Fast Inter-Mode Decision Based on Rate-Distortion Cost Characteristics

In this paper, a new fast mode decision (FMD) algorithm is proposed for the state-of-the-art video coding standard H.264/AVC. Firstly, based on Rate-Distortion (RD) cost characteristics, all inter modes are classified into two groups, one is Skip mode (including both Skip and Direct modes) and all the other inter modes are called non-Skip modes. In order to select the best mode for coding a Macroblock (MB), minimum RD costs of these two mode groups are predicted respectively. Then for Skip mode, an early Skip mode detection scheme is proposed; for non-Skip modes, a three-stage scheme is developed to speed up the mode decision process. Experimental results demonstrate that the proposed algorithm has good robustness in coding efficiency with different Quantization parameters (Qps) and various video sequences and is able to achieve about 54% time saving on average while with negligible degradation in Peak-Signal-to-Noise-Ratio (PSNR) and acceptable increase in bit rate.