Simplified Rate-Distortion Optimized Quantization for HEVC

Rate-distortion optimized quantization (RDOQ) is shown to provide significant coding gain in HEVC but it also suffers from huge computational complexity. In this paper, we simplify the RDOQ tool in HEVC by enforcing more zero levels at high frequency locations without sacrificing coding efficiency much. First, we analyze the properties of each quantized level at different frequency locations. Subsequently, we set the quantized level of value 1 to 0 at specified high frequency locations to save the RDOQ processing time. In addition, a smaller round offset for quantization is adaptively used to minimize coding loss at high frequency locations. Our scheme is shown to reduce total quantization time by an average of 15.6% with only 0.01% loss in BDBR under the all intra coding configuration, and 13.17% of average time saving with 0.07% BDBR loss under the Random Access configuration.