On 2022-07-06 10:54 am, "zhilizhao(赵志立)" wrote:
On Jul 6, 2022, at 12:09 PM, Gyan Doshi <ffm...@gyani.pro> wrote:
On 2022-07-06 08:23 am, "zhilizhao(赵志立)" wrote:
On Jul 5, 2022, at 10:33 PM, Gyan Doshi <ffm...@gyani.pro> wrote:
On 2022-07-05 07:05 pm, "zhilizhao(赵志立)" wrote:
On Jul 5, 2022, at 8:07 PM, Gyan Doshi <ffm...@gyani.pro> wrote:
On 2022-07-05 01:20 pm, Zhao Zhili wrote:
From: Zhao Zhili <zhiliz...@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 <zhiliz...@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.
Disable audio/video streams may create regression. It’s unlikely for random
and broken data stream.
Print a warning and assign a duration to each sample. Either 1 or if not zero/Inf,
st->duration/st->nb_frames.
Set sample_duration to 1 doesn’t work. Dts still far behind other streams.
Set sample_duration st->duration/st->nb_frames works for me, but I prefer
current strategy for the following reasons:
1. AVDISCARD_ALL is more close to AVERROR_INVALIDDATA by giving up instead
of trying correction and hope it works, which may not, e.g., st->duration
is broken, or bad interleave even though we fixed sample_duration.
It's not about hoping that it works. It's about not preventing the user from
acquiring the stream payload.
Can you test if setting -discard:d none -i INPUT allows reading the stream with
your patch?
Yes it does allow reading the stream. ’stts’ box is parsed during
avformat_find_stream_info(), AVStream->discard flag can be modified
after that. The patch has no effect if user changed AVStream->discard
flag.
What's the duration of the demuxed stream?
The demuxed data track has correct duration since there is a check
```
if (duration)
st->duration= FFMIN(st->duration, duration);
```
st->duration comes from ‘mdhd’ and not overwrite in this case.
Every packet has zero as timestamp, as expected:
./ffmpeg -debug_ts -discard:d none -i ~/tmp/gopro.mp4 -map 0:4 -c copy
-copy_unknown -f data /tmp/test
demuxer -> ist_index:4 type:data next_dts:0 next_dts_time:0 next_pts:0
next_pts_time:0 pkt_pts:0 pkt_pts_time:0 pkt_dts:0 pkt_dts_time:0 duration:0
duration_time:0 off:0 off_time:0
demuxer+ffmpeg -> ist_index:4 type:data pkt_pts:0 pkt_pts_time:0 pkt_dts:0
pkt_dts_time:0 duration:0 duration_time:0 off:0 off_time:0
muxer <- type:data pkt_pts:0 pkt_pts_time:0 pkt_dts:0 pkt_dts_time:0 duration:0
duration_time:0 size:16
Ok, change the log from
"discard the stream"
to
"stream set to be discarded. Override using -discard or AVStream->discard"
Regards,
Gyan
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