[Matroska-users] Bug in audio with mkvmerge ?

Moritz Bunkus moritz at bunkus.org
Fri Nov 14 21:42:01 CET 2003


> a) I don't understand what this step is but I do it. resulting : an
> unused frameno.avi file

I should update the documentation. Using this three pass method is not
recommended anymore. Instead you should activate audio processing in
both passes.

The steps required now look like this:

1) extract the audio to PCM:

mplayer -ao pcm -aofile audio.wav -vo null -vc dummy dvd://1

2) normalize, use oggenc etc. just like described earlier

3) Use mencoder twice with '-oac copy', copying your example:

> f) I use :
> ~ mencoder cyclo.avi -oac copy -ovc lavc -lavcopts
> vcodec=mpeg4:vhq=4:vpass=1  -vop scale=360:158,crop=720:316 -o /dev/null

Second time with vpass=1 and '-o video.avi'. 'video.avi' will actually
contain the original audio as well but that is being discarded when the
stuff is muxed into Matroska.

> e) I don't understand this step

Sorry, I'm pretty tired at the moment. Please read some articles about
the basics of video encoding. This is basic bitrate calculation stuff.

> but, the sound in the movie is awful !

This is probably due to the new lacing schemes used. Please recompile
mplayer with libebml 0.6.2 and libmatroska 0.6.1 and make ABSOLUTELY
sure that you don't have any older version of both libs lying around
anywhere. This should solve the problem of the sound being ugly.

If you want to check whether this is really the problem then add
'--disable-lacing' to mkvmerge's command line.

> PS : I have segfaut of mmg on my system ? is it normal ?

Of course not. Recompile mkvtoolnix with debug options (add
'--enable-debug' to the configure command). Then run mmg inside of gdb
and when the segfault occurs type 'bt' in gdb. Then send me the output,

 ==> Ciao, Mosu (Moritz Bunkus)

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