On 17/06/2019 10:23, Gyan wrote:
On 17-06-2019 01:37 PM, Alfred E. Heggestad wrote:
From c69b63a7af5531257753754e64ac33b7ef530e75 Mon Sep 17 00:00:00 2001
From: "Alfred E. Heggestad" <alfred.hegges...@gmail.com>
Date: Mon, 17 Jun 2019 10:04:08 +0200
Subject: [PATCH] movenc: calculate track_duration without packet duration
---
libavformat/movenc.c | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)
diff --git a/libavformat/movenc.c b/libavformat/movenc.c
index 46d314ff17..fa5833962b 100644
--- a/libavformat/movenc.c
+++ b/libavformat/movenc.c
@@ -5486,7 +5486,7 @@ int ff_mov_write_packet(AVFormatContext *s,
AVPacket *pkt)
"this case.\n",
pkt->stream_index, pkt->dts);
}
- trk->track_duration = pkt->dts - trk->start_dts + pkt->duration;
+ trk->track_duration = pkt->dts - trk->start_dts;
Why?
trk->last_sample_is_subtitle_end = 0;
if (pkt->pts == AV_NOPTS_VALUE) {
the background for this change is the check done in check_pkt():
if (trk->entry) {
ref = trk->cluster[trk->entry - 1].dts;
} else if ( trk->start_dts != AV_NOPTS_VALUE
&& !trk->frag_discont) {
ref = trk->start_dts + trk->track_duration;
} else
ref = pkt->dts; // Skip tests for the first packet
if (trk->dts_shift != AV_NOPTS_VALUE) {
/* With negative CTS offsets we have set an offset to the DTS,
* reverse this for the check. */
ref -= trk->dts_shift;
}
duration = pkt->dts - ref;
if (pkt->dts < ref || duration >= INT_MAX) {
av_log(s, AV_LOG_ERROR, "Application provided duration:
%"PRId64" / timestamp: %"PRId64" is out of range for mov/mp4 format\n",
duration, pkt->dts
);
pkt->dts = ref + 1;
pkt->pts = AV_NOPTS_VALUE;
}
it requires that the DTS of the packet is larger than
"ref" which in some cases is equal to track_duration.
line 5015:
track->track_duration = pkt.dts - track->start_dts;
line 5489:
trk->track_duration = pkt->dts - trk->start_dts + pkt->duration;
line 5615:
trk->track_duration = pkt->dts - trk->start_dts;
setting track_duration is inconsistent; some times it includes
duration and some times not.
here is an example with a stream of AVPacket's that increment
the DTS by approx. 10 (and duration is set to 0):
pkt: dts:
1 0
2 10
3 20
4 30
5 40
6 50
after packet 6 has arrived, the "ref" value in check_pkt will now
be calculated to 50 + 10 = 60. the code assumes a duration of 10.
when packet 7 arrives it has a DTS of 59 (which is valid).
but this packet will fail in check_pkt and print a warning,
because 59 < 60.
/alfred
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