Abstract
The study of bit-rate conversion and face region emphasis of video transcoding for multipoint video conferencing is carried out in this thesis. A Multipoint Control Unit (MCU) is a central server in a wide-area network, which is used to distribute the video and audio streams to multiple participants in a video conferencing. Video transcoding is used in an MCU to combine the incoming image sequences into a single sequence. The bit-rate of the combined video should be adapted to meet the channel bandwidths. Bit-rate conversion from high bit-rate to low bit-rate will introduce video quality degradation. Our proposed scheme adjusts the frame layer bit-allocation according to the sub-window complexity. More bits will be allocated in the active sub-window than others. Our scheme can also improve the quality of face region in multipoint video conferencing, since the face region is the main focus in video conferencing. The quality of face region can be improved at most frames in our simulation results.