The frame rate is the number of frames to be processed per unit time in video. It is usually expressed as a number per second and uses the unit of fps (frame / sec).
For USB, the upper limit (the maximum value on the theoretical value) is determined regarding to PC function.
USB 2.0 is 480 Mbps (= 60 MB / s)
USB 3.0 is 5120 Mbps (= 640 MB / s)
If it is a USB camera with USB 2.0, theoretically
If color data of 1.3 million pixels (1280 X 1024), it is about 15 fps
If it is color data of 2 million pixels (1600 X 1200), it is about 10 fps
If color data of 3 million pixels (2048 X 1535), it is about 6 fps
. (It will not change significantly with camera performance or price.)
However, It is a theoretical value, it varies greatly depending on the capabilities of the CPU, memory and other environments (eg: regular software).
Actual measurement seems to be mostly about 60% or less of the theoretical value.
Among them, there is also a way to raise the frame speed slightly.
(Refer to “How to Increase the Frame Speed”)