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

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

On Sun, Jul 3, 2022 at 2:13 PM Andreas Rheinhardt
<andreas.rheinhardt@outlook.com> wrote:
>
> Pierre-Anthony Lemieux:
> > 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().
> >
>
> The reason for this is that pts_wrap_bits is irrelevant for muxing.

Do you have in mind:

(a) a single av_stream_params_copy(), which copies all parameters
(b) two separate functions av_stream_demux_params_copy() and
av_stream_mux_params_copy(), which copies only relevant parameters?
(c) something else?

In the case of (b), should both be defined now, or only
av_stream_demux_params_copy() be implemented now since avformat/imfdec
would only use av_stream_demux_params_copy()?

I have not seen anyone else chime in.

>
> >>
> >>> 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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