[FFmpeg-devel] [PATCH] avformat/mov: discard data streams with all zero sample_delta

[Gyan Doshi]

On 2022-07-05 01:20 pm, Zhao Zhili wrote:
> From: Zhao Zhili <zhilizhao at tencent.com>
>
> Streams with all zero sample_delta in 'stts' have all zero dts.
> They have higher chance be chose by mov_find_next_sample(), which
> leads to seek again and again.
>
> For example, GoPro created a 'GoPro SOS' stream:
>    Stream #0:4[0x5](eng): Data: none (fdsc / 0x63736466), 13 kb/s (default)
>      Metadata:
>        creation_time   : 2022-06-21T08:49:19.000000Z
>        handler_name    : GoPro SOS
>
> With 'ffprobe -show_frames http://example.com/gopro.mp4', ffprobe
> blocks until all samples in 'GoPro SOS' stream are consumed first.
>
> Signed-off-by: Zhao Zhili <zhilizhao at tencent.com>
> ---
>   libavformat/mov.c | 14 ++++++++++++++
>   1 file changed, 14 insertions(+)
>
> diff --git a/libavformat/mov.c b/libavformat/mov.c
> index 88669faa70..2a4eb79f27 100644
> --- a/libavformat/mov.c
> +++ b/libavformat/mov.c
> @@ -3062,6 +3062,20 @@ static int mov_read_stts(MOVContext *c, AVIOContext *pb, MOVAtom atom)
>       st->nb_frames= total_sample_count;
>       if (duration)
>           st->duration= FFMIN(st->duration, duration);
> +
> +    // All samples have zero duration. They have higher chance be chose by
> +    // mov_find_next_sample, which leads to seek again and again.
> +    //
> +    // It's AVERROR_INVALIDDATA actually, but such files exist in the wild.
> +    // So only mark data stream as discarded for safety.
> +    if (!duration && sc->stts_count &&
> +            st->codecpar->codec_type == AVMEDIA_TYPE_DATA) {
> +        av_log(c->fc, AV_LOG_WARNING,
> +               "All samples in data stream index:id [%d:%d] have zero duration, "
> +               "discard the stream\n",
> +               st->index, st->id);
> +        st->discard = AVDISCARD_ALL;
> +    }
>       sc->track_end = duration;
>       return 0;
>   }

So this will allow audio and video streams to be demuxed, but not data?  
That distinction seems arbitrary.

Print a warning and assign a duration to each sample. Either 1 or if not 
zero/Inf, st->duration/st->nb_frames.

Regards,
Gyan