Hi, I'm considering using Showtime for stimulus presentation with Matlab pr=
imarily because the QuickTime movie format loads much quicker than loading i=
ndividual frames in some other format (e.g. TIF). However, just by looking a=
t ShowtimeDemo.m, it's not clear to me how timing works, and I couldn't find=
an answer from my reading of Apple's rather daunting QuickTime API literatu=
re. Did I miss a critical piece of Showtime documentation?
My understanding of Showtime is that movies are assigned a given (or desire=
d) framerate that may or may not match the display's refresh rate. Although =
ShowtimeDemo.m takes display frame rate into account when it creates the mov=
ie, the movie could be played on displays with different temporal settings. =
If the movie and display's framerates don't match, I think QT uses frame int=
erpolation. Although QT may do a pretty good job at key frame interpolation,=
two obvious questions are how good a job and how does this impact my stimul=
i?
Ideally, I'd like to prevent QT from interpolating altogether and simply di=
splay every key frame synchronized to the display, whatever the display's fr=
ame rate is. Would one way of achieving this be:
for frameIndex = 1:nFrames
Showtime('MovieFrameDisplay', movie, frameIndex);
SCREEN(0, 'WaitBlanking');
end
Insight appreciated.
Stéphane
imarily because the QuickTime movie format loads much quicker than loading i=
ndividual frames in some other format (e.g. TIF). However, just by looking a=
t ShowtimeDemo.m, it's not clear to me how timing works, and I couldn't find=
an answer from my reading of Apple's rather daunting QuickTime API literatu=
re. Did I miss a critical piece of Showtime documentation?
My understanding of Showtime is that movies are assigned a given (or desire=
d) framerate that may or may not match the display's refresh rate. Although =
ShowtimeDemo.m takes display frame rate into account when it creates the mov=
ie, the movie could be played on displays with different temporal settings. =
If the movie and display's framerates don't match, I think QT uses frame int=
erpolation. Although QT may do a pretty good job at key frame interpolation,=
two obvious questions are how good a job and how does this impact my stimul=
i?
Ideally, I'd like to prevent QT from interpolating altogether and simply di=
splay every key frame synchronized to the display, whatever the display's fr=
ame rate is. Would one way of achieving this be:
for frameIndex = 1:nFrames
Showtime('MovieFrameDisplay', movie, frameIndex);
SCREEN(0, 'WaitBlanking');
end
Insight appreciated.
Stéphane