Re: vga_waitretrace()

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From: Michal Moskal (malekith@pld.org.pl)
Date: Thu 31 May 2001 - 12:08:35 IDT


On Thu, May 31, 2001 at 02:48:11AM -0500, Tijs van Bakel wrote:
> John McCutchan <ttb@tentacle.dhs.org> writes:
> 
> > Is there a more accurate way do this? When I use it i get a shaky screen
> > from time to time. and when I don't I occasionally get a line going up
> > the screen.
> 
> What do you mean with 'shaky'?  Do you mean that you miss a retrace
> every now and then?  (ie, the framerate is not constant as you would
> like it to be)  If so, you could schedule your program to use SCHED_RR.
> 
>   #include <sched.h>
> 
>   struct sched_param sp;
>   sp.sched_priority = sched_get_priority_min (SCHED_RR);
>   if (sched_setscheduler (0, SCHED_RR, &sp))
>     fprintf (stderr, "could not set realtime scheduling.\n");
> 
> 
> If with shaky you mean that the screen actually moves, then I have no
> clue what is causing this.  In that case it would be interesting to
> know what videocard you use.
> 
> Another approach to get rid of the tearing line is to use page
> flipping.  Depending on which videomode you use this might be
> preferable or not.

I guess the problem can be that vga_waitretrace() doesn't work for
all cards (or am i wrong? but it didn't seem to work for my i740...).

-- 
: Michal ``,/\/\,       '' Moskal    | |            : GCS {C,UL}++++$
:          |    |alekith      @    |)|(| . org . pl : {E--, W, w-,M}-
:                                  |                : {b,e>+}++ !tv h
: Current project:  http://aleph-0.dhs.org/ywindow/ : PLD Team member

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