The capSetCallbackOnCapControl macro sets a callback function in the application giving it precise recording control. You can use this macro or explicitly call the WM_CAP_SET_CALLBACK_CAPCONTROL message.
void capSetCallbackOnCapControl( hwnd, fpProc );
Handle to a capture window.
Pointer to the callback function, of type capControlCallback . Specify NULL for this parameter to disable a previously installed callback function.
A single callback function is used to give the application precise control over the moments that streaming capture begins and completes. The capture window first calls the procedure with nState set to CONTROLCALLBACK_PREROLL after all buffers have been allocated and all other capture preparations have finished. This gives the application the ability to preroll video sources, returning from the callback function at the exact moment recording is to begin. A return value of TRUE from the callback function continues capture, and a return value of FALSE aborts capture. After capture begins, this callback function will be called frequently with nState set to CONTROLCALLBACK_CAPTURING to allow the application to end capture by returning FALSE.
|Minimum supported client||Windows 2000 Professional [desktop apps only]|
|Minimum supported server||Windows 2000 Server [desktop apps only]|