const
 WM_CAP_START = WM_USER;
 WM_CAP_DRIVER_CONNECT = WM_CAP_START + 10;
 WM_CAP_GRAB_FRAME = WM_CAP_START + 60;

function capCreateCaptureWindowA(lpszWindowName: PCHAR;
 dwStyle: longint;
 x: integer;
 y: integer;
 nWidth: integer;
 nHeight: integer;
 ParentWin: HWND;
 nId: integer): HWND;
 stdcall external 'AVICAP32.DLL';

procedure TForm1.OpenVideoClick(Sender: TObject);
begin
 hWndC := capCreateCaptureWindowA('My Own Capture Window',
   WS_CHILD or WS_VISIBLE,
   Panel1.Left,
   Panel1.Top,
   Panel1.Width,
   Panel1.Height,
   Form1.Handle,
   0);
 if hWndC <> 0 then
   SendMessage(hWndC, WM_CAP_DRIVER_CONNECT, 0, 0);
end;

procedure TForm1.GrabFrameClick(Sender: TObject);
begin
 if hWndC <> 0 then
   SendMessage(hWndC, WM_CAP_GRAB_FRAME, 0, 0);
end;