Opening and Handling Devices: Save And Restore a Video Cacpture Device Properties

The sample application's window looks as follows:

First of all, an MFC - Dialog based application is created. Additionally, there are four buttons for opening the video capture device, show the IC Imaging Control's built-in property dialog and save and load the device from an .xml file.

An instance of the Grabber class must be created as member of the dialog class.

DShowLib::Grabber        m_cGrabber; // The instance of the Grabber class.

In the "Device" button event handler a video capture device is to be selected. First of all, it must be checked, whether the current Grabber object contains already a running video capture device, before IC Imaging Control's built-in "Device Selection" dialog can be called. The "Device Settings" dialog is shown with a call to Grabber::showDevicePage(). After the "Device Settings" dialog has been left, it is checked whehter a valid video capture device has been selected. If the video capture device in the Grabber object is valid, then the image data stream is started with a call to Grabber::startLive().

void CSaveRestorePropertiesDlg::OnBnClickedDevice()
{
    if(m_cGrabber.isDevValid() && m_cGrabber.isLive())
    {
        m_cGrabber.stopLive();
    }

    m_cGrabber.showDevicePage(this->m_hWnd);

    if(m_cGrabber.isDevValid())
    {
        m_cGrabber.startLive();
    }
}

The "Properties" button event handler shows the build-in dialog for device proiperties with a call to Grabber::showVCDPropertyPage():

void CSaveRestorePropertiesDlg::OnBnClickedProperties()
{
    if( m_cGrabber.isDevValid())
    {
        m_cGrabber.showVCDPropertyPage(this->m_hWnd);
    }
}

The method Grabber::saveDeviceStateToFile() saves the current settings and properties of a video capture deivce to an XML file:

void CSaveRestorePropertiesDlg::OnBnClickedSave()
{
    if( m_cGrabber.isDevValid())
    {
        m_cGrabber.saveDeviceStateToFile("device.xml");
    }
}

The method Grabber::loadDeviceStateFromFile restores a previously saved video capture device and its properties from an XML file. As for the device selection dialog, it is necessary to stop a probably running live video before a new video capture device can be opened. If a valid video capture device was loaded, the image data stream will be started using Grabber.startLive():

void CSaveRestorePropertiesDlg::OnBnClickedRestore()
{
    if(m_cGrabber.isDevValid() && m_cGrabber.isLive())
    {
        m_cGrabber.stopLive();
    }

    if( m_cGrabber.loadDeviceStateFromFile( "device.xml"))
    {
        if( m_cGrabber.isDevValid())
            m_cGrabber.startLive();
    }
}