[mythtv-users] Strange X CPU usage for 720p input streams

Paul Robertson paulrobertson at swbell.net
Fri Jun 30 13:46:06 UTC 2006


My system config is very similar (Athlon 2200+,  Nvidia 5200FX, 512MB, FC5,
gnome), and I have been struggling with this same issue for some time.  Here
is some CPU usage data I collected to illustrate:

 

Source             %frontend         %Xorg  %Idle

-----------           -------------        --------  -------

480 SD             10                    0.5       85

720p HD           40                    59        1

1080i HD          35                    0.5       62

 

Note the high % CPU usage  for Xorg when running 720p.  I have tried a lot
of experiments to try and isolate, but without much luck.

 

Try 1) I am using the 8178 nvidia driver currently,  but tried both older
and more recent versions.  Same result.

 

Try 2) Adjusted all settings available in nvidia-settings configuration
tool,  .nothing made a difference

 

Try 3) I'm using xrandr to set display size to exactly match source on play
back.  Above numbers were taken this way.  If I don't do this, the Xorg %CPU
usage goes up dramatically for all cases.  I presume this is due to overhead
required to scale the output.  .so reverse logic would make me think maybe
720p is getting scaled some how despite the fact I am displaying it on
720x1280.

 

Try 4) Tried KDE instead of GNOME,  same.  Also tried running X with a
simple window manager, like tvm.  Although initially this appeared to fix
the problem,  it did not.

 

Try 5 ) 720x1280 is what I run my mythtv menus at.  Hmm..., coincidence
maybe?  .so changed my default gnome desktop size and mythtv menus to
480x720.  Made no difference.

 

Initially had this setup running with a Athlon 1100 and had same issue.
This is what prompted me to swap in a faster processor,  but it made no
difference.   

 

Any ideas?

 

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