[FFmpeg-devel] [PATCH] doc/ffmpeg: extend -dts_delta_threshold option description

[Stefano Sabatini]

On date Thursday 2023-02-09 00:41:18 +0100, Michael Niedermayer wrote:
> On Mon, Feb 06, 2023 at 02:25:23AM +0100, Stefano Sabatini wrote:
[...]
> > Subject: [PATCH 2/2] ffmpeg: review -dts_delta_threshold and -dts_delta_error
> >  options
> > 
> > Review handling of -dts_delta_threshold and -dts_delta_error options,
> > specify them as floating point expressed in seconds.
> > 
> > Also, review and simplify logic. Adjust values for tests, since in
> > some cases the new values does not trigger the correction logic.
> > 
> > PR: https://patchwork.ffmpeg.org/project/ffmpeg/list/?series=8252
> > ---
> >  doc/ffmpeg.texi             | 36 ++++++++++++++++---
> >  fftools/ffmpeg.c            | 72 ++++++++++++++++++++-----------------
> >  fftools/ffmpeg.h            |  2 ++
> >  fftools/ffmpeg_demux.c      |  3 ++
> >  tests/fate/filter-audio.mak |  2 +-
> >  tests/fate/mpeg4.mak        |  2 +-
> >  6 files changed, 77 insertions(+), 40 deletions(-)
> 
> This seems to break a case with concat and vsync
> ./ffmpeg -y -i 'concat:///home/michael/videos/angels.mpg|/home/michael/videos/angels.mpg'  -vsync 0 -an file.avi
> 
> ...
> cpb: bitrate max/min/avg: 0/0/200000 buffer size: 0 vbv_delay: N/A
> [mpeg4 @ 0x55e051b8d4c0] Invalid pts (0) <= last (11)00.00 bitrate=N/A speed=   0x    
> [vost#0:0/mpeg4 @ 0x55e051b9d700] Error submitting video frame to the encoder
> Conversion failed!
>
> 
> Ill mail you the angels.mpg, i think its online somewhere but i cant
> find it

Fixed, now the code should be equivalent to the previous
implementation.

What happened in this case (and apparently in the other fate tests
failing), is that some sort of limit correction is applied:

detected dts:-0.041711 < dts_limit:0.358789
ts delta 0.5005 applied => ts_offset_discont:0.5005 dts:0.458789

preventing the invalid pts error.

The limit correction, hardcoded in the ffmpeg.c code, is completely
unrelated to the dts_delta_threshold value, no idea if it would make
sense to make this parametric (but at least now it should be a bit
more clear from the code/logs).
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