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dashenc: Use pts for MPD timeline timestamps
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This should be more correct. This also should give more sensible
switching between video streams with different amount of b-frame
delay.

The current dash.js release (1.2.0) fails to start playback of
such files from the start (if the start pts is > 0), but this has
been fixed in the current git version of dash.js.

Also enable the use of edit lists, so that streams in many cases
start at pts=0.

Signed-off-by: Martin Storsjö <[email protected]>
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@mstorsjo
mstorsjo committed Jan 2, 2015
1 parent c5e7ea1 commit 7a1a63e
Showing 1 changed file with 23 additions and 17 deletions.
40 changes: 23 additions & 17 deletions libavformat/dashenc.c
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Original file line number Diff line number Diff line change
Expand Up @@ -68,7 +68,7 @@ typedef struct OutputStream {
int init_range_length;
int nb_segments, segments_size, segment_index;
Segment **segments;
int64_t first_dts, start_dts, end_dts;
int64_t first_pts, start_pts, max_pts;
int bit_rate;
char bandwidth_str[64];

Expand Down Expand Up @@ -627,6 +627,7 @@ static int dash_write_header(AVFormatContext *s)
os->init_start_pos = 0;

av_dict_set(&opts, "movflags", "frag_custom+dash+delay_moov", 0);
av_dict_set(&opts, "use_editlist", "1", 0);
if ((ret = avformat_write_header(ctx, &opts)) < 0) {
goto fail;
}
Expand All @@ -647,8 +648,8 @@ static int dash_write_header(AVFormatContext *s)
c->has_audio = 1;

set_codec_str(s, os->ctx->streams[0]->codec, os->codec_str, sizeof(os->codec_str));
os->first_dts = AV_NOPTS_VALUE;
os->end_dts = AV_NOPTS_VALUE;
os->first_pts = AV_NOPTS_VALUE;
os->max_pts = AV_NOPTS_VALUE;
os->segment_index = 1;
}

Expand Down Expand Up @@ -687,6 +688,8 @@ static int add_segment(OutputStream *os, const char *file,
return AVERROR(ENOMEM);
av_strlcpy(seg->file, file, sizeof(seg->file));
seg->time = time;
if (seg->time < 0) // If pts<0, it is expected to be cut away with an edit list
seg->time = 0;
seg->duration = duration;
seg->start_pos = start_pos;
seg->range_length = range_length;
Expand Down Expand Up @@ -770,7 +773,7 @@ static int dash_flush(AVFormatContext *s, int final, int stream)
start_pos = avio_tell(os->ctx->pb);

if (!c->single_file) {
dash_fill_tmpl_params(filename, sizeof(filename), c->media_seg_name, i, os->segment_index, os->bit_rate, os->start_dts);
dash_fill_tmpl_params(filename, sizeof(filename), c->media_seg_name, i, os->segment_index, os->bit_rate, os->start_pts);
snprintf(full_path, sizeof(full_path), "%s%s", c->dirname, filename);
snprintf(temp_path, sizeof(temp_path), "%s.tmp", full_path);
ret = ffurl_open(&os->out, temp_path, AVIO_FLAG_WRITE, &s->interrupt_callback, NULL);
Expand All @@ -795,7 +798,7 @@ static int dash_flush(AVFormatContext *s, int final, int stream)
if (ret < 0)
break;
}
add_segment(os, filename, os->start_dts, os->end_dts - os->start_dts, start_pos, range_length, index_length);
add_segment(os, filename, os->start_pts, os->max_pts - os->start_pts, start_pos, range_length, index_length);
av_log(s, AV_LOG_VERBOSE, "Representation %d media segment %d written to: %s\n", i, os->segment_index, full_path);
}

Expand Down Expand Up @@ -834,25 +837,25 @@ static int dash_write_packet(AVFormatContext *s, AVPacket *pkt)

// If forcing the stream to start at 0, the mp4 muxer will set the start
// timestamps to 0. Do the same here, to avoid mismatches in duration/timestamps.
if (os->first_dts == AV_NOPTS_VALUE &&
if (os->first_pts == AV_NOPTS_VALUE &&
s->avoid_negative_ts == AVFMT_AVOID_NEG_TS_MAKE_ZERO) {
pkt->pts -= pkt->dts;
pkt->dts = 0;
}

if (os->first_dts == AV_NOPTS_VALUE)
os->first_dts = pkt->dts;
if (os->first_pts == AV_NOPTS_VALUE)
os->first_pts = pkt->pts;

if ((!c->has_video || st->codec->codec_type == AVMEDIA_TYPE_VIDEO) &&
pkt->flags & AV_PKT_FLAG_KEY && os->packets_written &&
av_compare_ts(pkt->dts - os->first_dts, st->time_base,
av_compare_ts(pkt->pts - os->first_pts, st->time_base,
seg_end_duration, AV_TIME_BASE_Q) >= 0) {
int64_t prev_duration = c->last_duration;

c->last_duration = av_rescale_q(pkt->dts - os->start_dts,
c->last_duration = av_rescale_q(pkt->pts - os->start_pts,
st->time_base,
AV_TIME_BASE_Q);
c->total_duration = av_rescale_q(pkt->dts - os->first_dts,
c->total_duration = av_rescale_q(pkt->pts - os->first_pts,
st->time_base,
AV_TIME_BASE_Q);

Expand All @@ -873,12 +876,15 @@ static int dash_write_packet(AVFormatContext *s, AVPacket *pkt)
// If we wrote a previous segment, adjust the start time of the segment
// to the end of the previous one (which is the same as the mp4 muxer
// does). This avoids gaps in the timeline.
if (os->end_dts != AV_NOPTS_VALUE)
os->start_dts = os->end_dts;
if (os->max_pts != AV_NOPTS_VALUE)
os->start_pts = os->max_pts;
else
os->start_dts = pkt->dts;
os->start_pts = pkt->pts;
}
os->end_dts = pkt->dts + pkt->duration;
if (os->max_pts == AV_NOPTS_VALUE)
os->max_pts = pkt->pts + pkt->duration;
else
os->max_pts = FFMAX(os->max_pts, pkt->pts + pkt->duration);
os->packets_written++;
return ff_write_chained(os->ctx, 0, pkt, s);
}
Expand All @@ -892,10 +898,10 @@ static int dash_write_trailer(AVFormatContext *s)
// If no segments have been written so far, try to do a crude
// guess of the segment duration
if (!c->last_duration)
c->last_duration = av_rescale_q(os->end_dts - os->start_dts,
c->last_duration = av_rescale_q(os->max_pts - os->start_pts,
s->streams[0]->time_base,
AV_TIME_BASE_Q);
c->total_duration = av_rescale_q(os->end_dts - os->first_dts,
c->total_duration = av_rescale_q(os->max_pts - os->first_pts,
s->streams[0]->time_base,
AV_TIME_BASE_Q);
}
Expand Down

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