First thank you Vytautas for this real good job!
I have no opinion on whether audioinfo, audiowrit/read or octave integration should be done first, but here is my 2 cts about the library to be chosen if you go the audio... route :
ffmpeg is already used for the purpose of reading videos (octave-forge video package). It seems like it also could do the job for audio files. Further more, from this page [1] I can see that the only documented option to compile libsnd on windows platform is cross-compilation.