Research And Implementation Of H.264/AVC Spatial Resolution Transcoding

With the development of network and multimedia communication technology, and the wide use of the mobile terminal devices such as mobile phones, PDAs, etc, people require more for the service given by the mobile network. As we know, terminal devices have some common characteristics like small display screen, low computational capability. At the same time the mobile network is limited by the channel bandwidth. Compressed video bitstream is often converted from one format to another to meet the constrained transmission bandwidth and terminal capabilities. The new generation video coding standard H.264/AVC has higher coding efficiency than the previous standards. It has been widely used because of its excellent performance. Aiming at the characteristics of mobile video terminals, this thesis focuses on the spatial resolution transcoding for H.264/AVC.First, in order to obtain a better video quality, bi-cubic interpolation is used to achieve image scaling in spatial resolution transcoding. And in order to increase the speed of spatial resolution transcoding, the program has been fully optimized by using MMX/SSE-2 instructions, which not only guarantees the quality of the image but also greatly improves the computation efficiency.Second, a fast mode decision algorithm is proposed to decrease computational complexity during transcoding. The computation complexity is very high in H.264/AVC, because H.264/AVC adopts many modes for motion estimation. To reduce the complexity of transcoding, we analyze the decoded information and experimental result then directly find the best motion estimation mode by using proper merge and split operations during motion estimation process. Experimental results show that our proposed algorithm can significantly increase the speed of transcoding,meanwhile, our algorithm has a steady rate-distortion performance and can guarantee the subjective and objective video quality.