Replace QCameraViewfinder with QVideoWidget in Qt 6

Question

I am trying to port some code to Qt 6's reworked QtMultimedia framework and running into a lot of issues of disappearing APIs.

One of these is QCameraViewfinder, which as I understand it, is a simple viewer of the current QCamera image feed. It used to be a subclass of QVideoWidget, which still exists, and its documentation helpfully states the following:

Attaching a QVideoWidget to a QMediaPlayer or QCamera allows it to display the video or image output of that object.
player = new QMediaPlayer;
player->setSource(QUrl("http://example.com/myclip1.mp4"));

videoWidget = new QVideoWidget;
player->setVideoOutput(videoWidget);

videoWidget->show();
player->play();
Note: Only a single display output can be attached to a media object at one time.

Problem is, there is no way to do QCamera::setVideoOutput(QVideoWidget*) as that function does not exist. Neither can I find an alternative API that connects the two. Is this something that they forgot to provide or am I missing something? I looked through the relevant classes' source code and documentation, but can't for the life of me find the magic incantation that's supposed to give me a simple view into a QCamera's current video feed.

score 1 · Accepted Answer · answered Oct 26 '21 at 18:23

You have to use QMediaCaptureSession:

#include <QApplication>
#include <QCamera>
#include <QMediaDevices>
#include <QMediaCaptureSession>
#include <QVideoWidget>

int main(int argc, char *argv[])
{
    QApplication a(argc, argv);

    QVideoWidget videoWidget;
    videoWidget.resize(640, 480);
    videoWidget.show();

    QCamera camera(QMediaDevices::defaultVideoInput());
    camera.start();

    QMediaCaptureSession mediaCaptureSession;
    mediaCaptureSession.setCamera(&camera);
    mediaCaptureSession.setVideoOutput(&videoWidget);

    return a.exec();
}

Replace QCameraViewfinder with QVideoWidget in Qt 6

1 Answers1