Abstract: H.264 provides several predicting modes and directions for intra prediction in the spatial region，and the optimal mode is selected by Rate Distortion Optimization（RDO） with high coding complexity.In order to solve this problem，a fast algorithm of intra prediction for H.264 based on direction measure is proposed.The algorithm utilizes direction measure to estimate the flatness and texture direction of a block，and precludes some less probable prediction modes to avoid unnecessary cost computations.Experimental results show that the proposed algorithm can averagely reduce encoding time by 60% with 0.05 dB PSNR loss and 1.27% bit rate increase on average.

Key words: H.264, intra prediction, direction measure, mode selection

摘要： H.264在空间域上从多个方向进行多种模式的帧内预测，并使用率失真优化算法选择最佳模式，使编码的复杂度大幅增加。为此，提出了一种基于方向测度的快速帧内预测算法。该算法使用方向测度来判断块的平坦程度和纹理方向，它可以预先排除可能性小的预测模式，避免了不必要的代价计算。实验结果表明，算法在保持信噪比平均降低0.05 dB和码率平均增加1.27%基础上，编码时间平均减少了39.16%。

关键词: H.264标准, 帧内预测, 方向测度, 模式选择