/usr/share/psychtoolbox-3/PsychTests/SyncedCLUTUpdateTest.m is in psychtoolbox-3-common 3.0.11.20131230.dfsg1-1build1.
This file is owned by root:root, with mode 0o644.
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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 | function SyncedCLUTUpdateTest(synced)
% SyncedCLUTUpdateTest
%
% Perceptual test to test synchronization of hardware gamma table
% updates to the vertical refresh and to Screen('Flip').
%
% The command Screen('LoadNormalizedGammaTable') provides the optional parameter
% 'loadOnNextFlip'. If set to 1, Psychtoolbox is requested to defer the upload
% of the specified gamma table until next execution of the Screen('Flip') command,
% i.e. swapping the back- and front buffers and update of the gamma table should
% happen synchronously with each other and with vertical retrace.
%
% This test allows to perceptually check correctness of this mechanism. In a loop
% it shows two alternating stimuli: A gray-level ramp of range 0-255, displayed
% with a hardware lut of *half* intensity range 0-0.5. Then, after next retrace, a
% gray-level ramp of *half* range 0-128 with a hardware lut of *full* intensity range
% 0-1.0. If update of the visual stimulus (the graylevel ramp) and of the corresponding
% clut happens synchronously at the same vertical retrace during the 'Flip' command,
% as expected, then the half intensity stim + full intensity lut or full intensity stim +
% half intensity lut should cancel each other out, resulting in the perception of a
% half-intensity gray-ramp with no or only minimal flicker. If, on the other hand,
% synchronisation of clut update and flip doesn't work properly, then one should see
% a strong flicker of the gray-ramp due to non-matching stimulus and clut.
%
% You can easily produce the visual impression of failed sync by providing the optional
% parameter synced = 0 to enforce non-synced updates.
%
% Even if synced updates work, you may see some artifacts at the top of the display,
% due to the inability of slow gfx-hardware to update the lut quickly enough. Either
% avoid that display area for your stim or buy a faster graphics card. Enabling realtime
% scheduling via Priority() command may also help.
%
% The accuracy of stimulus onset timestamps may be reduced on M$-Windows when using
% this mode of operation.
%
% History:
% 24.07.2006 Written (MK).
% This script calls Psychtoolbox commands available only in OpenGL-based
% versions of the Psychtoolbox. The Psychtoolbox command AssertPsychOpenGL will issue
% an error message if someone tries to execute this script on a computer without
% an OpenGL Psychtoolbox
AssertOpenGL;
if nargin < 1
synced = 1; % Default to synchronized updates.
end
synced
try
% Get the list of screens and choose the one with the highest screen number.
% Screen 0 is, by definition, the display with the menu bar. Often when
% two monitors are connected the one without the menu bar is used as
% the stimulus display. Chosing the display with the highest dislay number is
% a best guess about where you want the stimulus displayed.
screens=Screen('Screens');
screenNumber=max(screens);
% Open a double buffered fullscreen window:
w=Screen('OpenWindow',screenNumber);
% Store a backup copy of original LUT into origLUT.
origLUT=Screen('ReadNormalizedGammaTable', screenNumber);
% Build a simple gray-level ramp as a single texture.
[width, height]=Screen('WindowSize', w);
s=floor(min(width, height)/2)-1;
[x,y]=meshgrid(-s:s, -s:s);
fintex=ones(2*s+1,2*s+1);
fintex(:,:)=mod(x,255)+1;
% tex1 is a full intensity ramp...
tex1=Screen('MakeTexture', w, fintex);
% ...with a half intensity clut.
lut1=origLUT * 0.5;
% tex2 is a half intensity ramp...
tex2=Screen('MakeTexture', w, fintex * 0.5);
% ...with a full intensity clut.
lut2=origLUT * 1;
% Switch to realtime-mode for smooth animation:
priorityLevel=MaxPriority(w);
Priority(priorityLevel);
% Query monitor refresh interval:
ifi = Screen('GetFlipInterval', w);
% Initial Flip to sync us to vbl and get a timestamp:
vbl = Screen('Flip', w);
i=0;
t1=GetSecs;
% Test loop: Runs until keypress or 1000 iterations have passed:
while (1)
% Update the hardware CLUT with our lut 1: Defer update
% until Screen('Flip'), if synced == 1
Screen('LoadNormalizedGammaTable', w, lut1, synced);
% Draw corresponding stimulus:
Screen('DrawTexture', w, tex1);
% Show at next retrace after given deadline and update clut:
vbl = Screen('Flip', w, vbl + 1.5 * ifi);
% Update the hardware CLUT with our lut 2: Defer update
% until Screen('Flip'), if synced == 1
Screen('LoadNormalizedGammaTable', w, lut2, synced);
% Draw corresponding stimulus:
Screen('DrawTexture', w, tex2);
% Show at next retrace after given deadline and update clut:
vbl = Screen('Flip', w, vbl + 1.5 * ifi);
% Increment framecount:
i=i+1;
% Abort after 1000 iterations or on a key-press:
if KbCheck || (i>1000)
break;
end;
end;
% Some stats...
avgfps = i / (GetSecs - t1)
% Disable realtime scheduling:
Priority(0);
% Restore the original origLUT CLUT lookup table:
Screen('LoadNormalizedGammaTable', screenNumber, origLUT);
% Close window, we're done:
Screen('CloseAll');
catch
%this "catch" section executes in case of an error in the "try" section
%above. Importantly, it closes the onscreen window if its open.
Priority(0);
if exist('origLUT', 'var')
Screen('LoadNormalizedGammaTable', screenNumber, origLUT);
end
Screen('CloseAll');
psychrethrow(lasterror);
end %try..catch..
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