video stutter due to audio?

[rallynavvie]

I've been getting video stutter (more like a quick fast-forward at regular intervals) when playing back HD content recorded in Media Center ever since I got an HD tuner. I re-installed MCE and started from scratch and the issue remained. Originally I thought it was the tuner or a poor digital signal but then it floated to video card and then to MPEG2 codec. For a more thorough history of that troubleshooting, as well as some good info on the Hauppauge HD tuner, read the thread here:
https://forum.videohelp.com/topic330091.html

Now I forgot to install AC3Filter until just yesterday. Fired up an HD program in Media Center and it played stutter-free. I was amazed that the issue had just solved itself. However I then noticed that my receiver was only seeing stereo, not surround like these shows had been recorded. I had left AC3Filter defaults on so I enabled SPDIF and opened up media center and my old problem returned. So somehow it's the SPDIF output that's causing the problem, even if I leave it on stereo instead of Dolby. Yet the only connection to my receiver is through optical.

Any suggestions? I've tried almost every setting in AC3Filter but only toggling the SPDIF recreates the issue.

Some additional info if needed:
Onboard sound card is ADI 1980 chip (AC97)
MPEG2 codec is the nVidia PureVideo Gold-edition
Any other info you need to help me out just let me know.

[Soopafresh]

You know how difficult these things can be to track down. As a non SPDIF user, the only thing I can think of is either the A/V splitter might need updating, or you can try the SPDIF functions located in the latest version of ffdshow.

[rallynavvie]

Perhaps. Audio has never been my strong suit when it comes to A/V.

I forgot to mention that when I check the box to force the audio to re-synch after seek/pause it works for a while before the audio gradually goes out of synch. I have to think it's the onboard sound, but since it's always worked for Dolby output via SPDIF before I started using HD content it seems strange. Maybe I need an HD Audio chipset instead of the AC97? Seems silly to me.

[rallynavvie]

Solved.

The issue was with the codec outputting to an un-supported chipset. I just put in a Creative X-Fi that I got for free from a friend and the SPDIF passthrough works just fine now with HD playback.

If you're using PureVideo HD then you need to use a sound card that's listed on nVidia's supported list.