avformat/movenc: implicitly enable negative CTS offsets for ismv

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.

diff --git a/doc/muxers.texi b/doc/muxers.texi
index 33f1f7bbaf7e09ca3f1e0f7c75bdcba541d2c72c..268c15202334754877110ff48e7c66b3fe08d8fb 100644 (file)
--- a/doc/muxers.texi
+++ b/doc/muxers.texi
@@ -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

diff --git a/libavformat/movenc.c b/libavformat/movenc.c
index dd6aa02525a0ca9a83e108d33088276fb0dd78c4..72a6e12d5280c6423cb2be06e263aa65151cb849 100644 (file)
--- a/libavformat/movenc.c
+++ b/libavformat/movenc.c
@@ -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;

diff --git a/tests/ref/fate/movenc b/tests/ref/fate/movenc
index 872796ebce66ea41a142edfaa1d6ea0b44cf2403..5e8f324ea37554d4b6ef122355a6c026b6609b38 100644 (file)
--- a/tests/ref/fate/movenc
+++ b/tests/ref/fate/movenc
@@ -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

diff --git a/tests/ref/lavf/ismv b/tests/ref/lavf/ismv
index f29b5ff3ef9da280926fce4272b487a4c8faa22c..7b4a46609675923a4d199a32035277858d63783d 100644 (file)
--- a/tests/ref/lavf/ismv
+++ b/tests/ref/lavf/ismv
@@ -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