/usr/share/psychtoolbox-3/PsychTests/FrameSequentialStereoTest.m is in psychtoolbox-3-common 3.0.11.20131230.dfsg1-1build1.
This file is owned by root:root, with mode 0o644.
The actual contents of the file can be viewed below.
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65 66 67 68 69 70 71 72 73 74 75 76 77 78 79 80 81 82 83 84 85 86 87 88 89 90 91 92 93 94 95 96 97 98 99 100 101 102 103 104 105 106 107 108 109 110 111 112 113 114 115 116 117 118 119 120 121 122 123 124 125 126 127 128 129 130 131 132 133 134 135 136 137 138 139 140 141 142 143 144 145 146 147 148 149 150 151 152 153 154 155 156 157 158 159 160 161 162 163 164 165 | function FrameSequentialStereoTest(screenid)
% FrameSequentialStereoTest(screenid)
%
% Tests presentation order and timing of stimulus onset in frame sequential
% stereo mode. This is a perceptual test.
%
% The test will run on the screen with the highest number by default, but
% you can pass a 'screenid' to it, if you want.
%
% After startup, the display will show a mostly constant yellow, red or
% green display. Depending on what you see, it tells you how your graphics
% hardware syncs buffer onset:
%
% A) If you see a constant yellow screen, then your hardware always makes sure
% that a full stereo cycle is presented before executing a Screen('flip')
% command, however its not defined if onset of a new stimulus will happen
% with the left buffer first or with the right buffer. You'd need
% measurement equipment to verify which is the startbuffer. The granularity
% of buffer swaps will be reduced to the duration of two video refresh
% intervals, as indicated by the 'ifi' number printed to the Matlab window.
%
% B) If you see either a constant green or a constant red at each run of the
% script (always red or always green, never anything else), then your
% hardware will sync bufferswaps always to the onset of the left stereo
% buffer (if you see red) or to the right buffer (if you see green).
%
% C) If you see either a constant green or a constant red during one run of the
% script, but you observe different colors at repeated runs of the script,
% or a slow switching between red and green, then that means that your
% hardware doesn't care about syncing bufferswaps to a fixed buffer,
% instead it just swaps at the next VBL, so either the left- or the right-
% stereo buffer of a new stimulus will show first. The maximum flip rate is
% equal to the monitor refresh rate.
%
% In case C) you are out of luck if you use Microsoft Windows. If you use
% Linux, then contact the forum with a feature request, we may implement a
% solution for you. If you run MacOS/X, you can 'force' the graphics
% hardware to always synchronize stimulus onset (flip) to either the left-
% or the right buffers display cycle, and you can query which buffer was
% displayed first after flip, left- or right. However this is a software
% trick which needs calibration. To test if the trick works on your setup,
% do the following:
%
% 1. Wait until color of the display settles to either red or green.
% 2. If its green, press the 'g' key, if its red, press the 'r' key.
% 3. After a short period, the display should settle to a nice green,
% indicating that the trick works, and PTB should write 'GREEN' to the
% Matlab window.
% 4. If the display doesn't stabilize to green, but at least the output of
% the Matlab window corresponds with your percept (GREEN for green, RED for
% red) then that means that your system has very noisy timing.
% History:
% 08/14/07 Written (MK).
% Running on PTB-3?
AssertOpenGL;
% Same keymappings for all platforms:
KbName('UnifyKeyNames');
redfield = -1;
if nargin < 1
screenid = [];
end
if isempty(screenid)
screenid = max(Screen('Screens'));
end
if IsOSX==0
fprintf('Caution: While the perceptual test in this script will still work (perceptually),\n');
fprintf('query of the stereobuffer presentation with which flip was synchronized and control\n');
fprintf('of target stereobuffer to which flip should synchronize, will not work on your operating\n');
fprintf('system. This feature is only available on Macintosh OS/X systems, and scheduled for inclusion\n');
fprintf('on GNU/Linux systems. No support for MS-Windows is planned, due to limitations of that OS.\n\n');
end
% Open double-buffered frame-sequential stereo window on display
% 'screenid', background clear color is black (==0):
win = Screen('OpenWindow', screenid, 0, [], [], [], 1);
ifi = Screen('GetFlipInterval', win)
% Wait until all keys are released:
while KbCheck; end;
count = 0;
delta=[];
% Initialize target field to zero. This is purely random coice and will get
% properly set, once we know the real assignment of buffers to fields.
targetfield = -1;
% Run test loop until keypress:
while 1
% Count iterations:
count = count + 1;
% Show both stereo buffers in black:
Screen('SelectStereoDrawbuffer', win, 0, -1);
Screen('FillRect', win, 0);
Screen('SelectStereoDrawbuffer', win, 1);
Screen('FillRect', win, 0);
% Flip at earliest point in time:
t1 = Screen('Flip', win);
% Show left stereo buffer in red:
Screen('SelectStereoDrawbuffer', win, 0, targetfield);
Screen('FillRect', win, [255 0 0]);
% Show right stereo buffer in green:
Screen('SelectStereoDrawbuffer', win, 1);
Screen('FillRect', win, [0 255 0]);
% Flip at earliest point in time:
t2 = Screen('Flip', win);
% Query VBL count of the video frame corresponding to last flip:
winfo = Screen('GetWindowInfo', win);
fieldid = winfo.VBLCount;
if redfield~=-1
if mod(fieldid, 2) == redfield
fprintf('RED\n');
else
fprintf('GREEN\n');
end
% Select target start field for flips to be a green frame. If
% everything works, then the user should only see green after
% calibration:
targetfield = 1-redfield;
else
fprintf('UNKNOWN: Press g if screen is green, r if screen is red.\n');
end
delta(count) = t2 - t1;
[down secs keycode] = KbCheck;
if down
if keycode(KbName('ESCAPE'))
break;
end
if keycode(KbName('r'))
redfield = mod(fieldid, 2);
end
if keycode(KbName('g'))
redfield = mod(fieldid+1, 2);
end
if keycode(KbName('x'))
while KbCheck; end;
KbWait;
end
end
end
% Close display:
Screen('CloseAll');
med = median(delta)
avg = mean(delta)
% Done.
return;
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