Patent ID: 7869517

Claim:
A machine-implemented method of generating a measure of quality for a digital video signal that has been encoded using a compression algorithm utilizing a variable quantizer step size and a two-dimensional transform, such that the encoded signal includes a quantizer step size parameter and, for blocks of the picture, transform coefficients, the method comprising using at least one signal processor having an input which receives said encoded video signal and an output which provides data representing said measure of quality, said at least one processor being configured to: a) generate a first quality measure which is a function of said quantizer step size parameter; b) generate a second quality measure which is a function of the number of blocks having a single transform coefficient; and c) combine the first and second measures to produce said output measure of quality; wherein the second quality measure is determined as a function of the number of blocks determined to be blocky, (i) wherein a block is defined as blocky if the block has been encoded without reference to an earlier frame of the picture and the block has only one transform coefficient; and (ii) wherein a block is defined as blocky if it has been encoded by reference to an earlier frame of the picture and the block has no transform coefficients and the corresponding block of the respective earlier picture has also been defined as blocky.