Virtual Dub can't codec anything, Avidemux can't do anything else but spastic error messages and everything else is either too old to work, equally stupid of not free.
I'm temped to spontanously spend 50€ on buying video editing software because of that. The only thing I want to do is merge an audio and a video stream but no program can even remotely grasp that the only thing that is required is to decode, mix and code channel data! Seriously, what sort of idiot can think of something else and call himself a programmer. If something doesn't fit, CAST IT to the target type... Applyable to data types AND codecs!