Problem with implementing some streaming, QML, CPP

vgvg

How can I implement some classes on cpp side, which can handle camera stream, and then put it something in QML to watch it?

VideoOutput - unavailable in cpp
MediaPlayer - source only by url

How can I achieve this goal? Any help, please. Any help appreciated even without code. Where should I dig into docs?

SGaist

Hi and welcome to devnet,

Which version of Qt are you using ?
On which OS ?

mrdebug

Hi. If you need an object to manage rtsp and webcam stream you can use this:
https://github.com/denisgottardello/QtFFmpegPlayer

The object emits some events:

CONNECTION_STATE_CONNECTED,
CONNECTION_STATE_CONNECTED_DATA_RECEIVED,
CONNECTION_STATE_CONNECTING,
CONNECTION_STATE_IDLE,

so you can create a machine state to resume the connection after a the remote device disconnection.
The example is based on widgets but, to use it in qml is easy.

Ronel_qtmaster

@vgvg this is how you should proceed
On the cpp side, create a new class e.g CameraFilter , that inherits from QAbstractVideoFilter that will return a filter Runnable.
Still on the header create a new class that represent the filter Runnable. That class will inherit from QVideoFilterRunnable. inside the filter runnable class reimplement the run(QVideoFrame *input, const QVideoSurfaceFormat &surfaceFormat, RunFlags flags); function, that will return the current QVideoFrame. So your filter class should be something like this:

class MyFilter : public QAbstractVideoFilter {
Q_OBJECT
public:
QVideoFilterRunnable *createFilterRunnable();
~MyFilter();
signals:
private:
};
class MyFilterRunnable : public QVideoFilterRunnable {

public:
MyFilterRunnable(MyFilter *creator) {filter = creator;}
QVideoFrame run(QVideoFrame *input, const QVideoSurfaceFormat &surfaceFormat, RunFlags flags);
private:
MyFilter *filter;

};
uses qmlRegisterType to register your filter in main.cpp

Now on the QML side, create a Camera element. Add Also a VideoOutput element. as the source of the VideoOutput set the camera. The VideoOutput has a property called filter. There you can put your custom filter. Something like this.

MyFilter
{
    id:myfilter
    
}

Camera
{
id:camera
}
VideoOutput{
width: parent.width - 50
height: parent.height -50
anchors.centerIn: parent
autoOrientation: false
source:camera
id:video
filters: [myfilter]

vgvg

Thank you for your all answers. I guess VideoOutput has no source member in Qt 6.10.

The main idea is - I create custom class, which inherited from some class from Video section. Then, I register qml type and it's done?

Thank you very much!

vgvg

I am still confused:

   QMediaCaptureSession* captureSession;
    QCamera* camera;
    QVideoSink* videoSink;

I have class with this fields. How should I show what will be in my videoSink in QML?

vgvg

In other words I need to create custom video output. How to do that?

GrecKo

In c++, you'll need to create and expose to QML a QVideoSink.

Here's a overview of how you could do that : https://doc.qt.io/qt-6/qtqml-cppintegration-overview.html

QVideoSink has a setVideoFrame method if you want to pass it a custom frame.

If you only need to display the frames from a normal camera you don't need that.

vgvg

// Main.qml

import QtCore
import QtMultimedia
import QtQuick
import QtQuick.Controls
import VWC 1.0

ApplicationWindow {
width: Screen.width
height: Screen.height
visible: true
title: qsTr("VWC: Virtual Web Camera")

Switch {
    id: toggleCameraSwtich
    onCheckedChanged: {
        if (checked) {
            videoOutput.visible = true
            Controller.cameraStart()
        } else {
            Controller.cameraStop()
            videoOutput.visible = false
        }
    }
}

VideoOutput {
    id: videoOutput
    anchors.fill: parent
    Component.onCompleted: {
        Controller.setVideoOutput(videoOutput)
    }
}

CameraPermission {
    id: permissionController
    Component.onCompleted: {
        if (permissionController.status !== Qt.PermissionStatus.Granted) {
            permissionController.request()
        }
    }
}

}

// Controller.h
class Controller : public QObject
{
Q_OBJECT
public:
explicit Controller(QObject *parent = nullptr);

Q_INVOKABLE void setVideoOutput(QObject* videoOutput);
Q_INVOKABLE void cameraStart();
Q_INVOKABLE void cameraStop();

signals:

public slots:

private:
QMediaCaptureSession* captureSession;
QCamera* camera;
};

// main.cpp
int main(int argc, char *argv[])
{
QGuiApplication app(argc, argv);

QQmlApplicationEngine engine;

Controller* controller = new Controller{&app};

qmlRegisterSingletonInstance("VWC", 1, 0, "Controller", controller);

QObject::connect(
    &engine, &QQmlApplicationEngine::objectCreationFailed,
    &app, []() { QCoreApplication::exit(-1); },
    Qt::QueuedConnection);

engine.loadFromModule("VWC", "Main");

return app.exec();

}

I need to get frames from QCamera in the same time when stream is turned on. How?

JolianD

This post is deleted!