MAC QT5.13 delete QCamera class make corruption

[mingzhi]

I have a USB camera that not needed driver and In my writen code when the USB camera disappear from my computer, I will delete the QCamera class, but when I delete the QCamera, the program cooruption, here is the debug information,the last page is the corruption occur

Please helpt me, thanks

[jsulm]

@mingzhi Maybe you should first call https://doc.qt.io/qt-5/qcamera.html#stop ?

[mingzhi]

@jsulm I try first call stop,no changed,also corruption

[ChrisW67]

@mingzhi Please do not post screen shots when a simple text copy and paste is far more readable.

How are you detecting that the camera device has gone away?
Have you called QCamera::unload()?
What else have you tried?

[mingzhi]

@ChrisW67 In the Init ,I first use QCameraInfo class to finde all avaliable cameraInfo, and create a Qcamera class which I want camerInfo and add this cameraInfo to a QList, then create a Timertask to detect QCameraInfo and when the QCameraInfo::avaliables() doesn't have the QList's camerainfo, I send a signal to slot, in slot I delete QCamera

[mingzhi]

@ChrisW67 befort delete QCamera , unload, unlock, stop, all those I all try, here is the main create and dropp code, cameraConnected function and cameraDropped function are all slot fuction for cameraconnect signal and cameradrop signal

void MainWindow::cameraConnected( QList<QCameraInfo> connectedCameras )
{
foreach( const QCameraInfo& cameraInfo, connectedCameras ) {
if( false == fAvailableCameras.contains( cameraInfo ) ) {
fAvailableCameras.append( cameraInfo );

        if( nullptr == fCurrentCamera ) {
            setCamera( cameraInfo );
        }
    }
}

}

void MainWindow::setCamera( const QCameraInfo& cameraInfo )
{
delete fMediaRecorder;
delete fImageCapture;
delete fCurrentCamera;
delete fAudioProbe;

fMediaRecorder = nullptr;
fImageCapture = nullptr;
fCurrentCamera = nullptr;
fAudioProbe = nullptr;

fCurrentCamera = new QCamera( cameraInfo );

connect( fCurrentCamera, SIGNAL( stateChanged( QCamera::State ) ),
         this, SLOT( updateCameraState( QCamera::State ) ) );
connect( fCurrentCamera, SIGNAL( error( QCamera::Error ) ),
         this, SLOT( cameraError( QCamera::Error ) ) );

fMediaRecorder = new QMediaRecorder( fCurrentCamera );
connect( fMediaRecorder, SIGNAL( stateChanged( QMediaRecorder::State ) ),
         this, SLOT( updateRecorderState( QMediaRecorder::State ) ) );

qDebug() << fMediaRecorder->videoSettings().encodingOptions();
qDebug() << fMediaRecorder->supportedContainers();

fImageCapture = new QCameraImageCapture( fCurrentCamera );

connect( fMediaRecorder, SIGNAL( durationChanged( qint64 ) ),
         this, SLOT( updateRecordTime( qint64 ) ) );
connect( fMediaRecorder, SIGNAL( error( QMediaRecorder::Error ) ),
         this, SLOT( recorderError( QMediaRecorder::Error ) ) );

fMediaRecorder->setMetaData( QMediaMetaData::Title, QVariant( QLatin1String( "SurgiCam" ) ) );

//connect( ui->exposureCompensation, SIGNAL(valueChanged(int)), SLOT(setExposureCompensation(int))) ;

fCurrentCamera->setViewfinder( fCameraViewfinder->videoSurface() );

fCurrentCamera->imageProcessing()->setWhiteBalanceMode( QCameraImageProcessing::WhiteBalanceManual );
fCurrentCamera->imageProcessing()->setManualWhiteBalance( 50 );
fCurrentCamera->imageProcessing()->setBrightness( 0 );
fCurrentCamera->imageProcessing()->setContrast( 0 );
fCurrentCamera->imageProcessing()->setSaturation( 0 );
fCurrentCamera->imageProcessing()->setSharpeningLevel( 0 );
fCurrentCamera->imageProcessing()->setDenoisingLevel( 0 );

fAudioProbe = new QAudioProbe();

if( false == fAudioProbe->setSource( fCurrentCamera ) ) {
    connect( fAudioProbe, SIGNAL( audioBufferProbed( QAudioBuffer ) ), this, SLOT( updateAudioLevel( QAudioBuffer ) ) );
}

fIsFullScreen = false;
//connect( fActionToggleFullScreen, SIGNAL( toggled( bool ) ), fCameraViewfinder, SLOT( setFullScreen( bool ) ) );
connect( fActionToggleFullScreen, SIGNAL( toggled( bool ) ), this, SLOT( toggleFullScreenMode( bool ) ) );
connect( fActionToggleFullScreenNative, SIGNAL( toggled( bool ) ), this, SLOT( toggleFullScreenMode( bool ) ) );

updateCameraState( fCurrentCamera->state() );
updateCameraLockState( fCurrentCamera->lockStatus(), QCamera::UserRequest );
updateRecorderState( fMediaRecorder->state() );

connect( fImageCapture, SIGNAL( readyForCaptureChanged( bool ) ),
         this, SLOT( readyForCapture( bool ) ) );
connect( fImageCapture, SIGNAL( imageCaptured( int, QImage ) ),
         this, SLOT( capturedImage( int, QImage ) ) );
connect( fImageCapture, SIGNAL( imageSaved( int, QString ) ),
         this, SLOT( imageSaved( int, QString ) ) );
connect( fImageCapture, SIGNAL( error( int, QCameraImageCapture::Error, QString ) ),
         this, SLOT( captureError( int, QCameraImageCapture::Error, QString ) ) );

connect( fCurrentCamera, SIGNAL( lockStatusChanged( QCamera::LockStatus, QCamera::LockChangeReason ) ),
         this, SLOT( updateCameraLockState( QCamera::LockStatus, QCamera::LockChangeReason ) ) );

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

// updateCaptureMode();

fCurrentCamera->load();

qDebug() << "Supported audio codec: " << fMediaRecorder->supportedAudioCodecs();
qDebug() << "Supported audio sample-rate: " << fMediaRecorder->supportedAudioSampleRates();
qDebug() << "Supported video codec: " << fMediaRecorder->supportedVideoCodecs();
qDebug() << "Supported video resolutions: " << fImageCapture->supportedResolutions();
qDebug() << "Supported video frame-rate: " << fMediaRecorder->supportedFrameRates();

fCurrentCamera->setCaptureMode( QCamera::CaptureStillImage );

fCurrentCamera->start();
fCurrentCameraInfo = cameraInfo;

fMediaPlayerWidget->stop();
fStackedPlayersWidget->setCurrentIndex( 1 );
fWaitingForCameraWidget->stop();

fVideoEncoderSettings = fMediaRecorder->videoSettings();
fAudioEncoderSettings = fMediaRecorder->audioSettings();
fVideoContainerFormat = QString();

fSupportedResolution.clear();
QList<QSize> supportedResolution = fImageCapture->supportedResolutions();

for( int i = supportedResolution.count() - 1; i >= 0; --i ) {
    fSupportedResolution.append( supportedResolution[i] );

    if( 4 == fSupportedResolution.count() ) {
        break;
    }
}

if( fCurrentCameraInfo.description().startsWith( fSupportedCameraDescriptions[0] ) ) {
    fSelectedResolution = 0;
}
else {
    fSelectedResolution = 3;
}

for( int i = 0; i < 4; ++i ) {
    fActionResolutions[i]->setText( QString( "%1 x %2" ).arg( fSupportedResolution[i].width() ).arg( fSupportedResolution[i].height() ) );

    fActionResolutions[i]->setChecked( i == fSelectedResolution );
}

fSelectedRotation = 0;

for( int i = 0; i < 4; ++i ) {
    fActionRotations[i]->setChecked( i == fSelectedRotation );
}

fVideoEncoderSettings.setResolution( fSupportedResolution[fSelectedResolution] );
fMediaRecorder->setEncodingSettings( fAudioEncoderSettings, fVideoEncoderSettings );

fLiveMode = true;
fInformationFileNameEdit->setText( fLiveFileName );
fInformationDoctorNameEdit->setText( fLiveDoctorName );
fInformationPatientNameEdit->setText( fLivePatientName );
fInformationHospitalNameEdit->setText( fLiveHospitalName );
fInformationCommentEdit->setText( fLiveComment );

setupIdleUIState();

}
void MainWindow::cameraDropped( QList<QCameraInfo> droppedCameras )
{
bool dropCurrent = false;

foreach( const QCameraInfo& cameraInfo, droppedCameras ) {
    if( false != fAvailableCameras.removeOne( cameraInfo ) ) {
        if( nullptr != fCurrentCamera && cameraInfo == fCurrentCameraInfo ) {
            if( nullptr != fMediaRecorder ) {
                if( QMediaRecorder::RecordingState == fMediaRecorder->state() ) {
                    fMediaRecorder->stop();
                }

                if( nullptr != fFileSplitTask ) {
                    fFileSplitTask->abort();
                    fFileSplitTask = nullptr;
                }
            }

            fVideoCaptureAnimationLabel->toggle( false );
            fVideoCaptureButton->setChecked( false );

            delete fMediaRecorder;
            delete fImageCapture;
            delete fCurrentCamera;
            delete fAudioProbe;

            fMediaRecorder = nullptr;
            fImageCapture = nullptr;
            fCurrentCamera = nullptr;
            fAudioProbe = nullptr;

            fCurrentCameraInfo = QCameraInfo();

            fMediaPlayerWidget->stop();
            fStackedPlayersWidget->setCurrentIndex( 0 );
            fWaitingForCameraWidget->start();

            setupInvaildUIState();

            dropCurrent = true;
        }
    }
}

if( false != dropCurrent ) {
    if( 0 < fAvailableCameras.count() ) {
        setCamera( fAvailableCameras[0] );
    }
}

}

[ChrisW67]

@mingzhi said in MAC QT5.13 delete QCamera class make corruption:

In the Init ,I first use QCameraInfo class to finde all avaliable cameraInfo, and create a Qcamera class which I want camerInfo and add this cameraInfo to a QList, then create a Timertask to detect QCameraInfo and when the QCameraInfo::avaliables() doesn't have the QList's camerainfo, I send a signal to slot, in slot I delete QCamera

So, you will not detect the absence of the camera until some indeterminate time after the device has actually gone. I do not know whether your camera object pointer will still be valid at that point in time.

Have you looked at the QCamera::statusChanged() signal to see what that Qt is telling you before the crash?

[mingzhi]

@ChrisW67 but in windows the code run normally

[mingzhi]

@ChrisW67 if before delete QCamera I used stop and load the status is:

[mingzhi]

@ChrisW67 if before delete QCamera I use stop and unload as the follow:

(fCurrentCamera is a QCamera class)
fCurrentCamera->stop(); ---------( QCamera::statusChanged() ->LoadedState)
fCurrentCamera->unload(); ---------( QCamera::statusChanged() ->UnloadedState)
delete fCurrentCamera; ---------(crash)

and if I not used stop and unload to delete QCamera directly The QCamera::statusChanged() will not happened if I out USB Camera

[mingzhi]

@ChrisW67 sorry I also test now, if I not used stop and unload to delete QCamera directly The QCamera::statusChanged() will be UnloadedState after I use delete QCamera and then crash, but the Crash occurred during the delete process and before I delete QCamera I have detected the Camera removed from my computer

[mingzhi]

@ChrisW67 I am not delete QCamera in other place, so the pointer shoulde be valid

[mingzhi]

@ChrisW67and in my debug picture the QCamera Destructor function occur, so the pointer shoulde vaild

[mingzhi]

@ChrisW67 sorry, I used Qt 5.15