A Fast TU Mode Decision Algorithm Based on
the Gradient of Residual and Zero Block Detection for HEVC

ABSTRACT

High Efficiency Video Coding (HEVC) is a new video coding standard that improves the coding efficiency significantly. A residual quadtree (RQT), which provides the nested quadtree-based transform coding for various characteristics of prediction blocks is adopted in transform unit (TU). The heuristic examination of TU sizes cost additional computational complexity comparing with previous video coding standard. Thus, to develop a method that can efficiently eliminate inefficient TU mode candidates is critical.Two early termination schemes are developed in this thesis. All required information for the proposed mode decision criteria can be derived before transform coding. First, Zeng et. al. [11] has concluded the existence of the zero block inheritance (ZBI) property that could be used to skip many child TUs. We propose an early termination algorithm by combining the ZBI and all-zero block detection technique. Second, we use the gradient of residual to represent the similarity of coefficients. The similarity is employed to skip current TU mode or stop the TU splitting process.Experimental results show that our proposed method saves about 63% on average and up to 76% TU encoding time with negligible rate-distortion loss compared to HM6.1.