A camera problem.

jenya7

@jenya7 Please run through debugger and post the stack trace.
Also, you should post your current code with enabled viewfinder.

void Camera::setCamera(const QCameraInfo &cameraInfo)
{
    m_camera.reset(new QCamera(cameraInfo));

    connect(m_camera.data(), &QCamera::stateChanged, this, &Camera::updateCameraState);
    connect(m_camera.data(), QOverload<QCamera::Error>::of(&QCamera::error), this, &Camera::displayCameraError);

    m_mediaRecorder.reset(new QMediaRecorder(m_camera.data()));
    connect(m_mediaRecorder.data(), &QMediaRecorder::stateChanged, this, &Camera::updateRecorderState);

    m_imageCapture.reset(new QCameraImageCapture(m_camera.data()));

    connect(m_mediaRecorder.data(), &QMediaRecorder::durationChanged, this, &Camera::updateRecordTime);
    connect(m_mediaRecorder.data(), QOverload<QMediaRecorder::Error>::of(&QMediaRecorder::error),
            this, &Camera::displayRecorderError);

    m_mediaRecorder->setMetaData(QMediaMetaData::Title, QVariant(QLatin1String("Test Title")));

    //connect(ui->exposureCompensation, &QAbstractSlider::valueChanged, this, &Camera::setExposureCompensation);

//here the exception occurs
   QCameraViewfinder *v_finder = new QCameraViewfinder();
    //v_finder->setFixedSize(240, 320);
    //v_finder->show();
    v_finder->setAttribute(Qt::WA_NoSystemBackground);
    m_camera->setViewfinder(v_finder);

    updateCameraState(m_camera->state());
    updateLockStatus(m_camera->lockStatus(), QCamera::UserRequest);
    updateRecorderState(m_mediaRecorder->state());

    connect(m_imageCapture.data(), &QCameraImageCapture::readyForCaptureChanged, this, &Camera::readyForCapture);
    connect(m_imageCapture.data(), &QCameraImageCapture::imageCaptured, this, &Camera::processCapturedImage);
    connect(m_imageCapture.data(), &QCameraImageCapture::imageSaved, this, &Camera::imageSaved);
    connect(m_imageCapture.data(), QOverload<int, QCameraImageCapture::Error, const QString &>::of(&QCameraImageCapture::error),
            this, &Camera::displayCaptureError);

    connect(m_imageCapture.data(), &QCameraImageCapture::imageAvailable, this, &Camera::ImageAvailable);

    connect(m_camera.data(), QOverload<QCamera::LockStatus, QCamera::LockChangeReason>::of(&QCamera::lockStatusChanged),
            this, &Camera::updateLockStatus);

    //ui->captureWidget->setTabEnabled(0, (m_camera->isCaptureModeSupported(QCamera::CaptureStillImage)));
    //ui->captureWidget->setTabEnabled(1, (m_camera->isCaptureModeSupported(QCamera::CaptureVideo)));

    updateCaptureMode(0);
    m_camera->start();
}

and a call stack

1  __GI_raise                                                  raise.c      50  0xb5830f14 
2  __GI_abort                                                  abort.c      79  0xb581c230 
3  QMessageLogger::fatal(const char *, ...) const                               0xb5c1c004 
4  QWidgetPrivate::QWidgetPrivate(int)                                          0xb698e204 
5  QWidget::QWidget(QWidget *, QFlags<Qt::WindowType>)                          0xb69ab42c 
6  QVideoWidget::QVideoWidget(QVideoWidgetPrivate&, QWidget *)                  0xb6f3ed70 
7  QCameraViewfinder::QCameraViewfinder(QWidget *)                              0xb6f388f4 
8  Camera::setCamera                                           camera.cpp   148 0x5a000        //this line is focused
9  Camera::Camera                                              camera.cpp   112 0x599ec    
10 __static_initialization_and_destruction_0                   camera.cpp   69  0x5bd58    
11 _GLOBAL__sub_I_camera.cpp(void)                             camera.cpp   544 0x5bdb4    
12 __libc_csu_init                                                              0xbed54    
13 __libc_start_main                                           libc-start.c 264 0xb581c6ac 
14 _start

jsulm

@jenya7 I'm confused by the code you posted: sometimes you use m_camera. and sometimes m_camera->! How can this even compile?!

Try to set a parent on QCameraViewfinder to see whether it makes a difference.

jenya7

@jsulm said in A camera problem.:

@jenya7 I'm confused by the code you posted: sometimes you use m_camera. and sometimes m_camera->! How can this even compile?!

Try to set a parent on QCameraViewfinder to see whether it makes a difference.

Hmm..It's an example from the official Qt/Examples folder. I guess those with a dot - the intrinsic methods, not from a Camera class.

for example - m_camera.reset
from - C:\Qt\5.12.0\mingw73_64\include\QtCore\qscopedpointer.h

jsulm

@jenya7 No, this belongs to C++ basics: if m_camera is a pointer then you have to use -> if it is not a pointer then you have to use dot. So, what is m_camera in YOUR code?

jenya7

@jsulm said in A camera problem.:

@jenya7 No, this belongs to C++ basics: if m_camera is a pointer then you have to use -> if it is not a pointer then you have to use dot. So, what is m_camera in YOUR code?

in camera.h

class Camera : public QMainWindow
{
    Q_OBJECT

public:
    Camera(QObject *parent = nullptr);

     void takeImage();

private slots:
    void setCamera(const QCameraInfo &cameraInfo);

    void startCamera();
    void stopCamera();

    void record();
    void pause();
    void stop();
    void setMuted(bool);

    void toggleLock();
    void displayCaptureError(int, QCameraImageCapture::Error, const QString &errorString);

    void configureCaptureSettings();
    void configureVideoSettings();
    void configureImageSettings();
    void displayRecorderError();
    void displayCameraError();

    void updateCameraDevice(QAction *action);

    void updateCameraState(QCamera::State);
    void updateCaptureMode();
    void updateRecorderState(QMediaRecorder::State state);
    void setExposureCompensation(int index);

    void updateRecordTime();

    void processCapturedImage(int requestId, const QImage &img);
    void updateLockStatus(QCamera::LockStatus, QCamera::LockChangeReason);

    void displayViewfinder();
    void displayCapturedImage();

    void readyForCapture(bool ready);
    void imageSaved(int id, const QString &fileName);

protected:
    void keyPressEvent(QKeyEvent *event) override;
    void keyReleaseEvent(QKeyEvent *event) override;
    void closeEvent(QCloseEvent *event) override;

private:
    Ui::Camera *ui;

    QScopedPointer<QCamera> m_camera;

    QScopedPointer<QCameraImageCapture> m_imageCapture;
    QScopedPointer<QMediaRecorder> m_mediaRecorder;

    QImageEncoderSettings m_imageSettings;
    QAudioEncoderSettings m_audioSettings;
    QVideoEncoderSettings m_videoSettings;
    QString m_videoContainerFormat;
    bool m_isCapturingImage = false;
    bool m_applicationExiting = false;
};

It's a private member initialized after the camera found in a constructor.

Camera::Camera(QObject *parent) : QObject(parent) 
{
      //some code
      if (cameraInfo == QCameraInfo::defaultCamera())
              videoDeviceAction->setChecked(true);

       setCamera(QCameraInfo::defaultCamera());
}

jsulm

@jenya7 OK, now it makes sense. Did you try to set parent on the viewfinder?

jenya7

@jsulm said in A camera problem.:

@jenya7 OK, now it makes sense. Did you try to set parent on the viewfinder?

That's it - they use the widget int the app. What should I choose as a parent?

jsulm

@jenya7 Do you have any other UI/widgets in your application?

jenya7

@jsulm said in A camera problem.:

@jenya7 Do you have any other UI/widgets in your application?

well...I can put one just for debug sake. right now it's a window with a text box for a command line receiving.

I did so

QWidget *viewfinderPage;
viewfinderPage = new QWidget();
v_finder = new QCameraViewfinder(viewfinderPage);

and I get the same exception on
viewfinderPage = new QWidget();

jsulm

@jenya7 said in A camera problem.:

and I get the same exception on
viewfinderPage = new QWidget();

You get same crash if you instanciate a QWidget?
Then something is really broken in your setup.
Can you build and execute a simple Qt widget application?

jenya7

@jsulm said in A camera problem.:

@jenya7 said in A camera problem.:

and I get the same exception on
viewfinderPage = new QWidget();

You get same crash if you instanciate a QWidget?
Then something is really broken in your setup.
Can you build and execute a simple Qt widget application?

actually viewfinderPage is null pointed. I have to create it. I'll try.

jenya7

well...I added in a main window

QCameraViewfinder *m_viewfinder =  new QCameraViewfinder(this);

and then in camera class

camera->setViewfinder(m_viewfinder );

But still get the message - "Image Capture Error: Camera not ready"
I get it on
m_imageCapture->capture();
When I try to go into capture() - I can't - the source unavailable, can not debug it to see why m_imageCapture decides the camera isn't ready.

Bonnie

According to https://doc.qt.io/qt-5/qcamera.html#State-enum :

In the active state as soon as camera is started the viewfinder displays video frames and the camera is ready for capture.

So capture should not be called right after start.
After calling start, you should asynchronously wait until the state turns to Active before performing any capturing.

jenya7

@Bonnie said in A camera problem.:

According to https://doc.qt.io/qt-5/qcamera.html#State-enum :
In the active state as soon as camera is started the viewfinder displays video frames and the camera is ready for capture.
So capture should not be called right after start.
After calling start, you should asynchronously wait until the state turns to Active before performing any capturing.

so I did

void Camera::takeImage()
{
    m_camera->start();
    m_camera->searchAndLock();

     while (m_imageCapture->isReadyForCapture() == false) ;

    m_isCapturingImage = true;
    m_imageCapture->capture();

    m_camera->unlock();
}

it's never ready. never gets out of while.

SGaist

Hi,

Your tight loop does not allow Qt's event loop to run. You should either use an event loop to "block" the execution or properly implement this through signals and slots.

jenya7

@SGaist said in A camera problem.:

Hi,

Your tight loop does not allow Qt's event loop to run. You should either use an event loop to "block" the execution or properly implement this through signals and slots.

OK. Did so

connect(m_imageCapture.data(), &QCameraImageCapture::isReadyForCapture, this, &Camera::IsReadyForCapture);

void Camera::takeImage()
{
    m_camera->start();
    m_camera->searchAndLock();

   // while (m_imageCapture->isReadyForCapture() == false) ;

    //m_isCapturingImage = true;
    //m_imageCapture->capture();

    //m_camera->unlock();
}

void Camera::IsReadyForCapture()
{
    m_isCapturingImage = true;
    m_imageCapture->capture();

    m_camera->unlock();
}

It never happens.

JonB

@jenya7 said in A camera problem.:

connect(m_imageCapture.data(), &QCameraImageCapture::isReadyForCapture, this, &Camera::IsReadyForCapture);

Did this go through without complaint? I am "surprised", as QCameraImageCapture::isReadyForCapture() is not a signal, would have thought connect() would barf on that.... Try using void QCameraImageCapture::readyForCaptureChanged(bool ready) signal?

jenya7

@JonB said in A camera problem.:

@jenya7 said in A camera problem.:

connect(m_imageCapture.data(), &QCameraImageCapture::isReadyForCapture, this, &Camera::IsReadyForCapture);

Did this go through without complaint? I am "surprised", as QCameraImageCapture::isReadyForCapture() is not a signal, would have thought connect() would barf on that.... Try using void QCameraImageCapture::readyForCaptureChanged(bool ready) signal?

did so

connect(m_imageCapture.data(), &QCameraImageCapture::readyForCaptureChanged, this, &Camera::ReadyForCaptureChanged);

void Camera::takeImage()
{
    m_camera->start();
    m_camera->searchAndLock();
}

void Camera::ReadyForCaptureChanged(bool ready)
{
    m_isCapturingImage = true;
    m_imageCapture->capture();

    m_camera->unlock();
}

never get into ReadyForCaptureChanged

jsulm

@jenya7 said in A camera problem.:

never get into ReadyForCaptureChanged

Sure? How did you verify that?

jenya7

@jsulm said in A camera problem.:

@jenya7 said in A camera problem.:

never get into ReadyForCaptureChanged

Sure? How did you verify that?

I set a break point inside. I see it goes into takeImage but never gets to ReadyForCaptureChanged
Now I don't get any errors but it prints
Starting camera without viewfinder available
Is it OK?