I got a52dec and it seems to be fine, but I can't automate AC3 support in Snd because, as far as I can tell, there's no way (besides the "ac3" extension) to recognize an AC3 file. You could call a52dec from Snd via (define (play-ac3 name) (system (format #f "a52dec ~A" name)) and something similar (see examp.scm OGG code) to translate such a file so that Snd can edit it.