| With the development of multimedia and network, that has promoted the advancement of the technology of video conferencing, and has caused more and more video conferencing products used widely by the society. The main components of video conferencing include MCU (Multipoint Control Unit), video terminals and gatekeepers. Multi-image composition is the most important but also the most time-consuming function of MCU. In order to decrease the burden of data-processing and MCU design complexity, a high-performance multimedia processing chip will be adopted to improve the efficiency of video conference. It is to be having great value for application when combining data-processing of DSP with advanced image compression and developing communication video decoding systems compatible with multiple standards.This article is based on the project "development on DSP video communication system" and focuses on the high-performance DSP application of MCU design. TI TMS320DM642 was be chosen as a DSP of our hardware platform and the latest video standard H.264/AVC was chosen as a standard with which our system is compatible. Many modules has been designed and implemented, including PCI communication module for multi-image composition on pixel field and video decoding module. Several schemes of task schedules on the DSP have been presented, and the conflicts of concurrent operations on the share buffer have been solved by using the message-passing mechanism.Transplant of the DSP platform for H264 encoder and decoder transplant has been also implemented. The software has been optimized from memory distribution, C coding and assembly coding, and that greatly improve the coding efficiency. Now a DSP can process 4-channels H264 decoding simultaneously and our system breaks through the performance bottlenecks in multi-image composition on pixel fields.These schemes and technologies presented in the article have been applied to the MCU high-end products of video conferencing. |
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