[mythtv-users] How to minimize CPU usage

Kevin Kuphal kuphal at dls.net
Sat Jan 28 23:16:51 UTC 2006


Jerry Rubinow wrote:
> On 1/28/06, Kevin Kuphal <kuphal at dls.net> wrote:
>   
>> Jerry Rubinow wrote:
>>     
>>> I'm running myth with separate front/back end computers.  The frontend
>>> is a 2.8GHz P4 with 512MB ram, trying to display 720p HD, but I'm
>>> maxing out the CPU - myth ~65+%, X around 30+%.  The video is at times
>>> choppy when there's a lot of stuff changing in the frame.  What can I
>>> do to reduce CPU usage?
>>>
>>> Here's what I've done so far:
>>> -compiled myth with --enable-proc-opt (using SVN from less than a week ago)
>>> -using ratpoison for window manager
>>> -not using any deinterlacing
>>>
>>> Note: XvMC is not an option.
>>>
>>> I'm running FC4.
>>>
>>> mythfrontend -v playback reports that it's using Xvideo, format I420,
>>> using realtime priority, video timing method: RTC (glx vsync not
>>> supported in my driver).  Then I get a lot of video ahead of audio
>>> dropping frames messages, and then a lot of audio ahead of video
>>> messages.
>>>
>>> /proc/meminfo says there's 100MB free while running myth, so I guess
>>> it's not swapping.
>>>
>>> What might be causing the high CPU?  I've read about people with
>>> 2.4Ghz P4s not having a problem with HD, so it seems like there should
>>> be something I can do.  Would compiling my own kernel help?  With what
>>> options?  Anything else I can try first?
>>>
>>>       
>> Try using libmpeg2 for your playback.  I'd suggest looking into
>> hyperthreading support in your kernel to see if it is enabled.  I
>> believe this means using an SMP kernel.  I'm not sure if that will make
>> a difference but it might.  And lastly, your video card and drivers do
>> help alot.  I've struggled with my choice of ATI on one of my frontends
>> and as I'm moving to HD, I'm biting the bullet and spending the $40 on
>> an Nvidia FX card and it will be one of the best $40 I've spent on my
>> system as it means HD playback on my 2.4ghz Celeron with XvMC.
>>
>> Kevin
>>     
>
> Sorry, I left out that I'm using libmpeg2.  Hyperthreading - hmm,
> unfortunately I just checked and my CPU doesn't support hyperthreading
> (it's a 533MHz bus 2.8GHz P4).  I tried going the FX 5200 route, only
> to discover that I I can't achieve the transfer speeds I need over PCI
> (my motherboard only has two slots, both PCI).  1280x720x(24 or 32)
> bits, 30 frames a second (or 60, even worse) - PCI's max throughput is
> 600 to 700 Mbits/sec.  I tried XvMC on the 5200 but it was always a
> bit glitchy.  The onboard graphics is AGP, but now instead of being
> limited by bus speed, it's by CPU speed.  Very frustrating, since it's
> soooo close to working properly.
>
>   
Hmm.  I'm about to buy an FX5500 PCI for use in my frontend.  Are you 
saying that you can't drive HD content to the PCI card because it is 
PCI, not AGP?  I'm using XvMC on my MX440 AGP and it works great with 
Myth and the 7676 Nvidia drivers on the SVN.  You might want to give 
XvMC with that driver version another shot when 0.19 is released on your 
FX5200.  I've found it to be very solid.

Kevin


More information about the mythtv-users mailing list