1. A method of operating an encoder apparatus to encode stereoscopic image data representing pairs of first and second eye images, each first eye image in an image pair corresponding to one of a left eye image and a right eye image, the second eye image of each image pair corresponding to the other one of the left and right eye images, the method comprising: determining an amount of difference between a first eye image and a second eye image of a first image pair; performing a negative parallax detection operation to detect image regions in said second eye image of said first image pair which are in negative parallax relative to a corresponding portion of said first eye image of said first image pair; and when it is determined that there is a non-zero amount of difference between the first eye image and the second eye image of said first image pair, performing the steps of: i) performing an entropy reduction operation on second eye image data representing the second eye image of the first image pair to produce entropy reduced second eye image data, wherein said entropy reduction operation includes performing at least one of an FFT based filtering operation or a neighborhood filtering operation on said second eye image data to smooth the second eye image of said first image pair; ii) encoding first eye image data representing the first one of the eye images of said first image pair to generate compressed first eye image data; and iii) encoding said entropy reduced second eye image data to generate compressed second eye image data; and storing or transmitting the compressed first eye image data and compressed second eye image data; and storing information identifying at least one detected image region of negative parallax in said second eye image of said first image pair in a file with said compressed first eye image data and compressed second eye image data.