Ran into this same problem on osx two weeks ago using Microsoft HD webcams. The resolution was fine on Linux (which I built the patch in) but wouldn't do HD on osx. It will work in windows, so we switched out machines for the final project. The HD video does come through at full resolution on osx in other applications, but not in PD. I agree I think it's a Gem problem with osx. Running a virtual linux machine on osx I was able to use the full resolution, but alas the mac osx only allows one USB port per camera, so that solution wasn't going to work for my problem. Running a virtual machine for a professional application is probably too risky in terms of latency and complexity, but there's always boot camp for macs, and Linux is free.
-Alex
Eh no. Both Quicktime and now AVFoundation can do H264 decoding in video streams. I think the issue is that GEM doesn't yet support it on OSX as Iohannes has repeatedly sought OSX dev help ...
Unfortunately, Apple has not implemented this compression feature into their crappy usb camera drivers, so you stick to good old standard definition on OSX.
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Dan Wilcox
@danomatika