# Audio timing problems

**URL:** <https://psychtoolbox.discourse.group/t/audio-timing-problems/1694>\
**Category:** Uncategorized\
**Created:** [September 26, 2006, 10:24am UTC](https://psychtoolbox.discourse.group/t/audio-timing-problems/1694 "2006-09-26T10:24:19Z")\
**Posts on this page:** 1\
**Page:** 1

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**Author:** ![Allen\_Ingling](https://avatars.discourse-cdn.com/v4/letter/a/a183cd/32.png) [@Allen\_Ingling](https://psychtoolbox.discourse.group/u/Allen_Ingling)\
**Post date:** [September 26, 2006, 10:24am UTC](https://psychtoolbox.discourse.group/t/audio-timing-problems/1694/1 "2006-09-26T10:24:19Z")

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Hi,  
  
I'm programming an experiment which includes audio and visual stimuli.  
I've programmed the visual aspect - randomised pictures displayed for  
90 ms each. Now I have to find a way to encorporate the audio. I need  
to play the audio stimuli asynchronously, but the beginning of such  
stimuli must correspond to the beginning of a picture. I've tried  
using the Snd mex file, but I'm having problems - it makes a loud  
sound and then doesn't play for a while. I've also tried using the  
Matlab audioplayer, which works quite well, but I find that after a  
about a minute, I get a delay in the pictures display (misses a  
refresh), ever 10 pictures or so (every 900 ms).  
Timing is of utmost importance to me - delays above 5 ms are very  
problematic, especially so often.  
I'm not sure if the problem lies in the functions, or in the driver,  
or the OS. I'm working on Matlab 7 on Windows XP, and my sound card is  
a RealTeck AC'97 Audio.  
  
Here is the bit of code which displays the stimuli. This is just a  
test - which is why I used one of Window's wav files to play around with.  
  
% configure sound  
[y, f, nbits] = wavread('C:\WINDOWS\Media\Windows XP Menu Command.wav');  
player = audioplayer(y,f,nbits);  
playblocking(player);  
  
%%%%%%%%% DISPLAY OF PICTURES %%%%%%%%%%%%%%%%%%%%  
  
%Priority(2);  
  
% display distractors and targets  
for j = 1:length(trial)  
 play(player);  
 Screen('CopyWindow',winarray(trial(j)),window); %copy buffer  
window to screen  
 t1(j,1) = time; %get timing  
 wait(ontime); %wait ontime  
 t2(j,1) = time;%get timing  
 if(offtime ~= 0)  
 Screen(window,'FillRect',white, rect); %fill window with empty  
white block  
 t3(j,1) = time; %get timing  
 wait(offtime); %wait offtime  
 t4 (j,1) = time; %get timing  
 end  
end  
  
%Priority(0);  
  
I'd appreciate any insight on the matter, since I'm not very familiar  
with programming realtime audio.  
  
Thanks very much,  
Galit