I'm having troubles getting recordmydesktop run properly with Compiz. I'm running Debian/Lenny with the latest propieretary fglrx driver and the latest Compiz version from the Lenny repository.

As soon as I start recordmydesktop it sucks up all of my CPU power and there's no way to record a smooth video. I searched various places for solutions to my problem but wasn't able to find anything that would work. I tried all the command-line switches that could help, enabling the sound on the record, etc. fglrx wouldn't let me switch to a color depth of 16 bpp. It claims it doesn't support that mode.
I have a relatively strong CPU (Core 2 Duo @ 3GHz) and a strong video card (ATI Radeon HD 4870).
Although I start to believe that maybe the video card is the source of the problem. I read on multiple places, that ATI cards and the ATI driver do make troubles with Compiz + recordmydesktop. The free driver radeonhd wouldn't work with my card though (I believe it doesn't support 4800 series).
What could I try to improve my performance? Any hints, suggestions or ideas?

btw, Direct Rendering is enabled:
glxinfo | grep "direct rendering":
direct rendering: Yes

glxgears draw well:
55428 frames in 5.0 seconds = 11085.410 FPS
56452 frames in 5.0 seconds = 11290.237 FPS
57227 frames in 5.0 seconds = 11445.363 FPS

Allthough the rendering area flickers a bit. I don't know if this is of any relevance.
This effect is not visible if I use fgl_glxgears instead.

Thank you,