On 09/26/2017 05:12 PM, Michael Niedermayer wrote:
Hi
On Mon, Sep 25, 2017 at 02:12:26PM -0700, John Stebbins wrote:
On 09/25/2017 01:12 PM, Carl Eugen Hoyos wrote:
2017-09-25 19:10 GMT+02:00 John Stebbins <jstebb...@jetheaddev.com>:
When keyframe intervals of dash segments are not perfectly aligned,
fragments in the stream can overlap in time. Append new "trun" index
entries to the end of the index instead of sorting by timestamp.
Sorting by timestamp causes packets to be read out of decode order and
results in decode errors.
---
libavformat/mov.c | 4 ++--
1 file changed, 2 insertions(+), 2 deletions(-)
diff --git a/libavformat/mov.c b/libavformat/mov.c
index 2519707345..b2bc7c2c3d 100644
--- a/libavformat/mov.c
+++ b/libavformat/mov.c
@@ -4339,8 +4339,8 @@ static int mov_read_trun(MOVContext *c, AVIOContext *pb,
MOVAtom atom)
MOV_FRAG_SAMPLE_FLAG_DEPENDS_YES));
if (keyframe)
distance = 0;
- ctts_index = av_add_index_entry(st, offset, dts, sample_size, distance,
- keyframe ? AVINDEX_KEYFRAME : 0);
+ ctts_index = add_index_entry(st, offset, dts, sample_size, distance,
+ keyframe ? AVINDEX_KEYFRAME : 0);
I can confirm that this fixes playback with FFplay but it shows
many warnings (Non-monotonous DTS) with ffmpeg: Is this
unavoidable?
Fixing the non-monotonous DTS in ffmpeg would require more consideration. The
overlapping frames need to be dropped
somewhere after they are decoded and before they are presented.
I've given this some thought, but other ideas are certainly welcome. The
demuxer is probably the most appropriate place
for marking the frames as needing to be dropped since it has the "knowledge"
about why there are overlapping
timestamps. I.e. you only want to drop frames in this particular scenario and
not generally when timestamps go
backwards. I don't think there is currently any facility for marking frames to
be dropped after decoding, but it seems
like AVPacketSideData would be the appropriate mechanism for such marking.
FYI, such a facility for marking frames to
drop would also be useful for frame accurate playback of MP4 edit lists.
This sounds like:
/**
* Flag is used to discard packets which are required to maintain valid
* decoder state but are not required for output and should be dropped
* after decoding.
**/
#define AV_PKT_FLAG_DISCARD 0x0004
Oh, that's awesome. Thanks for pointing that out. There's even a sample
flag that can be set in the index which is the next thing I was
"worried" about. I'll follow up with a patch to fix the non-monotonous
DTS.
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