[MPlayer-users] audio stream dumping question

[Massimiliano Cirri]

I would like to know why the audio streams you can obtain issuing the 
following commands are different:

mplayer piratesofcaribbean.vob -aid 128 -dumpaudio -dumpfile pirates.ac3_1
mencoder piratesofcaribbean.vob -ovc lavc -oac copy -lavcopts 
vcodec=mpeg2video:vbitrate=3682:mbd=2:vpass=1 -srate 48000 -of mpeg 
-ofps 25 -o /dev/null
mencoder piratesofcaribbean.vob -ovc lavc -oac copy -lavcopts 
vcodec=mpeg2video:vbitrate=3682:mbd=2:vpass=2 -srate 48000 -of mpeg 
-ofps 25 -o pirates.mpg
mplayer  pirates.mpg -dumpaudio -dumpfile pirates.ac3_2

if I compares the two pirates.ac3 they have different size. If I mplex the pirates.ac3_2 with the video stream of pirates.mpeg I can obtain a sync result, with the other the result is out of sync.

I hope that somebody could explain me the difference.

regards, Massimiliano.