[FFmpeg-devel] [PATCH] lavf/movenc: Replace dts by pts to calculate duration

[Michael Niedermayer]

On Thu, Nov 07, 2019 at 05:55:18PM +0800, manuelyuan wrote:
> From: Mengyang Yuan <manuelyuan at 163.com>
> 
> In this case, the input video is of dynamic frame rate and we don't want to
> duplicate or drop frames, but the output video duration calculated by DTS is
> incorrect, I solved it by using PTS.
> There are many UGC videos with dynamic frame rates, which are represented by
> PTS jumps. After transcoding with ffmpeg -vsync 0 or -vsync 2, the output
> video duration becomes longer.By reading the code of x264/encoder/encoder.c,
> I found that in order to predict the B frame, x264 needs to ensure that there
> are enough reference frames when DTS = 0, so the DTS of these reference frames
> will subtract the cache time. However, the cache time includes the part of PTS
> jumps, which results in the abnormal small DTS.
> 
> Signed-off-by: Mengyang Yuan <manuelyuan at 163.com>
> ---
>  libavformat/movenc.c  | 23 ++++++++++++++---------
>  libavformat/movenc.h  |  2 ++
>  tests/ref/fate/movenc | 20 ++++++++++----------
>  tests/ref/lavf/mov    |  4 ++--
>  tests/ref/lavf/mp4    |  4 ++--
>  5 files changed, 30 insertions(+), 23 deletions(-)

breaks fate-binsub-movtextenc
...

[mp4 @ 0x29327c0] Estimating the duration of the last packet in a fragment, consider setting the duration field in AVPacket instead.
size=       1kB time=00:00:05.85 bitrate=   1.3kbits/s speed=6.03e+04x    
video:0kB audio:0kB subtitle:0kB other streams:0kB global headers:0kB muxing overhead: 1809.803955%
make: *** [fate-binsub-movtextenc] Error 1

[...]
-- 
Michael     GnuPG fingerprint: 9FF2128B147EF6730BADF133611EC787040B0FAB

Any man who breaks a law that conscience tells him is unjust and willingly 
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the community on the injustice of the law is at that moment expressing the 
very highest respect for law. - Martin Luther King Jr
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