Added depricated_backends list. Added new information masseges. It needs to inform user, when he tries to use depricated or not uses backend

modules/videoio/src/cap.cpp

@@ -212,6 +212,19 @@ bool VideoCapture::open(const String& filename, int apiPreference, const std::ve
         CV_Error_(Error::StsError, ("could not open '%s'", filename.c_str()));
     }
 
+    if (cv::videoio_registry::checkDeprecatedBackend(apiPreference))
+    {
+        CV_LOG_DEBUG(NULL,
+            cv::format("VIDEOIO(%s): backend is removed from OpenCV",
+                cv::videoio_registry::getBackendName((VideoCaptureAPIs) apiPreference).c_str()));
+    }
+    else
+    {
+        CV_LOG_DEBUG(NULL, "VIDEOIO: choosen backend does not work or wrong. "
+            "Please make sure that your computer support chosen backend and OpenCV built "
+            "with right flags.");
+    }
+
     return false;
 }
 
@@ -337,6 +350,19 @@ bool VideoCapture::open(int cameraNum, int apiPreference, const std::vector<int>
         CV_Error_(Error::StsError, ("could not open camera %d", cameraNum));
     }
 
+    if (cv::videoio_registry::checkDeprecatedBackend(apiPreference))
+    {
+        CV_LOG_DEBUG(NULL,
+            cv::format("VIDEOIO(%s): backend is removed from OpenCV",
+                cv::videoio_registry::getBackendName((VideoCaptureAPIs) apiPreference).c_str()));
+    }
+    else
+    {
+        CV_LOG_DEBUG(NULL, "VIDEOIO: choosen backend does not work or wrong."
+            "Please make sure that your computer support chosen backend and OpenCV built "
+            "with right flags.");
+    }
+
     return false;
 }
 
@@ -640,6 +666,20 @@ bool VideoWriter::open(const String& filename, int apiPreference, int fourcc, do
             }
         }
     }
+
+    if (cv::videoio_registry::checkDeprecatedBackend(apiPreference))
+    {
+        CV_LOG_DEBUG(NULL,
+            cv::format("VIDEOIO(%s): backend is removed from OpenCV",
+                cv::videoio_registry::getBackendName((VideoCaptureAPIs) apiPreference).c_str()));
+    }
+    else
+    {
+        CV_LOG_DEBUG(NULL, "VIDEOIO: choosen backend does not work or wrong."
+            "Please make sure that your computer support chosen backend and OpenCV built "
+            "with right flags.");
+    }
+
     return false;
 }
 

modules/videoio/src/videoio_registry.cpp

@@ -183,6 +183,18 @@ static const struct VideoBackendInfo builtin_backends[] =
     // dropped backends: MIL, TYZX
 };
 
+static const struct VideoDeprecatedBackendInfo deprecated_backends[] =
+{
+#ifdef _WIN32
+    {CAP_VFW, "Video for Windows"},
+#endif
+    {CAP_QT, "QuickTime"},
+    {CAP_UNICAP, "Unicap"},
+    {CAP_OPENNI, "OpenNI"},
+    {CAP_OPENNI_ASUS, "OpenNI"},
+    {CAP_GIGANETIX, "GigEVisionSDK"}
+};
+
 bool sortByPriority(const VideoBackendInfo &lhs, const VideoBackendInfo &rhs)
 {
     return lhs.priority > rhs.priority;
@@ -351,6 +363,16 @@ std::vector<VideoBackendInfo> getAvailableBackends_Writer()
     return result;
 }
 
+bool checkDeprecatedBackend(int api) {
+    const int M = sizeof(deprecated_backends) / sizeof(deprecated_backends[0]);
+    for (size_t i = 0; i < M; i++)
+    {
+        if (deprecated_backends[i].id == api)
+            return true;
+    }
+    return false;
+}
+
 cv::String getBackendName(VideoCaptureAPIs api)
 {
     if (api == CAP_ANY)
@@ -362,6 +384,14 @@ cv::String getBackendName(VideoCaptureAPIs api)
         if (backend.id == api)
             return backend.name;
     }
+
+    const int M = sizeof(deprecated_backends) / sizeof(deprecated_backends[0]);
+    for (size_t i = 0; i < M; i++)
+    {
+        if (deprecated_backends[i].id == api)
+            return deprecated_backends[i].name;
+    }
+
     return cv::format("UnknownVideoAPI(%d)", (int)api);
 }
 

modules/videoio/src/videoio_registry.hpp

@@ -29,11 +29,17 @@ struct VideoBackendInfo {
     Ptr<IBackendFactory> backendFactory;
 };
 
+struct VideoDeprecatedBackendInfo {
+    VideoCaptureAPIs id;
+    const char* name;
+};
+
 namespace videoio_registry {
 
 std::vector<VideoBackendInfo> getAvailableBackends_CaptureByIndex();
 std::vector<VideoBackendInfo> getAvailableBackends_CaptureByFilename();
 std::vector<VideoBackendInfo> getAvailableBackends_Writer();
+bool checkDeprecatedBackend(int api);
 
 } // namespace