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.



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



case WM_CLOSE:


// Use the capSetCallbackOnFrame macro to

// disable the frame callback. Similar calls exist for the other

// callback functions.

capSetCallbackOnFrame(hWndC, NULL);



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