[mythtv-users] Choppy Playback & prebuffering message

[Scott Petler]

Nate,

I don't understand the 100% cpu utilization, but I had similar problems with
a similar machine that was a frontend only. 
1GB
2.6.15.6 kernel
2.53GHz P4 Socket 478
Gigabyte 81848P Mobo
GeForce 6600 dual dvi w/ dual 21" LCD monitors

I tried all of the "priority" methods, realtime module, suid etc; 
nothing helped.
Kept getting the pre-buffering messages.  Eventually I used lspci -v to 
examine
the latency numbers for the pci bus.  I found that by setting the 
latency HIGHER
on the LAN and SATA(disk) controller, my problems went away.

On the frontend machine, my cpu utilization is about 13% when watching 
live tv.
I'm using the svideo input on a pvr150 on my server, and when watching 
live tv
the server is almost idle, since it only has to store the encoded data 
to disk and then
read data from disk and send it out the LAN interface.

The backend server machine is a dual opteron 248 w/ 4GB memory 1TB raid 
5 w 4 350GB
sata disks and 2 10krpm disks for os/swap.

Try out the setpci command on your frontend machine to mess with your 
latencies and see if that helps.
Remember the lspci displays latency in decimal, whereas setpci uses hex....

Scott

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
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