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

[Zhao Zhili]

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>
---
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;
 }
-- 
2.35.3