delphi 用AVICap实现视频捕获 有个有关问题 请大家帮忙看看

delphi 用AVICap实现视频捕获 有个问题 请大家帮忙看看？
delphi 用AVICap实现视频捕获 有个问题 请大家帮忙看看？ 捕获不到图像 是黑色的 

下面是代码

unit Unit1;

interface

uses
  Windows, Messages, SysUtils, Variants, Classes, Graphics, Controls, Forms,
  Dialogs, StdCtrls, ExtCtrls;

type
  TForm1 = class(TForm)
    Panel1: TPanel;
    btn1: TButton;
    procedure btn1Click(Sender: TObject);
  private
  hWndC : THandle;  
    { Private declarations }
  public
    { Public declarations }
  end;

var
  Form1: TForm1;

implementation

{$R *.dfm}
const WM_CAP_START = WM_USER;
const WM_CAP_STOP = WM_CAP_START + 68;
const WM_CAP_DRIVER_CONNECT = WM_CAP_START + 10;
const WM_CAP_DRIVER_DISCONNECT = WM_CAP_START + 11;
const WM_CAP_SAVEDIB = WM_CAP_START + 25;
const WM_CAP_GRAB_FRAME = WM_CAP_START + 60;
const WM_CAP_SEQUENCE = WM_CAP_START + 62;
const WM_CAP_FILE_SET_CAPTURE_FILEA = WM_CAP_START + 20;
const WM_CAP_SEQUENCE_NOFILE =WM_CAP_START+ 63;
const WM_CAP_SET_OVERLAY =WM_CAP_START+ 51;
const WM_CAP_SET_PREVIEW =WM_CAP_START+ 50;
const WM_CAP_SET_CALLBACK_VIDEOSTREAM = WM_CAP_START +6;
const WM_CAP_SET_CALLBACK_ERROR=WM_CAP_START +2;
const WM_CAP_SET_CALLBACK_STATUSA= WM_CAP_START +3;
const WM_CAP_SET_CALLBACK_FRAME= WM_CAP_START +5;
const WM_CAP_SET_SCALE=WM_CAP_START+ 53;
const WM_CAP_SET_PREVIEWRATE=WM_CAP_START+ 52;

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.btn1Click(Sender: TObject);
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 
begin
SendMessage(hWndC, WM_CAP_SET_CALLBACK_VIDEOSTREAM, 0, 0);
SendMessage(hWndC, WM_CAP_SET_CALLBACK_ERROR, 0, 0);
SendMessage(hWndC, WM_CAP_SET_CALLBACK_STATUSA, 0, 0);
SendMessage(hWndC, WM_CAP_DRIVER_CONNECT, 0, 0);
SendMessage(hWndC, WM_CAP_SET_SCALE, 1, 0);
SendMessage(hWndC, WM_CAP_SET_PREVIEWRATE, 66, 0);
SendMessage(hWndC, WM_CAP_SET_OVERLAY, 1, 0);
SendMessage(hWndC, WM_CAP_SET_PREVIEW, 1, 0);

end.

------最佳解决方案--------------------
代码没有问题。

换个摄像头吧，软件兼容问题！
------其他解决方案--------------------
我用DSPack这套组件没黑屏
用别的组件也黑屏了。。

procedure Tform1.startcap;

begin

 SysDev:= TSysDevEnum.Create(CLSID_VideoInputDeviceCategory);

 if SysDev.CountFilters > 0 then

  begin

    Filter.BaseFilter.Moniker := SysDev.GetMoniker(0);