I want to see what's involved in talking to a USB video camera using a
    standalone processor.

At ESC, I talked to the folks at Cypress about microcontrollers with USB
"master" interfaces (rather than the client side used in mice and
cameras and such.)  There are apparently a lot of issues with doing
something like this - a master device would normally have to be involved
in the scheduling of all 128 (?) possible client devices, hub
management, and so on.  They asked me if a master that would only talk
to a single client would be an interesting product (and since I was
mostly interested from a theoretical point of view, I didn't have an
answer...

BillW