[Openchrome-users] [PATCH] Re: MythTv judder: XvMCPutSurface using a lot of CPU

[Terry Barnaby]

Terry Barnaby wrote:
> Terry Barnaby wrote:
>> Hi,
>>
>> I am trying to track down a problem I have with MythTv under Fedora 8 
>> using
>> the openchrome driver and libchromeXvMC library.
>> MythTv has a lot of juddering and glitches even though the XvMC VLD
>> acceleration is in use.
>> This is also present with the stock via driver and libviaXvMC library.
>>
>> Using the old mp2decoder XvMC test program I see that sending one
>> frame at 25Hz uses about 12% CPU. If I modify  mp2decoder to send
>> two frames at 50Hz (Just calling XvMCPutSurface twice with the same
>> frame) the CPU usage shoots up to 98%. This is equivalent to
>> MythTv outputting in BOB de-interlace mode and appears to show the
>> same problem I have with MythTv.
>>
>> I guess this could be a libchromeXvMC/libviaXvMC or DRM issue.
>> Has anyone any idaes on this ?
>>
>> Cheers
>>
>>
>> Terry
>>
>>
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>>
> 
> I have tracked this down a bit further.
> The syncVideo() routine is being called from pciFlush() with doSleep = 0.
> This is sitting in a tight loop for 20ms (I guess until the next VSYNC ??).
> Even setting doSleep to 1 does not fix the issue as in MythTv the
> output thread is a Realtime thread and nanosleep() is, I believe, 
> implemented
> as a tight loop when call from a real-time thread.
> 
> I'm not sure of exactly the best way to fix this issue ...
> Does syncVideo() wait for the next VSYNC period ?
> 
> Cheers
> 
> 
> Terry
Hi,

The enclosed patches reduce the CPU usage while using MythTv from 98% to about 
40% on a Via M10K. One is for the Openchrome library and the other is for the
stock via library. These may not be the best way of curing this problem, but I
thought it might help some people or at least give a pointer to possible
solutions.

Cheers


Terry

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