Onboard sound from PC to receiver

[jtvang125]

I already have a very nice sound card (Omega Striker 7.1) with digital and coax outputs in my htpc at the moment. The thing that is bugging me is that when playing 1080p x.264 files the sound gets out of sync with the video (4-5 seconds off). Sound also stutterrs now and then too. 720p plays perfect with no problems. My htpc should be more than capable of playing 1080p smoothly.

What I want to test out is just using the onboard analog sound to see if it will solve the audio out of synch problem. Problem is, my receiver has no analog inputs. I don't think there's really any cheap ways to make this work, correct?

HTPC specs:
Core 2 Duo E4300
2gb of DDR
Vista Home Prem
8500GT
Codecs - Nvidia PureVideo decoder and FFDShow

 

[Modelworks]

I basically have the same sound card {auzentech xplosion} and haven't had problems with hd content and skipping on analog or digital outputs.

Maybe a service or application is taking up clock cycles causing the loss of sync.
I'm using VLC to play the videos.

 

[jtvang125]

I only have the very bare basics, not even anti-virus running on my htpc. I'm using Vista Media Center. I haven't tried VLC but that really defeats my purpose of using a htpc if I have to use the mouse and keyboard everytime I want to watch a movie.

 

[Auric]

AVC decode is demanding and it cannot be assumed that a CPU is up to the task of high resolution and bitrates. Typical x264 re-encodes are not usually high bitrate but they are often problematic for other reasons (dodgy non-compliant encoder and MKV container, novice user, &c.). It is really a bad idea to use them for testing or assume a problem based upon how well they play.

What is the CPU utilization. Is the framerate constant at the expected value? What is the audio format and are associated software decoders appropriately disabled if passing to external hardware?

Do standard, professionally encoded AVC sources behave the same?