Preprocessing Techniques For Increasing Video Quality And Coding Efficiency

In order to obtain high video quality and high compression performance, video preprocessing technique plays more important role in video processing and communications. In this dissertation, two processing modules between the video sensor and the output of the capture device are deeply studied. We pay more attention on the background flicker reduction and image interpolation.Background flicker which is caused by varied light environment and the auto exposure function of video cameras can extremely degrade the video quality and compression efficiency. A new luminance flicker reduction algorithm is proposed in this paper under the circumstances. Firstly, the reference picture for illumination compensation is found out in the proposed algorithm, and then the parameters of the response function of background luminance between the reference picture and the current picture is obtained using the least-square method. Finally, the luminance flicker can be reduced by illumination compensation. Experimental results show that the background luminance flicker can be effectively reduced using this algorithm and bit rate can be saved by 20%-30% when the compensated video sequences are encoded and transmitted. The developed algorithm has been successfully applied to video products of Huawei limited technology cooperation company.To remove blurring effect and zigzag edges occurring in traditional interpolated images, a new algorithm based on direct-judgment is proposed in his paper. The basic idea is to compute the gradient values of four directions to determine the interpolated directions and its corresponding weighted coefficients, then, the final image is obtained using weighting interpolation. The experimental results show that relatively higher quality images with high definition are achieved.