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ffmpeg
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dashenc: separate segments based on current segment duration 

The current implementation creates new segments comparing

  pkt->pts - first_pts > nb_segs * min_seg_duration

This works fine, but if the keyframe interval is smaller than "min_seg_duration"
segments shorter than the minimum segment duration are created.

Example: keyint=50, min_seg_duration=3000000
 segment 1 contains keyframe 1 (duration=2s <  total_duration=3s)
                and keyframe 2 (duration=4s >= total_duration=3s)
 segment 2 contains keyframe 3 (duration=6s >= total_duration=6s)
 segment 3 contains keyframe 4 (duration=8s <  total_duration=9s)
                and keyframe 5 (duration=10s >= total_duration=9s)
 ...

Segment 2 is only 2s long, shorter than min_seg_duration = 3s.

To fix this, new segments are created based on the actual written duration.
Otherwise the option name "min_seg_duration" is misleading.

Signed-off-by: Peter Große <pegro@friiks.de>
Signed-off-by: Martin Storsjö <martin@martin.st>
This commit is contained in:
Peter Große 2017-01-29 15:26:25 +01:00 committed by Martin Storsjö
parent 1920382aa9
commit e519dcd937
1 changed files with 2 additions and 3 deletions
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5
libavformat/dashenc.c
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@ -868,7 +868,6 @@ static int dash_write_packet(AVFormatContext *s, AVPacket *pkt)
DASHContext *c = s->priv_data;
AVStream *st = s->streams[pkt->stream_index];
OutputStream *os = &c->streams[pkt->stream_index];
int64_t seg_end_duration = (os->segment_index) * (int64_t) c->min_seg_duration;
int ret;
ret = update_stream_extradata(s, os, st->codecpar);
@ -898,8 +897,8 @@ static int dash_write_packet(AVFormatContext *s, AVPacket *pkt)
if ((!c->has_video || st->codecpar->codec_type == AVMEDIA_TYPE_VIDEO) &&
pkt->flags & AV_PKT_FLAG_KEY && os->packets_written &&
av_compare_ts(pkt->pts - os->first_pts, st->time_base,
seg_end_duration, AV_TIME_BASE_Q) >= 0) {
av_compare_ts(pkt->pts - os->start_pts, st->time_base,
c->min_seg_duration, AV_TIME_BASE_Q) >= 0) {
int64_t prev_duration = c->last_duration;
c->last_duration = av_rescale_q(pkt->pts - os->start_pts,