capSetCallbackOnCapControl macro (vfw.h)

Article
02/22/2024

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.

Syntax

void capSetCallbackOnCapControl(
   hwnd,
   fpProc
);

Parameters

hwnd

Handle to a capture window.

fpProc

Pointer to the callback function, of type capControlCallback . Specify NULL for this parameter to disable a previously installed callback function.

Return value

None

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.

Requirements

Requirement	Value
Minimum supported client	Windows 2000 Professional [desktop apps only]
Minimum supported server	Windows 2000 Server [desktop apps only]
Target Platform	Windows
Header	vfw.h