You didn't tell us which operating system/PTB you use.
That's the most crucial info for any request as features
differ between the different PTB's.
WaitBlanking on OS9 or Win will wait for VBL onset on the
display that the onscreen window belongs to. If both
displays are running in sync with each other and you
can paint your stim fast enough for both views you're done.
In theory - in practice there may be limitations imposed
by the specific device driver of your graphics hardware.
OS-X PTB contains two different algorithms for synced
multi-display flips, both untested. I don't have access to
dual-display on OS-X and the person who requested this
feature didn't give me any feedback if it works for him.
In theory, each of them should be better than the
old solutions, in practice nobody knows until tested...
A simple visual test on old PTBs is to display an alternating
black-white pattern in an endless loop...
while(1)
Screen('WaitBlanking",....)
Screen('FillRect', ...., [255 255 255]);
Screen('WaitBlanking",....)
Screen('FillRect', ...., [0 0 0]);
end;
If you get homogenous black-white flicker, syncing is
probably ok. If you get tearing on a display you'll know
vbl sync is screwed. If you get a static horizontal "crack" on some
line you'll have to place your stimulus properly to avoid trouble.
-mario
--- In
psychtoolbox@yahoogroups.com, "jesterdo" <cord.westhoff@r...>
wrote:
>
> Thanks!
> Now I'm working with a resolution of 2048x768, and another question
> appeared: What about the vertical sync of the two screens? I.e., when
> I use the 'WaitBlanking', are both screens cleared at the same time?
> Or how can I be sure that stimuli on the screens appear at exactly the
> same time?
>
>
> --- In psychtoolbox@yahoogroups.com, "Mario Kleiner"
> <mario.kleiner@t...> wrote:
> >
> > Hi,
> >
> > the OS-X Psychtoolbox and afaik the OS-9 Psychtoolbox
> > do support simultaneous use of multiple displays,
> > but according to
> > <http://www.psychtoolbox.org/win.html#differences>,
> > the Windows Psychtoolbox doesn't support simultaneous
> > use of multiple displays (if this information is still
> > up to date).
> >
> > -mario
> >
> >
> > --- In psychtoolbox@yahoogroups.com, "jesterdo" <cord.westhoff@r...>
> > wrote:
> > >
> > > Might be interesting:
> > >
> > > [win, res]=screen(0,'OpenWindow',0,[],8);
> > > waitsecs(1)
> > > clear mex
> > >
> > > ...causes BOTH screens to go black...whereas...
> > >
> > > [win, res]=screen(0,'OpenWindow',0,[],16);
> > > waitsecs(1)
> > > clear mex
> > >
> > > ...(i.e., with a 16bit-window) only causes the FIRST screen to go
> black.
> > >
> >
>