Added command line option to select VideoCapture backend.

apps/interactive-calibration/main.cpp

@@ -6,7 +6,7 @@
 #include <opencv2/calib3d.hpp>
 #include <opencv2/cvconfig.h>
 #include <opencv2/highgui.hpp>
-
+#include <opencv2/videoio/registry.hpp>
 
 #include <string>
 #include <vector>
@@ -23,9 +23,25 @@
 
 using namespace calib;
 
-const std::string keys  =
+static std::string getVideoIoBackendsString()
+{
+    std::string result;
+    auto backs = cv::videoio_registry::getBackends();
+    for (const auto& b: backs)
+    {
+        if (!result.empty())
+            result += ", ";
+
+        result += cv::videoio_registry::getBackendName(b);
+    }
+
+    return result;
+}
+
+const char* keys  =
         "{v        |         | Input from video file }"
-        "{ci       | 0       | Default camera id }"
+        "{ci       | 0       | Camera id }"
+        "{vb       |         | Video I/O back-end. One of: %s }"
         "{flip     | false   | Vertical flip of input frames }"
         "{t        | circles | Template for calibration (circles, chessboard, dualCircles, charuco, symcircles) }"
         "{sz       | 16.3    | Distance between two nearest centers of circles or squares on calibration board}"
@@ -95,11 +111,13 @@ static void undistortButton(int state, void* data)
 
 int main(int argc, char** argv)
 {
-    cv::CommandLineParser parser(argc, argv, keys);
+    cv::CommandLineParser parser(argc, argv, cv::format(keys, getVideoIoBackendsString().c_str()));
+
     if(parser.has("help")) {
         parser.printMessage();
         return 0;
     }
+
     std::cout << consoleHelp << std::endl;
     parametersController paramsController;