What does framerate message really do with jit.qt.grab ?

    Dec 23 2009 | 10:59 pm
    NB : All this post is related to the use of jit.qt.grab under Mac OS X 10.6 with Max 5.1.1
    I am experiencing strange behaviors with jit.qt.grab and the framerate message. What does this message really do ? I think it sets the QuickTime framerate attribute available via the settings message. But it remains unclear for my eyes. I saw that Thierry Fournier and Mathieu Chamagne has already ask something similar a year ago but with no answer, I hope I will get some useful help...
    First it is said in the jit.qt.grab reference : "The digitizer has to be closed and re-opened before changes to framerate take effect." Whereas the message seems to take effect on the fly, without the need to re-open the digitizer.
    Then I can't reach 90 fps in 640x480 with my Sony XCD-V60. When I sent the "framerate 90" to jit.qt.grab, quicktime got the right framerate (in the setting dialog) but the digitizer send only 60 fp. The chain is just jit.qt.grab -> jit.fpsgui and the proc loading is about 20%.
    Moreover when the dimension of jit.qt.grab are set to 320 x 240, I got 4 times brighter images than in 640 x 480. I've got the same effect by using the 2x2 binning mode of the camera (each image pixel is made with the sum of 4 CCD sensor signals). But the CSR setting are : with 320 x 240 : Format_7 Mode_4 with 640 x 480 : Format_0 Mode_5 (which explain that it can't go faster than 60 fps)
    Does anyone has an idea ? How can I get the full capacity of my camera ? (just remember, I works well on Windows...)