Bug#698503: tearing with Radeon HD 6970

[Alex Deucher]

On Sat, Jan 19, 2013 at 8:59 AM, Marc Dequènes <duck at duckcorp.org> wrote:
> Package: xserver-xorg-video-radeon
> Version: 1:6.14.4-6
> Severity: normal
>
>
> Coin,
>
> At the end of the 2012 year, i upgraded my desktop machine, switching from
> Radeon HD 4890 to Radeon HD 6970. Since then i experience tearing, easily
> visible when watching videos for example. I was using Unagi at the time, so
> i stopped using it which only reduced the effect.
>
> It is not easy to show the resulting effect so i tried some camera shots
> (see attached) using the following video :
>   http://www.youtube.com/watch?v=ceX18O9pvLs
> Unfortunately, it does not seem to show anything proving I'm not drunk. The
> other machine i can test on has got a Mobility Radeon X300 and besides some
> slowness display it properly ; shots on this machine also show "brightness
> blocks", even if less blocks and with a perfect separation line.
>
> Tell me if i can test anything else.

What are you using to render the videos (Xv, GL)?  Did you also change
your desktop environment?  Note that if you are using a compositing
manager (compiz, gnome shell, kwm, etc.), the compositing manager is
responsible for preventing tearing by syncing screen updates to vsync.
 If you are using Xv, the driver's anti-tearing Xv features only work
when rendering directly to the display buffer.  If you are using a
composting manager, the driver renders to an offscreen buffer and the
compositor is responsible for updating the display buffer with the new
Xv data.

Alex