An encoder, decoder, and corresponding method are disclosed for deblocking pixel data processed with block transformations, the encoder including a conditional deblocking filter for filtering only block transitions meeting chroma difference measure criteria; the decoder including a conditional deblocking filter for filtering only block transitions meeting chroma difference measure criteria; and the method for deblocking including receiving chroma level signals for at least two pixels disposed on opposite sides of a block transition, computing a distance measure between the chroma levels of the at least two pixels, comparing the distance measure with at least one threshold, and conditionally filtering adjacent pixels including the at least two pixels at the block transition in response to the comparison.