I used YACC for a long long time, and it is decent. But, it is a little buggy when trying to compress hundreds of ISOs in batch (it crashes here and there). But, the one thing that really upset me was that the program could not batch decompress when I needed it. I found PSPConv and never looked back. It can batch compress AND decompress...and I ran it on over 500 ISOs at a time with no crashes EVER.