Low Bit Rate Video Transmission System

Nowadayses the technology of multimedia communication developed greatly,there comes all kinds of devices for multimedia communication and coresponding protocols.Among the varieties,the communication device based on PSTN net is of great importance.This paper introduces a video communication system which is based on H.234,a recommendation of low bit rate,and has put into practice.In addition,the system based on PCs.First,this paper introduces H.234,analyzes H.223-Multiplexing protocol for multimedia communication and H.245-protocol for communication control,and presents the solution for the difficulties in the protocols.Then.this paper analyzes H.263-protocol for video coding which is the core part of the system.The H.263 protocol integrates the prediction coding DCT transform coding and entropy coding to realize the compression for video data.In addition,it describes the codec architecture and data format.This paper (1) presents a effective algorithm of motion estimation for inter-frame prediction coding;(2)analyzes the way implementing 2 dimension DCT transform by algorithm of 1 dimension fast DCT transform;(3) optimizes the above procedures with the MMX and SSE of intel.then comes up with an effective DCT algorithm.At last,the paper introduces the software structure of the system,presents how to design the video-processing module with VFW.and how to optimize the structure employing multithreading to insure the synchronization and real-time of the system.Up to now,the system has run very well,which proved the feasibility of the techniques presented in this paper.