C# 打开视频问题
我写的打开视频不知道为什么，只能打开一次，再打开就是黑的。什么都没有，必须重启，然后第一次打开，才可以。帮忙看看我这代码
 [DllImport("avicap32.dll")]
  public static extern IntPtr capCreateCaptureWindowA(byte[] lpszWindowName, int dwStyle, int x, int y, int nWidth, int nHeight, IntPtr hWndParent, int nID);
  [DllImport("avicap32.dll")]
  public static extern bool capGetDriverDescriptionA(short wDriver, byte[] lpszName, int cbName, byte[] lpszVer, int cbVer);
  [DllImport("User32.dll")]
  public static extern bool SendMessage(IntPtr hWnd, int wMsg, bool wParam, int lParam);
  [DllImport("User32.dll")]
  public static extern bool SendMessage(IntPtr hWnd, int wMsg, short wParam, int lParam);

  // 常量
  public const int WM_USER = 0x400;
  public const int WS_CHILD = 0x40000000;
  public const int WS_VISIBLE = 0x10000000;
  public const int SWP_NOMOVE = 0x2;
  public const int SWP_NOZORDER = 0x4;
  public const int WM_CAP_DRIVER_CONNECT = WM_USER + 10;
  public const int WM_CAP_DRIVER_DISCONNECT = WM_USER + 11;
  public const int WM_CAP_SET_CALLBACK_FRAME = WM_USER + 5;
  public const int WM_CAP_SET_PREVIEW = WM_USER + 50;
  public const int WM_CAP_SET_PREVIEWRATE = WM_USER + 52;
  public const int WM_CAP_SET_VIDEOFORMAT = WM_USER + 45;
  public const int WM_CAP_START = WM_USER;
  public const int WM_CAP_SAVEDIB = WM_CAP_START + 25;
//打开视频设备
  byte[] lpszName = new byte[100];
  byte[] lpszVer = new byte[100];

  capGetDriverDescriptionA(0, lpszName, 100, lpszVer, 100);
  this.lwndC = capCreateCaptureWindowA(lpszName, VideoAPI.WS_CHILD | VideoAPI.WS_VISIBLE, 0, 0, mWidth, mHeight, mControlPtr, 0);

  if (SendMessage(lwndC, VideoAPI.WM_CAP_DRIVER_CONNECT, 0, 0))
  {
  SendMessage(lwndC, VideoAPI.WM_CAP_SET_PREVIEWRATE, 100, 0);
  SendMessage(lwndC, VideoAPI.WM_CAP_SET_PREVIEW, true, 0);
  }

------解决方案--------------------
模拟头和数字头写法不一样的，我不知道你用的是什么

int intOne = axNetDvrOne.Login(strNetIPOne, intPrtOne, strNetUsOne, strNetPsOne);
就这一句，是登录硬盘录像机然后打开摄像头的。这是模拟摄像头。数字摄像头的写法不是这样的。

lpServerIP：硬盘录像机的IP地址
lPort：硬盘录像机端口号
lpUserName：登陆的用户名
lpPassword：登陆的密码
返回值：lUserID提供给其他接口使用。-1表示注册失败。