Currently skip_samples is set to start_pad if sample_time is lesser or
equal to 0. This can cause issues if the stream starts with packets that
have negative pts. Calling avformat_seek_file() with ts set to 0 on such
streams makes the mov demuxer return the right corresponding packets
(near the 0 timestamp) but set skip_samples to start_pad which is
incorrect as the audio decoder will discard the returned samples
according to skip_samples from the first packet it receives (which has
its timestamp near 0).
For example, considering the following audio stream with start_pad=1344:
[PKT pts=-1344] [PKT pts=-320] [PKT pts=704] [PKT pts=1728] [...]
Calling avformat_seek_file() with ts=0 makes the next call to
av_read_frame() return the packet with pts=-320 and a skip samples
side data set to 1344 (start_pad). This makes the audio decoder
incorrectly discard (1344 - 320) samples.
This commit makes the move demuxer adjust skip_samples according to the
stream start_pad, seek timestamp and first sample timestamp.
The above example will now result in av_read_frame() still returning the
packet with pts=-320 but with a skip samples side data set to 320
(src_pad - (seek_timestamp - first_timestamp)). This makes the audio
decoder only discard 320 samples (from pts=-320 to pts=0).
---
libavformat/mov.c | 18 ++++++++++++++++--
1 file changed, 16 insertions(+), 2 deletions(-)
diff --git a/libavformat/mov.c b/libavformat/mov.c
index dd0db6bca79..f99cb0df25a 100644
--- a/libavformat/mov.c
+++ b/libavformat/mov.c
@@ -8098,20 +8098,34 @@ static int mov_read_seek(AVFormatContext *s, int
stream_index, int64_t sample_ti
return sample;
if (mc->seek_individually) {
+ MOVStreamContext *sc = s->streams[stream_index]->priv_data;
+
/* adjust seek timestamp to found sample timestamp */
+ int64_t first_timestamp = st->internal->index_entries[0].timestamp;
int64_t seek_timestamp = st->internal->index_entries[sample].timestamp;
+ /* adjust skip samples according to stream start_pad, seek timestamp
and first timestamp */
+ int64_t skip_samples = FFMAX(sc->start_pad - (seek_timestamp -
first_timestamp), 0);
+ st->internal->skip_samples = skip_samples;
+
for (i = 0; i < s->nb_streams; i++) {
int64_t timestamp;
MOVStreamContext *sc = s->streams[i]->priv_data;
st = s->streams[i];
- st->internal->skip_samples = (sample_time <= 0) ? sc->start_pad :
0;
if (stream_index == i)
continue;
timestamp = av_rescale_q(seek_timestamp,
s->streams[stream_index]->time_base, st->time_base);
- mov_seek_stream(s, st, timestamp, flags);
+ sample = mov_seek_stream(s, st, timestamp, flags);
+ if (sample >= 0) {
+ first_timestamp = st->internal->index_entries[0].timestamp;
+ seek_timestamp = st->internal->index_entries[sample].timestamp;
+
+ /* adjust skip samples according to stream start_pad, seek
timestamp and first timestamp */
+ skip_samples = FFMAX(sc->start_pad - (seek_timestamp -
first_timestamp), 0);
+ st->internal->skip_samples = skip_samples;
+ }
}
} else {
for (i = 0; i < s->nb_streams; i++) {
--
2.29.2
_______________________________________________
ffmpeg-devel mailing list
ffmpeg-devel@ffmpeg.org
https://ffmpeg.org/mailman/listinfo/ffmpeg-devel
To unsubscribe, visit link above, or email
ffmpeg-devel-requ...@ffmpeg.org with subject "unsubscribe".
