Bug#878170: xserver-xorg-video-radeon: Fails to match video to vsync

Michel Dänzer michel at daenzer.net
Wed Oct 11 08:40:59 UTC 2017

On 10/10/17 07:50 PM, Anton Ivanov wrote:
> Package: xserver-xorg-video-radeon
> Version: 1:7.8.0-1+b1
> Severity: important
> Dear Maintainer,
> Radeon (and amdgpu for that matter) in stretch no longer match frames
> to vsync correctly. This is observable with vdpau, opengl and plain
> xvideo. 
> This used to work correctly in jessie so this is a recent regression.
> This is also observable in both full screen and windowed mode. The
> bottom ~5-10% of the picture updates on the wrong vsycn which is
> clearly visible especially in action sequences and animation.
> Tested with vlc, mplayer, xine and other software in a variety of
> output modes. I think I have eliminated other possible common factors
> leaving the video driver (and/or firmware) the most likely culprit.

The only possibilities for reliably avoiding tearing in Xorg have always

1. Using a compositing manager which uses OpenGL for rendering
2. Running an application in fullscreen, using page flipping (i.e. the
   application must use something like OpenGL / VDPAU / VA-API / ... for
   rendering / presentation, but not something like XVideo or even pure
3. Enabling TearFree

Note that 1.+2. are not sufficient when using rotation or other
transforms via the RandR extension.

Does your setup fall under any of these cases? If not, you may just have
gotten lucky before.

Earthling Michel Dänzer               |               http://www.amd.com
Libre software enthusiast             |             Mesa and X developer

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