Re: [FFmpeg-devel] [PATCH v3] avformat/mov: discard data streams with all zero sample_delta

["\"zhilizhao(赵志立)\"" <quinkblack@foxmail.com>]

> On Jul 6, 2022, at 3:05 PM, Zhao Zhili <quinkblack@foxmail.com> wrote:
> 
> From: Zhao Zhili <zhilizhao@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@tencent.com>
> ---
> v3: 'for ffmpeg' -> 'for ffmpeg command.'
> v2: suggest how to override discard flag in log message.
> libavformat/mov.c | 15 +++++++++++++++
> 1 file changed, 15 insertions(+)
> 
> diff --git a/libavformat/mov.c b/libavformat/mov.c
> index 88669faa70..9a24e5effa 100644
> --- a/libavformat/mov.c
> +++ b/libavformat/mov.c
> @@ -3062,6 +3062,21 @@ 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, stream set to be discarded by default. Override "
> +               "using AVStream->discard or -discard for ffmpeg command.\n",
> +               st->index, st->id);
> +        st->discard = AVDISCARD_ALL;
> +    }
>     sc->track_end = duration;
>     return 0;
> }

Will apply tomorrow if no more comments.

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