Improved techniques for dual-bitstream MPEG video streaming with VCR functionalities

A new dual-bitstream technique for videocassette recording (VCR) functionality and a transcoding technique of the motion vectors (mvs) between dual bitstreams are introduced in this paper. In the dual-bitstream technique, a direct reference bitstream is proposed to replace the original reverse bitstream to reduce the required network bandwidth and decoder effort of VCR requests. The close formula of the average number of the transmitted frames for a random-access or fast-forward request is proved for the proposed dual-bitstream technique. In the transcoding technique, the mvs in the forward bitstream are first reused to generate the mvs in the reverse bitstream and the direct reference bitstream. If the obtained error is larger than a preset threshold, the mvs are refined step-by-step from the inner to the outer of a refinement window. The experimental results show that the PSNR degradation between the proposed transcoding technique and the full search technique is very little and only about 1% ~ 6% computations re required.