QuickCam Pro 9000 image scaling

Hi,

The QuickCam Pro 9000 has a CMOS-sensor with a resolution of 1600x1200 and its size is 6mm x 4mm (I meassured it). Since I'm using the webcam in USB 1.1 mode I'm limited to max 800x600. When I'm using this mode how is it generating this 800x600 image? A crude way is to use just one quarter of the CMOS-sensor, you could also use the whole sensor and e.g. skip pixels with even x / y coordinates or you could capture at 1600x1200 and scale that back. What is the hardware doing? It matters for the image quality.

Thanks,
Roderick