Two Alternative Forced Choice (2AFC) Subjective Experiment
The 2AFC protocol displays the original and distorted images
side by side in the center of the screen (center of the browser here).
The position of the original image (or distorted) is unknown
(left/right part of the screen).
The index of the current image is shown on top of the page.
The observers is asked to select the distorted image.
The observers must click on one of the two images, when he believes it is the distorted version.
A selection is mandatory, even when no distortions are perceived.
This is a modified 2AFC protocol.
There are no restrictions on the display time.
Test conditions:
At the beginning of the subjective experiment, the observer is asked
for his name and a checkbox is here to display the playlist in a random
order.
The test duration varies according to the number of displayed images.
The playlist can be seen here:
http://websubjexp.polytech.univ-nantes.fr/2AFC/data/playlist.txt
The observers should remain seated at the same distance from the screen during all the test duration.
The viewing distance should be approximately 6 times the height of the displayed images.
Once the experiment is finished, the observer can acces the resulting scores here:
http://websubjexp.polytech.univ-nantes.fr/2AFC/data/Scores_<NAME>.txt
A value of 1 stands for a correct designation of the distorted image (0 means the distorted image couldn't be found).
Observers can run the experiment more than once, the collected scores will thus be appended in the results file.