1. An image quality evaluation system for evaluating an image quality of an image, comprising: a bit extraction unit that, for predetermined data expressive of an image, frame of a first image extracts continuous predetermined bits of which a bit number is fewer than the bit number necessary for expressing the above data per one piece of data except for predetermined high order bits and predetermined low order bits of the above data; and an image quality evaluation unit that, based upon the value being expressed with bit sequences extracted by said bit extraction unit, and the value of data equivalent to the data that has become a target of extracting the above bit sequences in a second image, estimates a difference between said first image and said second image, and evaluates the image quality of said first image or second image; an image sending apparatus for encoding the original image and transmitting said encoded image, and image reception apparatus for obtaining the transmitted image by receiving said encoded image from said image sending apparatus and decoding it: wherein the image sending apparatus comprises: a bit extraction unit that, for the predetermined data expressive of the original image, extracts predetermined bits of which a bit number is fewer than the bit number necessary for expressing the above data per one piece of data; and a feature transmission unit that transmits the value being expressed with the bit sequences extracted by said bit extraction unit as a feature of said original image to the image reception apparatus, being a transmission destination of said encoded image; and wherein the image reception apparatus comprises an image quality evaluation unit that estimates a difference between the original image and the transmitted image based upon the value that is expressed with the bit sequences extracted by said bit sequence extraction unit, said value being received as a feature of said original image, and the value of data equivalent to the data that has become a target of extracting the above bit sequences in the image frame of the transmitted image, thereby to evaluate the image quality of the transmitted image.