[FFmpeg-devel] [PATCH 1/2] avformat/mxfenc: Fix guess frame_rate

[Tomas Härdin]

sön 2024-09-01 klockan 12:53 +0200 skrev Anton Khirnov:
> Quoting Nicolas Gaullier (2024-08-22 18:55:32)
> > The input time_base was a bad guess.
> > 
> > Currently, fate-time_base test data assumed that overriding the
> > input
> > time_base would affect the frame_rate, but this behaviour is not
> > documented, so just fix the fate data now that this is fixed.
> > 
> > Fix regression since 10185e2d4c1e9839bc58a1d6a63c861677b13fd0:
> > previously, when streamcopying, the time_base was guessed from the
> > frame_rate considering it is often constant, so guessing the
> > frame_rate
> > back from the time_base was often not a problem.
> > 
> > To reproduce:
> > ffmpeg -i fate-suite/mpeg2/dvd_still_frame.vob -an -c copy out.mxf
> > 
> > Signed-off-by: Nicolas Gaullier <nicolas.gaullier at cji.paris>
> > ---
> >  libavformat/mxfenc.c     | 9 +++++++--
> >  tests/ref/fate/time_base | 2 +-
> >  2 files changed, 8 insertions(+), 3 deletions(-)
> > 
> > diff --git a/libavformat/mxfenc.c b/libavformat/mxfenc.c
> > index 4ac6a2d715..a814f15609 100644
> > --- a/libavformat/mxfenc.c
> > +++ b/libavformat/mxfenc.c
> > @@ -2894,8 +2894,13 @@ static int mxf_init(AVFormatContext *s)
> >  
> >          if (st->codecpar->codec_type == AVMEDIA_TYPE_VIDEO) {
> >              const AVPixFmtDescriptor *pix_desc =
> > av_pix_fmt_desc_get(st->codecpar->format);
> > -            // TODO: should be avg_frame_rate
> > -            AVRational tbc = st->time_base;
> > +            AVRational frame_rate = (AVRational){ 0, 1 };
> > +            if (st->avg_frame_rate.num > 0 && st-
> > >avg_frame_rate.den > 0)
> > +                frame_rate = st->avg_frame_rate;
> > +            else if (st->r_frame_rate.num > 0 && st-
> > >r_frame_rate.den > 0)
> > +                frame_rate = st->r_frame_rate;
> > +            AVRational tbc = av_inv_q(frame_rate);
> 
> Should it not still fall back to time_base when neither
> avg_frame_rate
> nor r_frame_rate is set?

Might be better to error out since time_base can be wildly off what is
intended..

/Tomas