Starting with mencoder leads to the fact that regarding the original avi-Standard multiple audio streams are not supported.
Ok then, a long parameter series for ffmpeg should do the thing – but it simply doesn’t. The added audiostream is fine, but the one from the avi is heavily broken.
The solution is as simple as we speak:
apt-get install transcode
avimerge -o test.avi -i video.avi -p audio.mp3
Make sure the user running this command owns all files!
More 2 follow, like complete encoding scripts…