Help: demultiplex avi to convert original ac3 to mp3 and remultiplex

[Grunter]

Hi, i've several avi with xvid/divx video and ac3 audio. I notice that on my player in this type of avi audio is too low, so i want to convert the original ac3 audio to stereo mp3. I usually use autogk but i realize that there are no option for direct stream video copy and i don't want to reencoding video. I know i can use belight+besweet to convert ac3 to mp3 and virtualdub to "re"multiplex but what can i use to demultiplex? I try virtualdub mod but it seems that cannot recognize the ac3 original audio. Summarizing I want to:
-demultiplex ac3 audio from avi
-convert ac3 to stereo mp3
-"re"multplex video with mp3 stereo audio
Can you help me?
Thanks.

[kalaminu]

avidemux :-) You can stream copy the video and convert the audio to mp3 and remux it all in that :-)