基于多尺寸特征融合的快速转码算法

为了降低H.264转码器的运算复杂度，满足视频转码实时应用的要求，提出一种结合多尺寸视频特征的快速视频转码帧内预测算法。首先利用二维直方图提取小尺寸视频中宏块的空间特性，结合双阈值的方法，选择Intra 16×16或Intra 4×4模式。然后从输入的视频码流中提取编码信息组成多维特征向量训练支持向量机(SVM)分类器模型,通过SVM建立大尺寸视频编码信息与小尺寸视频宏块编码模式之间的联系，进而对Intra 4×4中的9种模式进行细分。此算法减少了预测模式数量，实现率失真优化算法的提前终止，在高效转码的同时保证了转码后视频的高质量。

Fast video transcoding algorithm based on hybrid characteristic of multi-scale videos

A fast intra mode decision scheme for down-sizing video transcoding in H.264 based on hybrid characteristic of multi-scale videos was presented. In order to reduce the high computational complexity of using conventional intra prediction in the H.264 re-encoder, the proposed scheme firstly utilized 2D-histogram to extract the spatial characteristic of macro-blocks in the low-resolution video to choose from intra 16×16 and intra 4×4. Then the Support Vector Machine (SVM) was used to exploit the correlation between coding information extracted from the input high-resolution bit-stream and the coding modes of macro-blocks in down-sized video frames. With the SVM classifier, the improbable modes in the nine intra 4×4 modes were eliminated and only a small number of candidate modes were carried out using the RDO operations. Hence, remarkable computation time can be saved, while maintaining nearly the same quality of the transcoded pictures.