Acquire Video Format Information

This example demonstrates how to acquire information about the available video formats.

The program can be found in the %TOPLEVEL%\Samples\VC71\VideoNormFormat directory. A VC6 version can be found in the directory %TOPLEVEL%\Samples\VC6. In order to run the program, open the solution file VidNormFormat.sln in this directory and select Build -> Build VideoNormFormat in the menu. Then the program can be executed by selecting Debug -> Start.

Opening a Device

The program will generate a list of all available video capture devices and prompt the user for the device to open.

Grabber::tVidCapDevListPtr pVidCapDevList = grabber.getAvailableVideoCaptureDevices();
if( pVidCapDevList == 0 || pVidCapDevList->empty() )
{
    return -1; // No device available.
}
 
int choice = presentUserChoice( toStringArrayPtr( pVidCapDevList ) );
// Open the selected video capture device.
if( choice == -1 )
{
    return -1;
}
grabber.openDev( pVidCapDevList->at( choice ) );

First, Grabber::getAvailableVideoCaptureDevices is called to retrieve a list with the video capture devices connected to the computer. The helper function presentUserChoice from %TOPLEVEL%\Samples\VC71\Common\CmdHelper.h is called to output the available devices to the console and let the user input a number.

The selected video capture device is opened by calling Grabber::openDev.

Selecting a Video Norm

If the selected device supports multiple video norms, all available video norms will be printed to the screen and the user will be asked for a norm. If the user selects a norm, all video formats available for the selected norm are printed on the screen and the user is again prompted for a video norm until he terminates the program by pressing "q".

// Check whether video norms are available with the current video capture device.
if( grabber.isVideoNormAvailableWithCurDev() )
{
    // Query for all available video norms.
    Grabber::tVidNrmListPtr pVidNrmList = grabber.getAvailableVideoNorms();
 
    if( pVidNrmList == 0 )
    {
        std::cerr << "Error: " << grabber.getLastError().toString() << std::endl;
        return -1;
    }
    while ( true )
    {
        std::cout << "Video Norms available for " << grabber.getDev().toString() << std::endl;
 
        int choice = presentUserChoice( *pVidNrmList );
        if( choice != -1 )
        {
            // Set the selected video norm before
            // retrieving the according video formats.
            grabber.setVideoNorm( pVidNrmList->at( choice ) );

Grabber::isVideoNormAvailableWithCurDev is called to check whether the opened video capture device supports video norms. In this case, a list with the available video norms is retrieved by calling Grabber::getAvailableVideoNorms.

After the user selected one of the video norms in presentUserChoice, Grabber::setVideoNorm is used to set the selected norm.

Displaying the Available Video Formats

When a video norm was selected, or video norms are not supported, the available video formats are printed to the screen:

Grabber::tVidFmtListPtr pVidFmtList = grabber.getAvailableVideoFormats();
 
if( pVidFmtList == 0 ) // No video formats available?
{
    std::cerr << "Error : " << grabber.getLastError().toString() << std::endl;
}
else
{
    unsigned int counter = 0;
    // List the available video formats.
    for( Grabber::tVidFmtList::iterator it = pVidFmtList->begin(); 
        it != pVidFmtList->end(); 
        ++it )
    {
        std::cout << "\t[" << counter++ << "] " << it->toString() << std::endl;
    }
}

Grabber::getAvailableVideoFormats returns a list containing the available video formats. In a loop, the names of the formats are displayed. You can get the name of a video format by calling VideoFormatItem::toString.

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