item c/chrom
- Do chrominance filtering, too (default).
- @item y/nochrom
- Do luminance filtering only (no chrominance).
- @item n/noluma
- Do chrominance filtering only (no luminance).
- @end table
- These options can be appended after the subfilter name, separated by a ':'.
- Available subfilters are:
- @table @option
- @item hb/hdeblock[:difference[:flatness]]
- Horizontal deblocking filter
- @table @option
- @item difference
- Difference factor where higher values mean more deblocking (default: @code{32}).
- @item flatness
- Flatness threshold where lower values mean more deblocking (default: @code{39}).
- @end table
- @item vb/vdeblock[:difference[:flatness]]
- Vertical deblocking filter
- @table @option
- @item difference
- Difference factor where higher values mean more deblocking (default: @code{32}).
- @item flatness
- Flatness threshold where lower values mean more deblocking (default: @code{39}).
- @end table
- @item ha/hadeblock[:difference[:flatness]]
- Accurate horizontal deblocking filter
- @table @option
- @item difference
- Difference factor where higher values mean more deblocking (default: @code{32}).
- @item flatness
- Flatness threshold where lower values mean more deblocking (default: @code{39}).
- @end table
- @item va/vadeblock[:difference[:flatness]]
- Accurate vertical deblocking filter
- @table @option
- @item difference
- Difference factor where higher values mean more deblocking (default: @code{32}).
- @item flatness
- Flatness threshold where lower values mean more deblocking (default: @code{39}).
- @end table
- @end table
- The horizontal and vertical deblocking filters share the difference and
- flatness values so you cannot set different horizontal and vertical
- thresholds.
- @table @option
- @item h1/x1hdeblock
- Experimental horizontal deblocking filter
- @item v1/x1vdeblock
- Experimental vertical deblocking filter
- @item dr/dering
- Deringing filter
- @item tn/tmpnoise[:threshold1[:threshold2[:threshold3]]], temporal noise reducer
- @table @option
- @item threshold1
- larger -> stronger filtering
- @item threshold2
- larger -> stronger filtering
- @item threshold3
- larger -> stronger filtering
- @end table
- @item al/autolevels[:f/fullyrange], automatic brightness / contrast correction
- @table @option
- @item f/fullyrange
- Stretch luminance to @code{0-255}.
- @end table
- @item lb/linblenddeint
- Linear blend deinterlacing filter that deinterlaces the given block by
- filtering all lines with a @code{(1 2 1)} filter.
- @item li/linipoldeint
- Linear interpolating deinterlacing filter that deinterlaces the given block by
- linearly interpolating every second line.
- @item ci/cubicipoldeint
- Cubic interpolating deinterlacing filter deinterlaces the given block by
- cubically interpolating every second line.
- @item md/mediandeint
- Median deinterlacing filter that deinterlaces the given block by applying a
- median filter to every second line.
- @item fd/ffmpegdeint
- FFmpeg deinterlacing filter that deinterlaces the given block by filtering every
- second line with a @code{(-1 4 2 4 -1)} filter.
- @item l5/lowpass5
- Vertically applied FIR lowpass deinterlacing filter that deinterlaces the given
- block by filtering all lines with a @code{(-1 2 6 2 -1)} filter.
- @item fq/forceQuant[:quantizer]
- Overrides the quantizer table from the input with the constant quantizer you
- specify.
- @table @option
- @item quantizer
- Quantizer to use
- @end table
- @item de/default
- Default pp filter combination (@code{hb:a,vb:a,dr:a})
- @item fa/fast
- Fast pp filter combination (@code{h1:a,v1:a,dr:a})
- @item ac
- High quality pp filter combination (@code{ha:a:128:7,va:a,dr:a})
- @end table
- @subsection Examples
- @itemize
- @item
- Apply horizontal and vertical deblocking, deringing and automatic
- brightness/contrast:
- @example
- pp=hb/vb/dr/al
- @end example
- @item
- Apply default filters without brightness/contrast correction:
- @example
- pp=de/-al
- @end example
- @item
- Apply default filters and temporal denoiser:
- @example
- pp=default/tmpnoise:1:2:3
- @end example
- @item
- Apply deblocking on luminance only, and switch vertical deblocking on or off
- automatically depending on available CPU time:
- @example
- pp=hb:y/vb:a
- @end example
- @end itemize
- @section removelogo
- Suppress a TV station logo, using an image file to determine which
- pixels comprise the logo. It works by filling in the pixels that
- comprise the logo with neighboring pixels.
- This filter requires one argument which specifies the filter bitmap
- file, which can be any image format supported by libavformat. The
- width and height of the image file must match those of the video
- stream being processed.
- Pixels in the provided bitmap image with a value of zero are not
- considered part of the logo, non-zero pixels are considered part of
- the logo. If you use white (255) for the logo and black (0) for the
- rest, you will be safe. For making the filter bitmap, it is
- recommended to take a screen capture of a black frame with the logo
- visible, and then using a threshold filter followed by the erode
- filter once or twice.
- If needed, little splotches can be fixed manually. Remember that if
- logo pixels are not covered, the filter quality will be much
- reduced. Marking too many pixels as part of the logo does not hurt as
- much, but it will increase the amount of blurring needed to cover over
- the image and will destroy more information than necessary, and extra
- pixels will slow things down on a large logo.
- @section scale
- Scale (resize) the input video, using the libswscale library.
- The scale filter forces the output display aspect ratio to be the same
- of the input, by changing the output sample aspect ratio.
- This filter accepts a list of named options in the form of
- @var{key}=@var{value} pairs separated by ":". If the key for the first
- two options is not specified, the assumed keys for the first two
- values are @code{w} and @code{h}. If the first option has no key and
- can be interpreted like a video size specification, it will be used
- to set the video size.
- A description of the accepted options follows.
- @table @option
- @item width, w
- Set the video width expression, default value is @code{iw}. See below
- for the list of accepted constants.
- @item height, h
- Set the video heiht expression, default value is @code{ih}.
- See below for the list of accepted constants.
- @item interl
- Set the interlacing. It accepts the following values:
- @table @option
- @item 1
- force interlaced aware scaling
- @item 0
- do not apply interlaced scaling
- @item -1
- select interlaced aware scaling depending on whether the source frames
- are flagged as interlaced or not
- @end table
- Default value is @code{0}.
- @item flags
- Set libswscale scaling flags. If not explictly specified the filter
- applies a bilinear scaling algorithm.
- @item size, s
- Set the video size, the value must be a valid abbreviation or in the
- form @var{width}x@var{height}.
- @end table
- The values of the @var{w} and @var{h} options are expressions
- containing the following constants:
- @table @option
- @item in_w, in_h
- the input width and height
- @item iw, ih
- same as @var{in_w} and @var{in_h}
- @item out_w, out_h
- the output (cropped) width and height
- @item ow, oh
- same as @var{out_w} and @var{out_h}
- @item a
- same as @var{iw} / @var{ih}
- @item sar
- input sample aspect ratio
- @item dar
- input display aspect ratio, it is the same as (@var{iw} / @var{ih}) * @var{sar}
- @item hsub, vsub
- horizontal and vertical chroma subsample values. For example for the
- pixel format "yuv422p" @var{hsub} is 2 and @var{vsub} is 1.
- @end table
- If the input image format is different from the format requested by
- the next filter, the scale filter will convert the input to the
- requested format.
- If the value for @var{width} or @var{height} is 0, the respective input
- size is used for the output.
- If the value for @var{width} or @var{height} is -1, the scale filter will
- use, for the respective output size, a value that maintains the aspect
- ratio of the input image.
- @subsection Examples
- @itemize
- @item
- Scale the input video to a size of 200x100:
- @example
- scale=200:100
- @end example
- This is equivalent to:
- @example
- scale=w=200:h=100
- @end example
- or:
- @example
- scale=200x100
- @end example
- @item
- Specify a size abbreviation for the output size:
- @example
- scale=qcif
- @end example
- which can also be written as:
- @example
- scale=size=qcif
- @end example
- @item
- Scale the input to 2x:
- @example
- scale=2*iw:2*ih
- @end example
- @item
- The above is the same as:
- @example
- scale=2*in_w:2*in_h
- @end example
- @item
- Scale the input to 2x with forced interlaced scaling:
- @example
- scale=2*iw:2*ih:interl=1
- @end example
- @item
- Scale the input to half size:
- @example
- scale=iw/2:ih/2
- @end example
- @item
- Increase the width, and set the height to the same size:
- @example
- scale=3/2*iw:ow
- @end example
- @item
- Seek for Greek harmony:
- @example
- scale=iw:1/PHI*iw
- scale=ih*PHI:ih
- @end example
- @item
- Increase the height, and set the width to 3/2 of the height:
- @example
- scale=3/2*oh:3/5*ih
- @end example
- @item
- Increase the size, but make the size a multiple of the chroma:
- @example
- scale="trunc(3/2*iw/hsub)*hsub:trunc(3/2*ih/vsub)*vsub"
- @end example
- @item
- Increase the width to a maximum of 500 pixels, keep the same input
- aspect ratio:
- @example
- scale='min(500\, iw*3/2):-1'
- @end example
- @end itemize
- @section setdar, setsar
- The @code{setdar} filter sets the Display Aspect Ratio for the filter
- output video.
- This is done by changing the specified Sample (aka Pixel) Aspect
- Ratio, according to the following equation:
- @example
- @var{DAR} = @var{HORIZONTAL_RESOLUTION} / @var{VERTICAL_RESOLUTION} * @var{SAR}
- @end example
- Keep in mind that the @code{setdar} filter does not modify the pixel
- dimensions of the video frame. Also the display aspect ratio set by
- this filter may be changed by later filters in the filterchain,
- e.g. in case of scaling or if another "setdar" or a "setsar" filter is
- applied.
- The @code{setsar} filter sets the Sample (aka Pixel) Aspect Ratio for
- the filter output video.
- Note that as a consequence of the application of this filter, the
- output display aspect ratio will change according to the equation
- above.
- Keep in mind that the sample aspect ratio set by the @code{setsar}
- filter may be changed by later filters in the filterchain, e.g. if
- another "setsar" or a "setdar" filter is applied.
- The @code{setdar} and @code{setsar} filters accept a string in the
- form @var{num}:@var{den} expressing an aspect ratio, or the following
- named options, expressed as a sequence of @var{key}=@var{value} pairs,
- separated by ":".
- @table @option
- @item max
- Set the maximum integer value to use for expressing numerator and
- denominator when reducing the expressed aspect ratio to a rational.
- Default value is @code{100}.
- @item r, ratio:
- Set the aspect ratio used by the filter.
- The parameter can be a floating point number string, an expression, or
- a string of the form @var{num}:@var{den}, where @var{num} and
- @var{den} are the numerator and denominator of the aspect ratio. If
- the parameter is not specified, it is assumed the value "0".
- In case the form "@var{num}:@var{den}" the @code{:} character should
- be escaped.
- @end table
- If the keys are omitted in the named options list, the specifed values
- are assumed to be @var{ratio} and @var{max} in that order.
- For example to change the display aspect ratio to 16:9, specify:
- @example
- setdar='16:9'
- @end example
- The example above is equivalent to:
- @example
- setdar=1.77777
- @end example
- To change the sample aspect ratio to 10:11, specify:
- @example
- setsar='10:11'
- @end example
- To set a display aspect ratio of 16:9, and specify a maximum integer value of
- 1000 in the aspect ratio reduction, use the command:
- @example
- setdar=ratio='16:9':max=1000
- @end example
- @section setfield
- Force field for the output video frame.
- The @code{setfield} filter marks the interlace type field for the
- output frames. It does not change the input frame, but only sets the
- corresponding property, which affects how the frame is treated by
- following filters (e.g. @code{fieldorder} or @code{yadif}).
- This filter accepts a single option @option{mode}, which can be
- specified either by setting @code{mode=VALUE} or setting the value
- alone. Available values are:
- @table @samp
- @item auto
- Keep the same field property.
- @item bff
- Mark the frame as bottom-field-first.
- @item tff
- Mark the frame as top-field-first.
- @item prog
- Mark the frame as progressive.
- @end table
- @section showinfo
- Show a line containing various information for each input video frame.
- The input video is not modified.
- The shown line contains a sequence of key/value pairs of the form
- @var{key}:@var{value}.
- A description of each shown parameter follows:
- @table @option
- @item n
- sequential number of the input frame, starting from 0
- @item pts
- Presentation TimeStamp of the input frame, expressed as a number of
- time base units. The time base unit depends on the filter input pad.
- @item pts_time
- Presentation TimeStamp of the input frame, expressed as a number of
- seconds
- @item pos
- position of the frame in the input stream, -1 if this information in
- unavailable and/or meaningless (for example in case of synthetic video)
- @item fmt
- pixel format name
- @item sar
- sample aspect ratio of the input frame, expressed in the form
- @var{num}/@var{den}
- @item s
- size of the input frame, expressed in the form
- @var{width}x@var{height}
- @item i
- interlaced mode ("P" for "progressive", "T" for top field first, "B"
- for bottom field first)
- @item iskey
- 1 if the frame is a key frame, 0 otherwise
- @item type
- picture type of the input frame ("I" for an I-frame, "P" for a
- P-frame, "B" for a B-frame, "?" for unknown type).
- Check also the documentation of the @code{AVPictureType} enum and of
- the @code{av_get_picture_type_char} function defined in
- @file{libavutil/avutil.h}.
- @item checksum
- Adler-32 checksum (printed in hexadecimal) of all the planes of the input frame
- @item plane_checksum
- Adler-32 checksum (printed in hexadecimal) of each plane of the input frame,
- expressed in the form "[@var{c0} @var{c1} @var{c2} @var{c3}]"
- @end table
- @section smartblur
- Blur the input video without impacting the outlines.
- The filter accepts the following parameters:
- @var{luma_radius}:@var{luma_strength}:@var{luma_threshold}[:@var{chroma_radius}:@var{chroma_strength}:@var{chroma_threshold}]
- Parameters prefixed by @var{luma} indicate that they work on the
- luminance of the pixels whereas parameters prefixed by @var{chroma}
- refer to the chrominance of the pixels.
- If the chroma parameters are not set, the luma parameters are used for
- either the luminance and the chrominance of the pixels.
- @var{luma_radius} or @var{chroma_radius} must be a float number in the
- range [0.1,5.0] that specifies the variance of the gaussian filter
- used to blur the image (slower if larger).
- @var{luma_strength} or @var{chroma_strength} must be a float number in
- the range [-1.0,1.0] that configures the blurring. A value included in
- [0.0,1.0] will blur the image whereas a value included in [-1.0,0.0]
- will sharpen the image.
- @var{luma_threshold} or @var{chroma_threshold} must be an integer in
- the range [-30,30] that is used as a coefficient to determine whether
- a pixel should be blurred or not. A value of 0 will filter all the
- image, a value included in [0,30] will filter flat areas and a value
- included in [-30,0] will filter edges.
- @anchor{subtitles}
- @section subtitles
- Draw subtitles on top of input video using the libass library.
- To enable compilation of this filter you need to configure FFmpeg with
- @code{--enable-libass}. This filter also requires a build with libavcodec and
- libavformat to convert the passed subtitles file to ASS (Advanced Substation
- Alpha) subtitles format.
- This filter accepts the following named options, expressed as a
- sequence of @var{key}=@var{value} pairs, separated by ":".
- @table @option
- @item filename, f
- Set the filename of the subtitle file to read. It must be specified.
- @item original_size
- Specify the size of the original video, the video for which the ASS file
- was composed. Due to a misdesign in ASS aspect ratio arithmetic, this is
- necessary to correctly scale the fonts if the aspect ratio has been changed.
- @end table
- If the first key is not specified, it is assumed that the first value
- specifies the @option{filename}.
- For example, to render the file @file{sub.srt} on top of the input
- video, use the command:
- @example
- subtitles=sub.srt
- @end example
- which is equivalent to:
- @example
- subtitles=filename=sub.srt
- @end example
- @section split
- Split input video into several identical outputs.
- The filter accepts a single parameter which specifies the number of outputs. If
- unspecified, it defaults to 2.
- For example
- @example
- ffmpeg -i INPUT -filter_complex split=5 OUTPUT
- @end example
- will create 5 copies of the input video.
- For example:
- @example
- [in] split [splitout1][splitout2];
- [splitout1] crop=100:100:0:0 [cropout];
- [splitout2] pad=200:200:100:100 [padout];
- @end example
- will create two separate outputs from the same input, one cropped and
- one padded.
- @section super2xsai
- Scale the input by 2x and smooth using the Super2xSaI (Scale and
- Interpolate) pixel art scaling algorithm.
- Useful for enlarging pixel art images without reducing sharpness.
- @section swapuv
- Swap U & V plane.
- @section thumbnail
- Select the most representative frame in a given sequence of consecutive frames.
- It accepts as argument the frames batch size to analyze (default @var{N}=100);
- in a set of @var{N} frames, the filter will pick one of them, and then handle
- the next batch of @var{N} frames until the end.
- Since the filter keeps track of the whole frames sequence, a bigger @var{N}
- value will result in a higher memory usage, so a high value is not recommended.
- The following example extract one picture each 50 frames:
- @example
- thumbnail=50
- @end example
- Complete example of a thumbnail creation with @command{ffmpeg}:
- @example
- ffmpeg -i in.avi -vf thumbnail,scale=300:200 -frames:v 1 out.png
- @end example
- @section tile
- Tile several successive frames together.
- It accepts a list of options in the form of @var{key}=@var{value} pairs
- separated by ":". A description of the accepted options follows.
- @table @option
- @item layout
- Set the grid size (i.e. the number of lines and columns) in the form
- "@var{w}x@var{h}".
- @item margin
- Set the outer border margin in pixels.
- @item padding
- Set the inner border thickness (i.e. the number of pixels between frames). For
- more advanced padding options (such as having different values for the edges),
- refer to the pad video filter.
- @item nb_frames
- Set the maximum number of frames to render in the given area. It must be less
- than or equal to @var{w}x@var{h}. The default value is @code{0}, meaning all
- the area will be used.
- @end table
- Alternatively, the options can be specified as a flat string:
- @var{layout}[:@var{nb_frames}[:@var{margin}[:@var{padding}]]]
- For example, produce 8x8 PNG tiles of all keyframes (@option{-skip_frame
- nokey}) in a movie:
- @example
- ffmpeg -skip_frame nokey -i file.avi -vf 'scale=128:72,tile=8x8' -an -vsync 0 keyframes%03d.png
- @end example
- The @option{-vsync 0} is necessary to prevent @command{ffmpeg} from
- duplicating each output frame to accomodate the originally detected frame
- rate.
- Another example to display @code{5} pictures in an area of @code{3x2} frames,
- with @code{7} pixels between them, and @code{2} pixels of initial margin, using
- mixed flat and named options:
- @example
- tile=3x2:nb_frames=5:padding=7:margin=2
- @end example
- @section tinterlace
- Perform various types of temporal field interlacing.
- Frames are counted starting from 1, so the first input frame is
- considered odd.
- This filter accepts options in the form of @var{key}=@var{value} pairs
- separated by ":".
- Alternatively, the @var{mode} option can be specified as a value alone,
- optionally followed by a ":" and further ":" separated @var{key}=@var{value}
- pairs.
- A description of the accepted options follows.
- @table @option
- @item mode
- Specify the mode of the interlacing. This option can also be specified
- as a value alone. See below for a list of values for this option.
- Available values are:
- @table @samp
- @item merge, 0
- Move odd frames into the upper field, even into the lower field,
- generating a double height frame at half framerate.
- @item drop_odd, 1
- Only output even frames, odd frames are dropped, generating a frame with
- unchanged height at half framerate.
- @item drop_even, 2
- Only output odd frames, even frames are dropped, generating a frame with
- unchanged height at half framerate.
- @item pad, 3
- Expand each frame to full height, but pad alternate lines with black,
- generating a frame with double height at the same input framerate.
- @item interleave_top, 4
- Interleave the upper field from odd frames with the lower field from
- even frames, generating a frame with unchanged height at half framerate.
- @item interleave_bottom, 5
- Interleave the lower field from odd frames with the upper field from
- even frames, generating a frame with unchanged height at half framerate.
- @item interlacex2, 6
- Double frame rate with unchanged height. Frames are inserted each
- containing the second temporal field from the previous input frame and
- the first temporal field from the next input frame. This mode relies on
- the top_field_first flag. Useful for interlaced video displays with no
- field synchronisation.
- @end table
- Numeric values are deprecated but are accepted for backward
- compatibility reasons.
- Default mode is @code{merge}.
- @item flags
- Specify flags influencing the filter process.
- Available value for @var{flags} is:
- @table @option
- @item low_pass_filter, vlfp
- Enable vertical low-pass filtering in the filter.
- Vertical low-pass filtering is required when creating an interlaced
- destination from a progressive source which contains high-frequency
- vertical detail. Filtering will reduce interlace 'twitter' and Moire
- patterning.
- Vertical low-pass filtering can only be enabled for @option{mode}
- @var{interleave_top} and @var{interleave_bottom}.
- @end table
- @end table
- @section transpose
- Transpose rows with columns in the input video and optionally flip it.
- The filter accepts parameters as a list of @var{key}=@var{value}
- pairs, separated by ':'. If the key of the first options is omitted,
- the arguments are interpreted according to the syntax
- @var{dir}:@var{passthrough}.
- @table @option
- @item dir
- Specify the transposition direction. Can assume the following values:
- @table @samp
- @item 0, 4
- Rotate by 90 degrees counterclockwise and vertically flip (default), that is:
- @example
- L.R L.l
- . . -> . .
- l.r R.r
- @end example
- @item 1, 5
- Rotate by 90 degrees clockwise, that is:
- @example
- L.R l.L
- . . -> . .
- l.r r.R
- @end example
- @item 2, 6
- Rotate by 90 degrees counterclockwise, that is:
- @example
- L.R R.r
- . . -> . .
- l.r L.l
- @end example
- @item 3, 7
- Rotate by 90 degrees clockwise and vertically flip, that is:
- @example
- L.R r.R
- . . -> . .
- l.r l.L
- @end example
- @end table
- For values between 4-7, the transposition is only done if the input
- video geometry is portrait and not landscape. These values are
- deprecated, the @code{passthrough} option should be used instead.
- @item passthrough
- Do not apply the transposition if the input geometry matches the one
- specified by the specified value. It accepts the following values:
- @table @samp
- @item none
- Always apply transposition.
- @item portrait
- Preserve portrait geometry (when @var{height} >= @var{width}).
- @item landscape
- Preserve landscape geometry (when @var{width} >= @var{height}).
- @end table
- Default value is @code{none}.
- @end table
- For example to rotate by 90 degrees clockwise and preserve portrait
- layout:
- @example
- transpose=dir=1:passthrough=portrait
- @end example
- The command above can also be specified as:
- @example
- transpose=1:portrait
- @end example
- @section unsharp
- Sharpen or blur the input video.
- It accepts the following parameters:
- @var{luma_msize_x}:@var{luma_msize_y}:@var{luma_amount}:@var{chroma_msize_x}:@var{chroma_msize_y}:@var{chroma_amount}
- Negative values for the amount will blur the input video, while positive
- values will sharpen. All parameters are optional and default to the
- equivalent of the string '5:5:1.0:5:5:0.0'.
- @table @option
- @item luma_msize_x
- Set the luma matrix horizontal size. It can be an integer between 3
- and 13, default value is 5.
- @item luma_msize_y
- Set the luma matrix vertical size. It can be an integer between 3
- and 13, default value is 5.
- @item luma_amount
- Set the luma effect strength. It can be a float number between -2.0
- and 5.0, default value is 1.0.
- @item chroma_msize_x
- Set the chroma matrix horizontal size. It can be an integer between 3
- and 13, default value is 5.
- @item chroma_msize_y
- Set the chroma matrix vertical size. It can be an integer between 3
- and 13, default value is 5.
- @item chroma_amount
- Set the chroma effect strength. It can be a float number between -2.0
- and 5.0, default value is 0.0.
- @end table
- @example
- # Strong luma sharpen effect parameters
- unsharp=7:7:2.5
- # Strong blur of both luma and chroma parameters
- unsharp=7:7:-2:7:7:-2
- # Use the default values with @command{ffmpeg}
- ffmpeg -i in.avi -vf "unsharp" out.mp4
- @end example
- @section vflip
- Flip the input video vertically.
- @example
- ffmpeg -i in.avi -vf "vflip" out.avi
- @end example
- @section yadif
- Deinterlace the input video ("yadif" means "yet another deinterlacing
- filter").
- The filter accepts parameters as a list of @var{key}=@var{value}
- pairs, separated by ":". If the key of the first options is omitted,
- the arguments are interpreted according to syntax
- @var{mode}:@var{parity}:@var{deint}.
- The description of the accepted parameters follows.
- @table @option
- @item mode
- Specify the interlacing mode to adopt. Accept one of the following
- values:
- @table @option
- @item 0, send_frame
- output 1 frame for each frame
- @item 1, send_field
- output 1 frame for each field
- @item 2, send_frame_nospatial
- like @code{send_frame} but skip spatial interlacing check
- @item 3, send_field_nospatial
- like @code{send_field} but skip spatial interlacing check
- @end table
- Default value is @code{send_frame}.
- @item parity
- Specify the picture field parity assumed for the input interlaced
- video. Accept one of the following values:
- @table @option
- @item 0, tff
- assume top field first
- @item 1, bff
- assume bottom field first
- @item -1, auto
- enable automatic detection
- @end table
- Default value is @code{auto}.
- If interlacing is unknown or decoder does not export this information,
- top field first will be assumed.
- @item deint
- Specify which frames to deinterlace. Accept one of the following
- values:
- @table @option
- @item 0, all
- deinterlace all frames
- @item 1, interlaced
- only deinterlace frames marked as interlaced
- @end table
- Default value is @code{all}.
- @end table
- @c man end VIDEO FILTERS
- @chapter Video Sources
- @c man begin VIDEO SOURCES
- Below is a description of the currently available video sources.
- @section buffer
- Buffer video frames, and make them available to the filter chain.
- This source is mainly intended for a programmatic use, in particular
- through the interface defined in @file{libavfilter/vsrc_buffer.h}.
- It accepts a list of options in the form of @var{key}=@var{value} pairs
- separated by ":". A description of the accepted options follows.
- @table @option
- @item video_size
- Specify the size (width and height) of the buffered video frames.
- @item pix_fmt
- A string representing the pixel format of the buffered video frames.
- It may be a number corresponding to a pixel format, or a pixel format
- name.
- @item time_base
- Specify the timebase assumed by the timestamps of the buffered frames.
- @item time_base
- Specify the frame rate expected for the video stream.
- @item pixel_aspect
- Specify the sample aspect ratio assumed by the video frames.
- @item sws_param
- Specify the optional parameters to be used for the scale filter which
- is automatically inserted when an input change is detected in the
- input size or format.
- @end table
- For example:
- @example
- buffer=size=320x240:pix_fmt=yuv410p:time_base=1/24:pixel_aspect=1/1
- @end example
- will instruct the source to accept video frames with size 320x240 and
- with format "yuv410p", assuming 1/24 as the timestamps timebase and
- square pixels (1:1 sample aspect ratio).
- Since the pixel format with name "yuv410p" corresponds to the number 6
- (check the enum AVPixelFormat definition in @file{libavutil/pixfmt.h}),
- this example corresponds to:
- @example
- buffer=size=320x240:pixfmt=6:time_base=1/24:pixel_aspect=1/1
- @end example
- Alternatively, the options can be specified as a flat string, but this
- syntax is deprecated:
- @var{width}:@var{height}:@var{pix_fmt}:@var{time_base.num}:@var{time_base.den}:@var{pixel_aspect.num}:@var{pixel_aspect.den}[:@var{sws_param}]
- @section cellauto
- Create a pattern generated by an elementary cellular automaton.
- The initial state of the cellular automaton can be defined through the
- @option{filename}, and @option{pattern} options. If such options are
- not specified an initial state is created randomly.
- At each new frame a new row in the video is filled with the result of
- the cellular automaton next generation. The behavior when the whole
- frame is filled is defined by the @option{scroll} option.
- This source accepts a list of options in the form of
- @var{key}=@var{value} pairs separated by ":". A description of the
- accepted options follows.
- @table @option
- @item filename, f
- Read the initial cellular automaton state, i.e. the starting row, from
- the specified file.
- In the file, each non-whitespace character is considered an alive
- cell, a newline will terminate the row, and further characters in the
- file will be ignored.
- @item pattern, p
- Read the initial cellular automaton state, i.e. the starting row, from
- the specified string.
- Each non-whitespace character in the string is considered an alive
- cell, a newline will terminate the row, and further characters in the
- string will be ignored.
- @item rate, r
- Set the video rate, that is the number of frames generated per second.
- Default is 25.
- @item random_fill_ratio, ratio
- Set the random fill ratio for the initial cellular automaton row. It
- is a floating point number value ranging from 0 to 1, defaults to
- 1/PHI.
- This option is ignored when a file or a pattern is specified.
- @item random_seed, seed
- Set the seed for filling randomly the initial row, must be an integer
- included between 0 and UINT32_MAX. If not specified, or if explicitly
- set to -1, the filter will try to use a good random seed on a best
- effort basis.
- @item rule
- Set the cellular automaton rule, it is a number ranging from 0 to 255.
- Default value is 110.
- @item size, s
- Set the size of the output video.
- If @option{filename} or @option{pattern} is specified, the size is set
- by default to the width of the specified initial state row, and the
- height is set to @var{width} * PHI.
- If @option{size} is set, it must contain the width of the specified
- pattern string, and the specified pattern will be centered in the
- larger row.
- If a filename or a pattern string is not specified, the size value
- defaults to "320x518" (used for a randomly generated initial state).
- @item scroll
- If set to 1, scroll the output upward when all the rows in the output
- have been already filled. If set to 0, the new generated row will be
- written over the top row just after the bottom row is filled.
- Defaults to 1.
- @item start_full, full
- If set to 1, completely fill the output with generated rows before
- outputting the first frame.
- This is the default behavior, for disabling set the value to 0.
- @item stitch
- If set to 1, stitch the left and right row edges together.
- This is the default behavior, for disabling set the value to 0.
- @end table
- @subsection Examples
- @itemize
- @item
- Read the initial state from @file{pattern}, and specify an output of
- size 200x400.
- @example
- cellauto=f=pattern:s=200x400
- @end example
- @item
- Generate a random initial row with a width of 200 cells, with a fill
- ratio of 2/3:
- @example
- cellauto=ratio=2/3:s=200x200
- @end example
- @item
- Create a pattern generated by rule 18 starting by a single alive cell
- centered on an initial row with width 100:
- @example
- cellauto=p=@@:s=100x400:full=0:rule=18
- @end example
- @item
- Specify a more elaborated initial pattern:
- @example
- cellauto=p='@@@@ @@ @@@@':s=100x400:full=0:rule=18
- @end example
- @end itemize
- @section mandelbrot
- Generate a Mandelbrot set fractal, and progressively zoom towards the
- point specified with @var{start_x} and @var{start_y}.
- This source accepts a list of options in the form of
- @var{key}=@var{value} pairs separated by ":". A description of the
- accepted options follows.
- @table @option
- @item end_pts
- Set the terminal pts value. Default value is 400.
- @item end_scale
- Set the terminal scale value.
- Must be a floating point value. Default value is 0.3.
- @item inner
- Set the inner coloring mode, that is the algorithm used to draw the
- Mandelbrot fractal internal region.
- It shall assume one of the following values:
- @table @option
- @item black
- Set black mode.
- @item convergence
- Show time until convergence.
- @item mincol
- Set color based on point closest to the origin of the iterations.
- @item period
- Set period mode.
- @end table
- Default value is @var{mincol}.
- @item bailout
- Set the bailout value. Default value is 10.0.
- @item maxiter
- Set the maximum of iterations performed by the rendering
- algorithm. Default value is 7189.
- @item outer
- Set outer coloring mode.
- It shall assume one of following values:
- @table @option
- @item iteration_count
- Set iteration cound mode.
- @item normalized_iteration_count
- set normalized iteration count mode.
- @end table
- Default value is @var{normalized_iteration_count}.
- @item rate, r
- Set frame rate, expressed as number of frames per second. Default
- value is "25".
- @item size, s
- Set frame size. Default value is "640x480".
- @item start_scale
- Set the initial scale value. Default value is 3.0.
- @item start_x
- Set the initial x position. Must be a floating point value between
- -100 and 100. Default value is -0.743643887037158704752191506114774.
- @item start_y
- Set the initial y position. Must be a floating point value between
- -100 and 100. Default value is -0.131825904205311970493132056385139.
- @end table
- @section mptestsrc
- Generate various test patterns, as generated by the MPlayer test filter.
- The size of the generated video is fixed, and is 256x256.
- This source is useful in particular for testing encoding features.
- This source accepts an optional sequence of @var{key}=@var{value} pairs,
- separated by ":". The description of the accepted options follows.
- @table @option
- @item rate, r
- Specify the frame rate of the sourced video, as the number of frames
- generated per second. It has to be a string in the format
- @var{frame_rate_num}/@var{frame_rate_den}, an integer number, a float
- number or a valid video frame rate abbreviation. The default value is
- "25".
- @item duration, d
- Set the video duration of the sourced video. The accepted syntax is:
- @example
- [-]HH:MM:SS[.m...]
- [-]S+[.m...]
- @end example
- See also the function @code{av_parse_time()}.
- If not specified, or the expressed duration is negative, the video is
- supposed to be generated forever.
- @item test, t
- Set the number or the name of the test to perform. Supported tests are:
- @table @option
- @item dc_luma
- @item dc_chroma
- @item freq_luma
- @item freq_chroma
- @item amp_luma
- @item amp_chroma
- @item cbp
- @item mv
- @item ring1
- @item ring2
- @item all
- @end table
- Default value is "all", which will cycle through the list of all tests.
- @end table
- For example the following:
- @example
- testsrc=t=dc_luma
- @end example
- will generate a "dc_luma" test pattern.
- @section frei0r_src
- Provide a frei0r source.
- To enable compilation of this filter you need to install the frei0r
- header and configure FFmpeg with @code{--enable-frei0r}.
- The source supports the syntax:
- @example
- @var{size}:@var{rate}:@var{src_name}[@{=|:@}@var{param1}:@var{param2}:...:@var{paramN}]
- @end example
- @var{size} is the size of the video to generate, may be a string of the
- form @var{width}x@var{height} or a frame size abbreviation.
- @var{rate} is the rate of the video to generate, may be a string of
- the form @var{num}/@var{den} or a frame rate abbreviation.
- @var{src_name} is the name to the frei0r source to load. For more
- information regarding frei0r and how to set the parameters read the
- section @ref{frei0r} in the description of the video filters.
- For example, to generate a frei0r partik0l source with size 200x200
- and frame rate 10 which is overlayed on the overlay filter main input:
- @example
- frei0r_src=200x200:10:partik0l=1234 [overlay]; [in][overlay] overlay
- @end example
- @section life
- Generate a life pattern.
- This source is based on a generalization of John Conway's life game.
- The sourced input represents a life grid, each pixel represents a cell
- which can be in one of two possible states, alive or dead. Every cell
- interacts with its eight neighbours, which are the cells that are
- horizontally, vertically, or diagonally adjacent.
- At each interaction the grid evolves according to the adopted rule,
- which specifies the number of neighbor alive cells which will make a
- cell stay alive or born. The @option{rule} option allows to specify
- the rule to adopt.
- This source accepts a list of options in the form of
- @var{key}=@var{value} pairs separated by ":". A description of the
- accepted options follows.
- @table @option
- @item filename, f
- Set the file from which to read the initial grid state. In the file,
- each non-whitespace character is considered an alive cell, and newline
- is used to delimit the end of each row.
- If this option is not specified, the initial grid is generated
- randomly.
- @item rate, r
- Set the video rate, that is the number of frames generated per second.
- Default is 25.
- @item random_fill_ratio, ratio
- Set the random fill ratio for the initial random grid. It is a
- floating point number value ranging from 0 to 1, defaults to 1/PHI.
- It is ignored when a file is specified.
- @item random_seed, seed
- Set the seed for filling the initial random grid, must be an integer
- included between 0 and UINT32_MAX. If not specified, or if explicitly
- set to -1, the filter will try to use a good random seed on a best
- effort basis.
- @item rule
- Set the life rule.
- A rule can be specified with a code of the kind "S@var{NS}/B@var{NB}",
- where @var{NS} and @var{NB} are sequences of numbers in the range 0-8,
- @var{NS} specifies the number of alive neighbor cells which make a
- live cell stay alive, and @var{NB} the number of alive neighbor cells
- which make a dead cell to become alive (i.e. to "born").
- "s" and "b" can be used in place of "S" and "B", respectively.
- Alternatively a rule can be specified by an 18-bits integer. The 9
- high order bits are used to encode the next cell state if it is alive
- for each number of neighbor alive cells, the low order bits specify
- the rule for "borning" new cells. Higher order bits encode for an
- higher number of neighbor cells.
- For example the number 6153 = @code{(12<<9)+9} specifies a stay alive
- rule of 12 and a born rule of 9, which corresponds to "S23/B03".
- Default value is "S23/B3", which is the original Conway's game of life
- rule, and will keep a cell alive if it has 2 or 3 neighbor alive
- cells, and will born a new cell if there are three alive cells around
- a dead cell.
- @item size, s
- Set the size of the output video.
- If @option{filename} is specified, the size is set by default to the
- same size of the input file. If @option{size} is set, it must contain
- the size specified in the input file, and the initial grid defined in
- that file is centered in the larger resulting area.
- If a filename is not specified, the size value defaults to "320x240"
- (used for a randomly generated initial grid).
- @item stitch
- If set to 1, stitch the left and right grid edges together, and the
- top and bottom edges also. Defaults to 1.
- @item mold
- Set cell mold speed. If set, a dead cell will go from @option{death_color} to
- @option{mold_color} with a step of @option{mold}. @option{mold} can have a
- value from 0 to 255.
- @item life_color
- Set the color of living (or new born) cells.
- @item death_color
- Set the color of dead cells. If @option{mold} is set, this is the first color
- used to represent a dead cell.
- @item mold_color
- Set mold color, for definitely dead and moldy cells.
- @end table
- @subsection Examples
- @itemize
- @item
- Read a grid from @file{pattern}, and center it on a grid of size
- 300x300 pixels:
- @example
- life=f=pattern:s=300x300
- @end example
- @item
- Generate a random grid of size 200x200, with a fill ratio of 2/3:
- @example
- life=ratio=2/3:s=200x200
- @end example
- @item
- Specify a custom rule for evolving a randomly generated grid:
- @example
- life=rule=S14/B34
- @end example
- @item
- Full example with slow death effect (mold) using @command{ffplay}:
- @example
- ffplay -f lavfi life=s=300x200:mold=10:r=60:ratio=0.1:death_color=#C83232:life_color=#00ff00,scale=1200:800:flags=16
- @end example
- @end itemize
- @section color, nullsrc, rgbtestsrc, smptebars, testsrc
- The @code{color} source provides an uniformly colored input.
- The @code{nullsrc} source returns unprocessed video frames. It is
- mainly useful to be employed in analysis / debugging tools, or as the
- source for filters which ignore the input data.
- The @code{rgbtestsrc} source generates an RGB test pattern useful for
- detecting RGB vs BGR issues. You should see a red, green and blue
- stripe from top to bottom.
- The @code{smptebars} source generates a color bars pattern, based on
- the SMPTE Engineering Guideline EG 1-1990.
- The @code{testsrc} source generates a test video pattern, showing a
- color pattern, a scrolling gradient and a timestamp. This is mainly
- intended for testing purposes.
- These sources accept an optional sequence of @var{key}=@var{value} pairs,
- separated by ":". The description of the accepted options follows.
- @table @option
- @item color, c
- Specify the color of the source, only used in the @code{color}
- source. It can be the name of a color (case insensitive match) or a
- 0xRRGGBB[AA] sequence, possibly followed by an alpha specifier. The
- default value is "black".
- @item size, s
- Specify the size of the sourced video, it may be a string of the form
- @var{width}x@var{height}, or the name of a size abbreviation. The
- default value is "320x240".
- @item rate, r
- Specify the frame rate of the sourced video, as the number of frames
- generated per second. It has to be a string in the format
- @var{frame_rate_num}/@var{frame_rate_den}, an integer number, a float
- number or a valid video frame rate abbreviation. The default value is
- "25".
- @item sar
- Set the sample aspect ratio of the sourced video.
- @item duration, d
- Set the video duration of the sourced video. The accepted syntax is:
- @example
- [-]HH[:MM[:SS[.m...]]]
- [-]S+[.m...]
- @end example
- See also the function @code{av_parse_time()}.
- If not specified, or the expressed duration is negative, the video is
- supposed to be generated forever.
- @item decimals, n
- Set the number of decimals to show in the timestamp, only used in the
- @code{testsrc} source.
- The displayed timestamp value will correspond to the original
- timestamp value multiplied by the power of 10 of the specified
- value. Default value is 0.
- @end table
- For example the following:
- @example
- testsrc=duration=5.3:size=qcif:rate=10
- @end example
- will generate a video with a duration of 5.3 seconds, with size
- 176x144 and a frame rate of 10 frames per second.
- The following graph description will generate a red source
- with an opacity of 0.2, with size "qcif" and a frame rate of 10
- frames per second.
- @example
- color=c=red@@0.2:s=qcif:r=10
- @end example
- If the input content is to be ignored, @code{nullsrc} can be used. The
- following command generates noise in the luminance plane by employing
- the @code{geq} filter:
- @example
- nullsrc=s=256x256, geq=random(1)*255:128:128
- @end example
- @c man end VIDEO SOURCES
- @chapter Video Sinks
- @c man begin VIDEO SINKS
- Below is a description of the currently available video sinks.
- @section buffersink
- Buffer video frames, and make them available to the end of the filter
- graph.
- This sink is mainly intended for a programmatic use, in particular
- through the interface defined in @file{libavfilter/buffersink.h}.
- It does not require a string parameter in input, but you need to
- specify a pointer to a list of supported pixel formats terminated by
- -1 in the opaque parameter provided to @code{avfilter_init_filter}
- when initializing this sink.
- @section nullsink
- Null video sink, do absolutely nothing with the input video. It is
- mainly useful as a template and to be employed in analysis / debugging
- tools.
- @c man end VIDEO SINKS
- @chapter Multimedia Filters
- @c man begin MULTIMEDIA FILTERS
- Below is a description of the currently available multimedia filters.
- @section aselect, select
- Select frames to pass in output.
- These filters accept a single option @option{expr} or @option{e}
- specifying the select expression, which can be specified either by
- specyfing @code{expr=VALUE} or specifying the expression
- alone.
- The select expression is evaluated for each input frame. If the
- evaluation result is a non-zero value, the frame is selected and
- passed to the output, otherwise it is discarded.
- The expression can contain the following constants:
- @table @option
- @item n
- the sequential number of the filtered frame, starting from 0
- @item selected_n
- the sequential number of the selected frame, starting from 0
- @item prev_selected_n
- the sequential number of the last selected frame, NAN if undefined
- @item TB
- timebase of the input timestamps
- @item pts
- the PTS (Presentation TimeStamp) of the filtered video frame,
- expressed in @var{TB} units, NAN if undefined
- @item t
- the PTS (Presentation TimeStamp) of the filtered video frame,
- expressed in seconds, NAN if undefined
- @item prev_pts
- the PTS of the previously filtered video frame, NAN if undefined
- @item prev_selected_pts
- the PTS of the last previously filtered video frame, NAN if undefined
- @item prev_selected_t
- the PTS of the last previously selected video frame, NAN if undefined
- @item start_pts
- the PTS of the first video frame in the video, NAN if undefined
- @item start_t
- the time of the first video frame in the video, NAN if undefined
- @item pict_type @emph{(video only)}
- the type of the filtered frame, can assume one of the following
- values:
- @table @option
- @item I
- @item P
- @item B
- @item S
- @item SI
- @item SP
- @item BI
- @end table
- @item interlace_type @emph{(video only)}
- the frame interlace type, can assume one of the following values:
- @table @option
- @item PROGRESSIVE
- the frame is progressive (not interlaced)
- @item TOPFIRST
- the frame is top-field-first
- @item BOTTOMFIRST
- the frame is bottom-field-first
- @end table
- @item consumed_sample_n @emph{(audio only)}
- the number of selected samples before the current frame
- @item samples_n @emph{(audio only)}
- the number of samples in the current frame
- @item sample_rate @emph{(audio only)}
- the input sample rate
- @item key
- 1 if the filtered frame is a key-frame, 0 otherwise
- @item pos
- the position in the file of the filtered frame, -1 if the information
- is not available (e.g. for synthetic video)
- @item scene @emph{(video only)}
- value between 0 and 1 to indicate a new scene; a low value reflects a low
- probability for the current frame to introduce a new scene, while a higher
- value means the current frame is more likely to be one (see the example below)
- @end table
- The default value of the select expression is "1".
- @subsection Examples
- @itemize
- @item
- Select all frames in input:
- @example
- select
- @end example
- The example above is the same as:
- @example
- select=1
- @end example
- @item
- Skip all frames:
- @example
- select=0
- @end example
- @item
- Select only I-frames:
- @example
- select='eq(pict_type\,I)'
- @end example
- @item
- Select one frame every 100:
- @example
- select='not(mod(n\,100))'
- @end example
- @item
- Select only frames contained in the 10-20 time interval:
- @example
- select='gte(t\,10)*lte(t\,20)'
- @end example
- @item
- Select only I frames contained in the 10-20 time interval:
- @example
- select='gte(t\,10)*lte(t\,20)*eq(pict_type\,I)'
- @end example
- @item
- Select frames with a minimum distance of 10 seconds:
- @example
- select='isnan(prev_selected_t)+gte(t-prev_selected_t\,10)'
- @end example
- @item
- Use aselect to select only audio frames with samples number > 100:
- @example
- aselect='gt(samples_n\,100)'
- @end example
- @item
- Create a mosaic of the first scenes:
- @example
- ffmpeg -i video.avi -vf select='gt(scene\,0.4)',scale=160:120,tile -frames:v 1 preview.png
- @end example
- Comparing @var{scene} against a value between 0.3 and 0.5 is generally a sane
- choice.
- @end itemize
- @section asendcmd, sendcmd
- Send commands to filters in the filtergraph.
- These filters read commands to be sent to other filters in the
- filtergraph.
- @code{asendcmd} must be inserted between two audio filters,
- @code{sendcmd} must be inserted between two video filters, but apart
- from that they act the same way.
- The specification of commands can be provided in the filter arguments
- with the @var{commands} option, or in a file specified by the
- @var{filename} option.
- These filters accept the following options:
- @table @option
- @item commands, c
- Set the commands to be read and sent to the other filters.
- @item filename, f
- Set the filename of the commands to be read and sent to the other
- filters.
- @end table
- @subsection Commands syntax
- A commands description consists of a sequence of interval
- specifications, comprising a list of commands to be executed when a
- particular event related to that interval occurs. The occurring event
- is typically the current frame time entering or leaving a given time
- interval.
- An interval is specified by the following syntax:
- @example
- @var{START}[-@var{END}] @var{COMMANDS};
- @end example
- The time interval is specified by the @var{START} and @var{END} times.
- @var{END} is optional and defaults to the maximum time.
- The current frame time is considered within the specified interval if
- it is included in the interval [@var{START}, @var{END}), that is when
- the time is greater or equal to @var{START} and is lesser than
- @var{END}.
- @var{COMMANDS} consists of a sequence of one or more command
- specifications, separated by ",", relating to that interval. The
- syntax of a command specification is given by:
- @example
- [@var{FLAGS}] @var{TARGET} @var{COMMAND} @var{ARG}
- @end example
- @var{FLAGS} is optional and specifies the type of events relating to
- the time interval which enable sending the specified command, and must
- be a non-null sequence of identifier flags separated by "+" or "|" and
- enclosed between "[" and "]".
- The following flags are recognized:
- @table @option
- @item enter
- The command is sent when the current frame timestamp enters the
- specified interval. In other words, the command is sent when the
- previous frame timestamp was not in the given interval, and the
- current is.
- @item leave
- The command is sent when the current frame timestamp leaves the
- specified interval. In other words, the command is sent when the
- previous frame timestamp was in the given interval, and the
- current is not.
- @end table
- If @var{FLAGS} is not specified, a default value of @code{[enter]} is
- assumed.
- @var{TARGET} specifies the target of the command, usually the name of
- the filter class or a specific filter instance name.
- @var{COMMAND} specifies the name of the command for the target filter.
- @var{ARG} is optional and specifies the optional list of argument for
- the given @var{COMMAND}.
- Between one interval specification and another, whitespaces, or
- sequences of characters starting with @code{#} until the end of line,
- are ignored and can be used to annotate comments.
- A simplified BNF description of the commands specification syntax
- follows:
- @example
- @var{COMMAND_FLAG} ::= "enter" | "leave"
- @var{COMMAND_FLAGS} ::= @var{COMMAND_FLAG} [(+|"|")@var{COMMAND_FLAG}]
- @var{COMMAND} ::= ["[" @var{COMMAND_FLAGS} "]"] @var{TARGET} @var{COMMAND} [@var{ARG}]
- @var{COMMANDS} ::= @var{COMMAND} [,@var{COMMANDS}]
- @var{INTERVAL} ::= @var{START}[-@var{END}] @var{COMMANDS}
- @var{INTERVALS} ::= @var{INTERVAL}[;@var{INTERVALS}]
- @end example
- @subsection Examples
- @itemize
- @item
- Specify audio tempo change at second 4:
- @example
- asendcmd=c='4.0 atempo tempo 1.5',atempo
- @end example
- @item
- Specify a list of drawtext and hue commands in a file.
- @example
- # show text in the interval 5-10
- 5.0-10.0 [enter] drawtext reinit 'fontfile=FreeSerif.ttf:text=hello world',
- [leave] drawtext reinit 'fontfile=FreeSerif.ttf:text=';
- # desaturate the image in the interval 15-20
- 15.0-20.0 [enter] hue reinit s=0,
- [enter] drawtext reinit 'fontfile=FreeSerif.ttf:text=nocolor',
- [leave] hue reinit s=1,
- [leave] drawtext reinit 'fontfile=FreeSerif.ttf:text=color';
- # apply an exponential saturation fade-out effect, starting from time 25
- 25 [enter] hue s=exp(t-25)
- @end example
- A filtergraph allowing to read and process the above command list
- stored in a file @file{test.cmd}, can be specified with:
- @example
- sendcmd=f=test.cmd,drawtext=fontfile=FreeSerif.ttf:text='',hue
- @end example
- @end itemize
- @anchor{setpts}
- @section asetpts, setpts
- Change the PTS (presentation timestamp) of the input frames.
- @code{asetpts} works on audio frames, @code{setpts} on video frames.
- Accept in input an expression evaluated through the eval API, which
- can contain the following constants:
- @table @option
- @item FRAME_RATE
- frame rate, only defined for constant frame-rate video
- @item PTS
- the presentation timestamp in input
- @item N
- the count of the input frame, starting from 0.
- @item NB_CONSUMED_SAMPLES
- the number of consumed samples, not including the current frame (only
- audio)
- @item NB_SAMPLES
- the number of samples in the current frame (only audio)
- @item SAMPLE_RATE
- audio sample rate
- @item STARTPTS
- the PTS of the first frame
- @item STARTT
- the time in seconds of the first frame
- @item INTERLACED
- tell if the current frame is interlaced
- @item T
- the time in seconds of the current frame
- @item TB
- the time base
- @item POS
- original position in the file of the frame, or undefined if undefined
- for the current frame
- @item PREV_INPTS
- previous input PTS
- @item PREV_INT
- previous input time in seconds
- @item PREV_OUTPTS
- previous output PTS
- @item PREV_OUTT
- previous output time in seconds
- @end table
- @subsection Examples
- @itemize
- @item
- Start counting PTS from zero
- @example
- setpts=PTS-STARTPTS
- @end example
- @item
- Apply fast motion effect:
- @example
- setpts=0.5*PTS
- @end example
- @item
- Apply slow motion effect:
- @example
- setpts=2.0*PTS
- @end example
- @item
- Set fixed rate of 25 frames per second:
- @example
- setpts=N/(25*TB)
- @end example
- @item
- Set fixed rate 25 fps with some jitter:
- @example
- setpts='1/(25*TB) * (N + 0.05 * sin(N*2*PI/25))'
- @end example
- @item
- Apply an offset of 10 seconds to the input PTS:
- @example
- setpts=PTS+10/TB
- @end example
- @end itemize
- @section ebur128
- EBU R128 scanner filter. This filter takes an audio stream as input and outputs
- it unchanged. By default, it logs a message at a frequency of 10Hz with the
- Momentary loudness (identified by @code{M}), Short-term loudness (@code{S}),
- Integrated loudness (@code{I}) and Loudness Range (@code{LRA}).
- The filter also has a video output (see the @var{video} option) with a real
- time graph to observe the loudness evolution. The graphic contains the logged
- message mentioned above, so it is not printed anymore when this option is set,
- unless the verbose logging is set. The main graphing area contains the
- short-term loudness (3 seconds of analysis), and the gauge on the right is for
- the momentary loudness (400 milliseconds).
- More information about the Loudness Recommendation EBU R128 on
- @url{http://tech.ebu.ch/loudness}.
- The filter accepts the following named parameters:
- @table @option
- @item video
- Activate the video output. The audio stream is passed unchanged whether this
- option is set or no. The video stream will be the first output stream if
- activated. Default is @code{0}.
- @item size
- Set the video size. This option is for video only. Default and minimum
- resolution is @code{640x480}.
- @item meter
- Set the EBU scale meter. Default is @code{9}. Common values are @code{9} and
- @code{18}, respectively for EBU scale meter +9 and EBU scale meter +18. Any
- other integer value between this range is allowed.
- @end table
- Example of real-time graph using @command{ffplay}, with a EBU scale meter +18:
- @example
- ffplay -f lavfi -i "amovie=input.mp3,ebur128=video=1:meter=18 [out0][out1]"
- @end example
- Run an analysis with @command{ffmpeg}:
- @example
- ffmpeg -nostats -i input.mp3 -filter_complex ebur128 -f null -
- @end example
- @section settb, asettb
- Set the timebase to use for the output frames timestamps.
- It is mainly useful for testing timebase configuration.
- It accepts in input an arithmetic expression representing a rational.
- The expression can contain the constants "AVTB" (the
- default timebase), "intb" (the input timebase) and "sr" (the sample rate,
- audio only).
- The default value for the input is "intb".
- @subsection Examples
- @itemize
- @item
- Set the timebase to 1/25:
- @example
- settb=1/25
- @end example
- @item
- Set the timebase to 1/10:
- @example
- settb=0.1
- @end example
- @item
- Set the timebase to 1001/1000:
- @example
- settb=1+0.001
- @end example
- @item
- Set the timebase to 2*intb:
- @example
- settb=2*intb
- @end example
- @item
- Set the default timebase value:
- @example
- settb=AVTB
- @end example
- @end itemize
- @section concat
- Concatenate audio and video streams, joining them together one after the
- other.
- The filter works on segments of synchronized video and audio streams. All
- segments must have the same number of streams of each type, and that will
- also be the number of streams at output.
- The filter accepts the following named parameters:
- @table @option
- @item n
- Set the number of segments. Default is 2.
- @item v
- Set the number of output video streams, that is also the number of video
- streams in each segment. Default is 1.
- @item a
- Set the number of output audio streams, that is also the number of video
- streams in each segment. Default is 0.
- @item unsafe
- Activate unsafe mode: do not fail if segments have a different format.
- @end table
- The filter has @var{v}+@var{a} outputs: first @var{v} video outputs, then
- @var{a} audio outputs.
- There are @var{n}x(@var{v}+@var{a}) inputs: first the inputs for the first
- segment, in the same order as the outputs, then the inputs for the second
- segment, etc.
- Related streams do not always have exactly the same duration, for various
- reasons including codec frame size or sloppy authoring. For that reason,
- related synchronized streams (e.g. a video and its audio track) should be
- concatenated at once. The concat filter will use the duration of the longest
- stream in each segment (except the last one), and if necessary pad shorter
- audio streams with silence.
- For this filter to work correctly, all segments must start at timestamp 0.
- All corresponding streams must have the same parameters in all segments; the
- filtering system will automatically select a common pixel format for video
- streams, and a common sample format, sample rate and channel layout for
- audio streams, but other settings, such as resolution, must be converted
- explicitly by the user.
- Different frame rates are acceptable but will result in variable frame rate
- at output; be sure to configure the output file to handle it.
- Examples:
- @itemize
- @item
- Concatenate an opening, an episode and an ending, all in bilingual version
- (video in stream 0, audio in streams 1 and 2):
- @example
- ffmpeg -i opening.mkv -i episode.mkv -i ending.mkv -filter_complex \
- '[0:0] [0:1] [0:2] [1:0] [1:1] [1:2] [2:0] [2:1] [2:2]
- concat=n=3:v=1:a=2 [v] [a1] [a2]' \
- -map '[v]' -map '[a1]' -map '[a2]' output.mkv
- @end example
- @item
- Concatenate two parts, handling audio and video separately, using the
- (a)movie sources, and adjusting the resolution:
- @example
- movie=part1.mp4, scale=512:288 [v1] ; amovie=part1.mp4 [a1] ;
- movie=part2.mp4, scale=512:288 [v2] ; amovie=part2.mp4 [a2] ;
- [v1] [v2] concat [outv] ; [a1] [a2] concat=v=0:a=1 [outa]
- @end example
- Note that a desync will happen at the stitch if the audio and video streams
- do not have exactly the same duration in the first file.
- @end itemize
- @section showspectrum
- Convert input audio to a video output, representing the audio frequency
- spectrum.
- The filter accepts the following named parameters:
- @table @option
- @item size, s
- Specify the video size for the output. Default value is @code{640x480}.
- @item slide
- Specify if the spectrum should slide along the window. Default value is
- @code{0}.
- @end table
- The usage is very similar to the showwaves filter; see the examples in that
- section.
- @section showwaves
- Convert input audio to a video output, representing the samples waves.
- The filter accepts the following named parameters:
- @table @option
- @item n
- Set the number of samples which are printed on the same column. A
- larger value will decrease the frame rate. Must be a positive
- integer. This option can be set only if the value for @var{rate}
- is not explicitly specified.
- @item rate, r
- Set the (approximate) output frame rate. This is done by setting the
- option @var{n}. Default value is "25".
- @item size, s
- Specify the video size for the output. Default value is "600x240".
- @end table
- Some examples follow.
- @itemize
- @item
- Output the input file audio and the corresponding video representation
- at the same time:
- @example
- amovie=a.mp3,asplit[out0],showwaves[out1]
- @end example
- @item
- Create a synthetic signal and show it with showwaves, forcing a
- framerate of 30 frames per second:
- @example
- aevalsrc=sin(1*2*PI*t)*sin(880*2*PI*t):cos(2*PI*200*t),asplit[out0],showwaves=r=30[out1]
- @end example
- @end itemize
- @c man end MULTIMEDIA FILTERS
- @chapter Multimedia Sources
- @c man begin MULTIMEDIA SOURCES
- Below is a description of the currently available multimedia sources.
- @section amovie
- This is the same as @ref{movie} source, except it selects an audio
- stream by default.
- @anchor{movie}
- @section movie
- Read audio and/or video stream(s) from a movie container.
- It accepts the syntax: @var{movie_name}[:@var{options}] where
- @var{movie_name} is the name of the resource to read (not necessarily
- a file but also a device or a stream accessed through some protocol),
- and @var{options} is an optional sequence of @var{key}=@var{value}
- pairs, separated by ":".
- The description of the accepted options follows.
- @table @option
- @item format_name, f
- Specifies the format assumed for the movie to read, and can be either
- the name of a container or an input device. If not specified the
- format is guessed from @var{movie_name} or by probing.
- @item seek_point, sp
- Specifies the seek point in seconds, the frames will be output
- starting from this seek point, the parameter is evaluated with
- @code{av_strtod} so the numerical value may be suffixed by an IS
- postfix. Default value is "0".
- @item streams, s
- Specifies the streams to read. Several streams can be specified,
- separated by "+". The source will then have as many outputs, in the
- same order. The syntax is explained in the ``Stream specifiers''
- section in the ffmpeg manual. Two special names, "dv" and "da" specify
- respectively the default (best suited) video and audio stream. Default
- is "dv", or "da" if the filter is called as "amovie".
- @item stream_index, si
- Specifies the index of the video stream to read. If the value is -1,
- the best suited video stream will be automatically selected. Default
- value is "-1". Deprecated. If the filter is called "amovie", it will select
- audio instead of video.
- @item loop
- Specifies how many times to read the stream in sequence.
- If the value is less than 1, the stream will be read again and again.
- Default value is "1".
- Note that when the movie is looped the source timestamps are not
- changed, so it will generate non monotonically increasing timestamps.
- @end table
- This filter allows to overlay a second video on top of main input of
- a filtergraph as shown in this graph:
- @example
- input -----------> deltapts0 --> overlay --> output
- ^
- |
- movie --> scale--> deltapts1 -------+
- @end example
- Some examples follow.
- @itemize
- @item
- Skip 3.2 seconds from the start of the avi file in.avi, and overlay it
- on top of the input labelled as "in":
- @example
- movie=in.avi:seek_point=3.2, scale=180:-1, setpts=PTS-STARTPTS [movie];
- [in] setpts=PTS-STARTPTS, [movie] overlay=16:16 [out]
- @end example
- @item
- Read from a video4linux2 device, and overlay it on top of the input
- labelled as "in":
- @example
- movie=/dev/video0:f=video4linux2, scale=180:-1, setpts=PTS-STARTPTS [movie];
- [in] setpts=PTS-STARTPTS, [movie] overlay=16:16 [out]
- @end example
- @item
- Read the first video stream and the audio stream with id 0x81 from
- dvd.vob; the video is connected to the pad named "video" and the audio is
- connected to the pad named "audio":
- @example
- movie=dvd.vob:s=v:0+#0x81 [video] [audio]
- @end example
- @end itemize
- @c man end MULTIMEDIA SOURCES
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