This may be an especially noobie-type question, so I apologize in advance.

When I play 1080i using the standard MPEG2 decoder (XvMC turned off), the video plays fine for about 1 minute, but then becomes very choppy. Using the top command to monitor CPU usage, I see that the CPU% allocated to the frontend jumps from about 60% to 99.9% at the same time that the video becomes choppy.

What I don't understand is that the overall CPU usage indicator, above all of the other processes, never goes above 50%. What does this mean? How can a single process be using more CPU than the total? Is it possible that the frontend is prevented from using more than half the CPU?

I have a P4 3.2 Ghz HT and an evga 7600GS.

HT processors are treated as multiple cores. You're using 99.xxx% of one "CPU" but the other one isn't doing that much. You don't really get 200% with a HT CPU, especially in cases like this, but it's a reasonable approximation.

Thanks, tjc. That's helpful. I assume then that I'm getting as much CPU usage as I can with mythtv, and that there's no way to "spread" mythtv over multiple threads?