Forums > Jitter

Color differences between jit.qt.grab & jit.dx.grab?

March 16, 2010 | 10:41 pm

Hi everyone, I was testing my handycam last night using jit.qt.grab and jit.dx.grab separately on two computers (qtgrab on a PowerMac and dxgrab on a PC). I was using a RCA splitter cable to transmit the video signal from my camcorder to two DFG boxes, and then feed them to jit.qt.grab and jit.dx.grab.

The problem is, when I was comparing two videos displayed on pwindow, the color from jit.qt.grab is always looks "warmer" than jit.dx.grab, I double checked the "setting" message in both patches, and make sure the brightness, saturation, sharpness… all parameter are set to 50%, but still couldn’t get same color quality…!

Is this caused by the difference in jit.qt.grab and jit.dx.grab? Is there a way to synchronize their color display?


March 16, 2010 | 11:15 pm

Probably related to gamma correction, and/or YUV -> RGB conversion differences. Here’s an example which crossfades between original and a squared version to get gamma correction style results for cheap. Alternately, you can fill a lookup table with an appropriate exponential curve and use jit.charmap for fast color adjustment.

– Pasted Max Patch, click to expand. –

March 25, 2010 | 12:59 pm

Hi

I recently pointed out a difference between jit.qt.grab and jit.dx.grab: http://cycling74.com/forums/topic.php?id=24690

nobody has confirmed this phenomenon (but I am pretty sure), but maybe it is related?


March 25, 2010 | 3:05 pm

Totally unrelated issue. As mentioned on that thread, you should just avoid jit.qt.movie on windows, unless your application requires it.


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