AC3 Decoder is a convertor for AC3 files to WAV, MP3, WMA. AC3 file can contains up to 6 audio channels. AC3 Decoder combines all this information into two encoded channels that deliver to each of your ears, via conventional stereo headphones, its own unique sum of direct and reflected sound from each virtual speaker.
More info:
hxxp://www.mediatwins.com/products/ac3_decoder-download.htm

Hell good. WMA9 supports encoding multichannel audio files to Windows Media Audio 9 Professional. So this should be comptible with that. !!