Block-layer optimal bit allocation based on constant perceptual quality

Bit allocation is a key issue in image/video coding. An optimal bit allocation can improve the encoding performance, which means to maximize the image/video quality in the constraint of bit rate, or vice versa, to minimize the bit rate with a restrictive quality. We suggest that the bit allocation for macro blocks (MBs) can be optimized by aiming at the constant perceptual quality (CPQ) inside an image/a frame. Based on the MINMAX criterion, we proposed a multi-pass block-layer bit allocation scheme for intra frame encoding, in which all the local areas in a frame get approximately the same perceptual quality by choosing the quantization parameter (QP) for each MB. The experimental results show that the proposed method can improve the encoding performance obviously.