Abstract
We incorporate the early zero-block detection technique into the UMHexagonS algorithm, which has already been adopted in H.264/AVC JM reference software, to speed up the motion estimation process. A nearly sufficient condition is derived for early zero-block detection. Although the conventional early zero-block detection method can achieve significant improvement in computation reduction, the PSNR loss, to whatever extent, is not negligible especially for high quantization parameter (QP) or low bit-rate coding. This paper modifies the UMHexagonS algorithm with the early zero-block detection technique to improve its coding performance. The experimental results reveal that the improved UMHexagonS algorithm greatly reduces computation while maintaining very high coding efficiency.
Highlights
The newest international video coding standard H.264/AVC has recently been approved by the ITU-T and by ISO/IEC as the international standard MPEG-4 part 10 advanced video coding (AVC) standard [1]
The threshold of 20Qstep (corresponding to 5Qstep in 4 × 4 discrete cosine transform and quantization (DCT/Q)) is not sufficient, and it could improperly detect a great number of zero-blocks, leading to a severe degradation in coding performance
Some sufficient but not necessary conditions for zeroblock detection of DCT coefficients after quantization were derived by examining the sum of absolute differences (SADs) between the current macroblock and the reference macroblock [6, 7]
Summary
The newest international video coding standard H.264/AVC has recently been approved by the ITU-T (as recommendation H.264) and by ISO/IEC as the international standard MPEG-4 part 10 advanced video coding (AVC) standard [1]. The motion search stops when all zero-blocks are detected This results in significant computational savings, especially for low bit-rate coding. The threshold of 20Qstep (corresponding to 5Qstep in 4 × 4 discrete cosine transform and quantization (DCT/Q)) is not sufficient, and it could improperly detect a great number of zero-blocks, leading to a severe degradation in coding performance. Some sufficient but not necessary conditions for zeroblock detection of DCT coefficients after quantization were derived by examining the sum of absolute differences (SADs) between the current macroblock and the reference macroblock [6, 7]. The nearly sufficient condition for zero-block detection is applied to both motion search and DCT/Q calculation in the UMHexagonS algorithm. The experimental results reveal that a significant improvement in computation reduction can be achieved compared to methods using the other two sufficient conditions, while high coding efficiency is still maintained
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