Various Backends for Video Feeds for GPU Targets

Common/Cpp/Options/EnumDropdownDatabase.h

@@ -92,8 +92,7 @@ class EnumDropdownDatabase : public IntegerEnumDropdownDatabase{
 public:
     EnumDropdownDatabase() : IntegerEnumDropdownDatabase() {}
     EnumDropdownDatabase(std::initializer_list<Entry> list){
-        size_t index = 0;
-        for (auto iter = list.begin(); iter != list.end(); ++iter, index++){
+        for (auto iter = list.begin(); iter != list.end(); ++iter){
             add(
                 iter->value,
                 std::move(iter->slug),

SerialPrograms/CMakeLists.txt

@@ -78,10 +78,10 @@ if(WIN32 AND QT_DEPLOY_FILES)
     if(QT_CANDIDATE_DIR AND EXISTS "${QT_CANDIDATE_DIR}")
         message(STATUS "Using preferred Qt directory for Qt${QT_MAJOR} ${PREFERRED_QT_VER}: ${QT_CANDIDATE_DIR}")
         list(APPEND CMAKE_PREFIX_PATH "${QT_CANDIDATE_DIR}")
-        find_package(Qt${QT_MAJOR} ${PREFERRED_QT_VER} COMPONENTS Widgets SerialPort Multimedia MultimediaWidgets REQUIRED)
+        find_package(Qt${QT_MAJOR} ${PREFERRED_QT_VER} COMPONENTS Widgets SerialPort Multimedia MultimediaWidgets OpenGLWidgets Qml Quick QuickWidgets REQUIRED)
     else()
         # Find all subdirectories in the Qt base directory
-        find_package(Qt${QT_MAJOR} COMPONENTS Widgets SerialPort Multimedia MultimediaWidgets REQUIRED)
+        find_package(Qt${QT_MAJOR} COMPONENTS Widgets SerialPort Multimedia MultimediaWidgets OpenGLWidgets Qml Quick QuickWidgets REQUIRED)
         file(GLOB QT_SUBDIRS LIST_DIRECTORIES true "${QT_BASE_DIR}/${QT_MAJOR}*")
 
         # Filter and sort the directories to find the latest version
@@ -109,7 +109,7 @@ if(WIN32 AND QT_DEPLOY_FILES)
         REQUIRED
     )
 else()
-    find_package(Qt${QT_MAJOR} COMPONENTS Widgets SerialPort Multimedia MultimediaWidgets REQUIRED)
+    find_package(Qt${QT_MAJOR} COMPONENTS Widgets SerialPort Multimedia MultimediaWidgets OpenGLWidgets Qml Quick QuickWidgets REQUIRED)
 endif()
 
 # disable deprecated Qt APIs
@@ -188,7 +188,7 @@ endif()
 # Function to apply common properties to both library and executable targets
 function(apply_common_target_properties target_name)
     set_target_properties(${target_name} PROPERTIES LINKER_LANGUAGE CXX)
-    target_link_libraries(${target_name} PRIVATE Qt${QT_MAJOR}::Widgets Qt${QT_MAJOR}::SerialPort Qt${QT_MAJOR}::Multimedia Qt${QT_MAJOR}::MultimediaWidgets)
+    target_link_libraries(${target_name} PRIVATE Qt${QT_MAJOR}::Widgets Qt${QT_MAJOR}::SerialPort Qt${QT_MAJOR}::Multimedia Qt${QT_MAJOR}::MultimediaWidgets Qt${QT_MAJOR}::OpenGLWidgets Qt${QT_MAJOR}::Qml Qt${QT_MAJOR}::Quick Qt${QT_MAJOR}::QuickWidgets)
     target_link_libraries(${target_name} PRIVATE Threads::Threads)
 
     #add defines
@@ -468,10 +468,9 @@ else() # macOS and Linux
     endif() # end Linux
 
     # Find OpenCV
-    pkg_search_module(OpenCV REQUIRED opencv4 opencv)
-    target_include_directories(SerialProgramsLib SYSTEM PRIVATE ${OpenCV_INCLUDE_DIRS}) # "SYSTEM" to suppress warnings
-    target_link_directories(SerialProgramsLib PUBLIC ${OpenCV_LIBRARY_DIRS})
-    target_link_libraries(SerialProgramsLib PUBLIC ${OpenCV_LINK_LIBRARIES})
+    find_package(OpenCV REQUIRED)
+    target_include_directories(SerialProgramsLib SYSTEM PUBLIC ${OpenCV_INCLUDE_DIRS}) # "SYSTEM" to suppress warnings
+    target_link_libraries(SerialProgramsLib PUBLIC ${OpenCV_LIBS})
 
     #we hope to use our own Tesseract build in future so we can rid that dependency
     #but right now to run on Linux and Mac we need to use external Tesseract library

SerialPrograms/Source/CommonFramework/Main.cpp

@@ -227,11 +227,18 @@ int main(int argc, char *argv[]){
 #endif
 
 #if defined(__linux__)
-    // Qt multimedia, default to gstreamer to prevent flickering
-    // Easier than the alternative which is compiling qt6multimedia with QT_DEFAULT_MEDIA_BACKEND
+    // Enable libv4l2 for GStreamer by default to fix issues with cheap capture cards
+    // This helps prevent "Invalid argument (22)" buffer allocation errors on v4l2src.
+    if (qEnvironmentVariableIsEmpty("GST_V4L2_USE_LIBV4L2")) {
+        qputenv("GST_V4L2_USE_LIBV4L2", "1");
+    }
+
+    // Qt multimedia, default to ffmpeg to prevent GStreamer capture drops.
+    // GStreamer used to be preferred to prevent flickering but causes fatal 
+    // crashes (buffer allocation errors) with cheap capture cards on Linux.
     // See: https://doc.qt.io/qt-6.5/qtmultimedia-index.html
     if (qEnvironmentVariableIsEmpty("QT_MEDIA_BACKEND"))
-        qputenv("QT_MEDIA_BACKEND", "gstreamer");
+        qputenv("QT_MEDIA_BACKEND", "ffmpeg");
 #endif
 
     //  So far, this is only needed on Mac where static initialization is fucked up.

SerialPrograms/Source/CommonFramework/VideoPipeline/Backends/CameraImplementations.cpp

@@ -17,9 +17,14 @@
 #if 0
 #elif QT_VERSION_MAJOR == 6
 #include "CameraWidgetQt6.h"
-#if QT_VERSION_MINOR >= 5
 #include "CameraWidgetQt6.5.h"
+#include "CameraWidgetQt6_QVideoWidget.h"
+#include "CameraWidgetQt6_QML.h"
 #endif
+
+#if defined(__linux__) || defined(__APPLE__)
+#include "CameraWidgetOpenCV.h"
+#include "CameraWidgetOpenCV_QOpenGLWidget.h"
 #endif
 
 
@@ -50,11 +55,29 @@ struct CameraBackends{
     }
 
     CameraBackends(){
+#if defined(__linux__) || defined(__APPLE__)
+        m_backends.emplace_back(
+            "opencv-v4l2", "Linux: OpenCV V4L2",
+            std::make_unique<CameraOpenCV::CameraBackend>()
+        );
+        m_backends.emplace_back(
+            "opencv-v4l2-gl", "Linux: OpenCV V4L2 (GPU Offloaded)",
+            std::make_unique<CameraOpenCV_QOpenGLWidget::CameraBackend>()
+        );
+#endif
 #if QT_VERSION_MAJOR == 6
         m_backends.emplace_back(
             "qt6-QVideoSink", "Qt6: QVideoSink",
             std::make_unique<CameraQt6QVideoSink::CameraBackend>()
         );
+        m_backends.emplace_back(
+            "qt6-qvideowidget", "Qt6: GPU Offloaded (QOpenGLWidget)",
+            std::make_unique<CameraQt6QVideoWidget::CameraBackend>()
+        );
+        m_backends.emplace_back(
+            "qt6-qml", "Qt6: GPU Offloaded (QML QQuickWidget)",
+            std::make_unique<CameraQt6QML::CameraBackend>()
+        );
 #endif
 #if QT_VERSION_MAJOR == 6 && QT_VERSION_MINOR >= 5
         m_backends.emplace_back(

SerialPrograms/Source/CommonFramework/VideoPipeline/Backends/CameraImplementations.h

@@ -23,7 +23,7 @@ class VideoBackendOption : public IntegerEnumDropdownOption{
 
 // Abstract base class for camera backend implementation.
 // Call `get_camera_backend()` to get the camera backend singleton.
-// Current camera backend is implemented in CameraWidgetQt6.h/cpp.
+// Qt6 camera backends are implemented in CameraWidgetQt6*.h/cpp.
 class CameraBackend{
 public:
     virtual ~CameraBackend() = default;
@@ -47,7 +47,7 @@ class CameraBackend{
 
 
 // Get the camera backend singleton.
-// Current camera backend is implemented in CameraWidgetQt6.h/cpp.
+// Qt6 camera backends are implemented in CameraWidgetQt6*.h/cpp.
 const CameraBackend& get_camera_backend();
 
 // Call `get_camera_backend()` to get camera backend reference and get all cameras' info.