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

[Michael Niedermayer <michael@niedermayer.cc>]

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On Mon, Feb 06, 2023 at 02:25:23AM +0100, Stefano Sabatini wrote:
> On date Wednesday 2023-01-25 10:47:20 +0530, Gyan Doshi wrote:
> > 
> > 
> > On 2023-01-25 06:37 am, Stefano Sabatini wrote:
> > > ---
> > >   doc/ffmpeg.texi | 17 +++++++++++++++--
> > >   1 file changed, 15 insertions(+), 2 deletions(-)
> > > 
> > > diff --git a/doc/ffmpeg.texi b/doc/ffmpeg.texi
> > > index 67b3294256..122f7e3387 100644
> > > --- a/doc/ffmpeg.texi
> > > +++ b/doc/ffmpeg.texi
> > > @@ -1823,8 +1823,21 @@ results, but increase memory use and latency.
> > >   The default value is 10 seconds.
> > > -@item -dts_delta_threshold
> > > -Timestamp discontinuity delta threshold.
> > > +@item -dts_delta_threshold @var{threshold}
> > > +Timestamp discontinuity delta threshold, expressed as a floating point
> > > +number of @var{AV_TIME_BASE} units.
> > This is a CLI option and those users don't deal with AV_TIME_BASE . More
> > useful to say it's in seconds.
> > 
> > > +
> > > +If a timestamp discontinuity is detected whose absolute value is
> > > +greater than @var{threshold} * @var{AV_TIME_BASE}, ffmpeg will remove the
> > > +discontinuity by decreasing/increasing the current DTS and PTS by the
> > > +corresponding delta value.
> > 
> 
> > Might want to mention that this only applies to AV_FMT_DISCONT demuxers, or
> > rather give a few examples, like MPEG-TS, HLS..etc.
> > For all other formats that users normally work with, clarify that only
> > dts_error_threshold is relevant.
> 
> 
> > > +
> > > +Timestamp discontinuity correction can be inhibited by setting a big value for
> > > +@var{threshold}, and is automatically disabled when employing the
> > > +@code{-copy_ts} option.
> > 
> > For copy_ts, it is still applied for all negative deltas except the
> > smallest.
> 
> Which is a bit arbitrary.
> 
> > 
> > Not blocking, but I'm reworking this code at present. Shouldn't really
> > affect this patch. See
> > https://ffmpeg.org/pipermail/ffmpeg-devel/2023-January/305539.html
> 
> Updated (had to review the code to get some clarity on the current
> behavior).
> 
> Thanks.

>  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(-)
> 55e91624524749274a62bdc43cacdf8e47dd3598  0002-ffmpeg-review-dts_delta_threshold-and-dts_delta_erro.patch
> From 30ac56a14d66eb25428b71c9211f401f818bd057 Mon Sep 17 00:00:00 2001
> From: Stefano Sabatini <stefasab@gmail.com>
> Date: Fri, 1 Apr 2011 01:13:35 +0200
> 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

thx

[...]

-- 
Michael     GnuPG fingerprint: 9FF2128B147EF6730BADF133611EC787040B0FAB

"Nothing to hide" only works if the folks in power share the values of
you and everyone you know entirely and always will -- Tom Scott


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