Research On Outline-based Video Codec And Transmission

The rapid development of wired and wireless networks tremendously facilitates video communications between people. Traditional video communication is based,on the, technique, of coding and decoding such as DCT, quantization, motion estimation and compensation, which have high computational complexity and only can run under wider bandwidth and good devices. However, most of the current wireless networks still work in low bandwidths, and mobile devices still suffer from weak computational power, short battery lifetime and limited display capability.Therefore, this thesis deals with developing a very low bit-rate bi-level video coding technique, which can be used in video communications almost anywhere, anytime on any device as follows:(1) Convert true color video sequences from CCD and video card to grayscale ones,(2) Detect static region of successive frames by the sum of absolute differences(SAD) and update current frame using static region of previous frame, to decrease flicker.(3) Threshold the images to bi-level video sequences using Ridler's Iterative Selection.(4) Encode the bi-level video sequences using the adaptive context-based arithmatic encoding.This thesis presents the RTP/RTCP protocal based on UDP/TCP protocal to guarantee the validity of data and speed up transmition on the internet.This thesis also initially proposes and implements a circular queue to save compressed data and buffer the transmitting.The important techniques include video capture, encoding based on the outlines, transmitting, decoding and display are also introduced in this thesis.This method is especially suitable for small mobile devices such as handheld PCs, palm-size PCs and mobile phones that possess small display screens and light computational power, and work in low bandwidth wireless networks. The system RTBVideo based on the technique mentioned above typically provides QCIF-size video with a frame rate of 5-15 fps for a 9.6 Kbps bandwidth in the internet. It provides clearer shape, smoother motion and acceptable quality of video.