Video Grabber Library

Compilation Environment

1. You have to include vdograb.h in your code, and call CoInitialize(NULL) to initialize the COM use before calling any routine of the library. Of course, you have better to call CoUninitialize( ) when your application is about to terminated.
    
2. You have to link strmiids.lib and one of vdograb.lib (for release version) or vdograbd.lib (for debugging version). You don't have to install DirectX SDK for for library because strmiids.lib is already the necessary library extract from DirectX 9.0c SDK.

Programming Interface

1. After the web camera is properly linked to the computer, the application calls GrabberOpen() to connect the camera device. If the connection is successful, it returns TRUE.
   
   The argument pFriendlyName is the name of the camera shown in the hardware manager of the control panel. It specifies the camera device to be connected when there are multiple cameras linked to the computer. pFriendlyName can be NULL, and GrabberOpen() uses the first found camera device automatically.
   
   The prototype of the routine is:
   
       BOOL GrabberOpen(wchar_t *pFriendlyName, GRABBERCALLBACK pCallback);
   
   And the prototype of the callback function pCallback isdefined:
   
       typedef void (*GRABBERCALLBACK)(void *pBits, int width, int height, int size);
   
   This is a function provided by the application developer to receive the captured images. The format of the images is uncompressed 24-bit bottom-up DIB. Here is an example:
   
       void MyCallback(void *pBits, int width, int height, int size);
       {
           /* width and height are the dimensions of the image, and size is the data
              length of pBits. The application renders pBits or copies pBits inside
              the routine... */
       }
   
       /* Connect the first web camera by the statement in main procedure of the
          application. And ask the library to transport the captured images to
          MyCallback. */
       GrabberOpen(NULL, MyCallback);
   
   Remadk: The callback function and the main procedure of application are running in different  threads.
    
2. After a successful GrabberOpen() call, the camera device is connected but the video capturing is not started. It is started by calling GrabberStart(), and the callback function pCallback starts receiving the images.
   
   The prototype of the routine is:
   
       BOOL GrabberStart(void);
    
3. To stop the video capturing, simply call GrabberStop(). It can be re-started by another GrabberStart() call.
   
   The prototype of the routine is:
   
       void GrabberStop(void);
    
4. When the application is about to be terminated, or it wants to connect another camera device, call GrabberClose( ) to disconnect the camera device connected by previous GrabberOpen( ) call.
   
   The prototype of the routine is:
   
       void GrabberClose(void);

Last updated at 2006 / 11 / 27 by Shu-Kai Yang.