The Study On MPEG-2 Video Stream Transcoding For Network PVR Manipulation

With the blooming development of the Internet, network has gradually become an essential exchange platform. In order to make use of this transmission platform to a full extent, the aim of video coding standard has gradually changed: From the storage oriented MPEG-1 to both storage and transmission oriented MPEG-2, to the transmission oriented MPEG-4. The new standard H.264/AVC has made the abstract layer of the network a part of the standard to meet the requirement of transmitting media stream through the internet. With the tendancy of popularization of the Internet, the construction of high performance broadband network accelerates the development of HDTV. In the practical IPTV, the transport media stream transmitting through broadcasting network is coded according to the MPEG-2 standard which the Digital TV is coded in order to maintain the quality of the images. In the application of Time-shifted TV, the original stream is transcoded while the frames in the stream are dropped alternately to meet the requirement of the interactive PVR manipulation over the network.The framework and the flow of transcoding for PVR application are proposed. And to realize the transcoding in compressed domain can avoid the computational complexity bringing in by the computation of DCT/IDCT. So the realization of transcoding in compressed domain is discussed in this paper. The transforming matrixs used in the computation of the motion compensation are deduced. If the prediction mode is field prediction, the two fields of macroblocks are predicted using two different motion vector. The computation of prediction could be operated in the way of splitting the...