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An automatic camera focusing scheme used in video conference is presented.The proposed scheme consists of two phases:focus adjusting and focus monitoring.In the focus adjusting phase,mountain climbing algorithm is used to search the peak point of the focusing criteria function.The focus searching range is reduced by the concept of hyperfocal distance,and the searching step size is adapted dynamically.Therefore,the searching process is speeded up,and good subjective quality of pictures is guaranteed.Moreover,to eliminate the influence of scene changes during the searching process,a return-examination method is used.In the focus monitoring phase,focus adjusting is conditionally triggered based on the results of shot change detection,which helps to guarantee focus quality and avoid frequently refocusing.Experimental results validate the performance and robustness of the proposed scheme.It has been integrated in the products of video conference terminal.

A real-time scene cut detection algorithm is proposed which shares the results of motion estimation with the video encoder.To deal with different kinds of scene cuts,two metric functions are introduced based on the statistics of the first and second order difference between the original pictures and their motion compensated pictures.The detection thresholds for each metric are adaptively adjusted according to the scenes.The experimental results and analysis show that the recall and precision of the proposed algorithm are generally higher than other tested ones at the cost of little computation time increment.