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avformat/movenc: implicitly enable negative CTS offsets for ismv

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ISMV lacks any sort of edit list support, as well as tfxd is
effectively the PTS of the fragment for most intents and purposes.

Thus, if b-frames are requested without negative CTS offsets you
end up with N frames' worth of delay (tfxd PTS plus the CTS offset
of the first sample). Negative CTS offsets enable the first sample
to have CTS=DTS, and thus a/v desync due to b-frame reorder delay
is avoided.
This commit is contained in:
Jan Ekström 2018-07-26 02:51:38 +03:00
parent 701aca55fd
commit 1931761f18
4 changed files with 8 additions and 6 deletions
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2
doc/muxers.texi
View File

@ -1344,6 +1344,8 @@ be negative. This enables the initial sample to have DTS/CTS of zero, and
reduces the need for edit lists for some cases such as video tracks with
B-frames. Additionally, eases conformance with the DASH-IF interoperability
guidelines.
This option is implicitly set when writing ismv (Smooth Streaming) files.
@item -write_prft
Write producer time reference box (PRFT) with a specified time source for the
NTP field in the PRFT box. Set value as @samp{wallclock} to specify timesource

2
libavformat/movenc.c
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@ -6046,7 +6046,7 @@ static int mov_init(AVFormatContext *s)
/* Set other implicit flags immediately */
if (mov->mode == MODE_ISM)
mov->flags |= FF_MOV_FLAG_EMPTY_MOOV | FF_MOV_FLAG_SEPARATE_MOOF |
FF_MOV_FLAG_FRAGMENT;
FF_MOV_FLAG_FRAGMENT | FF_MOV_FLAG_NEGATIVE_CTS_OFFSETS;
if (mov->flags & FF_MOV_FLAG_DASH)
mov->flags |= FF_MOV_FLAG_FRAGMENT | FF_MOV_FLAG_EMPTY_MOOV |
FF_MOV_FLAG_DEFAULT_BASE_MOOF;

4
tests/ref/fate/movenc
View File

@ -17,10 +17,10 @@ write_data len 20, time nopts, type header atom ftyp
write_data len 1171, time nopts, type header atom -
write_data len 728, time 0, type sync atom moof
write_data len 828, time nopts, type unknown atom -
write_data len 728, time 1013106, type sync atom moof
write_data len 728, time 1046439, type sync atom moof
write_data len 812, time nopts, type unknown atom -
write_data len 148, time nopts, type trailer atom -
1f37c1a8e01651e8bebcd66f00b6a226 4435 ismv
49bf122c4c732a344ef68b58acd19be5 4435 ismv
write_data len 36, time nopts, type header atom ftyp
write_data len 1123, time nopts, type header atom -
write_data len 796, time 0, type sync atom moof

6
tests/ref/lavf/ismv
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@ -1,9 +1,9 @@
a9ccbb4cd1436d222ef4425567b4e03d *./tests/data/lavf/lavf.ismv
96053075a3f60d271131fe2d0765c267 *./tests/data/lavf/lavf.ismv
312542 ./tests/data/lavf/lavf.ismv
./tests/data/lavf/lavf.ismv CRC=0x9d9a638a
440d85f9fd5b9f63c2676638782b5c15 *./tests/data/lavf/lavf.ismv
7022701b4c693bc4ffe1e9f96dd82a02 *./tests/data/lavf/lavf.ismv
321448 ./tests/data/lavf/lavf.ismv
./tests/data/lavf/lavf.ismv CRC=0xe8130120
a9ccbb4cd1436d222ef4425567b4e03d *./tests/data/lavf/lavf.ismv
96053075a3f60d271131fe2d0765c267 *./tests/data/lavf/lavf.ismv
312542 ./tests/data/lavf/lavf.ismv
./tests/data/lavf/lavf.ismv CRC=0x9d9a638a