Comment 6 for bug 230749

Wow, I'm so happy I found this! I had exactly the same problems as you with VLC and MythTV. I've been spending weeks on this issue blameing everyone from MythTV, nvidia, Liferea, firefox, Xorg, and pulseaudio... I even spent time swapping video cards and drivers. My eyes finally opened up and realized that gnome-screensaver was the number 5 CPU time on my system, and I don't even use a screensaver. "killall gnome-screensaver" is the perfect interim solution to these Xorg CPU spike problems. Thanks to all that reported, confirmed, and upstream fixed it. Go Linux!!

In case anyone web searches for this problem in Myth, like I was trying to do for 2 weeks, if you are having jerky playback in Myth (with Myth's internal player) and see messages similar to the following when you run "mythfronend -v playback":

NVP: Video is x.xxxx frames ahead of audio, doubling video frame interval to slow down.

NVP: Video is x.xxxxx frames behind audio (too slow), dropping frame to catch up.

If you use a nVidia card with the proprietary drivers, and you're running Ubuntu with Gnome, then gnome-screensaver is actually what's causing your problem. "killall gnome-screensaver" is your friend.