Does 'Unredirect fullscreen Windows' option in compiz improve performance for video playback?

Question

I found this option in CCSM. It's unchecked by default. There's a tooltip explaining that it allows drawing on fullscreen windows to not be redirected to offscreen pixmaps.

Solution 1

This option causes drawing to occur directly on the screen rather than drawing off-screen and then copying the drawn content back onto the screen.

Thus, yes it can dramatically improve graphical performance.

However there can be a draw-back - on some graphics cards/monitors - using this option can result in dramatic flickering. Particularly - this flickering effect can occur on full-screen apps.

Thus - its work experimenting, but if you see flickering, its best not to use.

Remember using CCSM can break your desktop.

If you want to toggle this value, you can use:

gconftool-2 --set /apps/compizconfig-1/profiles/Default/plugins/composite/screen0/options/unredirect_fullscreen_windows --type bool 0

Change 0 for 1 to switch this option back-on.

Solution 2

If you use the Nvidia proprietary drivers, it is very important to unredirect fullscreen windows, otherwise XVideo will not use sync to vblank and you will see tearing while playing videos. The Nvidia driver manual says:

Note that the Xv adaptors will ignore the sync-to-vblank option when drawing into a redirected window.

Comments

[Elijah Lynn]

How would one do what you propose?

[Mihai Capotă]

Use gconftool-2, as explained by @fossfreedom in his answer.

[Bart van Heukelom]

I'm experiencing the opposite. I get tearing with the option "Unredirect Fullscreen Windows" checked, but no tearing with it it unchecked.

[Mina Michael]

@BartvanHeukelom same thing with me

[Admin]

I got contradictory results. With unredirect (default) I get heavy tearing (synced to vsync, about 15% from the top of the screen and jittering in height), but with the option off, tearing is gone.