[mythtv-users] Choppy Playback & prebuffering message

[Kevin Kuphal]

Nate Crosno wrote:
> Hi All,
>
> I'm having lots of frustration getting content to play back smoothly. 
> Sorry for the noob question. I'm sure you pros get this all the time.  
> I've been building up this myth box for about a couple weeks and cannot 
> get anywhere close to smooth playback.  I can usually sort these things 
> out on my own, but am loosing my patience. I've been using Linux on and 
> off since about 1998 and am a web developer by trade.  Most of my 
> experience is with back-end server type setups.
>
> Here is my hardware:
>  - Dell Dimension 2400
>  - Celeron 2.2Ghz
>  - 756MB RAM
>  - ATI HDTV Wonder capture card.
>  - Radeon 7000 PCI 64MB  (right now set to 1024x768 @ 60hz, dri and drm 
> seems to be loading fine according to the Xorg.0.log)
>  - 160GB Seagate drive UATA 7200RPM (dma enabled)
>  - On-board Intel audio
>  - Right now hooked up to a Dell 15" LCD monitor via VGA, but shooting 
> to hook it up to my Sony 50" LCD rear projection via the DVI port.
>
> Software:
>  - Gentoo linux kernel 2.6.15-gentoo-r1 (recompiled several times over 
> the past couple days to get things working)
>  - problem happens on both Gnome and blackbox
>  - latest mythtv build via 'emerge'
>
>
> When trying to view recorded content or watch live TV (either SD or HD) 
> I get the following:
>   - Pauses every 1-2 seconds (speeding up, slowing down, etc), this 
> includes breaks in the sound.
>   - in the mythfrontend terminal window I see lots of messages about 
> 'prebuffering pause'
>   - big pink vertical bar along the right edge of the content (on SD 
> content)
>   - if I turn off the sound (set the sound device to something invalid 
> in myth), then it seems to just play slowly
>   - while only mythbackend is running and recording HD content 'top' 
> shows only about 10% CPU usage.
>   - while trying to watch live tv or recorded content, the CPU gets 
> maxed out:
>        0% idle, 60% mythfrontend, 27% X
>        0% swap in use
>
> I'm hoping something here will catch your collective eye.
>
> I've tried many of the various settings like aggressive sound buffering 
> to no avail.
>
> Thanks a million!
> -Nate
>   
The pink bar is a result of the ATI hardware scaler bombing out.  First 
suggestion, try using 800x600 since that's what the MythTV themes are 
designed for.  Second, get an nvidia board.  It is amazing to me how 
poorly ATI products perform in general despite their claims of hardware 
acceleration and the 7000 isn't exactly a speed demon to begin with.  
And FYI, you're never going to be able to do HD on that system without 
transcoding.  You need at least a P4 3ghz or equivalent to do software 
playback of HD.

Kevin