[visionegg] Re: RT accuracy

I once wrote a custom presentation loop that drew once every 10 or so iterations, but polled at each iteration. It worked pretty well. I also used some utility that boosted my USB polling rate to like 500hz or something totally unnecessary. 


I've got it pasted below.
it worked for me last time I opened this file last october.
hope it helps
-a

#!/usr/bin/env python
import VisionEgg
VisionEgg.start_default_logging(); VisionEgg.watch_exceptions()
import VisionEgg
from VisionEgg.Core import *
import pygame
from pygame.locals import *

screen = get_default_screen()
screen.set( bgcolor = (0.0,0.0,0.0) ) # black (RGB)


frame_timer = FrameTimer() # start frame counter/timer
count = 0
quit_now = 0
tt = 0



#the alternative loop
while not quit_now:

    for event in pygame.event.get():
        if event.type in (QUIT,KEYDOWN,MOUSEBUTTONDOWN):
            quit_now = 1
    screen.clear()
    tt =tt + 1
    thePosition = (pygame.mouse.get_pos())
    #print thePosition
if tt % 4 ==0: #gives us empty frames to evaluate mouse position without waiting for the monitor 
        #this is the only time when the screen actually gets updated
                
                        swap_buffers() # display what we've drawn
                        frame_timer.tick() # register frame draw with timer
frame_timer.log_histogram()



On Sep 24, 2007, at 8:12 PM, Andrew Straw wrote:


Hi John,
It seems to me that you want to poll your response as often as possible 
but draw frames only once per vertical refresh. Do I get that right?

In this case, one option is to write to a multi-threaded (or
multi-process) application where these two tasks are de-coupled.

John Christie wrote:

    As some of you may have deduced from recent messages, I'm just
learning VisionEgg.
    I've got my stimuli coming up and the timing looks good but I've
got one issue. I can't seem to be able to assess the current state of 
my buttons to find out RT more than once per presentation frame.  How
can I have frame by frame presentation accuracy and RTs that are
better than that (on average)?

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