[MEncoder-users] Audio sync issue with x264 b-frames

Jonathan jonathan at kc8onw.net
Sat Dec 3 18:41:07 CET 2005

When encoding to x264 with b-frames enabled audio seems to be ahead of the
sound a fixed amount depending on the max # of b-frames set.  I don't know
if this a limitation of mencoder during the encode or ffmpeg during
playback or avi as the container format or what.  I tried using
libavformat to encode to mp4 but the sound was horribly messed up with
-oac pcm and didn't play at all with -oac copy.

The command lines I used are below the line with no b-frames had perfect
sync, I couldn't tell any difference between the DVD source and the avi
without bframes.
mencoder.exe dvd://1 -alang en -oac copy -ofps 24000/1001 -vf
pullup,softskip -o c:\test.b.avi -ovc x264 -x264encopts
-endpos 150s

mencoder.exe dvd://1 -alang en -oac copy -ofps 24000/1001 -vf
pullup,softskip -o c:\test.avi   -ovc x264 -x264encopts
psnr:subq=6:4x4mv:8x8dct:me=3:frameref=5:bitrate=450:pass=1 -endpos 150s

This is with CVS mplayer/mencoder
$ uname -a
MINGW32_NT-5.1 XXXXXXX 1.0.10(0.46/3/2) 2004-03-15 07:17 i686 unknown

$ gcc -v
Reading specs from g:/MinGW/bin/../lib/gcc-lib/mingw32/3.2.3/specs
Configured with: ../gcc/configure --with-gcc --with-gnu-ld --with-gnu-as
--host=mingw32 --target=mingw32 --prefix=/mingw --enable-threads
--disable-nls --enable-languages=c++,f77,objc --disable-win32-registry
--disable-shared --enable-sjlj-exceptions
Thread model: win32
gcc version 3.2.3 (mingw special 20030504-1)

$ ld -v
GNU ld version 2.13.90 20030111

$ as --version
GNU assembler 2.13.90 20030111
Copyright 2002 Free Software Foundation, Inc.
This program is free software; you may redistribute it under the terms of
the GNU General Public License.  This program has absolutely no warranty.
This assembler was configured for a target of `mingw32'.

I can provide mencoder/mplayer output if it would help, I thought I had
saved it but I can't find it now and I can't re-encode till I get home.


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