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

[Michael T. Dean]

On 04/06/2008 07:10 PM, Rick Hudson wrote:
> Jason Keirstead wrote:
>> But to my surprise it can't seem to handle HD content. No matter what 
>> decoder or deinterlacer I select, I get up to 95%-100% CPU, and the 
>> system starts choking.
>>     
> This sounds almost identical to the problem I'm having. I have a Pentium-M 
> 1.8GHz CPU and Intgel 82845 GPU and it can play SD video (720x576) with less 
> than 10% CPU load. But if I try playing HD it maxes out the CPU.
>
> 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 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'

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.)

>  
> After that, I'm assuming, that the video must be scaled in software - hence 
> the high CPU load.
>
> 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.

Mike