diff mbox series

[FFmpeg-devel,24/35] fftools/ffmpeg: use the sync queues to handle -frames

Message ID 20220616195534.5278-24-anton@khirnov.net
State New
Headers show
Series [FFmpeg-devel,01/35] fftools/ffmpeg_mux: add private muxer context | expand

Checks

Context Check Description
andriy/make_x86 success Make finished
andriy/make_fate_x86 success Make fate finished

Commit Message

Anton Khirnov June 16, 2022, 7:55 p.m. UTC
Same issues apply to it as to -shortest.

Changes the results of the following tests:
- matroska-flac-extradata-update
  The test reencodes two input FLAC streams into three output FLAC
  streams. The last output stream is limited to 8 frames. The current
  code results in the first two output streams having 12 frames, after
  this commit all three streams have 8 frames and are the same length.
  This new result is better, since it is predictable.
- mkv-1242
  The test streamcopies one video and one audio stream, video is limited
  to 11 frames. The new result shortens the audio stream so that it is
  not longer than the video.
---
 fftools/ffmpeg.c                              |  6 ------
 fftools/ffmpeg_mux.c                          | 10 +---------
 fftools/ffmpeg_opt.c                          | 18 ++++++++++++++---
 fftools/sync_queue.c                          | 20 +++++++++++++++++++
 fftools/sync_queue.h                          |  7 +++++++
 tests/ref/fate/matroska-flac-extradata-update | 16 +++++----------
 tests/ref/fate/mkv-1242                       |  3 ---
 7 files changed, 48 insertions(+), 32 deletions(-)

Comments

Andreas Rheinhardt June 16, 2022, 8:33 p.m. UTC | #1
Anton Khirnov:
> Same issues apply to it as to -shortest.
> 
> Changes the results of the following tests:
> - matroska-flac-extradata-update
>   The test reencodes two input FLAC streams into three output FLAC
>   streams. The last output stream is limited to 8 frames. The current
>   code results in the first two output streams having 12 frames, after
>   this commit all three streams have 8 frames and are the same length.
>   This new result is better, since it is predictable.

The point of the test was that only one stream is limited so that one
can see the extradata update directly in the test result: The unlimited
streams have a different extradata than the limited stream (because said
extradata contains an md5 of the decoded data). So it is expected that
the extradata hashes of the first two streams coincide and differ from
the hash of the last stream.
(The current test results btw show an imperfection: The extradata of the
last stream is not updated, as the encoder is not flushed (or the flush
packet does not arrive at the muxer). Fixing this (as seems to be the
case) is good.)

> - mkv-1242
>   The test streamcopies one video and one audio stream, video is limited
>   to 11 frames. The new result shortens the audio stream so that it is
>   not longer than the video.
> ---
>  fftools/ffmpeg.c                              |  6 ------
>  fftools/ffmpeg_mux.c                          | 10 +---------
>  fftools/ffmpeg_opt.c                          | 18 ++++++++++++++---
>  fftools/sync_queue.c                          | 20 +++++++++++++++++++
>  fftools/sync_queue.h                          |  7 +++++++
>  tests/ref/fate/matroska-flac-extradata-update | 16 +++++----------
>  tests/ref/fate/mkv-1242                       |  3 ---
>  7 files changed, 48 insertions(+), 32 deletions(-)
> 
> diff --git a/fftools/ffmpeg.c b/fftools/ffmpeg.c
> index 1a14637ece..a471fa0f8f 100644
> --- a/fftools/ffmpeg.c
> +++ b/fftools/ffmpeg.c
> @@ -3467,12 +3467,6 @@ static int need_output(void)
>  
>          if (ost->finished || of_finished(of))
>              continue;
> -        if (ost->frame_number >= ost->max_frames) {
> -            int j;
> -            for (j = 0; j < of->ctx->nb_streams; j++)
> -                close_output_stream(output_streams[of->ost_index + j]);
> -            continue;
> -        }
>  
>          return 1;
>      }
> diff --git a/fftools/ffmpeg_mux.c b/fftools/ffmpeg_mux.c
> index 641bdb98b0..56444770bf 100644
> --- a/fftools/ffmpeg_mux.c
> +++ b/fftools/ffmpeg_mux.c
> @@ -237,19 +237,11 @@ void of_submit_packet(OutputFile *of, AVPacket *pkt, OutputStream *ost)
>  
>      if (pkt) {
>          /*
> -         * Audio encoders may split the packets --  #frames in != #packets out.
> -         * But there is no reordering, so we can limit the number of output packets
> -         * by simply dropping them here.
>           * Counting encoded video frames needs to be done separately because of
>           * reordering, see do_video_out().
>           */
> -        if (!(st->codecpar->codec_type == AVMEDIA_TYPE_VIDEO && ost->encoding_needed)) {
> -            if (ost->frame_number >= ost->max_frames) {
> -                av_packet_unref(pkt);
> -                return;
> -            }
> +        if (!(st->codecpar->codec_type == AVMEDIA_TYPE_VIDEO && ost->encoding_needed))
>              ost->frame_number++;
> -        }
>      }
>  
>      if (of->mux->header_written) {
> diff --git a/fftools/ffmpeg_opt.c b/fftools/ffmpeg_opt.c
> index 2cd4d42f2a..22eb558ff3 100644
> --- a/fftools/ffmpeg_opt.c
> +++ b/fftools/ffmpeg_opt.c
> @@ -2331,6 +2331,7 @@ static int init_complex_filters(void)
>  static int setup_sync_queues(OutputFile *of, AVFormatContext *oc, int64_t buf_size_us)
>  {
>      int nb_av_enc = 0, nb_interleaved = 0;
> +    int limit_frames = 0, limit_frames_av_enc = 0;
>  
>  #define IS_AV_ENC(ost, type)  \
>      (ost->encoding_needed && (type == AVMEDIA_TYPE_VIDEO || type == AVMEDIA_TYPE_AUDIO))
> @@ -2345,14 +2346,19 @@ static int setup_sync_queues(OutputFile *of, AVFormatContext *oc, int64_t buf_si
>  
>          nb_interleaved += IS_INTERLEAVED(type);
>          nb_av_enc      += IS_AV_ENC(ost, type);
> +
> +        limit_frames        |=  ost->max_frames < INT64_MAX;
> +        limit_frames_av_enc |= (ost->max_frames < INT64_MAX) && IS_AV_ENC(ost, type);
>      }
>  
> -    if (!(nb_interleaved > 1 && of->shortest))
> +    if (!((nb_interleaved > 1 && of->shortest) ||
> +          (nb_interleaved > 0 && limit_frames)))
>          return 0;
>  
> -    /* if we have more than one encoded audio/video streams, then we
> +    /* if we have more than one encoded audio/video streams, or at least
> +     * one encoded audio/video stream is frame-limited, then we
>       * synchronize them before encoding */
> -    if (nb_av_enc > 1) {
> +    if ((of->shortest && nb_av_enc > 1) || limit_frames_av_enc) {
>          of->sq_encode = sq_alloc(SYNC_QUEUE_FRAMES, buf_size_us);
>          if (!of->sq_encode)
>              return AVERROR(ENOMEM);
> @@ -2371,6 +2377,9 @@ static int setup_sync_queues(OutputFile *of, AVFormatContext *oc, int64_t buf_si
>              ost->sq_frame = av_frame_alloc();
>              if (!ost->sq_frame)
>                  return AVERROR(ENOMEM);
> +
> +            if (ost->max_frames != INT64_MAX)
> +                sq_limit_frames(of->sq_encode, ost->sq_idx_encode, ost->max_frames);
>          }
>      }
>  
> @@ -2391,6 +2400,9 @@ static int setup_sync_queues(OutputFile *of, AVFormatContext *oc, int64_t buf_si
>              ost->sq_idx_mux = sq_add_stream(of->sq_mux);
>              if (ost->sq_idx_mux < 0)
>                  return ost->sq_idx_mux;
> +
> +            if (ost->max_frames != INT64_MAX)
> +                sq_limit_frames(of->sq_mux, ost->sq_idx_mux, ost->max_frames);
>          }
>      }
>  
> diff --git a/fftools/sync_queue.c b/fftools/sync_queue.c
> index 49f0600b6c..08c3cf4f2a 100644
> --- a/fftools/sync_queue.c
> +++ b/fftools/sync_queue.c
> @@ -36,6 +36,9 @@ typedef struct SyncQueueStream {
>      int64_t          head_ts;
>      /* no more frames will be sent for this stream */
>      int              finished;
> +
> +    uint64_t         frames_sent;
> +    uint64_t         frames_max;
>  } SyncQueueStream;
>  
>  struct SyncQueue {
> @@ -264,6 +267,10 @@ int sq_send(SyncQueue *sq, unsigned int stream_idx, SyncQueueFrame frame)
>  
>      stream_update_ts(sq, stream_idx, ts);
>  
> +    st->frames_sent++;
> +    if (st->frames_sent >= st->frames_max)
> +        finish_stream(sq, stream_idx);
> +
>      return 0;
>  }
>  
> @@ -362,6 +369,7 @@ int sq_add_stream(SyncQueue *sq)
>       * streams forever; cf. overflow_heartbeat() */
>      st->tb      = (AVRational){ 1, 1 };
>      st->head_ts = AV_NOPTS_VALUE;
> +    st->frames_max = UINT64_MAX;
>  
>      return sq->nb_streams++;
>  }
> @@ -381,6 +389,18 @@ void sq_set_tb(SyncQueue *sq, unsigned int stream_idx, AVRational tb)
>      st->tb = tb;
>  }
>  
> +void sq_limit_frames(SyncQueue *sq, unsigned int stream_idx, uint64_t frames)
> +{
> +    SyncQueueStream *st;
> +
> +    av_assert0(stream_idx < sq->nb_streams);
> +    st = &sq->streams[stream_idx];
> +
> +    st->frames_max = frames;
> +    if (st->frames_sent >= st->frames_max)
> +        finish_stream(sq, stream_idx);
> +}
> +
>  SyncQueue *sq_alloc(enum SyncQueueType type, int64_t buf_size_us)
>  {
>      SyncQueue *sq = av_mallocz(sizeof(*sq));
> diff --git a/fftools/sync_queue.h b/fftools/sync_queue.h
> index e08780b7bf..7beddf8c4a 100644
> --- a/fftools/sync_queue.h
> +++ b/fftools/sync_queue.h
> @@ -63,6 +63,13 @@ int sq_add_stream(SyncQueue *sq);
>   */
>  void sq_set_tb(SyncQueue *sq, unsigned int stream_idx, AVRational tb);
>  
> +/**
> + * Limit the number of output frames for stream with index stream_idx
> + * to max_frames.
> + */
> +void sq_limit_frames(SyncQueue *sq, unsigned int stream_idx,
> +                     uint64_t max_frames);
> +
>  /**
>   * Submit a frame for the stream with index stream_idx.
>   *
> diff --git a/tests/ref/fate/matroska-flac-extradata-update b/tests/ref/fate/matroska-flac-extradata-update
> index b0276f734d..84dcc9c1d0 100644
> --- a/tests/ref/fate/matroska-flac-extradata-update
> +++ b/tests/ref/fate/matroska-flac-extradata-update
> @@ -1,8 +1,8 @@
> -56ff5763fd81ad3bc02c22402cd685e2 *tests/data/fate/matroska-flac-extradata-update.matroska
> -2008 tests/data/fate/matroska-flac-extradata-update.matroska
> -#extradata 0:       34, 0x7acb09e7
> -#extradata 1:       34, 0x7acb09e7
> -#extradata 2:       34, 0x443402dd
> +8ec02dffd603f44e08b2ae3b81a0d5a0 *tests/data/fate/matroska-flac-extradata-update.matroska
> +1816 tests/data/fate/matroska-flac-extradata-update.matroska
> +#extradata 0:       34, 0x93650c81
> +#extradata 1:       34, 0x93650c81
> +#extradata 2:       34, 0x93650c81
>  #tb 0: 1/1000
>  #media_type 0: audio
>  #codec_id 0: flac
> @@ -42,9 +42,3 @@
>  0,        672,        672,       96,       26, 0x50dd042e
>  1,        672,        672,       96,       26, 0x50dd042e
>  2,        672,        672,       96,       26, 0x50dd042e
> -0,        768,        768,       96,       26, 0x53de0499
> -1,        768,        768,       96,       26, 0x53de0499
> -0,        864,        864,       96,       26, 0x53df04b4
> -1,        864,        864,       96,       26, 0x53df04b4
> -0,        960,        960,       42,       26, 0x5740044b
> -1,        960,        960,       42,       26, 0x5740044b
> diff --git a/tests/ref/fate/mkv-1242 b/tests/ref/fate/mkv-1242
> index e025701093..1d1a227832 100644
> --- a/tests/ref/fate/mkv-1242
> +++ b/tests/ref/fate/mkv-1242
> @@ -42,6 +42,3 @@
>  1,        383,        383,       21,      325, 0xcd7a9fd6
>  1,        404,        404,       22,      359, 0x6edeb91c
>  1,        426,        426,       21,      333, 0xb8999fb7
> -1,        447,        447,       21,      317, 0xf2589e1a
> -1,        468,        468,       21,      319, 0x82ed9572
> -1,        489,        489,       22,      473, 0xea54e696
Anton Khirnov June 17, 2022, 10:46 a.m. UTC | #2
Quoting Andreas Rheinhardt (2022-06-16 22:33:46)
> Anton Khirnov:
> > Same issues apply to it as to -shortest.
> > 
> > Changes the results of the following tests:
> > - matroska-flac-extradata-update
> >   The test reencodes two input FLAC streams into three output FLAC
> >   streams. The last output stream is limited to 8 frames. The current
> >   code results in the first two output streams having 12 frames, after
> >   this commit all three streams have 8 frames and are the same length.
> >   This new result is better, since it is predictable.
> 
> The point of the test was that only one stream is limited so that one
> can see the extradata update directly in the test result: The unlimited
> streams have a different extradata than the limited stream (because said
> extradata contains an md5 of the decoded data). So it is expected that
> the extradata hashes of the first two streams coincide and differ from
> the hash of the last stream.

Right, but my point is that the amount of data that ends up in those
unlimited streams is largely an accident of how the code happens to
work currently and is not guaranteed by anything.

Are you suggesting any specific changes to the test or the patch? E.g.
the atrim filter could be used to replicate previous behaviour if you'd
like to keep it.

> (The current test results btw show an imperfection: The extradata of the
> last stream is not updated, as the encoder is not flushed (or the flush
> packet does not arrive at the muxer). Fixing this (as seems to be the
> case) is good.)

Correct - frame-limiting is now done before sending frames to the
encoder, so all packets, including the one from flushing the encoder,
get to the muxer.
Andreas Rheinhardt June 22, 2022, 8:27 a.m. UTC | #3
Anton Khirnov:
> Quoting Andreas Rheinhardt (2022-06-16 22:33:46)
>> Anton Khirnov:
>>> Same issues apply to it as to -shortest.
>>>
>>> Changes the results of the following tests:
>>> - matroska-flac-extradata-update
>>>   The test reencodes two input FLAC streams into three output FLAC
>>>   streams. The last output stream is limited to 8 frames. The current
>>>   code results in the first two output streams having 12 frames, after
>>>   this commit all three streams have 8 frames and are the same length.
>>>   This new result is better, since it is predictable.
>>
>> The point of the test was that only one stream is limited so that one
>> can see the extradata update directly in the test result: The unlimited
>> streams have a different extradata than the limited stream (because said
>> extradata contains an md5 of the decoded data). So it is expected that
>> the extradata hashes of the first two streams coincide and differ from
>> the hash of the last stream.
> 
> Right, but my point is that the amount of data that ends up in those
> unlimited streams is largely an accident of how the code happens to
> work currently and is not guaranteed by anything.
> 

The documentation of frames reads:
"-frames[:stream_specifier] framecount (output,per-stream)
    Stop writing to the stream after framecount frames."
It does not say that the other streams end after one stream has reached
its framecount. So it is guaranteed by the documentation that the other
streams don't end prematurely.
(Why do you think that this is an accident?)

> Are you suggesting any specific changes to the test or the patch? E.g.
> the atrim filter could be used to replicate previous behaviour if you'd
> like to keep it.
> 
>> (The current test results btw show an imperfection: The extradata of the
>> last stream is not updated, as the encoder is not flushed (or the flush
>> packet does not arrive at the muxer). Fixing this (as seems to be the
>> case) is good.)
> 
> Correct - frame-limiting is now done before sending frames to the
> encoder, so all packets, including the one from flushing the encoder,
> get to the muxer.
>
Anton Khirnov June 22, 2022, 5:26 p.m. UTC | #4
Quoting Andreas Rheinhardt (2022-06-22 10:27:30)
> Anton Khirnov:
> > Quoting Andreas Rheinhardt (2022-06-16 22:33:46)
> >> Anton Khirnov:
> >>> Same issues apply to it as to -shortest.
> >>>
> >>> Changes the results of the following tests:
> >>> - matroska-flac-extradata-update
> >>>   The test reencodes two input FLAC streams into three output FLAC
> >>>   streams. The last output stream is limited to 8 frames. The current
> >>>   code results in the first two output streams having 12 frames, after
> >>>   this commit all three streams have 8 frames and are the same length.
> >>>   This new result is better, since it is predictable.
> >>
> >> The point of the test was that only one stream is limited so that one
> >> can see the extradata update directly in the test result: The unlimited
> >> streams have a different extradata than the limited stream (because said
> >> extradata contains an md5 of the decoded data). So it is expected that
> >> the extradata hashes of the first two streams coincide and differ from
> >> the hash of the last stream.
> > 
> > Right, but my point is that the amount of data that ends up in those
> > unlimited streams is largely an accident of how the code happens to
> > work currently and is not guaranteed by anything.
> > 
> 
> The documentation of frames reads:
> "-frames[:stream_specifier] framecount (output,per-stream)
>     Stop writing to the stream after framecount frames."
> It does not say that the other streams end after one stream has reached
> its framecount. So it is guaranteed by the documentation that the other
> streams don't end prematurely.
> (Why do you think that this is an accident?)

1) Documentation not saying what happens to the other streams does not imply
   any guarantees IMO, it implies a lack of any guarantees.
2) Documentation for ffmpeg has always been less than fully descriptive
   (to put it extremely mildly), so I would not rely on it as the
   ultimate source of truth.
3) The original commit adding this option in 2004 would terminate ALL
   output to the file on reaching the specified frame limit, not just
   the affected stream. This was broken by me in
   2f51ec2b9438e211f5b8abb2fcf5d8be678e7e8c, because need_output()
   terminates early and does not check max_frames for further streams if
   an earlier stream still allows output. I would consider this a bug,
   because it makes no sense to treat the option differently based on
   stream ordering. Presumably nobody noticed because nobody relies on
   this option producing consistent output with multiple streams.
   This is also the reason the test outputs all frames for the first two
   streams. If you changed "-frames:a:2 8" to "-frames:a:0 8", you would
   get:
   Output stream #0:0 (audio): 8 frames encoded (36864 samples); 8 packets muxed (208 bytes);
   Output stream #0:1 (audio): 7 frames encoded (32256 samples); 8 packets muxed (182 bytes);
   Output stream #0:2 (audio): 8 frames encoded (36864 samples); 9 packets muxed (208 bytes);
Michael Niedermayer June 23, 2022, 10:12 p.m. UTC | #5
On Thu, Jun 16, 2022 at 09:55:23PM +0200, Anton Khirnov wrote:
> Same issues apply to it as to -shortest.
> 
> Changes the results of the following tests:
> - matroska-flac-extradata-update
>   The test reencodes two input FLAC streams into three output FLAC
>   streams. The last output stream is limited to 8 frames. The current
>   code results in the first two output streams having 12 frames, after
>   this commit all three streams have 8 frames and are the same length.
>   This new result is better, since it is predictable.
> - mkv-1242
>   The test streamcopies one video and one audio stream, video is limited
>   to 11 frames. The new result shortens the audio stream so that it is
>   not longer than the video.

seems to break:
./ffmpeg -i tspacket_size_changeback.ts -vframes 2 -y -qscale 2  sizechangback.avi

0,          0,          0,        1,    81175, 0xa6efb96202 bitrate= 114.8kbits/s speed=N/A    
1,          0,          0,        1,      384, 0xdfabb6ef
1,          1,          1,        1,      384, 0x5abbbe00
1,          2,          2,        1,      384, 0x9930b9a2
1,          3,          3,        1,      384, 0x7c0cb08d
1,          4,          4,        1,      384, 0x0c54b25e
1,          5,          5,        1,      384, 0x8dafb427
1,          6,          6,        1,      384, 0x6c7eb911
1,          7,          7,        1,      384, 0x336fd87e
0,         51,         51,        1,    43825, 0x8dc20601, F=0x0
frame=    2 fps=0.0 q=-1.0 Lsize=       1kB time=00:00:01.04 bitrate=   6.7kbits/s speed=1.03e+04x    
video:122kB audio:3kB subtitle:0kB other streams:0kB global headers:0kB muxing overhead: unknown


after:
1,          0,          0,        1,      384, 0xdfabb6ef02 bitrate=  84.0kbits/s speed=N/A    
1,          1,          1,        1,      384, 0x5abbbe00
1,          2,          2,        1,      384, 0x9930b9a2
1,          3,          3,        1,      384, 0x7c0cb08d
1,          4,          4,        1,      384, 0x0c54b25e
1,          5,          5,        1,      384, 0x8dafb427
1,          6,          6,        1,      384, 0x6c7eb911
1,          7,          7,        1,      384, 0x336fd87e
frame=    0 fps=0.0 q=-1.0 Lsize=       1kB time=00:00:00.19 bitrate=  29.8kbits/s speed=4.47e+03x    
video:0kB audio:3kB subtitle:0kB other streams:0kB global headers:0kB muxing overhead: unknown

will mail the file privatly

[...]
diff mbox series

Patch

diff --git a/fftools/ffmpeg.c b/fftools/ffmpeg.c
index 1a14637ece..a471fa0f8f 100644
--- a/fftools/ffmpeg.c
+++ b/fftools/ffmpeg.c
@@ -3467,12 +3467,6 @@  static int need_output(void)
 
         if (ost->finished || of_finished(of))
             continue;
-        if (ost->frame_number >= ost->max_frames) {
-            int j;
-            for (j = 0; j < of->ctx->nb_streams; j++)
-                close_output_stream(output_streams[of->ost_index + j]);
-            continue;
-        }
 
         return 1;
     }
diff --git a/fftools/ffmpeg_mux.c b/fftools/ffmpeg_mux.c
index 641bdb98b0..56444770bf 100644
--- a/fftools/ffmpeg_mux.c
+++ b/fftools/ffmpeg_mux.c
@@ -237,19 +237,11 @@  void of_submit_packet(OutputFile *of, AVPacket *pkt, OutputStream *ost)
 
     if (pkt) {
         /*
-         * Audio encoders may split the packets --  #frames in != #packets out.
-         * But there is no reordering, so we can limit the number of output packets
-         * by simply dropping them here.
          * Counting encoded video frames needs to be done separately because of
          * reordering, see do_video_out().
          */
-        if (!(st->codecpar->codec_type == AVMEDIA_TYPE_VIDEO && ost->encoding_needed)) {
-            if (ost->frame_number >= ost->max_frames) {
-                av_packet_unref(pkt);
-                return;
-            }
+        if (!(st->codecpar->codec_type == AVMEDIA_TYPE_VIDEO && ost->encoding_needed))
             ost->frame_number++;
-        }
     }
 
     if (of->mux->header_written) {
diff --git a/fftools/ffmpeg_opt.c b/fftools/ffmpeg_opt.c
index 2cd4d42f2a..22eb558ff3 100644
--- a/fftools/ffmpeg_opt.c
+++ b/fftools/ffmpeg_opt.c
@@ -2331,6 +2331,7 @@  static int init_complex_filters(void)
 static int setup_sync_queues(OutputFile *of, AVFormatContext *oc, int64_t buf_size_us)
 {
     int nb_av_enc = 0, nb_interleaved = 0;
+    int limit_frames = 0, limit_frames_av_enc = 0;
 
 #define IS_AV_ENC(ost, type)  \
     (ost->encoding_needed && (type == AVMEDIA_TYPE_VIDEO || type == AVMEDIA_TYPE_AUDIO))
@@ -2345,14 +2346,19 @@  static int setup_sync_queues(OutputFile *of, AVFormatContext *oc, int64_t buf_si
 
         nb_interleaved += IS_INTERLEAVED(type);
         nb_av_enc      += IS_AV_ENC(ost, type);
+
+        limit_frames        |=  ost->max_frames < INT64_MAX;
+        limit_frames_av_enc |= (ost->max_frames < INT64_MAX) && IS_AV_ENC(ost, type);
     }
 
-    if (!(nb_interleaved > 1 && of->shortest))
+    if (!((nb_interleaved > 1 && of->shortest) ||
+          (nb_interleaved > 0 && limit_frames)))
         return 0;
 
-    /* if we have more than one encoded audio/video streams, then we
+    /* if we have more than one encoded audio/video streams, or at least
+     * one encoded audio/video stream is frame-limited, then we
      * synchronize them before encoding */
-    if (nb_av_enc > 1) {
+    if ((of->shortest && nb_av_enc > 1) || limit_frames_av_enc) {
         of->sq_encode = sq_alloc(SYNC_QUEUE_FRAMES, buf_size_us);
         if (!of->sq_encode)
             return AVERROR(ENOMEM);
@@ -2371,6 +2377,9 @@  static int setup_sync_queues(OutputFile *of, AVFormatContext *oc, int64_t buf_si
             ost->sq_frame = av_frame_alloc();
             if (!ost->sq_frame)
                 return AVERROR(ENOMEM);
+
+            if (ost->max_frames != INT64_MAX)
+                sq_limit_frames(of->sq_encode, ost->sq_idx_encode, ost->max_frames);
         }
     }
 
@@ -2391,6 +2400,9 @@  static int setup_sync_queues(OutputFile *of, AVFormatContext *oc, int64_t buf_si
             ost->sq_idx_mux = sq_add_stream(of->sq_mux);
             if (ost->sq_idx_mux < 0)
                 return ost->sq_idx_mux;
+
+            if (ost->max_frames != INT64_MAX)
+                sq_limit_frames(of->sq_mux, ost->sq_idx_mux, ost->max_frames);
         }
     }
 
diff --git a/fftools/sync_queue.c b/fftools/sync_queue.c
index 49f0600b6c..08c3cf4f2a 100644
--- a/fftools/sync_queue.c
+++ b/fftools/sync_queue.c
@@ -36,6 +36,9 @@  typedef struct SyncQueueStream {
     int64_t          head_ts;
     /* no more frames will be sent for this stream */
     int              finished;
+
+    uint64_t         frames_sent;
+    uint64_t         frames_max;
 } SyncQueueStream;
 
 struct SyncQueue {
@@ -264,6 +267,10 @@  int sq_send(SyncQueue *sq, unsigned int stream_idx, SyncQueueFrame frame)
 
     stream_update_ts(sq, stream_idx, ts);
 
+    st->frames_sent++;
+    if (st->frames_sent >= st->frames_max)
+        finish_stream(sq, stream_idx);
+
     return 0;
 }
 
@@ -362,6 +369,7 @@  int sq_add_stream(SyncQueue *sq)
      * streams forever; cf. overflow_heartbeat() */
     st->tb      = (AVRational){ 1, 1 };
     st->head_ts = AV_NOPTS_VALUE;
+    st->frames_max = UINT64_MAX;
 
     return sq->nb_streams++;
 }
@@ -381,6 +389,18 @@  void sq_set_tb(SyncQueue *sq, unsigned int stream_idx, AVRational tb)
     st->tb = tb;
 }
 
+void sq_limit_frames(SyncQueue *sq, unsigned int stream_idx, uint64_t frames)
+{
+    SyncQueueStream *st;
+
+    av_assert0(stream_idx < sq->nb_streams);
+    st = &sq->streams[stream_idx];
+
+    st->frames_max = frames;
+    if (st->frames_sent >= st->frames_max)
+        finish_stream(sq, stream_idx);
+}
+
 SyncQueue *sq_alloc(enum SyncQueueType type, int64_t buf_size_us)
 {
     SyncQueue *sq = av_mallocz(sizeof(*sq));
diff --git a/fftools/sync_queue.h b/fftools/sync_queue.h
index e08780b7bf..7beddf8c4a 100644
--- a/fftools/sync_queue.h
+++ b/fftools/sync_queue.h
@@ -63,6 +63,13 @@  int sq_add_stream(SyncQueue *sq);
  */
 void sq_set_tb(SyncQueue *sq, unsigned int stream_idx, AVRational tb);
 
+/**
+ * Limit the number of output frames for stream with index stream_idx
+ * to max_frames.
+ */
+void sq_limit_frames(SyncQueue *sq, unsigned int stream_idx,
+                     uint64_t max_frames);
+
 /**
  * Submit a frame for the stream with index stream_idx.
  *
diff --git a/tests/ref/fate/matroska-flac-extradata-update b/tests/ref/fate/matroska-flac-extradata-update
index b0276f734d..84dcc9c1d0 100644
--- a/tests/ref/fate/matroska-flac-extradata-update
+++ b/tests/ref/fate/matroska-flac-extradata-update
@@ -1,8 +1,8 @@ 
-56ff5763fd81ad3bc02c22402cd685e2 *tests/data/fate/matroska-flac-extradata-update.matroska
-2008 tests/data/fate/matroska-flac-extradata-update.matroska
-#extradata 0:       34, 0x7acb09e7
-#extradata 1:       34, 0x7acb09e7
-#extradata 2:       34, 0x443402dd
+8ec02dffd603f44e08b2ae3b81a0d5a0 *tests/data/fate/matroska-flac-extradata-update.matroska
+1816 tests/data/fate/matroska-flac-extradata-update.matroska
+#extradata 0:       34, 0x93650c81
+#extradata 1:       34, 0x93650c81
+#extradata 2:       34, 0x93650c81
 #tb 0: 1/1000
 #media_type 0: audio
 #codec_id 0: flac
@@ -42,9 +42,3 @@ 
 0,        672,        672,       96,       26, 0x50dd042e
 1,        672,        672,       96,       26, 0x50dd042e
 2,        672,        672,       96,       26, 0x50dd042e
-0,        768,        768,       96,       26, 0x53de0499
-1,        768,        768,       96,       26, 0x53de0499
-0,        864,        864,       96,       26, 0x53df04b4
-1,        864,        864,       96,       26, 0x53df04b4
-0,        960,        960,       42,       26, 0x5740044b
-1,        960,        960,       42,       26, 0x5740044b
diff --git a/tests/ref/fate/mkv-1242 b/tests/ref/fate/mkv-1242
index e025701093..1d1a227832 100644
--- a/tests/ref/fate/mkv-1242
+++ b/tests/ref/fate/mkv-1242
@@ -42,6 +42,3 @@ 
 1,        383,        383,       21,      325, 0xcd7a9fd6
 1,        404,        404,       22,      359, 0x6edeb91c
 1,        426,        426,       21,      333, 0xb8999fb7
-1,        447,        447,       21,      317, 0xf2589e1a
-1,        468,        468,       21,      319, 0x82ed9572
-1,        489,        489,       22,      473, 0xea54e696