Frame-based multithreading framework using pthreads

See doc/multithreading.txt for details on use in codecs.

Signed-off-by: Ronald S. Bultje <rsbultje@gmail.com>

doc/APIchanges

@@ -13,6 +13,11 @@ libavutil:   2009-03-08
 
 API changes, most recent first:
 
+2011-02-09 - XXXXXXX - lavc 52.111.0 - threading API
+  Add CODEC_CAP_FRAME_THREADS with new restrictions on get_buffer()/
+  release_buffer()/draw_horiz_band() callbacks for appropriate codecs.
+  Add thread_type and active_thread_type fields to AVCodecContext.
+
 2011-02-08 - 3940caa - lavf 52.98.0 - av_probe_input_buffer
   Add av_probe_input_buffer() to avformat.h for probing format from a
   ByteIOContext.

doc/multithreading.txt

@@ -0,0 +1,65 @@
+FFmpeg multithreading methods
+==============================================
+
+FFmpeg provides two methods for multithreading codecs.
+
+Slice threading decodes multiple parts of a frame at the same time, using
+AVCodecContext execute() and execute2().
+
+Frame threading decodes multiple frames at the same time.
+It accepts N future frames and delays decoded pictures by N-1 frames.
+The later frames are decoded in separate threads while the user is
+displaying the current one.
+
+Restrictions on clients
+==============================================
+
+Slice threading -
+* The client's draw_horiz_band() must be thread-safe according to the comment
+  in avcodec.h.
+
+Frame threading -
+* Restrictions with slice threading also apply.
+* For best performance, the client should set thread_safe_callbacks if it
+  provides a thread-safe get_buffer() callback.
+* There is one frame of delay added for every thread beyond the first one.
+  Clients must be able to handle this; the pkt_dts and pkt_pts fields in
+  AVFrame will work as usual.
+
+Restrictions on codec implementations
+==============================================
+
+Slice threading -
+ None except that there must be something worth executing in parallel.
+
+Frame threading -
+* Codecs can only accept entire pictures per packet.
+* Codecs similar to ffv1, whose streams don't reset across frames,
+  will not work because their bitstreams cannot be decoded in parallel.
+
+* The contents of buffers must not be read before ff_thread_await_progress()
+  has been called on them. reget_buffer() and buffer age optimizations no longer work.
+* The contents of buffers must not be written to after ff_thread_report_progress()
+  has been called on them. This includes draw_edges().
+
+Porting codecs to frame threading
+==============================================
+
+Find all context variables that are needed by the next frame. Move all
+code changing them, as well as code calling get_buffer(), up to before
+the decode process starts. Call ff_thread_finish_setup() afterwards. If
+some code can't be moved, have update_thread_context() run it in the next
+thread.
+
+If the codec allocates writable tables in its init(), add an init_thread_copy()
+which re-allocates them for other threads.
+
+Add CODEC_CAP_FRAME_THREADS to the codec capabilities. There will be very little
+speed gain at this point but it should work.
+
+Call ff_thread_report_progress() after some part of the current picture has decoded.
+A good place to put this is where draw_horiz_band() is called - add this if it isn't
+called anywhere, as it's useful too and the implementation is trivial when you're
+doing this. Note that draw_edges() needs to be called before reporting progress.
+
+Before accessing a reference frame or its MVs, call ff_thread_await_progress().

ffplay.c

@@ -1691,6 +1691,7 @@ static int input_init(AVFilterContext *ctx, const char *args, void *opaque)
         codec->get_buffer     = input_get_buffer;
         codec->release_buffer = input_release_buffer;
         codec->reget_buffer   = input_reget_buffer;
+        codec->thread_safe_callbacks = 1;
     }
 
     priv->frame = avcodec_alloc_frame();

libavcodec/avcodec.h

@@ -32,7 +32,7 @@
 #include "libavutil/cpu.h"
 
 #define LIBAVCODEC_VERSION_MAJOR 52
-#define LIBAVCODEC_VERSION_MINOR 110
+#define LIBAVCODEC_VERSION_MINOR 111
 #define LIBAVCODEC_VERSION_MICRO  0
 
 #define LIBAVCODEC_VERSION_INT  AV_VERSION_INT(LIBAVCODEC_VERSION_MAJOR, \
@@ -728,6 +728,10 @@ typedef struct RcOverride{
  * Codec is able to deal with negative linesizes
  */
 #define CODEC_CAP_NEG_LINESIZES    0x0800
+/**
+ * Codec supports frame-level multithreading.
+ */
+#define CODEC_CAP_FRAME_THREADS    0x1000
 
 //The following defines may change, don't expect compatibility if you use them.
 #define MB_TYPE_INTRA4x4   0x0001
@@ -1027,6 +1031,20 @@ typedef struct AVPanScan{
      * - decoding: Read by user.\
      */\
     int64_t pkt_dts;\
+\
+    /**\
+     * the AVCodecContext which ff_thread_get_buffer() was last called on\
+     * - encoding: Set by libavcodec.\
+     * - decoding: Set by libavcodec.\
+     */\
+    struct AVCodecContext *owner;\
+\
+    /**\
+     * used by multithreading to store frame-specific info\
+     * - encoding: Set by libavcodec.\
+     * - decoding: Set by libavcodec.\
+     */\
+    void *thread_opaque;\
 \
     /**\
      * frame timestamp estimated using various heuristics, in stream time base\
@@ -1246,6 +1264,10 @@ typedef struct AVCodecContext {
      * decoder to draw a horizontal band. It improves cache usage. Not
      * all codecs can do that. You must check the codec capabilities
      * beforehand.
+     * When multithreading is used, it may be called from multiple threads
+     * at the same time; threads might draw different parts of the same AVFrame,
+     * or multiple AVFrames, and there is no guarantee that slices will be drawn
+     * in order.
      * The function is also used by hardware acceleration APIs.
      * It is called at least once during frame decoding to pass
      * the data needed for hardware render.
@@ -1499,6 +1521,9 @@ typedef struct AVCodecContext {
      * if CODEC_CAP_DR1 is not set then get_buffer() must call
      * avcodec_default_get_buffer() instead of providing buffers allocated by
      * some other means.
+     * If frame multithreading is used and thread_safe_callbacks is set,
+     * it may be called from a different thread, but not from more than one at once.
+     * Does not need to be reentrant.
      * - encoding: unused
      * - decoding: Set by libavcodec, user can override.
      */
@@ -1508,6 +1533,8 @@ typedef struct AVCodecContext {
      * Called to release buffers which were allocated with get_buffer.
      * A released buffer can be reused in get_buffer().
      * pic.data[*] must be set to NULL.
+     * May be called from a different thread if frame multithreading is used,
+     * but not by more than one thread at once, so does not need to be reentrant.
      * - encoding: unused
      * - decoding: Set by libavcodec, user can override.
      */
@@ -1811,6 +1838,7 @@ typedef struct AVCodecContext {
 #define FF_DEBUG_VIS_QP      0x00002000
 #define FF_DEBUG_VIS_MB_TYPE 0x00004000
 #define FF_DEBUG_BUFFERS     0x00008000
+#define FF_DEBUG_THREADS     0x00010000
 
     /**
      * debug
@@ -2835,6 +2863,44 @@ typedef struct AVCodecContext {
      */
     AVPacket *pkt;
 
+    /**
+     * Whether this is a copy of the context which had init() called on it.
+     * This is used by multithreading - shared tables and picture pointers
+     * should be freed from the original context only.
+     * - encoding: Set by libavcodec.
+     * - decoding: Set by libavcodec.
+     */
+    int is_copy;
+
+    /**
+     * Which multithreading methods to use.
+     * Use of FF_THREAD_FRAME will increase decoding delay by one frame per thread,
+     * so clients which cannot provide future frames should not use it.
+     *
+     * - encoding: Set by user, otherwise the default is used.
+     * - decoding: Set by user, otherwise the default is used.
+     */
+    int thread_type;
+#define FF_THREAD_FRAME   1 //< Decode more than one frame at once
+#define FF_THREAD_SLICE   2 //< Decode more than one part of a single frame at once
+
+    /**
+     * Which multithreading methods are in use by the codec.
+     * - encoding: Set by libavcodec.
+     * - decoding: Set by libavcodec.
+     */
+    int active_thread_type;
+
+    /**
+     * Set by the client if its custom get_buffer() callback can be called
+     * from another thread, which allows faster multithreaded decoding.
+     * draw_horiz_band() will be called from other threads regardless of this setting.
+     * Ignored if the default get_buffer() is used.
+     * - encoding: Set by user.
+     * - decoding: Set by user.
+     */
+    int thread_safe_callbacks;
+
     /**
      * Current statistics for PTS correction.
      * - decoding: maintained and used by libavcodec
@@ -2897,6 +2963,26 @@ typedef struct AVCodec {
     uint8_t max_lowres;                     ///< maximum value for lowres supported by the decoder
     AVClass *priv_class;                    ///< AVClass for the private context
     const AVProfile *profiles;              ///< array of recognized profiles, or NULL if unknown, array is terminated by {FF_PROFILE_UNKNOWN}
+
+    /**
+     * @defgroup framethreading Frame-level threading support functions.
+     * @{
+     */
+    /**
+     * If defined, called on thread contexts when they are created.
+     * If the codec allocates writable tables in init(), re-allocate them here.
+     * priv_data will be set to a copy of the original.
+     */
+    int (*init_thread_copy)(AVCodecContext *);
+    /**
+     * Copy necessary context variables from a previous thread context to the current one.
+     * If not defined, the next thread will start automatically; otherwise, the codec
+     * must call ff_thread_finish_setup().
+     *
+     * dst and src will (rarely) point to the same context, in which case memcpy should be skipped.
+     */
+    int (*update_thread_context)(AVCodecContext *dst, const AVCodecContext *src);
+    /** @} */
 } AVCodec;
 
 /**

libavcodec/options.c

@@ -250,6 +250,7 @@ static const AVOption options[]={
 {"vis_qp", "visualize quantization parameter (QP), lower QP are tinted greener", 0, FF_OPT_TYPE_CONST, FF_DEBUG_VIS_QP, INT_MIN, INT_MAX, V|D, "debug"},
 {"vis_mb_type", "visualize block types", 0, FF_OPT_TYPE_CONST, FF_DEBUG_VIS_MB_TYPE, INT_MIN, INT_MAX, V|D, "debug"},
 {"buffers", "picture buffer allocations", 0, FF_OPT_TYPE_CONST, FF_DEBUG_BUFFERS, INT_MIN, INT_MAX, V|D, "debug"},
+{"thread_ops", "threading operations", 0, FF_OPT_TYPE_CONST, FF_DEBUG_THREADS, INT_MIN, INT_MAX, V|D, "debug"},
 {"vismv", "visualize motion vectors (MVs)", OFFSET(debug_mv), FF_OPT_TYPE_INT, DEFAULT, 0, INT_MAX, V|D, "debug_mv"},
 {"pf", "forward predicted MVs of P-frames", 0, FF_OPT_TYPE_CONST, FF_DEBUG_VIS_MV_P_FOR, INT_MIN, INT_MAX, V|D, "debug_mv"},
 {"bf", "forward predicted MVs of B-frames", 0, FF_OPT_TYPE_CONST, FF_DEBUG_VIS_MV_B_FOR, INT_MIN, INT_MAX, V|D, "debug_mv"},
@@ -431,6 +432,9 @@ static const AVOption options[]={
 {"cholesky", NULL, 0, FF_OPT_TYPE_CONST, AV_LPC_TYPE_CHOLESKY, INT_MIN, INT_MAX, A|E, "lpc_type"},
 {"lpc_passes", "number of passes to use for Cholesky factorization during LPC analysis", OFFSET(lpc_passes), FF_OPT_TYPE_INT, -1, INT_MIN, INT_MAX, A|E},
 {"slices", "number of slices, used in parallelized decoding", OFFSET(slices), FF_OPT_TYPE_INT, 0, 0, INT_MAX, V|E},
+{"thread_type", "select multithreading type", OFFSET(thread_type), FF_OPT_TYPE_INT, FF_THREAD_SLICE|FF_THREAD_FRAME, 0, INT_MAX, V|E|D, "thread_type"},
+{"slice", NULL, 0, FF_OPT_TYPE_CONST, FF_THREAD_SLICE, INT_MIN, INT_MAX, V|E|D, "thread_type"},
+{"frame", NULL, 0, FF_OPT_TYPE_CONST, FF_THREAD_FRAME, INT_MIN, INT_MAX, V|E|D, "thread_type"},
 {NULL},
 };
 

libavcodec/pthread.c

@@ -1,5 +1,6 @@
 /*
  * Copyright (c) 2004 Roman Shaposhnik
+ * Copyright (c) 2008 Alexander Strange (astrange@ithinksw.com)
  *
  * Many thanks to Steven M. Schultz for providing clever ideas and
  * to Michael Niedermayer <michaelni@gmx.at> for writing initial
@@ -21,9 +22,17 @@
  * License along with FFmpeg; if not, write to the Free Software
  * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
  */
+
+/**
+ * @file
+ * Multithreading support functions
+ * @see doc/multithreading.txt
+ */
+
 #include <pthread.h>
 
 #include "avcodec.h"
+#include "thread.h"
 
 typedef int (action_func)(AVCodecContext *c, void *arg);
 typedef int (action_func2)(AVCodecContext *c, void *arg, int jobnr, int threadnr);
@@ -45,6 +54,78 @@ typedef struct ThreadContext {
     int done;
 } ThreadContext;
 
+/// Max number of frame buffers that can be allocated when using frame threads.
+#define MAX_BUFFERS 32
+
+/**
+ * Context used by codec threads and stored in their AVCodecContext thread_opaque.
+ */
+typedef struct PerThreadContext {
+    struct FrameThreadContext *parent;
+
+    pthread_t      thread;
+    pthread_cond_t input_cond;      ///< Used to wait for a new packet from the main thread.
+    pthread_cond_t progress_cond;   ///< Used by child threads to wait for progress to change.
+    pthread_cond_t output_cond;     ///< Used by the main thread to wait for frames to finish.
+
+    pthread_mutex_t mutex;          ///< Mutex used to protect the contents of the PerThreadContext.
+    pthread_mutex_t progress_mutex; ///< Mutex used to protect frame progress values and progress_cond.
+
+    AVCodecContext *avctx;          ///< Context used to decode packets passed to this thread.
+
+    AVPacket       avpkt;           ///< Input packet (for decoding) or output (for encoding).
+    int            allocated_buf_size; ///< Size allocated for avpkt.data
+
+    AVFrame frame;                  ///< Output frame (for decoding) or input (for encoding).
+    int     got_frame;              ///< The output of got_picture_ptr from the last avcodec_decode_video() call.
+    int     result;                 ///< The result of the last codec decode/encode() call.
+
+    enum {
+        STATE_INPUT_READY,          ///< Set when the thread is awaiting a packet.
+        STATE_SETTING_UP,           ///< Set before the codec has called ff_thread_finish_setup().
+        STATE_GET_BUFFER,           /**<
+                                     * Set when the codec calls get_buffer().
+                                     * State is returned to STATE_SETTING_UP afterwards.
+                                     */
+        STATE_SETUP_FINISHED        ///< Set after the codec has called ff_thread_finish_setup().
+    } state;
+
+    /**
+     * Array of frames passed to ff_thread_release_buffer().
+     * Frames are released after all threads referencing them are finished.
+     */
+    AVFrame released_buffers[MAX_BUFFERS];
+    int     num_released_buffers;
+
+    /**
+     * Array of progress values used by ff_thread_get_buffer().
+     */
+    int     progress[MAX_BUFFERS][2];
+    uint8_t progress_used[MAX_BUFFERS];
+
+    AVFrame *requested_frame;       ///< AVFrame the codec passed to get_buffer()
+} PerThreadContext;
+
+/**
+ * Context stored in the client AVCodecContext thread_opaque.
+ */
+typedef struct FrameThreadContext {
+    PerThreadContext *threads;     ///< The contexts for each thread.
+    PerThreadContext *prev_thread; ///< The last thread submit_packet() was called on.
+
+    pthread_mutex_t buffer_mutex;  ///< Mutex used to protect get/release_buffer().
+
+    int next_decoding;             ///< The next context to submit a packet to.
+    int next_finished;             ///< The next context to return output from.
+
+    int delaying;                  /**<
+                                    * Set for the first N packets, where N is the number of threads.
+                                    * While it is set, ff_thread_en/decode_frame won't return any results.
+                                    */
+
+    int die;                       ///< Set when threads should exit.
+} FrameThreadContext;
+
 static void* attribute_align_arg worker(void *v)
 {
     AVCodecContext *avctx = v;
@@ -84,7 +165,7 @@ static av_always_inline void avcodec_thread_park_workers(ThreadContext *c, int t
     pthread_mutex_unlock(&c->current_job_lock);
 }
 
-void avcodec_thread_free(AVCodecContext *avctx)
+static void thread_free(AVCodecContext *avctx)
 {
     ThreadContext *c = avctx->thread_opaque;
     int i;
@@ -109,6 +190,9 @@ static int avcodec_thread_execute(AVCodecContext *avctx, action_func* func, void
     ThreadContext *c= avctx->thread_opaque;
     int dummy_ret;
 
+    if (!(avctx->active_thread_type&FF_THREAD_SLICE) || avctx->thread_count <= 1)
+        return avcodec_default_execute(avctx, func, arg, ret, job_count, job_size);
+
     if (job_count <= 0)
         return 0;
 
@@ -140,12 +224,11 @@ static int avcodec_thread_execute2(AVCodecContext *avctx, action_func2* func2, v
     return avcodec_thread_execute(avctx, NULL, arg, ret, job_count, 0);
 }
 
-int avcodec_thread_init(AVCodecContext *avctx, int thread_count)
+static int thread_init(AVCodecContext *avctx)
 {
     int i;
     ThreadContext *c;
-
-    avctx->thread_count = thread_count;
+    int thread_count = avctx->thread_count;
 
     if (thread_count <= 1)
         return 0;
@@ -184,3 +267,634 @@ int avcodec_thread_init(AVCodecContext *avctx, int thread_count)
     avctx->execute2 = avcodec_thread_execute2;
     return 0;
 }
+
+/**
+ * Codec worker thread.
+ *
+ * Automatically calls ff_thread_finish_setup() if the codec does
+ * not provide an update_thread_context method, or if the codec returns
+ * before calling it.
+ */
+static attribute_align_arg void *frame_worker_thread(void *arg)
+{
+    PerThreadContext *p = arg;
+    FrameThreadContext *fctx = p->parent;
+    AVCodecContext *avctx = p->avctx;
+    AVCodec *codec = avctx->codec;
+
+    while (1) {
+        if (p->state == STATE_INPUT_READY && !fctx->die) {
+            pthread_mutex_lock(&p->mutex);
+            while (p->state == STATE_INPUT_READY && !fctx->die)
+                pthread_cond_wait(&p->input_cond, &p->mutex);
+            pthread_mutex_unlock(&p->mutex);
+        }
+
+        if (fctx->die) break;
+
+        if (!codec->update_thread_context) ff_thread_finish_setup(avctx);
+
+        pthread_mutex_lock(&p->mutex);
+        avcodec_get_frame_defaults(&p->frame);
+        p->got_frame = 0;
+        p->result = codec->decode(avctx, &p->frame, &p->got_frame, &p->avpkt);
+
+        if (p->state == STATE_SETTING_UP) ff_thread_finish_setup(avctx);
+
+        p->state = STATE_INPUT_READY;
+
+        pthread_mutex_lock(&p->progress_mutex);
+        pthread_cond_signal(&p->output_cond);
+        pthread_mutex_unlock(&p->progress_mutex);
+
+        pthread_mutex_unlock(&p->mutex);
+    }
+
+    return NULL;
+}
+
+/**
+ * Updates the next thread's AVCodecContext with values from the reference thread's context.
+ *
+ * @param dst The destination context.
+ * @param src The source context.
+ * @param for_user 0 if the destination is a codec thread, 1 if the destination is the user's thread
+ */
+static int update_context_from_thread(AVCodecContext *dst, AVCodecContext *src, int for_user)
+{
+    int err = 0;
+
+    if (dst != src) {
+        dst->sub_id    = src->sub_id;
+        dst->time_base = src->time_base;
+        dst->width     = src->width;
+        dst->height    = src->height;
+        dst->pix_fmt   = src->pix_fmt;
+
+        dst->has_b_frames = src->has_b_frames;
+        dst->idct_algo    = src->idct_algo;
+        dst->slice_count  = src->slice_count;
+
+        dst->bits_per_coded_sample = src->bits_per_coded_sample;
+        dst->sample_aspect_ratio   = src->sample_aspect_ratio;
+        dst->dtg_active_format     = src->dtg_active_format;
+
+        dst->profile = src->profile;
+        dst->level   = src->level;
+
+        dst->bits_per_raw_sample = src->bits_per_raw_sample;
+        dst->ticks_per_frame     = src->ticks_per_frame;
+        dst->color_primaries     = src->color_primaries;
+
+        dst->color_trc   = src->color_trc;
+        dst->colorspace  = src->colorspace;
+        dst->color_range = src->color_range;
+        dst->chroma_sample_location = src->chroma_sample_location;
+    }
+
+    if (for_user) {
+        dst->coded_frame   = src->coded_frame;
+        dst->has_b_frames += src->thread_count - 1;
+    } else {
+        if (dst->codec->update_thread_context)
+            err = dst->codec->update_thread_context(dst, src);
+    }
+
+    return err;
+}
+
+/**
+ * Update the next thread's AVCodecContext with values set by the user.
+ *
+ * @param dst The destination context.
+ * @param src The source context.
+ */
+static void update_context_from_user(AVCodecContext *dst, AVCodecContext *src)
+{
+#define copy_fields(s, e) memcpy(&dst->s, &src->s, (char*)&dst->e - (char*)&dst->s);
+    dst->flags          = src->flags;
+
+    dst->draw_horiz_band= src->draw_horiz_band;
+    dst->get_buffer     = src->get_buffer;
+    dst->release_buffer = src->release_buffer;
+
+    dst->opaque   = src->opaque;
+    dst->hurry_up = src->hurry_up;
+    dst->dsp_mask = src->dsp_mask;
+    dst->debug    = src->debug;
+    dst->debug_mv = src->debug_mv;
+
+    dst->slice_flags = src->slice_flags;
+    dst->flags2      = src->flags2;
+
+    copy_fields(skip_loop_filter, bidir_refine);
+
+    dst->frame_number     = src->frame_number;
+    dst->reordered_opaque = src->reordered_opaque;
+#undef copy_fields
+}
+
+static void free_progress(AVFrame *f)
+{
+    PerThreadContext *p = f->owner->thread_opaque;
+    int *progress = f->thread_opaque;
+
+    p->progress_used[(progress - p->progress[0]) / 2] = 0;
+}
+
+/// Releases the buffers that this decoding thread was the last user of.
+static void release_delayed_buffers(PerThreadContext *p)
+{
+    FrameThreadContext *fctx = p->parent;
+
+    while (p->num_released_buffers > 0) {
+        AVFrame *f = &p->released_buffers[--p->num_released_buffers];
+
+        pthread_mutex_lock(&fctx->buffer_mutex);
+        free_progress(f);
+        f->thread_opaque = NULL;
+
+        f->owner->release_buffer(f->owner, f);
+        pthread_mutex_unlock(&fctx->buffer_mutex);
+    }
+}
+
+static int submit_packet(PerThreadContext *p, AVPacket *avpkt)
+{
+    FrameThreadContext *fctx = p->parent;
+    PerThreadContext *prev_thread = fctx->prev_thread;
+    AVCodec *codec = p->avctx->codec;
+    uint8_t *buf = p->avpkt.data;
+
+    if (!avpkt->size && !(codec->capabilities & CODEC_CAP_DELAY)) return 0;
+
+    pthread_mutex_lock(&p->mutex);
+
+    release_delayed_buffers(p);
+
+    if (prev_thread) {
+        int err;
+        if (prev_thread->state == STATE_SETTING_UP) {
+            pthread_mutex_lock(&prev_thread->progress_mutex);
+            while (prev_thread->state == STATE_SETTING_UP)
+                pthread_cond_wait(&prev_thread->progress_cond, &prev_thread->progress_mutex);
+            pthread_mutex_unlock(&prev_thread->progress_mutex);
+        }
+
+        err = update_context_from_thread(p->avctx, prev_thread->avctx, 0);
+        if (err) {
+            pthread_mutex_unlock(&p->mutex);
+            return err;
+        }
+    }
+
+    av_fast_malloc(&buf, &p->allocated_buf_size, avpkt->size + FF_INPUT_BUFFER_PADDING_SIZE);
+    p->avpkt = *avpkt;
+    p->avpkt.data = buf;
+    memcpy(buf, avpkt->data, avpkt->size);
+    memset(buf + avpkt->size, 0, FF_INPUT_BUFFER_PADDING_SIZE);
+
+    p->state = STATE_SETTING_UP;
+    pthread_cond_signal(&p->input_cond);
+    pthread_mutex_unlock(&p->mutex);
+
+    /*
+     * If the client doesn't have a thread-safe get_buffer(),
+     * then decoding threads call back to the main thread,
+     * and it calls back to the client here.
+     */
+
+    if (!p->avctx->thread_safe_callbacks &&
+         p->avctx->get_buffer != avcodec_default_get_buffer) {
+        while (p->state != STATE_SETUP_FINISHED && p->state != STATE_INPUT_READY) {
+            pthread_mutex_lock(&p->progress_mutex);
+            while (p->state == STATE_SETTING_UP)
+                pthread_cond_wait(&p->progress_cond, &p->progress_mutex);
+
+            if (p->state == STATE_GET_BUFFER) {
+                p->result = p->avctx->get_buffer(p->avctx, p->requested_frame);
+                p->state  = STATE_SETTING_UP;
+                pthread_cond_signal(&p->progress_cond);
+            }
+            pthread_mutex_unlock(&p->progress_mutex);
+        }
+    }
+
+    fctx->prev_thread = p;
+
+    return 0;
+}
+
+int ff_thread_decode_frame(AVCodecContext *avctx,
+                           AVFrame *picture, int *got_picture_ptr,
+                           AVPacket *avpkt)
+{
+    FrameThreadContext *fctx = avctx->thread_opaque;
+    int finished = fctx->next_finished;
+    PerThreadContext *p;
+    int err;
+
+    /*
+     * Submit a packet to the next decoding thread.
+     */
+
+    p = &fctx->threads[fctx->next_decoding];
+    update_context_from_user(p->avctx, avctx);
+    err = submit_packet(p, avpkt);
+    if (err) return err;
+
+    fctx->next_decoding++;
+
+    /*
+     * If we're still receiving the initial packets, don't return a frame.
+     */
+
+    if (fctx->delaying && avpkt->size) {
+        if (fctx->next_decoding >= (avctx->thread_count-1)) fctx->delaying = 0;
+
+        *got_picture_ptr=0;
+        return 0;
+    }
+
+    /*
+     * Return the next available frame from the oldest thread.
+     * If we're at the end of the stream, then we have to skip threads that
+     * didn't output a frame, because we don't want to accidentally signal
+     * EOF (avpkt->size == 0 && *got_picture_ptr == 0).
+     */
+
+    do {
+        p = &fctx->threads[finished++];
+
+        if (p->state != STATE_INPUT_READY) {
+            pthread_mutex_lock(&p->progress_mutex);
+            while (p->state != STATE_INPUT_READY)
+                pthread_cond_wait(&p->output_cond, &p->progress_mutex);
+            pthread_mutex_unlock(&p->progress_mutex);
+        }
+
+        *picture = p->frame;
+        *got_picture_ptr = p->got_frame;
+        picture->pkt_dts = p->avpkt.dts;
+
+        /*
+         * A later call with avkpt->size == 0 may loop over all threads,
+         * including this one, searching for a frame to return before being
+         * stopped by the "finished != fctx->next_finished" condition.
+         * Make sure we don't mistakenly return the same frame again.
+         */
+        p->got_frame = 0;
+
+        if (finished >= avctx->thread_count) finished = 0;
+    } while (!avpkt->size && !*got_picture_ptr && finished != fctx->next_finished);
+
+    update_context_from_thread(avctx, p->avctx, 1);
+
+    if (fctx->next_decoding >= avctx->thread_count) fctx->next_decoding = 0;
+
+    fctx->next_finished = finished;
+
+    return p->result;
+}
+
+void ff_thread_report_progress(AVFrame *f, int n, int field)
+{
+    PerThreadContext *p;
+    int *progress = f->thread_opaque;
+
+    if (!progress || progress[field] >= n) return;
+
+    p = f->owner->thread_opaque;
+
+    if (f->owner->debug&FF_DEBUG_THREADS)
+        av_log(f->owner, AV_LOG_DEBUG, "%p finished %d field %d\n", progress, n, field);
+
+    pthread_mutex_lock(&p->progress_mutex);
+    progress[field] = n;
+    pthread_cond_broadcast(&p->progress_cond);
+    pthread_mutex_unlock(&p->progress_mutex);
+}
+
+void ff_thread_await_progress(AVFrame *f, int n, int field)
+{
+    PerThreadContext *p;
+    int *progress = f->thread_opaque;
+
+    if (!progress || progress[field] >= n) return;
+
+    p = f->owner->thread_opaque;
+
+    if (f->owner->debug&FF_DEBUG_THREADS)
+        av_log(f->owner, AV_LOG_DEBUG, "thread awaiting %d field %d from %p\n", n, field, progress);
+
+    pthread_mutex_lock(&p->progress_mutex);
+    while (progress[field] < n)
+        pthread_cond_wait(&p->progress_cond, &p->progress_mutex);
+    pthread_mutex_unlock(&p->progress_mutex);
+}
+
+void ff_thread_finish_setup(AVCodecContext *avctx) {
+    PerThreadContext *p = avctx->thread_opaque;
+
+    if (!(avctx->active_thread_type&FF_THREAD_FRAME)) return;
+
+    pthread_mutex_lock(&p->progress_mutex);
+    p->state = STATE_SETUP_FINISHED;
+    pthread_cond_broadcast(&p->progress_cond);
+    pthread_mutex_unlock(&p->progress_mutex);
+}
+
+/// Waits for all threads to finish.
+static void park_frame_worker_threads(FrameThreadContext *fctx, int thread_count)
+{
+    int i;
+
+    for (i = 0; i < thread_count; i++) {
+        PerThreadContext *p = &fctx->threads[i];
+
+        if (p->state != STATE_INPUT_READY) {
+            pthread_mutex_lock(&p->progress_mutex);
+            while (p->state != STATE_INPUT_READY)
+                pthread_cond_wait(&p->output_cond, &p->progress_mutex);
+            pthread_mutex_unlock(&p->progress_mutex);
+        }
+    }
+}
+
+static void frame_thread_free(AVCodecContext *avctx, int thread_count)
+{
+    FrameThreadContext *fctx = avctx->thread_opaque;
+    AVCodec *codec = avctx->codec;
+    int i;
+
+    park_frame_worker_threads(fctx, thread_count);
+
+    if (fctx->prev_thread)
+        update_context_from_thread(fctx->threads->avctx, fctx->prev_thread->avctx, 0);
+
+    fctx->die = 1;
+
+    for (i = 0; i < thread_count; i++) {
+        PerThreadContext *p = &fctx->threads[i];
+
+        pthread_mutex_lock(&p->mutex);
+        pthread_cond_signal(&p->input_cond);
+        pthread_mutex_unlock(&p->mutex);
+
+        pthread_join(p->thread, NULL);
+
+        if (codec->close)
+            codec->close(p->avctx);
+
+        avctx->codec = NULL;
+
+        release_delayed_buffers(p);
+    }
+
+    for (i = 0; i < thread_count; i++) {
+        PerThreadContext *p = &fctx->threads[i];
+
+        avcodec_default_free_buffers(p->avctx);
+
+        pthread_mutex_destroy(&p->mutex);
+        pthread_mutex_destroy(&p->progress_mutex);
+        pthread_cond_destroy(&p->input_cond);
+        pthread_cond_destroy(&p->progress_cond);
+        pthread_cond_destroy(&p->output_cond);
+        av_freep(&p->avpkt.data);
+
+        if (i)
+            av_freep(&p->avctx->priv_data);
+
+        av_freep(&p->avctx);
+    }
+
+    av_freep(&fctx->threads);
+    pthread_mutex_destroy(&fctx->buffer_mutex);
+    av_freep(&avctx->thread_opaque);
+}
+
+static int frame_thread_init(AVCodecContext *avctx)
+{
+    int thread_count = avctx->thread_count;
+    AVCodec *codec = avctx->codec;
+    AVCodecContext *src = avctx;
+    FrameThreadContext *fctx;
+    int i, err = 0;
+
+    avctx->thread_opaque = fctx = av_mallocz(sizeof(FrameThreadContext));
+
+    fctx->threads = av_mallocz(sizeof(PerThreadContext) * thread_count);
+    pthread_mutex_init(&fctx->buffer_mutex, NULL);
+    fctx->delaying = 1;
+
+    for (i = 0; i < thread_count; i++) {
+        AVCodecContext *copy = av_malloc(sizeof(AVCodecContext));
+        PerThreadContext *p  = &fctx->threads[i];
+
+        pthread_mutex_init(&p->mutex, NULL);
+        pthread_mutex_init(&p->progress_mutex, NULL);
+        pthread_cond_init(&p->input_cond, NULL);
+        pthread_cond_init(&p->progress_cond, NULL);
+        pthread_cond_init(&p->output_cond, NULL);
+
+        p->parent = fctx;
+        p->avctx  = copy;
+
+        *copy = *src;
+        copy->thread_opaque = p;
+        copy->pkt = &p->avpkt;
+
+        if (!i) {
+            src = copy;
+
+            if (codec->init)
+                err = codec->init(copy);
+
+            update_context_from_thread(avctx, copy, 1);
+        } else {
+            copy->is_copy   = 1;
+            copy->priv_data = av_malloc(codec->priv_data_size);
+            memcpy(copy->priv_data, src->priv_data, codec->priv_data_size);
+
+            if (codec->init_thread_copy)
+                err = codec->init_thread_copy(copy);
+        }
+
+        if (err) goto error;
+
+        pthread_create(&p->thread, NULL, frame_worker_thread, p);
+    }
+
+    return 0;
+
+error:
+    frame_thread_free(avctx, i+1);
+
+    return err;
+}
+
+void ff_thread_flush(AVCodecContext *avctx)
+{
+    FrameThreadContext *fctx = avctx->thread_opaque;
+
+    if (!avctx->thread_opaque) return;
+
+    park_frame_worker_threads(fctx, avctx->thread_count);
+
+    if (fctx->prev_thread)
+        update_context_from_thread(fctx->threads->avctx, fctx->prev_thread->avctx, 0);
+
+    fctx->next_decoding = fctx->next_finished = 0;
+    fctx->delaying = 1;
+    fctx->prev_thread = NULL;
+}
+
+static int *allocate_progress(PerThreadContext *p)
+{
+    int i;
+
+    for (i = 0; i < MAX_BUFFERS; i++)
+        if (!p->progress_used[i]) break;
+
+    if (i == MAX_BUFFERS) {
+        av_log(p->avctx, AV_LOG_ERROR, "allocate_progress() overflow\n");
+        return NULL;
+    }
+
+    p->progress_used[i] = 1;
+
+    return p->progress[i];
+}
+
+int ff_thread_get_buffer(AVCodecContext *avctx, AVFrame *f)
+{
+    PerThreadContext *p = avctx->thread_opaque;
+    int *progress, err;
+
+    f->owner = avctx;
+
+    if (!(avctx->active_thread_type&FF_THREAD_FRAME)) {
+        f->thread_opaque = NULL;
+        return avctx->get_buffer(avctx, f);
+    }
+
+    if (p->state != STATE_SETTING_UP) {
+        av_log(avctx, AV_LOG_ERROR, "get_buffer() cannot be called after ff_thread_finish_setup()\n");
+        return -1;
+    }
+
+    pthread_mutex_lock(&p->parent->buffer_mutex);
+    f->thread_opaque = progress = allocate_progress(p);
+
+    if (!progress) {
+        pthread_mutex_unlock(&p->parent->buffer_mutex);
+        return -1;
+    }
+
+    progress[0] =
+    progress[1] = -1;
+
+    if (avctx->thread_safe_callbacks ||
+        avctx->get_buffer == avcodec_default_get_buffer) {
+        err = avctx->get_buffer(avctx, f);
+    } else {
+        p->requested_frame = f;
+        p->state = STATE_GET_BUFFER;
+        pthread_mutex_lock(&p->progress_mutex);
+        pthread_cond_signal(&p->progress_cond);
+
+        while (p->state != STATE_SETTING_UP)
+            pthread_cond_wait(&p->progress_cond, &p->progress_mutex);
+
+        err = p->result;
+
+        pthread_mutex_unlock(&p->progress_mutex);
+    }
+
+    pthread_mutex_unlock(&p->parent->buffer_mutex);
+
+    /*
+     * Buffer age is difficult to keep track of between
+     * multiple threads, and the optimizations it allows
+     * are not worth the effort. It is disabled for now.
+     */
+    f->age = INT_MAX;
+
+    return err;
+}
+
+void ff_thread_release_buffer(AVCodecContext *avctx, AVFrame *f)
+{
+    PerThreadContext *p = avctx->thread_opaque;
+
+    if (!(avctx->active_thread_type&FF_THREAD_FRAME)) {
+        avctx->release_buffer(avctx, f);
+        return;
+    }
+
+    if (p->num_released_buffers >= MAX_BUFFERS) {
+        av_log(p->avctx, AV_LOG_ERROR, "too many thread_release_buffer calls!\n");
+        return;
+    }
+
+    if(avctx->debug & FF_DEBUG_BUFFERS)
+        av_log(avctx, AV_LOG_DEBUG, "thread_release_buffer called on pic %p, %d buffers used\n",
+                                    f, f->owner->internal_buffer_count);
+
+    p->released_buffers[p->num_released_buffers++] = *f;
+    memset(f->data, 0, sizeof(f->data));
+}
+
+/**
+ * Set the threading algorithms used.
+ *
+ * Threading requires more than one thread.
+ * Frame threading requires entire frames to be passed to the codec,
+ * and introduces extra decoding delay, so is incompatible with low_delay.
+ *
+ * @param avctx The context.
+ */
+static void validate_thread_parameters(AVCodecContext *avctx)
+{
+    int frame_threading_supported = (avctx->codec->capabilities & CODEC_CAP_FRAME_THREADS)
+                                && !(avctx->flags & CODEC_FLAG_TRUNCATED)
+                                && !(avctx->flags & CODEC_FLAG_LOW_DELAY)
+                                && !(avctx->flags2 & CODEC_FLAG2_CHUNKS);
+    if (avctx->thread_count == 1) {
+        avctx->active_thread_type = 0;
+    } else if (frame_threading_supported && (avctx->thread_type & FF_THREAD_FRAME)) {
+        avctx->active_thread_type = FF_THREAD_FRAME;
+    } else {
+        avctx->active_thread_type = FF_THREAD_SLICE;
+    }
+}
+
+int avcodec_thread_init(AVCodecContext *avctx, int thread_count)
+{
+    if (avctx->thread_opaque) {
+        av_log(avctx, AV_LOG_ERROR, "avcodec_thread_init is ignored after avcodec_open\n");
+        return -1;
+    }
+
+    avctx->thread_count = FFMAX(1, thread_count);
+
+    if (avctx->codec) {
+        validate_thread_parameters(avctx);
+
+        if (avctx->active_thread_type&FF_THREAD_SLICE)
+            return thread_init(avctx);
+        else if (avctx->active_thread_type&FF_THREAD_FRAME)
+            return frame_thread_init(avctx);
+    }
+
+    return 0;
+}
+
+void avcodec_thread_free(AVCodecContext *avctx)
+{
+    if (avctx->active_thread_type&FF_THREAD_FRAME)
+        frame_thread_free(avctx, avctx->thread_count);
+    else
+        thread_free(avctx);
+}

libavcodec/thread.h

@@ -0,0 +1,111 @@
+/*
+ * Copyright (c) 2008 Alexander Strange <astrange@ithinksw.com>
+ *
+ * This file is part of FFmpeg.
+ *
+ * FFmpeg is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU Lesser General Public
+ * License as published by the Free Software Foundation; either
+ * version 2.1 of the License, or (at your option) any later version.
+ *
+ * FFmpeg is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+ * Lesser General Public License for more details.
+ *
+ * You should have received a copy of the GNU Lesser General Public
+ * License along with FFmpeg; if not, write to the Free Software
+ * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
+ */
+
+/**
+ * @file
+ * Multithreading support functions
+ * @author Alexander Strange <astrange@ithinksw.com>
+ */
+
+#ifndef AVCODEC_THREAD_H
+#define AVCODEC_THREAD_H
+
+#include "config.h"
+#include "avcodec.h"
+
+/**
+ * Waits for decoding threads to finish and resets internal
+ * state. Called by avcodec_flush_buffers().
+ *
+ * @param avctx The context.
+ */
+void ff_thread_flush(AVCodecContext *avctx);
+
+/**
+ * Submits a new frame to a decoding thread.
+ * Returns the next available frame in picture. *got_picture_ptr
+ * will be 0 if none is available.
+ *
+ * Parameters are the same as avcodec_decode_video2().
+ */
+int ff_thread_decode_frame(AVCodecContext *avctx, AVFrame *picture,
+                           int *got_picture_ptr, AVPacket *avpkt);
+
+/**
+ * If the codec defines update_thread_context(), call this
+ * when they are ready for the next thread to start decoding
+ * the next frame. After calling it, do not change any variables
+ * read by the update_thread_context() method, or call ff_thread_get_buffer().
+ *
+ * @param avctx The context.
+ */
+void ff_thread_finish_setup(AVCodecContext *avctx);
+
+/**
+ * Notifies later decoding threads when part of their reference picture
+ * is ready.
+ * Call this when some part of the picture is finished decoding.
+ * Later calls with lower values of progress have no effect.
+ *
+ * @param f The picture being decoded.
+ * @param progress Value, in arbitrary units, of how much of the picture has decoded.
+ * @param field The field being decoded, for field-picture codecs.
+ * 0 for top field or frame pictures, 1 for bottom field.
+ */
+void ff_thread_report_progress(AVFrame *f, int progress, int field);
+
+/**
+ * Waits for earlier decoding threads to finish reference pictures
+ * Call this before accessing some part of a picture, with a given
+ * value for progress, and it will return after the responsible decoding
+ * thread calls ff_thread_report_progress() with the same or
+ * higher value for progress.
+ *
+ * @param f The picture being referenced.
+ * @param progress Value, in arbitrary units, to wait for.
+ * @param field The field being referenced, for field-picture codecs.
+ * 0 for top field or frame pictures, 1 for bottom field.
+ */
+void ff_thread_await_progress(AVFrame *f, int progress, int field);
+
+/**
+ * Wrapper around get_buffer() for frame-multithreaded codecs.
+ * Call this function instead of avctx->get_buffer(f).
+ * Cannot be called after the codec has called ff_thread_finish_setup().
+ *
+ * @param avctx The current context.
+ * @param f The frame to write into.
+ */
+int ff_thread_get_buffer(AVCodecContext *avctx, AVFrame *f);
+
+/**
+ * Wrapper around release_buffer() frame-for multithreaded codecs.
+ * Call this function instead of avctx->release_buffer(f).
+ * The AVFrame will be copied and the actual release_buffer() call
+ * will be performed later. The contents of data pointed to by the
+ * AVFrame should not be changed until ff_thread_get_buffer() is called
+ * on it.
+ *
+ * @param avctx The current context.
+ * @param f The picture being released.
+ */
+void ff_thread_release_buffer(AVCodecContext *avctx, AVFrame *f);
+
+#endif /* AVCODEC_THREAD_H */

libavcodec/utils.c

@@ -37,6 +37,7 @@
 #include "dsputil.h"
 #include "libavutil/opt.h"
 #include "imgconvert.h"
+#include "thread.h"
 #include "audioconvert.h"
 #include "internal.h"
 #include <stdlib.h>
@@ -261,6 +262,11 @@ int avcodec_default_get_buffer(AVCodecContext *s, AVFrame *pic){
     (*picture_number)++;
 
     if(buf->base[0] && (buf->width != w || buf->height != h || buf->pix_fmt != s->pix_fmt)){
+        if(s->active_thread_type&FF_THREAD_FRAME) {
+            av_log_missing_feature(s, "Width/height changing with frame threads is", 0);
+            return -1;
+        }
+
         for(i=0; i<4; i++){
             av_freep(&buf->base[i]);
             buf->data[i]= NULL;
@@ -532,6 +538,14 @@ int attribute_align_arg avcodec_open(AVCodecContext *avctx, AVCodec *codec)
         goto free_and_end;
     }
     avctx->frame_number = 0;
+
+    if (HAVE_THREADS && !avctx->thread_opaque) {
+        ret = avcodec_thread_init(avctx, avctx->thread_count);
+        if (ret < 0) {
+            goto free_and_end;
+        }
+    }
+
     if (avctx->codec->max_lowres < avctx->lowres) {
         av_log(avctx, AV_LOG_ERROR, "The maximum value for lowres supported by the decoder is %d\n",
                avctx->codec->max_lowres);
@@ -543,7 +557,7 @@ int attribute_align_arg avcodec_open(AVCodecContext *avctx, AVCodec *codec)
     avctx->pts_correction_last_pts =
     avctx->pts_correction_last_dts = INT64_MIN;
 
-    if(avctx->codec->init){
+    if(avctx->codec->init && !(avctx->active_thread_type&FF_THREAD_FRAME)){
         ret = avctx->codec->init(avctx);
         if (ret < 0) {
             goto free_and_end;
@@ -674,13 +688,18 @@ int attribute_align_arg avcodec_decode_video2(AVCodecContext *avctx, AVFrame *pi
 
     avctx->pkt = avpkt;
 
-    if((avctx->codec->capabilities & CODEC_CAP_DELAY) || avpkt->size){
-        ret = avctx->codec->decode(avctx, picture, got_picture_ptr,
-                                avpkt);
+    if((avctx->codec->capabilities & CODEC_CAP_DELAY) || avpkt->size || (avctx->active_thread_type&FF_THREAD_FRAME)){
+        if (HAVE_PTHREADS && avctx->active_thread_type&FF_THREAD_FRAME)
+             ret = ff_thread_decode_frame(avctx, picture, got_picture_ptr,
+                                          avpkt);
+        else {
+            ret = avctx->codec->decode(avctx, picture, got_picture_ptr,
+                              avpkt);
+            picture->pkt_dts= avpkt->dts;
+        }
 
         emms_c(); //needed to avoid an emms_c() call before every return;
 
-        picture->pkt_dts= avpkt->dts;
         picture->best_effort_timestamp = guess_correct_pts(avctx,
                                                            picture->pkt_pts,
                                                            picture->pkt_dts);
@@ -809,6 +828,7 @@ av_cold int avcodec_close(AVCodecContext *avctx)
     if(avctx->codec && avctx->codec->encode)
         av_freep(&avctx->extradata);
     avctx->codec = NULL;
+    avctx->active_thread_type = 0;
     entangled_thread_counter--;
 
     /* Release any user-supplied mutex. */
@@ -1070,6 +1090,8 @@ void avcodec_init(void)
 
 void avcodec_flush_buffers(AVCodecContext *avctx)
 {
+    if(HAVE_PTHREADS && avctx->active_thread_type&FF_THREAD_FRAME)
+        ff_thread_flush(avctx);
     if(avctx->codec->flush)
         avctx->codec->flush(avctx);
 }
@@ -1270,3 +1292,30 @@ unsigned int ff_toupper4(unsigned int x)
             + (toupper((x>>16)&0xFF)<<16)
             + (toupper((x>>24)&0xFF)<<24);
 }
+
+#if !HAVE_PTHREADS
+
+int ff_thread_get_buffer(AVCodecContext *avctx, AVFrame *f)
+{
+    f->owner = avctx;
+    return avctx->get_buffer(avctx, f);
+}
+
+void ff_thread_release_buffer(AVCodecContext *avctx, AVFrame *f)
+{
+    f->owner->release_buffer(f->owner, f);
+}
+
+void ff_thread_finish_setup(AVCodecContext *avctx)
+{
+}
+
+void ff_thread_report_progress(AVFrame *f, int progress, int field)
+{
+}
+
+void ff_thread_await_progress(AVFrame *f, int progress, int field)
+{
+}
+
+#endif

libavcodec/w32thread.c

@@ -129,7 +129,13 @@ int avcodec_thread_init(AVCodecContext *s, int thread_count){
     ThreadContext *c;
     uint32_t threadid;
 
+    if(!(s->thread_type & FF_THREAD_SLICE)){
+        av_log(s, AV_LOG_WARNING, "The requested thread algorithm is not supported with this thread library.\n");
+        return 0;
+    }
+
     s->thread_count= thread_count;
+    s->active_thread_type= FF_THREAD_SLICE;
 
     if (thread_count <= 1)
         return 0;

libavformat/utils.c

@@ -930,6 +930,12 @@ static void compute_pkt_fields(AVFormatContext *s, AVStream *st,
     /* do we have a video B-frame ? */
     delay= st->codec->has_b_frames;
     presentation_delayed = 0;
+
+    // ignore delay caused by frame threading so that the mpeg2-without-dts
+    // warning will not trigger
+    if (delay && st->codec->active_thread_type&FF_THREAD_FRAME)
+        delay -= st->codec->thread_count-1;
+
     /* XXX: need has_b_frame, but cannot get it if the codec is
         not initialized */
     if (delay &&