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Code Issues Releases Activity

avformat/movenc: Fix flush fragment

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The follow cmd output corrupted file before the patch:

ffmpeg -f lavfi -i color=blue,trim=duration=0.04 \
	-f lavfi -i anullsrc,atrim=duration=2 \
	-movflags +empty_moov+hybrid_fragmented \
	-frag_duration 1000000 \
	-frag_interleave 1 \
	output.mp4

1. first_track is the first track with track->entry != 0. As in the
command above, video track (track index 0) has a single frame. When
flush the second fragment, first_track is 1, the audio track.

2. write_moof = i == first_track, so write_moof is false for i = 0.

3. When mov->frag_interleave != 0, mov->mdat_buf != NULL, because
it contains audio data. So avio_write is called before write_moof,
that is, the data write before moof, and mov_finish_fragment
executed with wrong mdat_start.

4. With normal fmp4 output, the error isn't obvious. With
hybrid_fragmented, ffplay output.mp4 shows a lot of error messages.

Signed-off-by: Zhao Zhili <zhilizhao@tencent.com>
This commit is contained in:
Zhao Zhili
2025-05-22 17:37:05 +08:00
parent 3d9b284ad1
commit 56cf1c084d
2 changed files with 7 additions and 2 deletions
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4
libavformat/movenc.c
View File

@ -6509,9 +6509,9 @@ static int mov_flush_fragment(AVFormatContext *s, int force)
int buf_size, write_moof = 1, moof_tracks = -1;
uint8_t *buf;
if (!track->entry)
continue;
if (mov->flags & FF_MOV_FLAG_SEPARATE_MOOF) {
if (!track->entry)
continue;
mdat_size = avio_tell(track->mdat_buf);
moof_tracks = i;
} else {

5
tests/fate/mov.mak
View File

@ -84,6 +84,11 @@ fate-mov-ibi-elst-starts-b: CMD = framemd5 -flags +bitexact -i $(TARGET_SAMPLES)
# Makes sure that we handle overlapping framgments
fate-mov-frag-overlap: CMD = framemd5 -i $(TARGET_SAMPLES)/mov/frag_overlap.mp4
fate-mov-mp4-frag-flush: CMD = md5 -f lavfi -i color=blue,format=rgb24,trim=duration=0.04 -f lavfi -i anullsrc,aformat=s16,atrim=duration=2 -c:v png -c:a pcm_s16le -movflags +empty_moov+hybrid_fragmented -frag_duration 1000000 -frag_interleave 1 -f mp4
fate-mov-mp4-frag-flush: CMP = oneline
fate-mov-mp4-frag-flush: REF = a10c0e2e2dfc120f31ca5e59e0e4392a
FATE_MOV-$(call ALLYES, LAVFI_INDEV, COLOR_FILTER, FORMAT_FILTER, TRIM_FILTER, ANULL_FILTER, AFORMAT_FILTER, ATRIM_FILTER, PNG_ENCODER, PCM_S16LE_ENCODER, MOV_MUXER) += fate-mov-mp4-frag-flush
# Makes sure that we pick the right frames according to edit list when there is no keyframe with PTS < edit list start.
# For example, when video starts on a B-frame, and edit list starts on that B-frame too.
# GOP structure : B B I in presentation order.