avformat/mov: don't read duration from mvhd atom

This duration is equal to the longest duration in all track's tkhd atoms, which
may be comprised of the sum of all edit lists in each track. Empty edit lists
in tracks represent start_time, and the actual media duration is stored in the
mdhd atom.
This change lets the generic demux code derive the longest track duration taken
from mdhd atoms, so the correct duration and start_time combination will be
reported.

Should fix ticket #9775.

Reviewed-by: zhilizhao(赵志立) <quinkblack@foxmail.com>
Signed-off-by: James Almer <jamrial@gmail.com>

libavformat/mov.c

@@ -1520,10 +1520,6 @@ static int mov_read_mvhd(MOVContext *c, AVIOContext *pb, MOVAtom atom)
     av_log(c->fc, AV_LOG_TRACE, "time scale = %i\n", c->time_scale);
 
     c->duration = (version == 1) ? avio_rb64(pb) : avio_rb32(pb); /* duration */
-    // set the AVFormatContext duration because the duration of individual tracks
-    // may be inaccurate
-    if (!c->trex_data)
-        c->fc->duration = av_rescale(c->duration, AV_TIME_BASE, c->time_scale);
     avio_rb32(pb); /* preferred scale */
 
     avio_rb16(pb); /* preferred volume */

tests/ref/fate/gaplessenc-itunes-to-ipod-aac

@@ -5,7 +5,7 @@ duration_ts=103326
 [/STREAM]
 [FORMAT]
 start_time=0.000000
-duration=2.344000
+duration=2.342993
 [/FORMAT]
 packet|pts=-1024|dts=-1024|duration=1024|flags=KD|side_data|