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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 640×480 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 2×2 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…)



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