Region of interest editing of MPEG-2 video streams in the compressed domain

We describe a method for dynamically variable region-of-interest editing of MPEG-2 video streams in the compressed domain to reduce bandwidth. This method is used in our second-generation mutually-immersive mobile telepresence system, where only the region containing a user's head in an acquired video stream needs to be displayed at the remote location. This editing is performed in a way that leaves the resulting stream consistent with the MPEG-2 standard. We currently reduce the transmission of data by skipping macroblocks or deleting DCT coefficients outside the region of interest in P and B pictures, and deleting DCT coefficients in 1 frames. This results in a savings of approximately 50% of the bandwidth of the original stream for our application. Since we are transmitting four video streams to the surrogate over our wireless network, the total bandwidth is reduced by about 5Mbps. As an added benefit, the CPU requirements for decoding the edited stream in software are also reduced by approximately 16%.