Abstract: A video input apparatus and image pickup system having a camera section having a camera unit, and a video processing section for processing an image signal from the camera section so as to supply to a host terminal. The camera section outputs a multiplexed signal on which synchronizing signals of an image signal are multiplexed on the image signal, to the video processing section through a cable. The video processing section separates the image signal and the synchronizing signals from the multiplexed signal and processes the image signal to output a video signal. The camera unit in the camera section is exchangeable, and the video processing section detects the type of the camera unit based on the separated synchronizing signals and processes the image signal in accordance with the detected type of the camera unit.