I am currently using Kubuntu 9.10 with 4.4.1 from the backports repository. I have a Quad Core and Nvidia GTX 275. With compiz and VDPAU I get extremely low cpu utilization. With Kubuntu and KWin I get much higher CPU usage and programs such as XBMC function extremely slow. I have looked at the various threads I could find on this topic but have not found a clear answer as to what causes it or how to fix it. It seems that it has to do with Direct Rendering and VDPAU conflicting. However, Compiz has found a way around these problems. Is there a way to work around these problems with KWin. I really want to switch full time to Kubuntu but I am not prepared to do so until I can solve this problem, as video playback is important to me. Does anyone have a clear solution, or could someone point me in the right direction. Thank you for your help.

I guess XBMC is running in fullscreen? In that case Compiz unredirects XBMC, while kwin does not (this is disabled in Kubuntu). To enable it again, open ~/.kde/share/config/kwinrc, find the section [Compositing] and add the line
UnredirectFullscreen=true

Then restart kwin and it should be much better, but this can cause flickering when using other fullscreen windows.

Yes it is running fullscreen. I have implemented the change you suggested and it is work perfectly. My question then becomes, why doesn't KDE do this by default? It may not be the ideal solution but it certainly looks better than having applications like XBMC appear broken under KDE. Also, does this solution have any impact on the CPU usage of VDPAU?

lakerssuperman wrote:My question then becomes, why doesn't KDE do this by default?

It is the default in KDE and Kubuntu changes it, which is in general nothing bad. There are good arguments for both enabling and disabling. E.g. I have disabled it, because it is useless for me. We probably should add a "window specific rule" to dynamically set this option, so that you can use it on a video player (where it makes sense) but disables it for a webbrowser (where it doesn't make sense).

I see. Yes, a switch of some sort, similar to what Compiz has, was what I was thinking. For me, your suggestion was no problem. However, if we were to tell that to an average user that was trying to adopt Linux it would not only scare them it ruins the presentation of Kubuntu which, in my opinion, is generally excellent. I always try to evaluate situations like this from the perspective of a user that doesn't know the technical side. For example, I have a friend who runs Kubuntu 9.10 on his laptop because he was tired of dealing with Windows. He isn't bad with computers but doesn't have a high level of technical know how. I would hate to tell him or other converts that they have to edit a text file. Just food for thought. I appreciate your help and comments by the way.

lakerssuperman wrote:He isn't bad with computers but doesn't have a high level of technical know how. I would hate to tell him or other converts that they have to edit a text file. Just food for thought. I appreciate your help and comments by the way.

Ideally, it shouldn't be necessary. Fully agreed.

However, if there's an option to be changed that can't (easily) be changed with the standard GUI I'd rather talk someone like your friend through "change this line in that file" using kwrite rather than tell them how to use the gconf-editor or regedit.

A text-editor is familiar grounds for most. A specialized piece of software like regedit isn't.

I completely agree that in the grand scheme of things this is a very straight forward change. Editing a text file is certainly better than messing around in a registry editor type program. This is just me hoping for a day when Linux achieves "just works" for little things like this. I think it will be sooner rather than later and KDE 4.4 goes a long way to making this a reality. Using KDE 4.4.1 feels very professional to me.

I was just reading and there are several reports of higher CPU usage in KDE 4.4. Factoring that in and it seems that video playback with VDPAU is not really that different than with Gnome/Compiz. Some reports claim that Nepumuk and Akonadi are to blame and that uninstalling them significantly reduces CPU usage. Any thoughts on this?