Actual video resolution in open sesame

Liat_Israeli_Ran · June 2020

Hey,

I have some troubles understanding the actual resolution the participants in my experiment see.

I collected data using Open Sesame (and pygaze add-ons) and Tobii pro eye-tracker.

The backend in the experiment is legacy and the experiment resolution is 1024*768

(the default and what is mention in the output file of pygaze).

One of my stimuli is a video with a 1920*1080 resolution, which is also my screen's resolution.

I found out that during the experiment, the video is resized to a larger size, such that only the center part of it is seen on the screen. About 30% of the X axis are trimmed (15% from the right edge and 15% from the left edge); and about 12.5% of the Y axis are trimmed (half of it from the top and half of it from the bottom).

I need to figure out what is the actual video resolution that was displayed, to calculate the correct XY coordinates of areas of interest in the screen - to analyze the eye tracking data.

Thanks

Liat

sebastiaan · June 2020

Hi @Liat_Israeli_Ran ,

The legacy backend changes the resolution of the monitor, in your case to 1024 × 768. Therefore:

X = 0 (left) as recorded by the eye tracker corresponds to X = (1920 - 1024) / 2 = 448 in video coordinates
Y = 0 (top) as recorded by the eye tracker corresponds to Y = (1080 - 768) / 2 = 156 in video coordinates
X = 1024 (right) as recorded by the eye tracker corresponds to X = 448 + 1024 = 1472 in video coordinates
Y = 768 (bottom) as recorded by the eye tracker corresponds to Y = 156 + 768 = 924 in video coordinates

I hope that helps!

Cheers,

Sebastiaan

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