H.264/AVC中计算复杂度可调的快速模式选择算法

Fast Mode Decision with Adjustable Computational-complexity for H.264/AVC Encoder

H．264／AVC视频编码标准采用多模式编码技术虽显著提高了编码效率，但由于该技术计算复杂度极高，因此为了降低计算复杂度，提出了一种计算复杂度可调的快速模式选择算法。该算法依据编码模式的特点和最佳模式分布规律，利用运动活性及已测试模式所得残差的量化系数来预测尚未测试模式的编码性能，并略过不必要测试的模式，通过选择恰当的阈值即可实现计算复杂度的调整。实验表明，与全模式选择算法相比，采用该算法编码速度可以提高2～4倍，而且重建质量和编码效率损失极小。

H. 264/AVC video coding standard employs multiple coding-modes and significantly improves coding efficieney at the cost of heavy computational load. To reduce the computation burden, a fast mode decision algorithm with adjustable computational-complexity is presented. According to the analysis of the characteristics of the coding-modes and statistical characteristics about the best mode, the proposed algorithm exploits motion activity and the quantized transform coefficients of the residue obtained by the tested coding-modes, to effectively predict the coding efficiency of the remaining modes and skip the unnecessary modes, further more thresholds used in this algorithm can be adjusted to regulate computational complexity. Experimental results show that the speed of the proposed method is about 2 -4 times faster than the full-mode decision algorithm without any noticeable loss of image quality and coding efficiency.