Hello! I am very new with psychtoolbox so I have an important question about timing. In the simple script below i am trying to make the word " FEEDBACK" appear on my screen for a certain amount of time. I've done this based on a demo i found online but I don't know for how long the word appears on screen. How can I make the presentation last for ...le'ts say 4 secs and display the presentation duration on my command line?
Thank you!
% Clear the workspace and the screen
close all;
clearvars;
sca
Screen('Preference', 'SkipSyncTests', 1);
% Here we call some default settings for setting up Psychtoolbox
PsychDefaultSetup(2);
% Get the screen numbers
screens = Screen('Screens');
% Select the external screen if it is present, else revert to the native
% screen
screenNumber = max(screens);
% Define black, white and grey
black = BlackIndex(screenNumber);
white = WhiteIndex(screenNumber);
grey = white / 2;
% Open an on screen window and color it grey
[window, windowRect] = PsychImaging('OpenWindow', screenNumber, grey);
% Set the blend funciton for the screen
Screen('BlendFunction', window, 'GL_SRC_ALPHA', 'GL_ONE_MINUS_SRC_ALPHA');
% Get the size of the on screen window in pixels
% For help see: Screen WindowSize?
[screenXpixels, screenYpixels] = Screen('WindowSize', window);
% Get the centre coordinate of the window in pixels
% For help see: help RectCenter
[xCenter, yCenter] = RectCenter(windowRect);
% Retreive the maximum priority number
topPriorityLevel = MaxPriority(window); %to window ths line 22
Priority(topPriorityLevel);
vbl = Screen('Flip', window);% to window ths line 22
% Query the frame duration
ifi = Screen('GetFlipInterval', window);
numSecs = 1;
numFrames = round(numSecs / ifi);
waitframes = 1;
for frame = 1:numFrames
% Draw text in the upper portion of the screen with the default font in red
Screen('TextSize', window, 70);
DrawFormattedText(window, 'FEEDBACK', 'center',...
screenYpixels * 0.25, [1 0 0]);
% Flip to the screen
vbl = Screen('Flip', window, vbl + (waitframes - 0.5) * ifi); %deixnei 'feedback' gia periorismeno xroniko diasthma
end
Priority(0);
sca;