rachel@behemoth:~/OpenCV-2.4.0/samples/python$ lsusb -t
/: Bus 04.Port 1: Dev 1, Class=root_hub, Driver=ohci_hcd/2p, 12M
/: Bus 03.Port 1: Dev 1, Class=root_hub, Driver=ohci_hcd/3p, 12M
/: Bus 02.Port 1: Dev 1, Class=root_hub, Driver=ohci_hcd/3p, 12M
/: Bus 01.Port 1: Dev 1, Class=root_hub, Driver=ehci_hcd/8p, 480M
|__ Port 3: Dev 20, If 0, Class='bInterfaceClass 0x0e not yet handled', Driver=uvcvideo, 480M
|__ Port 3: Dev 20, If 1, Class='bInterfaceClass 0x0e not yet handled', Driver=uvcvideo, 480M
|__ Port 3: Dev 20, If 2, Class=audio, Driver=snd-usb-audio, 480M
|__ Port 3: Dev 20, If 3, Class=audio, Driver=snd-usb-audio, 480M
|__ Port 4: Dev 21, If 0, Class='bInterfaceClass 0x0e not yet handled', Driver=uvcvideo, 480M
|__ Port 4: Dev 21, If 1, Class='bInterfaceClass 0x0e not yet handled', Driver=uvcvideo, 480M