Dump to a temp .wav file, and then play that one backwards. Most compressed media files (or really, any sort of compressed data), is designed to be decompressed and read in the forward direction. In order to go backwards, one would have to decompress in chunks, and then play those chunks backwards. However, most compression formats don't have sub-divided chunks. So you have to decompress the whole thing going forward, and then play the resultant buffered output backwards. Kul doog.