1. A signal processing apparatus comprising: a first image memory that stores input moving images corresponding to a plurality of screens; a noise reduction section that removes noise from the images corresponding to the plurality of screens and outputs noise-free images; an image switching section that selects and outputs one image of the input moving image and the output of the first image memory; a Y/C separation section that separates the image from the image switching section into a luminance signal and a color signal and gives the separated luminance signal and color signal to the noise reduction section; a second image memory that stores images from the noise reduction section corresponding to at least one screen; a blur amount calculation section that calculates an amount of blur of each screen of the input moving image based on the luminance signal separated by the Y/C separation section; a blur amount storage section that stores the amount of blur calculated by the blur amount calculation section in association with each screen of the input moving image; and a freeze control section that reads, when a freeze instruction is generated, images corresponding to two or more screens including the screen with a smallest amount of blur based on the amount of blur stored in the blur amount storage section and necessary to remove noise in the noise reduction section from the first image memory, causes the image switching section to output the images, and controls the second image memory so as to consecutively output noise-free images using the images corresponding to the two or more screens including the screen with the smallest amount of blur through the noise reduction section.