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Old 06-07-10, 09:30 PM   #7
mlord
Linux kernel hacker
 
Join Date: Feb 2009
Location: Ottawa, Canada
Posts: 173
Default Re: 256.29: Jerky VDPAU HD playback in MythTV

Quote:
Originally Posted by Stephen Warren View Post
mlord, I couldn't reproduce this locally. Are you sure it's the nvidia-settings command that's actually causing the issue, not e.g. sending commands to the VFD display with the result, or some other facet or processing the nvidia-settings results?
The app still does all of that other stuff, and no issues result from it. Only when adding the temperature query back in do I see the odd playback glitch. But even more obviously, the VFD's (software-driven) scrolling display is incredibly jerky with the temperature probing, and smooth as silk without it.. That was the first clue to the problem.

The system was also running all of mythfrontend's threads with realtime priorities, which is why I suspect some kind of priority inversion may have been happening. That's not normal for Mythtv -- it usually runs everything in SCHED_OTHER/NORMAL, rather than in realtime SCHED_FIFO. Which could explain difficulty in reproducing it.

Since then, I've fixed the priorities here, so that only a single playback thread in mythfrontend uses SCHED_FIFO now. This might cure the playback w/temperature thingie, though I have not reenabled it yet for retest. The next good opportunity for that is Wednesday evening, during the hockey game (lots of fast motion and high contrast makes any kind of jerkiness obvious).

I'm _very_ happy with 256.29 right now (without the temperature probing).

Good work, guys!
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