Sometimes i experience the problem that releases i downloaded won't have an audio track that my pch devices can play.
The reason for that is basically that it has a DTS audio track the pch though cant play this. So what you have to do now is convert this track to a ac3 one.
Here is how it is done in a few simple steps and without the need of downloading a crapload of codec packs.
Tools you need:
1. Open the mkv in avidemux
2. On the prompt when it warns you about the h.264 codec select: NO
3. When it asks to rebuild the index, select: YES
Now in the left hand pane you need to select.
Video = Copy
Audio = AC3 (aften) or AC3 (lav)
Configure = 384kbps
Format = MKV
Click save and depending on your CPU and HDD speed you get a new file rather quickly with working audio.