Hi Kevin,

I had a problem where libusb was unable to submit the isochronous
transfer request for video streaming: libusb_submit_transfer would
return -99, which was the result of a kIOUSBNotSent1Err error in the
OSX libusb module. libusb was updated to work around that issue in
2010, but there hasn't been a release since then; the version in
<git://git.libusb.org/libusb.git> might do better.

I think this is relevant:
<http://comments.gmane.org/gmane.comp.lib.libusb.devel.general/10637>.
The "unable to read from it" might be related, although that's an
error with an interrupt transfer, not an isochronous transfer.

I don't think I ever got an internal camera to work on a Mac; I
believe the OS was claiming it, and libusb wasn't able to take it
over, even after I moved a few .kext files out of the way. The cameras
do work with libuvc under Linux; the ones I tried were definitely
almost-correct UVC.

 - Ken