Study On The Technology Of Video And Pictures In Software-based Videoconference System

Software-based video conferencing systems are the future trends in the development of video conferencing, and the future development'primary technology of video conferencing is more advanced video codec technology and more professional image processing techniques. Following the most popularity video compress encoding standard H.264/AVC, some technology about video and Computer Digital Image are studied in this paper:First of all,the paper achieves video and picture data acquisition,including the video date stream from USB camera and the pictue date stream of desktopwindow;The fast picture format convertion programme from RGB to YCbCr is also discussed.Based on the analysis of advantage and disadvantage about traditional interpolation arithmetic, this paper bring forward a advanced mixed interpolation arithmetic based on block mode, and the threshold's precise calibration method is gived, which used in the advanced arithmetic of this paper. Aimed at the applications in desktop image scaling, the relationship between different-sized sub-block and time-consuming of algorithm is analysised through experiments; then the optimization algorithm is applied to the H.264, in this part, selection of different thresholds for the effects on image quality is analysised, the experimental results in this paper show that at video conferencing applications, compared with traditional algorithms, optimization algorithms can improve the video quality more than 1~2B generally; besides, experiments demonstrate that the optimization algorithm of this paper also has the universal applicability in other applications.In view of the situation in which the text of video image is not clear, give a selective enhancement algorithm of the text in color image based on Niblack. Algorithm based on the three primary colors of RGB color image is determined by preliminary text. Then select the use of the threshold range to further define the text content, and at the same time filter background noise; finally according to the brightness of the pixels in itself, the enhance strength is selected adaptively. Experiment proved that the algorithm achieve a certain desired effect.Using the immediately refresh characteristics of IDR image in H.264 standard, we propose and design the hybrid coding scheme of multi-resolution image sequence. With this hybrid coding scheme, we do not need to restart the entire system when the video source image resolution change. For these reasons, we ensure the coherence of the system.In addition, the RTP/RTCP real-time transport protocol and post-processing error concealment techniques are analyzed in the thesis. The importance of system-level design is illustrated by channel simulation. We also give a preliminary study of the video conferencing encryption method in the paper. We further two simple encryption measures that is applied to H.264 video conferencing system through the implementation of programming.