WM_CAP_SET_CALLBACK_CAPCONTROL
The
WM_CAP_SET_CALLBACK_CAPCONTROL message sets a callback function in the
application giving it precise recording control. You can send this message
explicitly or by using the capSetCallbackOnCapControl macro.
WM_CAP_SET_CALLBACK_CAPCONTROL
wParam = (WPARAM) 0;
lParam = (LPARAM) (LPVOID) (fpProc);
Parameters
fpProc
Address of
the callback function. Specify NULL for this parameter to disable a previously
installed callback function.
Return Values
Returns TRUE
if successful or FALSE if a streaming capture or a single-frame capture session
is in progress.
Remarks
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.
See Also