[Bug 39696] dual head: different vert refresh freq, applications sync to the wrong one

bugzilla-daemon at freedesktop.org bugzilla-daemon at freedesktop.org
Tue Aug 9 06:39:31 PDT 2011


--- Comment #4 from Michel Dänzer <michel at daenzer.net> 2011-08-09 06:39:31 PDT ---
(In reply to comment #3)
> > > and with synchronized vertical retrace?
> > 
> > There's no mechanism for that yet in general. However, if you manage to use the
> > same mode for both displays, you might be able to source both of them off the
> > same CRTC, in which case they should be perfectly synchronized.
> Can this be set using xrandr or something else?

Yeah, using the --crtc option. With xrandr --verbose you can see which CRTCs an
output can use.

> > > 2.) Is there a way to switch 3D and video application sync
> > > from the internal to the external vsync rate?
> > 
> > There's no such mechanism for 3D yet.
> From the user's point of view, xvattr would be expected to set both?

Not sure how xvattr could be expected to affect anything but XVideo.

Some random ideas: All other things being equal, the driver could synchronize
to the CRTC of the primary output, which can be changed using xrandr --primary.
Or if that's not good enough, we could add special RandR properties for this.

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