Merge pull request opencv#16246 from VadimLevin:dev/vlevin/videoio_classes_cleanup

Author: alalek

modules/videoio/include/opencv2/videoio.hpp

@@ -638,7 +638,7 @@ class CV_EXPORTS_W VideoCapture
     implementation if multiple are available: e.g. cv::CAP_FFMPEG or cv::CAP_IMAGES or cv::CAP_DSHOW.
     @sa The list of supported API backends cv::VideoCaptureAPIs
     */
-    CV_WRAP VideoCapture(const String& filename, int apiPreference = CAP_ANY);
+    CV_WRAP explicit VideoCapture(const String& filename, int apiPreference = CAP_ANY);
 
     /** @overload
     @brief  Opens a camera for video capturing
@@ -650,7 +650,7 @@ class CV_EXPORTS_W VideoCapture
 
     @sa The list of supported API backends cv::VideoCaptureAPIs
     */
-    CV_WRAP VideoCapture(int index, int apiPreference = CAP_ANY);
+    CV_WRAP explicit VideoCapture(int index, int apiPreference = CAP_ANY);
 
     /** @brief Default destructor