Adding Callback Functions to an Application
An application can register callback functions with the capture window so that
it notifies the application in the following circumstances:
- The status changes
- Errors occur
- Video frame and audio buffers become available
- The application should yield during streaming capture
The following example creates a capture window and registers status, error,
video stream, and frame callback functions in the message-processing loop of an
application. It also includes a sample statement for disabling a callback
function. Subsequent examples show simple status, error, and frame callback functions.
case WM_CREATE:
{
char achDeviceName[80] ;
char achDeviceVersion[100] ;
char achBuffer[100] ;
WORD wDriverCount = 0 ;
WORD wIndex ;
WORD wError ;
HMENU hMenu ;
// Create a capture window using the
capCreateCaptureWindow macro.
ghWndCap = capCreateCaptureWindow((LPSTR)"Capture Window",
WS_CHILD | WS_VISIBLE, 0, 0, 160, 120, (HWND) hWnd, (int) 0);
// Register the error callback function using the
//
capSetCallbackOnError macro.
capSetCallbackOnError(ghWndCap, fpErrorCallback);
// Register the status callback function using the
//
capSetCallbackOnStatus macro.
capSetCallbackOnStatus(ghWndCap, fpStatusCallback);
// Register the video-stream callback function using the
//
capSetCallbackOnVideoStream macro.
capSetCallbackOnVideoStream(ghWndCap, fpVideoCallback);
// Register the frame callback function using the
//
capSetCallbackOnFrame macro.
capSetCallbackOnFrame(ghWndCap, fpFrameCallback);
// Connect to a capture driver
break;
}
case WM_CLOSE:
{
// Use the
capSetCallbackOnFrame macro to
// disable the frame callback. Similar calls exist for the other
// callback functions.
capSetCallbackOnFrame(hWndC, NULL);
break;
}
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