How to record video as soon as application started?

[hix_boz]

Hello all,

I would like to record video as soon as my Qt application started. I have managed to start the video recordings with buttons but weirdly I couldnt record the video without any button signals and slots. How can I record the video from startup ? Here is the associated parts of my code with button signals and slots. Any help will be appreciated.

code_text
```    const QList<QCameraInfo> cameras = QCameraInfo::availableCameras();
    for (const QCameraInfo &cameraInfo : cameras) {
        qDebug() << cameraInfo.deviceName();
        if (cameraInfo.deviceName() == "/dev/video0"){
            camera = new QCamera(cameraInfo);
            mediaRecorder = new QMediaRecorder(camera);
            mediaRecorder->setContainerFormat("mp4");
            viewfinder = new QCameraViewfinder(this->ui->stackedWidget);
            viewfinder->setGeometry(0,0,900,400);
            viewfinder->show();
            connect(mediaRecorder, &QMediaRecorder::durationChanged, this, &MainWindow::updateRecordTime);

            camera->setViewfinder(viewfinder);

            camera->unload();
            camera->setCaptureMode(QCamera::CaptureVideo);
            camera->start();
        }

void MainWindow::on_pushButton_pressed()
{

    camera->setCaptureMode(QCamera::CaptureVideo);
    record();

    camera->setCaptureMode(QCamera::CaptureVideo);

    this->ui->pushButton_stop->setEnabled(true);
    if (mediaRecorder->state() == QMediaRecorder::RecordingState){
        qDebug() << "It is in recording state";
    }

}

void MainWindow::record()
{
    camera->setCaptureMode(QCamera::CaptureVideo);

    QString name = filename + QDateTime::currentDateTime().toString("dd.MM.yy-h-m-s");//3
    mediaRecorder->setOutputLocation(QUrl::fromLocalFile(outputpath + "/" + name + ".mp4"));
    mediaRecorder->record();
    this->ui->pushButton->setEnabled(false);

}

[Bonnie]

I think you should connect to the QCamera::statusChanged signal, and start the recorder after the status becomes QCamera::ActiveStatus (maybe also stop it when it is non-active).

[jsulm]

@hix_boz You can override https://doc.qt.io/qt-5/qwidget.html#showEvent and start recording there.

[hix_boz]

@jsulm
Hello jsulm,
Thanks fro your asnwer. I added the function like before.

void MainWindow::showEvent(QShowEvent *event){
    qDebug() << "////DEBUGGG////";
    QString name = filename + QDateTime::currentDateTime().toString("dd.MM.yy-h-m-s");//3
    mediaRecorder->setOutputLocation(QUrl::fromLocalFile(outputpath + "/" + name + ".mp4"));
    mediaRecorder->record();
    if (mediaRecorder->state() == QMediaRecorder::RecordingState){
        qDebug() << "It is in recording state";
    }
}

The function has been called and debug printed. It does not record the video and the recording state debug does not printed. What could be the problem? Thanks inadvanced.

[jsulm]

@hix_boz Please add error handling:
https://doc.qt.io/qt-5/qmediarecorder.html#error-1
https://doc.qt.io/qt-5/qmediarecorder.html#stateChanged

And I'm not sure you can expect state() to return QMediaRecorder::RecordingState just after calling record() - it can take some time until the sate changes.

[hix_boz]

@jsulm I have added the error handling like before,

connect(mediaRecorder, QOverload<QMediaRecorder::Error>::of(&QMediaRecorder::error),this, &MainWindow::displayRecorderError);

void MainWindow::displayRecorderError()
{
    QMessageBox::warning(this, tr("Capture Error"), mediaRecorder->errorString());
}

I got an error like "no template named 'QOverLoad'" . I have checked camera example of qt which records video and capture images application and I did almost same thing. I suspect the version incompatibility. Do you think version differences cause this issue?

[jsulm]

@hix_boz said in How to record video as soon as application started?:

Do you think version differences cause this issue?

What Qt version do you use?

[hix_boz]

@jsulm

Qt Creator 4.13.1
Based on Qt 5.15.1 (GCC 5.3.1 20160406 (Red Hat 5.3.1-6), 64 bit)

[Christian Ehrlicher]

@hix_boz said in How to record video as soon as application started?:

QOverload

I got an error like "no template named 'QOverLoad'"

QOverload != QOverLoad - please post the real code and the real error message.

[hix_boz]

@Christian-Ehrlicher
Do you ask to share all prject files when you say real code? Here the errors I got.

Additionaly, I took the error handler connect snippet from Qt camera example which is working with my Qt version.

[jsulm]

@hix_boz said in How to record video as soon as application started?:

Do you ask to share all prject files when you say real code?

No, your connect statement.
As @Christian-Ehrlicher pointed out it is QOverload NOT QOverLoad...

And the version you posted only says something about Qt version used to build QtCreator, not Qt version you're using...

[hix_boz]

@jsulm

After commanding "qmake --version" from terminal, I got this one.

QMake version 3.0
Using Qt version 5.5.1 in /usr/lib/x86_64-linux-gnu

I also typed "qtdiag" and the first line of response like below.

Qt 5.5.1 (x86_64-little_endian-lp64 shared (dynamic) release build; by GCC 5.4.0 20160609) on "xcb"

I tried either QOverLoad and QOverload and still got an error. As I said before, I took the connect part from camera example which has worked and I did not change anything. They used "QOverload" in connect line.

[jsulm]

@hix_boz According to Qt5.5 documentation (https://doc.qt.io/archives/qt-5.5/qmediarecorder.html#error-1):

connect(mediaRecorder, static_cast<void(QMediaRecorder::*)(QMediaRecorder::Error)>(&QMediaRecorder::error),
    [=](QMediaRecorder::Error error){ /* ... */ });

[Christian Ehrlicher]

@hix_boz said in How to record video as soon as application started?:

I tried either QOverLoad and QOverload and still got an error

No - there must be at least another error message, please post the error message when you use the correct function QOverload

[hix_boz]

@jsulm

It worked like this,

connect(mediaRecorder, static_cast<void(QMediaRecorder::*)(QMediaRecorder::Error)>(&QMediaRecorder::error),
         [=](QMediaRecorder::Error error){  qDebug() << mediaRecorder->errorString(); });

The error I got ,
"Service has not been started" .

Also the below message I keep getting.
(videoPlayer:9057): GStreamer-CRITICAL **: gst_mini_object_unref: assertion 'mini_object != NULL' failed

[Bonnie]

I think you should connect to the QCamera::statusChanged signal, and start the recorder after the status becomes QCamera::ActiveStatus (maybe also stop it when it is non-active).

[hix_boz]

@Bonnie
It works, thanks you so much.