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avformat/dashenc: add an option to enable low latency Dash manifest 

In combination with the streaming option it constrains the value of a few elements,
to prevet clients from buffering too much data before starting presentation.

Signed-off-by: James Almer <jamrial@gmail.com>
This commit is contained in:
James Almer 2019-10-04 12:54:55 -03:00
parent 7e5d143bb5
commit 21847e2a52
1 changed files with 30 additions and 2 deletions
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32
libavformat/dashenc.c
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@ -86,6 +86,7 @@ typedef struct AdaptationSet {
AVDictionary *metadata;
AVRational min_frame_rate, max_frame_rate;
int ambiguous_frame_rate;
int64_t max_frag_duration;
} AdaptationSet;
typedef struct OutputStream {
@ -126,6 +127,7 @@ typedef struct OutputStream {
int64_t total_pkt_duration;
int muxer_overhead;
int frag_type;
int64_t gop_size;
} OutputStream;
typedef struct DASHContext {
@ -171,11 +173,13 @@ typedef struct DASHContext {
SegmentType segment_type_option; /* segment type as specified in options */
int ignore_io_errors;
int lhls;
int ldash;
int master_publish_rate;
int nr_of_streams_to_flush;
int nr_of_streams_flushed;
int frag_type;
int write_prft;
int64_t max_gop_size;
} DASHContext;
static struct codec_string {
@ -646,6 +650,10 @@ static void output_segment_list(OutputStream *os, AVIOContext *out, AVFormatCont
avio_printf(out, "availabilityTimeOffset=\"%.3f\" ",
os->availability_time_offset);
}
if (c->ldash && !final && os->frag_type != FRAG_TYPE_NONE &&
(os->frag_type != FRAG_TYPE_DURATION || os->frag_duration != os->seg_duration))
avio_printf(out, "availabilityTimeComplete=\"false\" ");
avio_printf(out, "initialization=\"%s\" media=\"%s\" startNumber=\"%d\"", os->init_seg_name, os->media_seg_name, c->use_timeline ? start_number : 1);
if (c->presentation_time_offset)
avio_printf(out, " presentationTimeOffset=\"%"PRId64"\"", c->presentation_time_offset);
@ -793,6 +801,8 @@ static int write_adaptation_set(AVFormatContext *s, AVIOContext *out, int as_ind
avio_printf(out, " lang=\"%s\"", lang->value);
avio_printf(out, ">\n");
if (!final && c->ldash && as->max_frag_duration)
avio_printf(out, "\t\t\t<Resync dT=\"%"PRId64"\" type=\"0\"/>\n", as->max_frag_duration);
role = av_dict_get(as->metadata, "role", NULL, 0);
if (role)
avio_printf(out, "\t\t\t<Role schemeIdUri=\"urn:mpeg:dash:role:2011\" value=\"%s\"/>\n", role->value);
@ -828,6 +838,9 @@ static int write_adaptation_set(AVFormatContext *s, AVIOContext *out, int as_ind
avio_printf(out, "\t\t\t\t\t<UTCTiming schemeIdUri=\"urn:mpeg:dash:utc:http-xsdate:2014\" value=\"%s\"/>\n", c->utc_timing_url);
avio_printf(out, "\t\t\t\t</ProducerReferenceTime>\n");
}
if (!final && c->ldash && os->gop_size && os->frag_type != FRAG_TYPE_NONE &&
(os->frag_type != FRAG_TYPE_DURATION || os->frag_duration != os->seg_duration))
avio_printf(out, "\t\t\t\t<Resync dT=\"%"PRId64"\" type=\"1\"/>\n", os->gop_size);
output_segment_list(os, out, s, i, final);
avio_printf(out, "\t\t\t</Representation>\n");
}
@ -1076,7 +1089,8 @@ static int write_manifest(AVFormatContext *s, int final)
if (c->use_template && !c->use_timeline)
update_period = 500;
avio_printf(out, "\tminimumUpdatePeriod=\"PT%"PRId64"S\"\n", update_period);
avio_printf(out, "\tsuggestedPresentationDelay=\"PT%"PRId64"S\"\n", c->last_duration / AV_TIME_BASE);
if (!c->ldash)
avio_printf(out, "\tsuggestedPresentationDelay=\"PT%"PRId64"S\"\n", c->last_duration / AV_TIME_BASE);
if (c->availability_start_time[0])
avio_printf(out, "\tavailabilityStartTime=\"%s\"\n", c->availability_start_time);
format_date(now_str, sizeof(now_str), av_gettime());
@ -1089,7 +1103,7 @@ static int write_manifest(AVFormatContext *s, int final)
}
}
avio_printf(out, "\tminBufferTime=\"");
write_time(out, c->last_duration * 2);
write_time(out, c->ldash && c->max_gop_size ? c->max_gop_size : c->last_duration * 2);
avio_printf(out, "\">\n");
avio_printf(out, "\t<ProgramInformation>\n");
if (title) {
@ -1257,6 +1271,11 @@ static int dash_init(AVFormatContext *s)
c->lhls = 0;
}
if (c->ldash && !c->streaming) {
av_log(s, AV_LOG_WARNING, "LDash option will be ignored as streaming is not enabled\n");
c->ldash = 0;
}
if (c->global_sidx && !c->single_file) {
av_log(s, AV_LOG_WARNING, "Global SIDX option will be ignored as single_file is not enabled\n");
c->global_sidx = 0;
@ -1848,6 +1867,7 @@ 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];
AdaptationSet *as = &c->as[os->as_idx - 1];
int64_t seg_end_duration, elapsed_duration;
int ret;
@ -1909,6 +1929,7 @@ static int dash_write_packet(AVFormatContext *s, AVPacket *pkt)
os->availability_time_offset = ((double) os->seg_duration -
frame_duration) / AV_TIME_BASE;
as->max_frag_duration = FFMAX(frame_duration, as->max_frag_duration);
}
if (c->use_template && !c->use_timeline) {
@ -1987,10 +2008,16 @@ static int dash_write_packet(AVFormatContext *s, AVPacket *pkt)
AV_TIME_BASE_Q);
os->availability_time_offset = ((double) os->seg_duration -
frag_duration) / AV_TIME_BASE;
as->max_frag_duration = FFMAX(frag_duration, as->max_frag_duration);
}
}
}
if (pkt->flags & AV_PKT_FLAG_KEY && (os->packets_written || os->nb_segments) && !os->gop_size) {
os->gop_size = os->last_duration + av_rescale_q(os->total_pkt_duration, st->time_base, AV_TIME_BASE_Q);
c->max_gop_size = FFMAX(c->max_gop_size, os->gop_size);
}
if ((ret = ff_write_chained(os->ctx, 0, pkt, s, 0)) < 0)
return ret;
@ -2149,6 +2176,7 @@ static const AVOption options[] = {
{ "webm", "make segment file in WebM format", 0, AV_OPT_TYPE_CONST, {.i64 = SEGMENT_TYPE_WEBM }, 0, UINT_MAX, E, "segment_type"},
{ "ignore_io_errors", "Ignore IO errors during open and write. Useful for long-duration runs with network output", OFFSET(ignore_io_errors), AV_OPT_TYPE_BOOL, { .i64 = 0 }, 0, 1, E },
{ "lhls", "Enable Low-latency HLS(Experimental). Adds #EXT-X-PREFETCH tag with current segment's URI", OFFSET(lhls), AV_OPT_TYPE_BOOL, { .i64 = 0 }, 0, 1, E },
{ "ldash", "Enable Low-latency dash. Constrains the value of a few elements", OFFSET(ldash), AV_OPT_TYPE_BOOL, { .i64 = 0 }, 0, 1, E },
{ "master_m3u8_publish_rate", "Publish master playlist every after this many segment intervals", OFFSET(master_publish_rate), AV_OPT_TYPE_INT, {.i64 = 0}, 0, UINT_MAX, E},
{ "write_prft", "Write producer reference time element", OFFSET(write_prft), AV_OPT_TYPE_BOOL, {.i64 = 0}, 0, 1, E},
{ NULL },