[FFmpeg-devel] [PATCH v1] avformat/mxf: set stream frame rates for ST 422 essence containers

[Pierre-Anthony Lemieux]

On Sat, Sep 3, 2022 at 11:26 AM Tomas Härdin <tjoppen at acc.umu.se> wrote:
>
> sön 2022-08-28 klockan 08:31 -0700 skrev pal at sandflow.com:
> > From: Pierre-Anthony Lemieux <pal at palemieux.com>
> >
> > The MXF demuxer does not currently set AVStream::avg_frame_rate and
> > ::r_frame_rate
> > when J2K essence is wrapped according to SMPTE ST 422.
> >
> > ---
> >  libavformat/mxfdec.c | 25 +++++++++++++++++++++++++
> >  1 file changed, 25 insertions(+)
> >
> > diff --git a/libavformat/mxfdec.c b/libavformat/mxfdec.c
> > index feebff67aa..043e2e06ec 100644
> > --- a/libavformat/mxfdec.c
> > +++ b/libavformat/mxfdec.c
> > @@ -2140,6 +2140,13 @@ finish_decoding_index:
> >      return ret;
> >  }
> >
> > +static int mxf_is_st_422(const UID *essence_container_ul) {
> > +    static const uint8_t st_422_essence_container_ul[] = {
> > 0x06,0x0e,0x2b,0x34,0x04,0x01,0x01,0x07,0x0d,0x01,0x03,0x01,0x02,0x0c
> > };
> > +
> > +    return essence_container_ul &&
> > mxf_match_uid(*essence_container_ul, st_422_essence_container_ul,
> > +
> > sizeof(st_422_essence_container_ul));
> > +}
>
> Seems unnecessary to have a function for this

Ok. I was trying to avoid a long if() line but I am happy to move the
logic to mxf_parse_structural_metadata().

Would you like me to update the patch?

>
> > +
> >  static int mxf_is_intra_only(MXFDescriptor *descriptor)
> >  {
> >      return mxf_get_codec_ul(mxf_intra_only_essence_container_uls,
> > @@ -2892,6 +2899,24 @@ static int
> > mxf_parse_structural_metadata(MXFContext *mxf)
> >                      av_log(mxf->fc, AV_LOG_INFO, "Unknown frame
> > layout type: %d\n", descriptor->frame_layout);
> >              }
> >
> > +            if (mxf_is_st_422(essence_container_ul)) {
> > +                switch ((*essence_container_ul)[14]) {
> > +                case 2: /* Cn: Clip- wrapped Picture Element */
> > +                case 3: /* I1: Interlaced Frame, 1 field/KLV */
> > +                case 4: /* I2: Interlaced Frame, 2 fields/KLV */
> > +                case 6: /* P1: Frame- wrapped Picture Element */
> > +                    st->avg_frame_rate = source_track->edit_rate;
> > +                    st->r_frame_rate = st->avg_frame_rate;
> > +                    break;
> > +                case 5: /* F1: Field-wrapped Picture Element */
> > +                    st->avg_frame_rate = av_mul_q(av_make_q(2, 1),
> > source_track->edit_rate);
> > +                    st->r_frame_rate = st->avg_frame_rate;
> > +                    break;
> > +                default:
> > +                    break;
> > +                }
> > +            }
>
> Looks OK, but we should have a test for this as well I think

Ok. imf/countdown/countdown-small.mxf contained ST 422-wrapped essence
and ffprobe reports `24 fps`. Should this patchset include the test?

>
> At some point we'll probably need to implement proper timecode
> support..

+1

Happy to collaborate.

>
> /Tomas
>
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