I am new to this forum and I do have a similar issue.
I recently formatted my Windows 7 partition and now that I got everything up and running again, there's one thing that still doesn't work. The DTS 5.1 audio to my receiver.
I've been playing with this since forever and would appreciate some help if possible.
First of all, before I formatted the partition, I'd get DTS 5.1 just fine for my .mkv movies. All movies/shows that I have are in 5.1. My connection is a straight HDMI cable (no S/PDIF) for audio and video that goes from my Sony Vaio laptop into my receiver. Again, this always worked fine before, nothing has changed here.
All I get from my receiver's display (LG) is a PCM 2.00 instead of DTS 5.1. I was able to get all 5 speakers working simultaneously but only in 2.0, the audio signal was not split into 5.1. The receiver's display even says so (PCM 2.00).
What I've tried so far:
-updated audio drivers from Sony's website for Win7;
-installed the latest K-lite pack and messed around with the ffdshow codec settings (Output - Passthrough/HDMI checkboxes checked, not checked: DTS, AC3, etc;
-still under ffdshow, I went to 'Mixer' and changed the tab to 'same as input' (I believe that's how I got it working in the past) but still no luck, I also tried 5.1 there;
-then, I installed AC3 filter, applied the filter to External Filters tab in MPC-HC and set it as preferred. Under ac3 config, I tried all the combinations possible. S/PDIF checked (I get no audio at all when checked, not even 2.0), not checked; setting audio to 5.1 or none or 2.0, etc. Modified that on both 'Main' and 'S/PDIF' tabs. In fact, if I change one tab, the other one automatically changes to the same settings. I thought I could set them separately. Don't know if that's an issue or what.
This issue has been bugging me for the last 4 days at least and it's driving me crazy!! I think it should be working by now.
Can't think of anything else to do right now. If anyone could help, I'd appreciate.
Please let me know If more info is required and I'll post here what's needed.