1. A method for processing a digital video signal using a digital video processing system having at least one processing device, the method comprising: ordering pixels in an image of the digital video signal in groups of adjacent pixels; performing, for the pixels comprised in each of said groups, the operations of: truncating a respective string of bits, eliminating a given number of least-significant bits, thus generating a respective truncated string; adding to said truncated string an integration factor constituted by a power of two of a given order, thus generating a respective integrated string; calculating using the at least one processing device, first values of pixel error corresponding to a difference between said respective string and the respective truncated string and second values of pixel error corresponding to a difference between said respective string and the respective integrated string; calculating using the at least one processing device, for each of said groups of pixels, a set of values of global error comprising all the possible combinations of addition of said first and second values of pixel error on the pixels of the group; locating using the at least one processing device, a value of minimum error in said set of values of global error, identifying moreover, in the combination of addition that produces said value of minimum global error, a first number of pixels, whereby the contribution to said value of minimum global error is given by said first value of pixel error, and a second number of pixels, whereby the contribution to said value of minimum global error is given by the second value of pixel error; and using, as a compressed version of the video signals represented by the pixels in the group, a first number of said truncated strings and a second number of said integrated strings that are equal to said first number of pixels and to said second number of pixels respectively, said integrated strings being subjected to truncation by the elimination of said given number of least-significant bits.