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[FFmpeg-devel,v2,05/11] avformat/dashenc: setting @availabilityStartTime when the first frame is ready

Message ID 1522831048-7163-1-git-send-email-vdixit@akamai.com
State Superseded
Headers show

Commit Message

Dixit, Vishwanath April 4, 2018, 8:37 a.m. UTC 
From: Vishwanath Dixit <vdixit@akamai.com>

@availabilityStartTime specifies the anchor for the computation of the earliest
availability time (in UTC) for any Segment in the Media Presentation.

As per this requirement, the @AvailabilityStartTime should be set to the
wallclock time at which the first frame of the first segment begins encoding.
But, it was getting set only when the first segment was completely ready. Making
the required correction in this patch. This correction is mainly needed to reduce
the latency in live streaming use cases.
---
 libavformat/dashenc.c | 7 ++++---
 1 file changed, 4 insertions(+), 3 deletions(-)
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Patch

diff --git a/libavformat/dashenc.c b/libavformat/dashenc.c
index 1bac2c9..9e7a374 100644
--- a/libavformat/dashenc.c
+++ b/libavformat/dashenc.c
@@ -741,9 +741,6 @@  static int write_manifest(AVFormatContext *s, int final)
             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->availability_start_time[0] && s->nb_streams > 0 && c->streams[0].nb_segments > 0) {
-            format_date_now(c->availability_start_time, sizeof(c->availability_start_time));
-        }
         if (c->availability_start_time[0])
             avio_printf(out, "\tavailabilityStartTime=\"%s\"\n", c->availability_start_time);
         format_date_now(now_str, sizeof(now_str));
@@ -1288,6 +1285,10 @@  static int dash_write_packet(AVFormatContext *s, AVPacket *pkt)
     if (os->first_pts == AV_NOPTS_VALUE)
         os->first_pts = pkt->pts;
 
+    if (!c->availability_start_time[0])
+        format_date_now(c->availability_start_time,
+                        sizeof(c->availability_start_time));
+
     if (c->use_template && !c->use_timeline) {
         elapsed_duration = pkt->pts - os->first_pts;
         seg_end_duration = (int64_t) os->segment_index * c->seg_duration;