Early detection of all-zero 4×4 blocks in High Efficiency Video Coding

The value range of 4 × 4 quantized DCT coefficients in HEVC is analyzed.Two sufficient conditions to early detect all-zero 4 × 4 blocks in HEVC are derived.A prediction algorithm is designed to early detect all-zero 4 × 4 blocks.The proposed prediction algorithm keeps video quality and bit rates unchanged.Exhaustive experiments demonstrate the efficiency of the proposed algorithm. Similar to previous video coding standards, transform and quantization are employed in the most recent video coding standard High Efficiency Video Coding (HEVC), and there exist a large number of transform coefficients being quantized to zeros. In order to reduce the computations in transform and quantization, a novel prediction algorithm is designed to early detect all-zero 4 × 4 blocks prior to transform and quantization. A theoretical analysis is performed on the 4 × 4 Discrete Cosine Transform (DCT) and the related quantization functions in HEVC; consequently, two sufficient conditions to early detect all-zero 4 × 4 blocks are derived and the proposed prediction algorithm is developed while balancing the detection efficiency and computational overheads. Experimental results demonstrate that the proposed algorithm is able to efficiently predict all-zero 4 × 4 blocks and reduce redundant DCT and quantization computations while maintaining the same coding performance in terms of video quality and bit rates.