[mythtv-users] More XvMC data points

Steven Adeff adeffs.mythtv at gmail.com
Wed Nov 29 19:45:22 UTC 2006

On 11/29/06, Michael Tiller <michael.tiller at gmail.com> wrote:
> On 11/21/06, Mark Chang <mark.chang at gmail.com> wrote:
> > Just wanted to drop in a few data points to the list. You've all been
> > so helpful, so here is something for the archives in case someone else
> > is trying to build a cheap HD box.
> >
> > Trying to do HD frontend/backend on an Athlon64 3200+ with an Nvidia
> > 6200TC. Using stock, binary, Ubuntu Edgy installs, and an HDHomeRun.
> > This seems to be enough horsepower to decode all varieties of OTA
> > *without* XvMC if I only use Linear Blend. Bob and Kernel caused
> > stuttering. XvMC did nothing better, and it was perhaps even worse. I
> > was happy.
> >
> > Then I saw the XvMC portion of the wiki:
> > http://www.mythtv.org/wiki/index.php/XvMC#Tips_and_Tricks
> >
> > I turned off Sync to VBlank using nvidia-settings and voila, I can use
> > Bob and Kernel without XvMC. I am now happier! XvMC does NOT seem to
> > lower my CPU usage, however. I am seeing 65%-75% decoding high-bitrate
> > HD (7gb/hr) without XvMC and WITH Bob 2x.
> >
> > There. That's my two cents.
> Just out of curiosity...when you say 65-75% CPU utilization, how is that
> partitioned between the X server and the frontend?  I ask because if I try
> and watch without XvMC on my system, the X server is something like 30% and
> the frontend is like 70%.  I'm wondering if this load on the X server can be
> avoided somehow.  Then I might have a chance to watch HD natively.

on my 3200+ without XvMC I get about 10-15% X usage and 45% for 720p
and 65% average for 1080i with Bob.

> It seems crazy to me that with such fast CPUs, HD playback is not a given.
> My Windows machine (2.4GHz P4) can process HD streams from my HDHomerun
> without a hiccup?!?  Why should a 2.8 GHz (granted, it is a Celeron) have so
> much trouble?!?

that extra cache makes a big difference in video processing.

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