I have a centre back speaker but can't get audio from it when using my HTPC. My HTPC is conected to a Yamaha amp via SPDIF optical, I also have my DVD player connected to the amp via digi coax. Since I wasn't getting any audio from the centre back speaker when playing .mkv files via kmplayer I checked it with a copy of Lord of the Rings extended edition dvd. When I play the dvd through my dvd player and select the DTS ES 6.1 option, I get the Centre back audio but when I put the dvd in my HTPC, no Centre back audio. The amp still shows DTS ES, so I'm now confused as to what the problem is. I had a look at the KMplayer filters but to be honest i hadn't a clue what I was looking for. Any help woud be really appreciated.