Ubuntu – Screen tearing while watching video

Tearing in videos is caused by the video drawing not being synchronised with the refresh-rate of the display. This results in displaying the top part of one frame and the bottom half on the previous frame at the same time, which is particularly noticeable on sections of video with horizontal panning.

The open-source drivers, with DRI2, should be able to synchronise their drawing with the screen refresh properly, even when running with desktop effects enabled¹. The proprietary nVidia and ATi drivers may not do this properly.

Finally, disabling desktop effects should eliminate the tearing regardless of what driver you're using - all (sensible) drivers can sync-to-vblank for video in this case.

¹: Technically, the problem is having a compositing manager running, because that means that all windows are first drawn off-screen and then composited to the display by the compositing manager. Since the video is first “drawn” offscreen, it's not possible to synchronise this to the screen refresh.

This issue occurred after updating 14.04.2. To fix tearing in Chrome while watching Netflix full-screen do the following:

1. Install CompizConfig Settings Manager:

   sudo apt-get install compizconfig-settings-manager 
   

2. Open CompizConfig Settings Manager.

3. Click Composite.

4. In Unredirect Match, add & !(class=^Google-chrome) to the end of the line.

This prevents Chrome windows from being unriderected, while leaving other fullscreen windows unredirected. Unredirecting fullscreen windows lets fullscreen apps draw directly to the screen, which should result in higher performance. That also means the app drawing has to manage v-sync if it cares about it. Chrome does not do v-sync by itself when there's a compositing window manager. Thus it relies on Compiz to do it. That's why we need to let Compiz redirect Chrome and manage v-sync for it. In order to not hurt other apps' performance, we add an exception to the Unredirect Match rules instead of turning off the feature altogether. Note that !(class=google-chrome) is already there by default but it doesn't work. The current Chrome window class starts with a capital "G" whereas the default rule starts with a lowercase "g". It may be possible that the window class got changed during a Chrome update at some point between the rule being added to Ubuntu and now. It could also be a regression in Ubuntu that changed the leading "G" was changed to "g".