On 18-06-2019 02:00 PM, Alfred E. Heggestad wrote:
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.
It may be best to check the commits for these assignments to see if the
inconsistency is deliberate.
The track duration is written into the media header box for the track. I
also see it being used elsewhere to adjust dts. Do those roles remain
intact?
Does FATE pass?
Gyan
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.
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