high cpu load with gnome-shell and a window that shows TV

[Gerald Dachs <gda gmx de>]

Hi,

I am part of a team working on a HTPC distribution based on a minimal 
Ubuntu installation. Our main focus is viewing and recoding TV via 
DVB-C/S/T.
Currently I try to use the TV front end with gnome-shell, this is 
working not bad and is looking great. I believe the look & feel
of gnome-shell is perfect for this.

There is only one big problem. If I start the TV front end on my atom 
based test machine I get %35 CPU load from gnome-shell only.
Starting another front end like XBMC I get additional %35. The video 
decoding is made by the GPU using VDPAU. So the CPU has not much to do,
but this heavy load is too much for the CPU and I get frame drops.

Before gnome-shell I used openbox. Openbox needs less than %1.

What is the reason for this high load? Compositing? Did I make a 
configuration fault? Do I have to live with this?


Sorry for my bad English.

Regards
Gerald Dachs