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为提高I帧和P帧的编码效率,H.264视频编码标准采用多模式帧内预测和多子块模式帧间预测,并选择率失真最优的模式进行编码,导致编码复杂度很高.为此,提出一种基于小波变换的帧内模式快速选择结合帧间预测下帧内模式预判断的算法.利用小波变换后的低频子图做帧内模式选择,由此预判断宏块中每个4×4子块可能的预测模式,使原来9次的代价函数计算减少到平均3.75次;使用去均值的差值平方和,预判断宏块是否选择帧间预测下的帧内编码模式,减少P帧编码时间.实验表明,改进算法在峰值信噪比降低不超过0.0644 dB的情况下,编码速度平均提高19%左右.
In order to improve the coding efficiency of I-frames and P-frames, the H.264 video coding standard adopts the multi-mode intra prediction and the multi-sub-block mode inter-frame prediction, and selects the mode with the best rate distortion to encode, resulting in high coding complexity. Therefore, this paper proposes a fast intra-frame mode selection based on wavelet transform combined with inter-frame prediction mode pre-judgment algorithm.Using the wavelet transform of the low frequency sub-frame intra-mode selection, which pre-judge each macroblock A 4 × 4 sub-block possible prediction mode, so that the cost function of the original 9 times the calculation is reduced to an average of 3.75 times; using the mean square error of the difference, the pre-judge whether the macro-block under the inter prediction frame coding mode, The coding time of P frame is reduced.Experiments show that the improved algorithm can improve the coding speed by about 19% on the average when the peak SNR decreases by less than 0.0644 dB.