[mythtv-users] Unreasonably high CPU usage when playing HD content? Suggestions?

[Rick Hudson]

Michael T. Dean wrote:

>> After some investigation I found I can play up 1024x720 (probably 1024x1024) 
>> with basically the same CPU load (maybe up to 15%) but as soon as the 
>> horizontal res goes over 1024 (eg 1152x648) the CPU maxes out
> 
> Perhaps because your playback profile group has a resolution based
> comparison that causes it to switch profiles at/around that point.

I forgot to mention that configuration. My changeover point it at 1280x720 and 
what's more it's currently configured the same as the lower res profile.

>> I think some of the info on http://www.mythtv.org/wiki/index.php/XvMC is 
>> relevant to me where it says that many GPUs only support XV up to 1024x1024.
> 
> Find out with:
> 
> xvinfo | grep 'maximum XvImage size'

Ah. Thanks for that tip! It says:

maximum XvImage size: 1024 x 1088

Interesting that it's 1088 rows instead of 1024 which tends to suggest it's 
designed to handle 1080i video. However the 1024 width does appear to be a 
problem. :-(

> Unless you have some of the old, broken Intel drivers, I doubt this is
> the problem.  (I'm thinking the i810 driver is garbage and the new intel
> driver works, but don't quote me on that.)

What would that not be the problem? Is the XvImage size a restriction of the 
driver and not the hardware?

>> What I don't understand though is that my screen size is 1280x720 so I would 
>> have though it could play that resolution without scaling at all. There is 
>> obviously something about GPU data transfer I'm missing. Maybe there's a 
>> playback profile suitable for this unscaled situation that I haven't found yet.
> 
> For 720p, display on a 720p TV should be unscaled unless you've
> specified overscan in Myth and are using GUI size for playback or you're
> running Myth in a window or something--i.e. not displaying video at
> 1280x720.

So you're saying that playing an unscaled video should be possible regardless 
of whether it's bigger than the maximum XvImage size? I guess I need to find 
out if mythtv is indeed trying to scale the video to something else for some 
reason.

-- 
Rick Hudson