An adaptive perceptual quantization scheme improves the subjective image quality of the decoded image sequence. Previously, the variance or DCT coefficient of the local image was used to decide the perceptual weight of local images. But these methods could not efficiently alleviate the degradation of sharp edges of arbitary shape.
A new adaptive percetual quantization algorithm is proposed to cope with sharp edges. The edge portion in the local image block is detected and excluded, the smoothness of the rest portion is used as the perceptual importance measure of the whole block. Proposed scheme is applied to the MPEG-based HDTV encoder. The performace of the proposed scheme is investigated by computer simulation. In comparison with the adaptive quantization scheme in the MPEG-2 TM5 and DCT-based adaptive quatization method, the proposed scheme further alleviates the degradation of sharp edges.
