视频自动聚焦的实现研究

摘要:     提出了用于会议电视摄像机的自动聚焦方法.该方法由聚焦调节和聚焦监测两个过程组成.聚焦调节是寻找聚焦函数最大峰值的过程,在该过程中通过利用超焦距概念和动态自适应变步长搜索算法加快搜索速度,并保证了良好的视觉效果|同时,提出退回检查最大值点变化方法,防止搜索过程中因受到场景变化干扰而导致的聚焦失败.聚焦监测过程是在会议电视通话中,通过监测场景变化使聚焦调节工作适时启动的过程,提出有条件地重新调节聚焦,以始终保障良好的摄像聚焦效果,同时避免频繁调焦.实验结果表明,提出的摄像机自动聚焦方法性能优秀并有良好的顽健性.该方法已经用于华为ViewPoint 8020plus视频会议终端的实际产品.

Development of the Video Automatic Focus Method

 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.