Re: [FFmpeg-devel] [PATCH v1] avformat/imfdec: preserve stream information

[Pierre-Anthony Lemieux <pal@sandflow.com>]

On Sun, Jul 3, 2022 at 12:15 PM Andreas Rheinhardt
<andreas.rheinhardt@outlook.com> wrote:
>
> Pierre-Anthony Lemieux:
> > On Sun, Jul 3, 2022 at 11:28 AM Andreas Rheinhardt
> > <andreas.rheinhardt@outlook.com> wrote:
> >>
> >> pal@sandflow.com:
> >>> From: Pierre-Anthony Lemieux <pal@palemieux.com>
> >>>
> >>> As discussed at https://trac.ffmpeg.org/ticket/9818, the IMF demuxer does not
> >>> currently preserve stream information such as language in the case of audio
> >>> streams. This patch is modeled on copy_stream_props() at avformat/concatdec.c.
> >>>
> >>> ---
> >>>  libavformat/imfdec.c | 5 +++++
> >>>  1 file changed, 5 insertions(+)
> >>>
> >>> diff --git a/libavformat/imfdec.c b/libavformat/imfdec.c
> >>> index 71dfb26958..7aa66a06bf 100644
> >>> --- a/libavformat/imfdec.c
> >>> +++ b/libavformat/imfdec.c
> >>> @@ -580,11 +580,16 @@ static int set_context_streams_from_tracks(AVFormatContext *s)
> >>>              return AVERROR(ENOMEM);
> >>>          }
> >>>          asset_stream->id = i;
> >>> +        asset_stream->r_frame_rate = first_resource_stream->r_frame_rate;
> >>> +        asset_stream->avg_frame_rate = first_resource_stream->avg_frame_rate;
> >>> +        asset_stream->sample_aspect_ratio = first_resource_stream->sample_aspect_ratio;
> >>>          ret = avcodec_parameters_copy(asset_stream->codecpar, first_resource_stream->codecpar);
> >>>          if (ret < 0) {
> >>>              av_log(s, AV_LOG_ERROR, "Could not copy stream parameters\n");
> >>>              return ret;
> >>>          }
> >>> +        av_dict_copy(&asset_stream->metadata, first_resource_stream->metadata, 0);
> >>> +        ff_stream_side_data_copy(asset_stream, first_resource_stream);
> >>>          avpriv_set_pts_info(asset_stream,
> >>>                              first_resource_stream->pts_wrap_bits,
> >>>                              first_resource_stream->time_base.num,
> >>
> >> Seems to me like one should use ff_stream_encode_params_copy here. Of
> >> course, it would have to be renamed and moved if used in a demuxer.
> >
> > Would copy_stream_props() in concatdec.c need to be refactored as well?
> >
>
> I often wondered about this. The problem with copy_stream_props is that
> it is not only called during read_header, but lateron as well, but e.g.
> the documentation of AVStream.side_data says that it is populated when
> the stream is created and not later.
> This issue does of course not exist in your case.

ff_stream_encode_params_copy() does not seem to set pts_wrap_bits,
i.e. it does not call avpriv_set_pts_info().

>
> > Note that, in the case of avformat/imfdec.c, AVStream::id is not
> > copied across, so ff_stream_encode_params_copy() would need to be
> > followed by asset_stream->id = i;
> >
>
> Yeah, I know.
>
> - Andreas
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