So I have these .mkv files that neither my modded xbox or my ps3 can play. I can play them through my computer but the best audio that I get is 2 channel PCM. The xbox will play about two seconds of each file before it crashes and my receiver will light up with "DTS" or "Dolby Digital" so i know the files have multi-channel audio tracks on them. What I'm wondering is what I have to do to get my PC to output AC3 to my receiver. Here is my current audio setup:
I'm running an SPDIF coax cable from the built-in audio on an MSI P4N Diamond mobo running a Pentium 4 Dual. The cable goes to a Yamaha receiver cable of decoding DTS and DD-EX. The built-in audio is a SB Live! 24-bit. Last night I installed the Realtek ALC850 drivers, AC3filter, and SPDIFER. None of that helped

My current OS is XP Pro 32bit. If I have to buy a new sound card, recommend it. If I have to upgrade to a 64bit OS, recommend it. Just tell me what I have to do to get the AC3 or DTS audio stream to my receiver.

Your PS3 and Xbox can play MKV files, they just need to use a different container format from mkv. I only have a PS3 but convert them to .m2ts files using either mkv2vob or tsMuxerGUI. The only thing with the PS3 is that it won't stream DTS from media files, even VOBs so mkv2vob converts them to AC3.

Then they play fine, hope that's of some help.

...or use GOTSent