Re: [FFmpeg-devel] [FFmpeg-cvslog] avfilter/vf_tpad: if there is no frame to clone return early

[Thierry Foucu <tfoucu@gmail.com>]

On Thu, Feb 24, 2022 at 1:50 PM Paul B Mahol <onemda@gmail.com> wrote:

> On Thu, Feb 24, 2022 at 10:36 PM Thierry Foucu <tfoucu@gmail.com> wrote:
>
> > On Thu, Feb 24, 2022 at 1:28 PM Paul B Mahol <onemda@gmail.com> wrote:
> >
> > > On Thu, Feb 24, 2022 at 10:12 PM Thierry Foucu <tfoucu@gmail.com>
> wrote:
> > >
> > > > On Thu, Feb 24, 2022 at 12:30 PM Paul B Mahol <git@videolan.org>
> > wrote:
> > > >
> > > > > ffmpeg | branch: master | Paul B Mahol <onemda@gmail.com> | Thu
> Feb
> > 24
> > > > > 20:32:41 2022 +0100| [3715f2f8643695940582ce040b7a052cccfb9db2] |
> > > > > committer: Paul B Mahol
> > > > >
> > > > > avfilter/vf_tpad: if there is no frame to clone return early
> > > > >
> > > > > >
> > > > >
> > > >
> > >
> >
> http://git.videolan.org/gitweb.cgi/ffmpeg.git/?a=commit;h=3715f2f8643695940582ce040b7a052cccfb9db2
> > > > > ---
> > > > >
> > > > >  libavfilter/vf_tpad.c | 5 +++++
> > > > >  1 file changed, 5 insertions(+)
> > > > >
> > > > > diff --git a/libavfilter/vf_tpad.c b/libavfilter/vf_tpad.c
> > > > > index e5acece1e4..120dbcb4d3 100644
> > > > > --- a/libavfilter/vf_tpad.c
> > > > > +++ b/libavfilter/vf_tpad.c
> > > > > @@ -148,6 +148,11 @@ static int activate(AVFilterContext *ctx)
> > > > >                                frame->data, frame->linesize,
> > > > >                                0, 0, frame->width, frame->height);
> > > > >          } else if (s->stop_mode == 1) {
> > > > > +            if (!s->cache_stop) {
> > > > > +                s->pad_stop = 0;
> > > > > +                ff_outlink_set_status(outlink, AVERROR_EOF,
> s->pts);
> > > > > +                return 0;
> > > > > +            }
> > > > >              frame = av_frame_clone(s->cache_stop);
> > > > >              if (!frame)
> > > > >                  return AVERROR(ENOMEM);
> > > > >
> > > > >
> > > > The problem with this solution is that the tpad will then not do what
> > we
> > > > are expecting, which is padding video track, and the output file will
> > not
> > > > have the desired duration.
> > > > Will it not be better to just output black frame (aka stop_mode ==
> 0) ,
> > > > something like that?
> > > >
> > >
> > > I doubt that, clone is clone, there is no point in padding stream that
> > have
> > > no frames at all.
> > >
> > >
> > >
> > The sample I forwarded to JB has video frames. The problem was that there
> > was a re-init of the filter chain after a resolution change and after the
> > re-init, there were no frames but got frames before the re-init.
> > I will understand for a media file which has NEVER received a video frame
> > and in this case, this is the correct solution.
> >
>
> Hmm, so you encode output with resolution change, why not use scale filter
> as first filter and then no resolution ever change for rest of graph?
> Adding support for resolution changes to all filters is very time consuming
> task and I see no real benefit in doing that now.
>

We do have the scale filter in front of the tpad filter. Here is the filter
chain we are using
idet=1.04:1.5,yadif=0:-1:1,scale=+528:+864:flags=bicubic,setsar=1,fps=fps=16.601,tpad=stop_mode=clone:stop_duration=2808ms

And it does crash.

Even just fps=fps=16.601,tpad=stop_mode=clone:stop_duration=2808ms
reproduce the problem.


>
>
> >
> >
> > > >
> > > > iff --git a/libavfilter/vf_tpad.c b/libavfilter/vf_tpad.c
> > > > index e5acece1e4..5e4062e9f2 100644
> > > > --- a/libavfilter/vf_tpad.c
> > > > +++ b/libavfilter/vf_tpad.c
> > > > @@ -140,7 +140,7 @@ static int activate(AVFilterContext *ctx)
> > > >              ff_outlink_set_status(outlink, AVERROR_EOF, s->pts);
> > > >              return 0;
> > > >          }
> > > > -        if (s->stop_mode == 0) {
> > > > +        if (s->stop_mode == 0 || !s->cache_stop) {
> > > >              frame = ff_get_video_buffer(outlink, outlink->w,
> > > outlink->h);
> > > >              if (!frame)
> > > >                  return AVERROR(ENOMEM);
> > > >
> > > >
> > > >
> > > >
> > > > > _______________________________________________
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> > > > >
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> > > > >
> > > >
> > > >
> > > > --
> > > >
> > > > Thierry Foucu
> > > > _______________________________________________
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> >
> >
> > --
> >
> > Thierry Foucu
> > _______________________________________________
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-- 

Thierry Foucu
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