关键词: 降尺寸视频转码, 帧内预测, 二维直方图, 支持向量机, 率失真优化

Abstract: 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.

Key words: down-sizing video transcoding, intra prediction, 2D-histogram, Support Vector Machine (SVM), Rate Distortion Optimization (RDO)