1. A video input processor comprising: an imaging signal-generating portion configured to image a subject and producing first imaging signals containing visible light components and a second imaging signal containing near-infrared light components; a gain adjustment portion configured to adjustably set a maximum gain value according to a relative magnitude between the visible light components and the near-infrared light components and adjust a gain for the first imaging signals at the set maximum gain value; and a noise reduction portion configured to reduce noises in the first imaging signals after the gain has been adjusted.