[mythtv-users] Digital Pegs CPU

[Rod Smith]

On Tuesday 25 November 2008 08:24:01 pm Paulin wrote:
> Myth Community,
> I'm hoping someone can point me in the right direction on this one.
>
> I currently have a VIA EPIA M10000 (1ghz processor) with 512 RAM running
> MiniMyth.  When I run an analog program (recorded or live) from the backend
> it looks pretty good.  The CPU is running around 70%.  However when I run a
> Digital signal (live or recorded) the picture pauses regularly (about every
> 30 seconds), kinda like a buffer playing catchup.  Anyway I've noticed the
> CPU is pegged at 100% so I believe that is really the issue for the
> stuttering.

I think you need to be more precise concerning your recording types/formats. 
To MythTV, all recordings are digital, so there's something other than this 
that differentiates your recordings. (I know you mean analog transmission vs. 
digital transmission [or perhaps some other medium, like DVDs], but my point 
is that a factor that happens to be correlated with this distinction is the 
real culprit, not the analog vs. digital source per se.) There's a good 
chance that your recordings vary in their resolutions and/or bitrates. This 
is particularly true if your "digital" signal is in fact an HDTV broadcast. 
My suspicion is that an HD recording will strain a 1GHz CPU; depending on the 
precise format and various other options, such recordings can consume half or 
more of my 3GHz Intel Celeron-D CPU's time. Issues like recording format 
(MPEG-2 vs. MPEG-4 vs. other odd formats) can also play a role.

One factor that I found extremely important is proper X configuration. 
Specifically, with an nVidia video card, be sure the following line appears 
in the "Device" section for your video card in /etc/X11/xorg.conf:

    Option         "UseEvents" "True"

Without this line, X uses excessive CPU time, thus producing stuttering and 
other problems when playing back HD recordings on my system. It's conceivable 
you'd see similar symptoms even with SD content on a 1GHz system if this 
isn't set correctly.

There are lots of other potential culprits, too, like deinterlacing settings, 
XvMC support, etc.

-- 
Rod Smith