[mythtv-users] playback performance regression: show of hands (Allan Wilson)

[Guy Paddock]

>> I too had the same problem with HD content. Are you using the
>> 'denoise3d' playback filter? I suspect this has changed and is the cause
>> of the problem.
>> ...
>> Now I'm just using the kernel deinterlacing filter, and the CPU
>> consumption is totally reasonable again.
>>

I'm definitely running without deinterlace or filtering on an AMD Athlon XP
3200+ with Standard video mode, and it's playing back only 2-3 seconds of
video, then studdering, then playing back another 2-3 seconds, with the log
filling with "NVP: Prebuffering Pause" each time, every so often saying
"NVP: Video leading by 7 frames, slowing down". Using the "Use video as
timebase" helps a bit, but it still studders. Playback with VLC or xine of
the same content is fine.

If I switch to XVmC, it's even worse; the audio gets far more garbled and
the video only plays in segments of 1-2 seconds. I'm using the nVidia
drivers, 8756 I believe (the latest the wiki recommends).

>I read the wiki and looked in MythWeb to see if I was using any filters and
>it didn't look like it. Is there somewhere else that I should check to see
>if I am using any of these filters? Also why would you need these filters
>with HD content or is that what you are saying that they are designed for
>SD content therefore don't work right with HD?

Some filters, especially the 3D denoise filter, consume enough of the CPU
time on SD. On HD/1080, it's insane, and the denoise isn't needed for HD
content because there's really no analog noise (although, there are MPEG
artifacts, but they're mostly minimized by the scaling down of the frames to
your video mode). The denoise just is not fast enough on most systems, and
produces very little gain for an HD signal.

To check your filters while in the frontend: Settings->TV->Playback, then
look for the "Custom Filters" box. It's under the deinterlace settings. It
should be empty for no filtering, and the "Deinterlace" checkbox should be
unchecked.

--Guy