Capturing QCamera image in a separate thread problem

[s.maks]

I'm trying to catch images using QCamera. Fore more code look at this topic. Now I just want to execute CCameraCallback.Run() method in another thread. Here is the code:

class CCameraCallback
        : public QThread 
        , public IBaseCallback
{

    Q_OBJECT
    Q_INTERFACES(IBaseCallback)

private:
    QCamera*             pCamera;
    QCameraImageCapture* pImageCapture;

public:
    CCameraCallback();
    ~CCameraCallback();

    virtual void run();

    void SetParam(const QString &, const QVariant &);

private slots:
    void onBufferAvailable(int, const QVideoFrame&);

};


void CCameraCallback::Run() {

    if (pCamera->state() == QCamera::ActiveState) pCamera->stop();

    pCamera->start();
    pCamera->searchAndLock();

    pImageCapture->capture();

    this->exec();

}

/* rest of the code has not changed */

Every time run() method executes I'm got "Thread 0xcb0 has panicked. Category: KERN-EXEC; Reason: 0" message. It seems that pCamera->start() crashes. The question is why?

[s.maks]

It there any way to catch camera image in separate tread? I'm trying to do this using code from this topic. I just inherit CCameraCallback from QThread and adding this->exec() to run() method. Now every time i use CCameraCallback->start() i'm got "Thread 0xcb0 has panicked. Category: KERN-EXEC; Reason: 0" error. Can somebody explain why?

PS: oh, I thought my previous thread didn't added because of error =/ sorry

[wizard_hu_]

Your threads are merged now.

KERN-EXEC 0 is documented in the Symbian C++ SDK-s, it is about using an invalid handle. Invalid can also mean unavailable, which is the case here: the Symbian camera API does not allow sharing the object between threads. You have to use the camera in the same thread where you are creating it. If you need it in a secondary thread, try creating it there.

[s.maks]

I create QCamera and QCameraImageCapture objects in the CCameraCallback class constructor. I also use moveToThread(this) method in constructor. What am I doing wrong?

[wizard_hu_]

The Symbian C++ part of the QCamera object can not support moveToThread. It will always belong to the thread where it was created.
Try creating the QCamera object in run() (and invoke exec() after it).

[s.maks]

Now when I'm trying to create QCamera object in run() function I got "A data abort exception has occurred accessing 0x48".

void CCameraCallback::run() {

    if (!pCamera && !pImageCapture) {
        QByteArray lvCameraDevices = QCamera::availableDevices()[1];    
        pCamera = new QCamera(lvCameraDevices, this); /* error occurs on this line */
        pCamera->setCaptureMode(QCamera::CaptureStillImage);

        pImageCapture = new QCameraImageCapture(pCamera); 
        pImageCapture->setCaptureDestination(QCameraImageCapture::CaptureToBuffer); 
        pImageCapture->setBufferFormat(QVideoFrame::Format_Jpeg);    

        QObject::connect(
                    pImageCapture, SIGNAL( imageAvailable(int, QVideoFrame)),
                    this,          SLOT(onBufferAvailable(int, QVideoFrame))
        );
    }

    if (pCamera->state() == QCamera::ActiveState) pCamera->stop();

    pCamera->start();
    pCamera->searchAndLock();

    pImageCapture->capture();

}

[vladest]

Hi

1. its bad prctice to access pointer w/o checking if its valid:

pCamera->start();
pCamera->searchAndLock();

pImageCapture->capture();

2. How do you executing run() ?

[s.maks]

I'm just execute start() method of QThread class. For example:

  CCameraCallback lvCameraCallback();
  lvCameraCallback.start();