wm-cap-set-callback-frame.md

title	description	ms.assetid	keywords	topic_type	api_name	api_location	api_type	ms.topic	ms.date
WM_CAP_SET_CALLBACK_FRAME message (Vfw.h)	The WM\_CAP\_SET\_CALLBACK\_FRAME message sets a preview callback function in the application. AVICap calls this procedure when the capture window captures preview frames. You can send this message explicitly or by using the capSetCallbackOnFrame macro.	3882e6f6-c48c-4e50-9697-cbdf5b9342a5	WM_CAP_SET_CALLBACK_FRAME message Windows Multimedia	apiref	WM_CAP_SET_CALLBACK_FRAME	Vfw.h	HeaderDef	reference	05/31/2018

WM_CAP_SET_CALLBACK_FRAME message

The WM_CAP_SET_CALLBACK_FRAME message sets a preview callback function in the application. AVICap calls this procedure when the capture window captures preview frames. You can send this message explicitly or by using the capSetCallbackOnFrame macro.

WM_CAP_SET_CALLBACK_FRAME 
wParam = (WPARAM) 0; 
lParam = (LPARAM) (LPVOID) (fpProc); 

Parameters

fpProc

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

Return Value

Returns TRUE if successful or FALSE if streaming capture or a single-frame capture session is in progress.

Remarks

The capture window calls the callback function before displaying preview frames. This allows an application to modify the frame if desired. This callback function is not used during streaming video capture.

Requirements

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

See also

Video Capture

Video Capture Messages