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mov: fix DTS calculation for samples with negative stts duration 

A negative sample duration is invalid according to the spec, but there
are samples that use it for the DTS calculation, e.g.:
http://files.1f0.de/samples/mp4-negative-stts-problem.mp4

These currently get out of A/V sync.

Also change the logging type to AV_LOG_WARNING, because decoding the
sample can continue.

Reviewed-by: Michael Niedermayer <michaelni@gmx.at>
Signed-off-by: Andreas Cadhalpun <Andreas.Cadhalpun@googlemail.com>
This commit is contained in:
Andreas Cadhalpun 2015-05-27 23:57:50 +02:00
parent 403940de24
commit 153639cb9c
1 changed files with 23 additions and 6 deletions
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29
libavformat/mov.c
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@ -2234,12 +2234,6 @@ static int mov_read_stts(MOVContext *c, AVIOContext *pb, MOVAtom atom)
sample_count=avio_rb32(pb);
sample_duration = avio_rb32(pb);
/* sample_duration < 0 is invalid based on the spec */
if (sample_duration < 0) {
av_log(c->fc, AV_LOG_ERROR, "Invalid SampleDelta %d in STTS, at %d st:%d\n",
sample_duration, i, c->fc->nb_streams-1);
sample_duration = 1;
}
if (sample_count < 0) {
av_log(c->fc, AV_LOG_ERROR, "Invalid sample_count=%d\n", sample_count);
return AVERROR_INVALIDDATA;
@ -2439,10 +2433,13 @@ static void mov_build_index(MOVContext *mov, AVStream *st)
unsigned int distance = 0;
unsigned int rap_group_index = 0;
unsigned int rap_group_sample = 0;
int64_t last_dts = 0;
int64_t dts_correction = 0;
int rap_group_present = sc->rap_group_count && sc->rap_group;
int key_off = (sc->keyframe_count && sc->keyframes[0] > 0) || (sc->stps_count && sc->stps_data[0] > 0);
current_dts -= sc->dts_shift;
last_dts = current_dts;
if (!sc->sample_count || st->nb_index_entries)
return;
@ -2522,7 +2519,27 @@ static void mov_build_index(MOVContext *mov, AVStream *st)
current_offset += sample_size;
stream_size += sample_size;
/* A negative sample duration is invalid based on the spec,
* but some samples need it to correct the DTS. */
if (sc->stts_data[stts_index].duration < 0) {
av_log(mov->fc, AV_LOG_WARNING,
"Invalid SampleDelta %d in STTS, at %d st:%d\n",
sc->stts_data[stts_index].duration, stts_index,
st->index);
dts_correction += sc->stts_data[stts_index].duration - 1;
sc->stts_data[stts_index].duration = 1;
}
current_dts += sc->stts_data[stts_index].duration;
if (!dts_correction || current_dts + dts_correction > last_dts) {
current_dts += dts_correction;
dts_correction = 0;
} else {
/* Avoid creating non-monotonous DTS */
dts_correction += current_dts - last_dts - 1;
current_dts = last_dts + 1;
}
last_dts = current_dts;
distance++;
stts_sample++;
current_sample++;