virtualdub has a selection that brings up the audio compressors (and another that has the video compressors) that can be used to compress a stream. The audio compression list is empty, while the video one has all the ones I expect. Sounds like from a previous post that it's a problem of not related to the audio device.
well, other post says that no ACM driver is reported when there's no audio available... that's perhaps the program which disables the list when no audio is avail. could you mail me anyway the -debugmsg +msacm trace
TIA