I am a newbie and I have installed Knoppmyth with minimum trouble. Everything was working decent and I wanted to tweak my picture quality a little better. While playing with a few options, I unchecked the libmpeg option in Playback menu and that's when everything went to hell. My picture jumps periodically now and audio sometimes sounds as if it has an echo or is garbled. Ofcourse, I re-enabled the libmpeg option with no luck. When I record, the picture and audio are perfect. So in order to watch a TV show I have to record it to get decent quality.

I have checked 'top' utilization is between 30% - 50%. I can record a show while watching a video recording - no problems. I have XvMC enabled ( if i don't, picture is too jumpy). I changed my recording profile for live tv to match Default - resolution 640x480. I have lowered and raised resolution - does not work. Nothing significant in log files. DMA is enabled. If I "cat /dev/video0 > test.mpeg", test.mpeg is jumpy. Enabling/Disabling libmpeg should not have that much impact on live tv. The last thing I was working on before that, was installing a wireless card which is not working well. Everything was going good and I cannot figured this one out.

Here is my hardware:
Pentium III 750Mhz
PVR 150 S-Video
Nvidia GeForce 5200 PCI
Belkin Desktop Wireless G (work in progress)

I figued out the problem, although it doesn't make sense. I realized my recording jobs that i scheduled before the problems occurred were setup for commercial flagging and their quality was good with no jerky plackback issues. So I said what the hell, i re-enabled commercial flagging on live tv and it has been running for 5 days with no issues. Although it does get real jerky and jittery if i leave it on the same channel for 3 - 4 hours. I just simply change the channel to fix that. It is weird that enabling commflagging which is cpu intensive would fix the playback quality.

Your CPU is kind of minimal, which means you probably don't have that much headroom. Try using SSH to connect to that box while watching live TV (search for "putty") and running the "top" command to monitor your CU usage.