Qt6 + Gstreamer + CMake

Ami00

Cheers!

Trying to implement some desktop app that will have embedded video player, which will get video stream through rtp,rtsp or something similar.
I found the example project (https://gitlab.freedesktop.org/gstreamer/gstreamer/-/tree/main/subprojects/gst-plugins-good/tests/examples/qt6/qmlsink?ref_type=heads), built it, launched and everything goes smooth.
Then I created CMake project file in the same directory(because I'm not quite familiar with qmake, on top of that whole ecosystem(dozen of projects so far) use CMake), built it, launched and everything goes smooth once again!

Now I created new empty QT desktop App project, copy paste CMake file, added minor changes to process ui, moc whatever.
Built it, launched and got error:

QQmlApplicationEngine failed to load component
qrc:/VideoPlayer.qml:32:1: module "org.freedesktop.gstreamer.Qt6GLVideoItem" is not installed
[DBG] QML import paths:
"/home/user/code/project/build"
"qrc:/qt-project.org/imports"
"qrc:/qt/qml"
"/usr/lib/qt6/qml"

For some incomprehensible reasons, it now can't find qml module! I also added printf to get path it looked, and it's identical to those that the example app used.

CMake:

cmake_minimum_required(VERSION 3.14)

project(NewAppGstreamer)

set(CMAKE_AUTOUIC ON)
set(CMAKE_AUTOMOC ON)
set(CMAKE_AUTORCC ON)

# Set the C++ standard
set(CMAKE_CXX_STANDARD 17)

# Find Qt6
find_package(Qt6 REQUIRED COMPONENTS Core Quick Qml Widgets)

# Find GStreamer using pkg-config
find_package(PkgConfig REQUIRED)
pkg_check_modules(GSTREAMER REQUIRED gstreamer-1.0 gstreamer-video-1.0)

# Add additional include path for GStreamer
include_directories(${GSTREAMER_INCLUDE_DIRS} ../lib)

# Define the preprocessor macro (equivalent to DEFINES)
add_definitions(-DGST_USE_UNSTABLE_API)



qt_add_resources(RESOURCE_FILES resources.qrc)

# Create the executable
# add_executable(NewAppGstreamer main.cpp)
qt_add_executable(NewAppGstreamer
    mainwindow.cpp
    mainwindow.ui
    mainwindow.h
    main.cpp
    ${RESOURCE_FILES}
)
# Set up the QML resource file
# qt_add_resources(NewAppGstreamer "RESOURCES" qmlsink.qrc)

# Link the executable to Qt6 and GStreamer
target_link_libraries(NewAppGstreamer PRIVATE
    Qt6::Core
    Qt6::Quick
    Qt6::Qml
    Qt6::Widgets
    ${GSTREAMER_LIBRARIES}
)

# Ensure pkg-config is used for the build
set(PKG_CONFIG_EXECUTABLE ${PkgConfig_EXECUTABLE})

# Set the QML import path (if needed)
# Set your custom import paths if required
# set(QML_IMPORT_PATH "/path/to/your/qml/modules")

# Set the GST_PLUGIN_PATH environment variable
# This ensures GStreamer can find its plugins
set(ENV{GST_PLUGIN_PATH} "/usr/lib/gstreamer-1.0")

# Ensure Qt6 QML import path is included in the build process
target_compile_definitions(NewAppGstreamer PRIVATE QT_QML_IMPORT_PATH="${QML_IMPORT_PATH}")

drwxr-xr-x    - user 10 кві 11:55  build
.rw-r--r-- 1,6k user 10 кві 11:55  CMakeLists.txt
.rw-r--r--  34k user  9 кві 18:39  CMakeLists.txt.user
.rw-r--r--  525 user  9 кві 17:27  main.cpp
.rw-r--r-- 2,6k user  9 кві 18:07  mainwindow.cpp
.rw-r--r--  632 user  9 кві 17:32  mainwindow.h
.rw-r--r--  998 user  9 кві 14:04  mainwindow.ui
.rw-r--r--   94 user  9 кві 16:51  resources.qrc
.rw-r--r-- 2,8k user 10 кві 11:40  VideoPlayer.qml

cat resources.qrc
<RCC>
    <qresource prefix="/">
        <file>VideoPlayer.qml</file>
    </qresource>
</RCC>

QML file is copy of the one from the example prject

Now I'm lost, CMake file is pretty much the same, and I have no idea what could potentially lead to such a behavior.

Any help is appreciated, I'm new to Qt world.
Thanks in advance!

JoeCFD

The error does not mean qml module can not be found. Instead gstreamer good plug-in(has qml sink) can not be found.
Note(from the example code):
/* the plugin must be loaded before loading the qml file to register the
* GstGLVideoItem qml item */
GstElement *sink = gst_element_factory_make ("qml6glsink", NULL);

It can be deleted immediately since its only purpose is to load gstreamer good plug-in.

I prefer to add gstreamer libs as follows:

target_link_libraries(NewAppGstreamer PRIVATE
    Qt6::Core
    Qt6::Quick
    Qt6::Qml
    Qt6::Widgets
    PkgConfig::GSTREAMER
    PkgConfig::GSTREAMER-VIDEO
)

Ami00

Oops!

That was right under my nose, but I still managed to miss it.

Many thanks, good sir!