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- function [actual_frames, actual_seconds, nominal_frames, nominal_seconds] = MoBI_frames_Brescia(secs, ifi)
- % first output = number of frames output shortened by a 0.5 frames to be inserted into
- % the (Screen('Flip'), VBL) as waiting. This strategy allows to have
- % exactly the delay that is the closest one to the delay requested
- % second output = actual seconds to wait for the next flip to happen
- % example: the set delay is 0.21 secs, with a inter frame interval of
- % 0.0167 s (60 Hz refresh rate)
- % 0.21 s is not a multiple of the frame interval
- % so 0.21 is going to be rounded to the closer multple --> 13 frames (which corresponds to 0.2171s)
- % in order to avoid that Psuchtoolbox flips randomly at 13 or at 14 frames
- % the strategy is to reduce the delay to be inserted in the function by a
- % half frame. --> 12.5
- % then the function transforms back the 12.5 frames into seconds
- % thus the flipping will happen always and exactly at (13 frames * ifi) which is 0.2171s
- % [actual_frames actual_seconds, nominal_frames nominal_seconds] = MoBI_frames_Brescia(0.21, 0.0167)
- % actual_frames = 12.5000
- % actual_seconds = 0.2087
- % nominal_frames = 13
- % nominal_seconds = 0.2100
- % rounds the indicated time to an exact number of frames
- nominal_frames = round(secs/ifi);
- % subtract half frames in order not to risk an overshoot (longer duration than required)
- actual_frames = nominal_frames - 0.5;
- % true waiting
- actual_seconds = actual_frames*ifi;
- nominal_seconds = secs;
- end
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