Research On The Key Technologies For MPEG-4/H.264 Transcoding

Video transcoding can make it possible to realize the transmission of video data between the heterogenous networks and different terminals effectively, and it can also guarantee the quality of video service. Video transcoding has become the focus of research attention in multimedia system. MPEG-4 and H.264 are two video compression standards widely used, so the investigation of transcoding techniques between MPEG-4 and H.264 is very significant in practice. This paper investigates the transcoding techniques for MPEG-4 to H.264 transcoding. In order to reduce the complexity caused by multi-mode prediction of H.264 encoder in transcoding process, several efficient fast mode selection algorithms are proposed by reusing the mode and motion vector information from MPEG-4 decoder. These algorithms can select the prediction modes quickly by mode mapping, and then the motion vector estimation will be done by reusing the motion vector from MPEG-4 decoder. Experimental results demonstrate that these algorithms can significantly reduce the re-encoding complexity with negligible degradation in video quality.Deblocking filter is one of the most time-consuming parts of H.264 encoder and decoder, so it is in MPEG-4/H.264 transcoding. Especially in high-performance transcoding, mode decision saves a lot of time, so the deblocking filter make up the major part of the total time.In order to apply the video transcoding techniques above-mentioned into embedded DSP and to promote the speed of transcoding, this paper studies the optimization methods about deblocking filter in H.264 under TMS320C64xx platform. The information of four 4x4 blocks at the same side of one deblocking edge is similar, so we proposed a algorithm which can reduce the times of calculating Bs in TMS320C64xx DSP. Experimental results demonstrate that the algorithm can increase filter speed effectively with some degradation in video quality. To avoid too many time-consuming instructions of memory access in basic filter structure, we proposed a new filter structure which can take full advantage of the data correlation between neighboring 4x4 blocks in TMS320C64xx DSP. Experimental results demonstrate that the new filter structure can increase filter speed without any degradation in video quality.