A Rate-distortion Based Quantization Level Adjustment Algorithm in Block-based Video Compression

In this paper, a rate-distortion based quantization level adjustment (RDQLA) algorithm is presented. Based on rate-distortion criterion, the quantization level adjustment algorithm effectively improves coding efficiency by adaptively optimizing quantization levels of the signals near the boundaries of quantization cells and adjusting quantization levels per block. The proposed algorithm can be applied in any block based image and video coding method. In addition, it has no overhead and is fully compatible with the existing compression standards. The algorithm has been verified on the platform of H.263 and H.264. Experimental results show that the proposed algorithm improves the performance substantially. It is shown that the proposed algorithm has a gain of 1 dB comparing with the newest H.264 reference code and more than 1 dB comparing with H.263 standard for high bit rates.