opencv 设置摄像头
double cvGetCaptureProperty( CvCapture* capture, int property_id ) CV_CAP_PROP_POS_MSEC - 影片目前位置,为毫秒数或者视频获取时间戳 CV_CAP_PROP_POS_FRAMES - 将被下一步解压/ 获取的帧索引,以 0为起点 CV_CAP_PROP_POS_AVI_RA