A deblocking scheme suitable for use inside the codec loop

In many coding algorithms, one of the most annoying types of image deterioration occurring at lower bit rate is the so called blocking effect. It is caused by the unnatural way of dividing up images in rectangular blocks with a fixed grid. Because the coding of each block is independent, nothing assures the continuity of the coded image values at the border between blocks. This gives rise to sometimes prominent artificial edges in the coded image. In image sequences, a background grid of non-moving edges viewed against a moving scene, results in a very unnatural and unpleasing type of degradation. To prevent these blocking effects from occurring, a lot of algorithms have been used. However, many are not suitable for incorporation in the main codec loop, but can only be seen as a cosmetic post filter. The simple algorithm described here is usable for that purpose