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- @chapter Decoders
- @c man begin DECODERS
- Decoders are configured elements in FFmpeg which allow the decoding of
- multimedia streams.
- When you configure your FFmpeg build, all the supported native decoders
- are enabled by default. Decoders requiring an external library must be enabled
- manually via the corresponding @code{--enable-lib} option. You can list all
- available decoders using the configure option @code{--list-decoders}.
- You can disable all the decoders with the configure option
- @code{--disable-decoders} and selectively enable / disable single decoders
- with the options @code{--enable-decoder=@var{DECODER}} /
- @code{--disable-decoder=@var{DECODER}}.
- The option @code{-decoders} of the ff* tools will display the list of
- enabled decoders.
- @c man end DECODERS
- @chapter Video Decoders
- @c man begin VIDEO DECODERS
- A description of some of the currently available video decoders
- follows.
- @section rawvideo
- Raw video decoder.
- This decoder decodes rawvideo streams.
- @subsection Options
- @table @option
- @item top @var{top_field_first}
- Specify the assumed field type of the input video.
- @table @option
- @item -1
- the video is assumed to be progressive (default)
- @item 0
- bottom-field-first is assumed
- @item 1
- top-field-first is assumed
- @end table
- @end table
- @c man end VIDEO DECODERS
- @chapter Audio Decoders
- @c man begin AUDIO DECODERS
- A description of some of the currently available audio decoders
- follows.
- @section ac3
- AC-3 audio decoder.
- This decoder implements part of ATSC A/52:2010 and ETSI TS 102 366, as well as
- the undocumented RealAudio 3 (a.k.a. dnet).
- @subsection AC-3 Decoder Options
- @table @option
- @item -drc_scale @var{value}
- Dynamic Range Scale Factor. The factor to apply to dynamic range values
- from the AC-3 stream. This factor is applied exponentially.
- There are 3 notable scale factor ranges:
- @table @option
- @item drc_scale == 0
- DRC disabled. Produces full range audio.
- @item 0 < drc_scale <= 1
- DRC enabled. Applies a fraction of the stream DRC value.
- Audio reproduction is between full range and full compression.
- @item drc_scale > 1
- DRC enabled. Applies drc_scale asymmetrically.
- Loud sounds are fully compressed. Soft sounds are enhanced.
- @end table
- @end table
- @section ffwavesynth
- Internal wave synthetizer.
- This decoder generates wave patterns according to predefined sequences. Its
- use is purely internal and the format of the data it accepts is not publicly
- documented.
- @section libcelt
- libcelt decoder wrapper.
- libcelt allows libavcodec to decode the Xiph CELT ultra-low delay audio codec.
- Requires the presence of the libcelt headers and library during configuration.
- You need to explicitly configure the build with @code{--enable-libcelt}.
- @section libgsm
- libgsm decoder wrapper.
- libgsm allows libavcodec to decode the GSM full rate audio codec. Requires
- the presence of the libgsm headers and library during configuration. You need
- to explicitly configure the build with @code{--enable-libgsm}.
- This decoder supports both the ordinary GSM and the Microsoft variant.
- @section libilbc
- libilbc decoder wrapper.
- libilbc allows libavcodec to decode the Internet Low Bitrate Codec (iLBC)
- audio codec. Requires the presence of the libilbc headers and library during
- configuration. You need to explicitly configure the build with
- @code{--enable-libilbc}.
- @subsection Options
- The following option is supported by the libilbc wrapper.
- @table @option
- @item enhance
- Enable the enhancement of the decoded audio when set to 1. The default
- value is 0 (disabled).
- @end table
- @section libopencore-amrnb
- libopencore-amrnb decoder wrapper.
- libopencore-amrnb allows libavcodec to decode the Adaptive Multi-Rate
- Narrowband audio codec. Using it requires the presence of the
- libopencore-amrnb headers and library during configuration. You need to
- explicitly configure the build with @code{--enable-libopencore-amrnb}.
- An FFmpeg native decoder for AMR-NB exists, so users can decode AMR-NB
- without this library.
- @section libopencore-amrwb
- libopencore-amrwb decoder wrapper.
- libopencore-amrwb allows libavcodec to decode the Adaptive Multi-Rate
- Wideband audio codec. Using it requires the presence of the
- libopencore-amrwb headers and library during configuration. You need to
- explicitly configure the build with @code{--enable-libopencore-amrwb}.
- An FFmpeg native decoder for AMR-WB exists, so users can decode AMR-WB
- without this library.
- @section libopus
- libopus decoder wrapper.
- libopus allows libavcodec to decode the Opus Interactive Audio Codec.
- Requires the presence of the libopus headers and library during
- configuration. You need to explicitly configure the build with
- @code{--enable-libopus}.
- @c man end AUDIO DECODERS
- @chapter Subtitles Decoders
- @c man begin SUBTILES DECODERS
- @section dvdsub
- This codec decodes the bitmap subtitles used in DVDs; the same subtitles can
- also be found in VobSub file pairs and in some Matroska files.
- @subsection Options
- @table @option
- @item palette
- Specify the global palette used by the bitmaps. When stored in VobSub, the
- palette is normally specified in the index file; in Matroska, the palette is
- stored in the codec extra-data in the same format as in VobSub. In DVDs, the
- palette is stored in the IFO file, and therefore not available when reading
- from dumped VOB files.
- The format for this option is a string containing 16 24-bits hexadecimal
- numbers (without 0x prefix) separated by comas, for example @code{0d00ee,
- ee450d, 101010, eaeaea, 0ce60b, ec14ed, ebff0b, 0d617a, 7b7b7b, d1d1d1,
- 7b2a0e, 0d950c, 0f007b, cf0dec, cfa80c, 7c127b}.
- @end table
- @section libzvbi-teletext
- Libzvbi allows libavcodec to decode DVB teletext pages and DVB teletext
- subtitles. Requires the presence of the libzvbi headers and library during
- configuration. You need to explicitly configure the build with
- @code{--enable-libzvbi}.
- @subsection Options
- @table @option
- @item txt_page
- List of teletext page numbers to decode. You may use the special * string to
- match all pages. Pages that do not match the specified list are dropped.
- Default value is *.
- @item txt_chop_top
- Discards the top teletext line. Default value is 1.
- @item txt_format
- Specifies the format of the decoded subtitles. The teletext decoder is capable
- of decoding the teletext pages to bitmaps or to simple text, you should use
- "bitmap" for teletext pages, because certain graphics and colors cannot be
- expressed in simple text. You might use "text" for teletext based subtitles if
- your application can handle simple text based subtitles. Default value is
- bitmap.
- @item txt_left
- X offset of generated bitmaps, default is 0.
- @item txt_top
- Y offset of generated bitmaps, default is 0.
- @item txt_chop_spaces
- Chops leading and trailing spaces and removes empty lines from the generated
- text. This option is useful for teletext based subtitles where empty spaces may
- be present at the start or at the end of the lines or empty lines may be
- present between the subtitle lines because of double-sized teletext charactes.
- Default value is 1.
- @item txt_duration
- Sets the display duration of the decoded teletext pages or subtitles in
- miliseconds. Default value is 30000 which is 30 seconds.
- @item txt_transparent
- Force transparent background of the generated teletext bitmaps. Default value
- is 0 which means an opaque (black) background.
- @end table
- @c man end SUBTILES DECODERS
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