I recall that this came up a while back on the Firewire list, and the
consensus was that 2 iSights at 640x480 far exceed the FW400
bandwidth, so it "automagically" downgrades one to fill the remaining
bandwidth for the second camera. IIRC, a single 640x480 signal takes
up about 90% of the FW400 data bandwidth (but don't quote me on
that). A FW800 hub won't help, of course, since the iSights are
FW400, but if you had 2 FW800 cameras on the FW800 ports it should work.
HTH,
Roland
On Feb 3, 2006, at 4:05 PM, John C. Randolph wrote:
Ok, I got two more iSight cameras, and something's happening that I
don't understand.
With two cameras installed, I put two video input patches in my
composition. The first one shows me a 640x480 image. The second
one produces a 176x144 image. It's rather jarring visually for one
to have so much less resolution.
My system is a dual 2.0Ghz G5, with a GeForce 6800 Ultra, 256MB
VRAM, driving a 30" Cinema display. I have both of the cameras
plugged into the FW ports on the display. With three cameras, the
third input patch gives me an even smaller image.
I've looked at the device settings for both of the input patches,
and they're identical. How do I get them both to hand me a 640x480
image, or failing that, get them both to the same size?
Am I running out of FW bandwidth? Do I need to pick up a FW800
hub, and plug the cameras into that, or do I need to upgrade my
machine and video card?
The input patches all defaulted to using CCIR-601-uyvy compression,
and there are a LOT of other choices. Would any of them help?
Thanks,
-jcr
John C. Randolph <email@hidden> (408) 914-0013
Roaming Cocoa Engineer,
Available for your projects at great Expense and Inconvenience.
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