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

[Andreas Rheinhardt]

Pierre-Anthony Lemieux:
> On Sun, Jul 3, 2022 at 11:28 AM Andreas Rheinhardt
> <andreas.rheinhardt at outlook.com> wrote:
>>
>> pal at sandflow.com:
>>> From: Pierre-Anthony Lemieux <pal at 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.

> 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