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 I 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 5 Mbit/s. As an added benefit, the CPU requirements for decoding the edited stream in software are also reduced by approximately 16%.