From where do I get a SYNC signal?

Thread View: comp.sys.sgi.hardware

2 messages

[T] Back to Threads [V] Tree View [G] Group Articles

2 total messages Started by Dario Ringach, x3941 Thu, 07 Jan 1993 17:57

#72

Author: Dario Ringach, x3941
Date: Thu, 07 Jan 1993 17:57

10 lines
1003 bytes

I'd like to synchronize the screen refresh with external equipment for
a psychophysical experiment...  I only want a signal coincident with
the FIRST vertical SYNC of the monitor AFTER I call swapbuffers() (i.e.
exactly when the buffers are swapped).  Is there a way to do this?
Thank you!

---
Dario Ringach                           office: (212) 998-3941
Center for Neural Science               home:   (212) 727-9346
New York University                     e-mail: dario@cns.nyu.edu

Re: From where do I get a SYNC signal?

#79

Author: Marc van Kempen
Date: Sat, 09 Jan 1993 00:56

37 lines
1661 bytes

dario@cns.nyu.edu (Dario Ringach, x3941) writes:

>I'd like to synchronize the screen refresh with external equipment for
>a psychophysical experiment...  I only want a signal coincident with
>the FIRST vertical SYNC of the monitor AFTER I call swapbuffers() (i.e.
>exactly when the buffers are swapped).  Is there a way to do this?
>Thank you!

From the man page of GSYNC():

In some implementations gsync blocks immediately. In others, gsync
blocks only when a graphics call is made.

I think swapbuffers() does the same. It allows your program to continue
unless it performs a graphics function that would affect the
current frontbuffer, that is: after the call to swapbuffers, but before
the buffers have actualy been 'swapped'.

Maybe you should include a line in your code like:

unsigned long dummy;

swapbuffers();
lrectread(0,0,0,0,&dummy);

This should block your program until the next vertical retrace.

If your interested, I've written some (dirty) code that directly uses the
vertical retrace interupt adress. It only works on IP12 boards
though (Indigo-Elan, Iris). I'll post it if anybody can use it.

Marc.

BTW: can anybody at Silicon tell my if they have figured out what causes
my Indigo-Elan to hang in PAL mode?

Thread Navigation

This is a paginated view of messages in the thread with full content displayed inline.

Messages are displayed in chronological order, with the original post highlighted in green.

Use pagination controls to navigate through all messages in large threads.

Back to All Threads