关于 web cam 使用自家的摄像头实现 视频捕捉技术 高级篇

网络上一大堆的视频捕捉代码，比如：

代码

public class WebCameraEngine
    {
        //  showVideo  calls
        [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);
        [DllImport("User32.dll")]
        public static extern bool SendMessage(IntPtr hWnd, int wMsg, short wParam, FrameEventHandler lParam);
        [DllImport("User32.dll")]
        public static extern bool SendMessage(IntPtr hWnd, int wMsg, int wParam, ref BitMapInfo lParam);
        [DllImport("User32.dll")]
        public static extern int SetWindowPos(IntPtr hWnd, int hWndInsertAfter, int x, int y, int cx, int cy, int wFlags);
        [DllImport("avicap32.dll")]
        public static extern int capGetVideoFormat(IntPtr hWnd, IntPtr psVideoFormat, int wSize);

        //  constants
        public const int WM_USER = 0x400;

        public const int WS_CHILD = 0x40000000;
        public const int WS_VISIBLE = 0x10000000;

        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_START = WM_USER;
        public const int WM_CAP_STOP = WM_CAP_START + 68;

        public const int WM_CAP_SAVEDIB = WM_CAP_START + 25;
        public const int WM_CAP_GRAB_FRAME = WM_CAP_START + 60;
        public const int WM_CAP_FILE_SET_CAPTURE_FILEA = WM_CAP_START + 20;
        public const int WM_CAP_SEQUENCE = WM_CAP_START + 62;
        public const int WM_CAP_SEQUENCE_NOFILE = WM_CAP_START + 63;


        public const int WM_CAP_SET_OVERLAY = WM_CAP_START + 51;
        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_CALLBACK_VIDEOSTREAM = WM_CAP_START + 6;
        public const int WM_CAP_SET_CALLBACK_ERROR = WM_CAP_START + 2;
        public const int WM_CAP_SET_CALLBACK_STATUSA = WM_CAP_START + 3;
        public const int WM_CAP_SET_SCALE = WM_CAP_START + 53;
        public const int WM_CAP_SET_VIDEOFORMAT = WM_USER + 45;

        public const int SWP_NOMOVE = 0x2;
        public const int SWP_NOZORDER = 0x4;





        //  Structures
        [StructLayout(LayoutKind.Sequential)]
        public struct VideoHdr
        {
            [MarshalAs(UnmanagedType.I4)]
            public int lpData;
            [MarshalAs(UnmanagedType.I4)]
            public int dwBufferLength;
            [MarshalAs(UnmanagedType.I4)]
            public int dwBytesUsed;
            [MarshalAs(UnmanagedType.I4)]
            public int dwTimeCaptured;
            [MarshalAs(UnmanagedType.I4)]
            public int dwUser;
            [MarshalAs(UnmanagedType.I4)]
            public int dwFlags;
            [MarshalAs(UnmanagedType.ByValArray, SizeConst = 4)]
            public int[] dwReserved;
        }

        [StructLayout(LayoutKind.Sequential)]
        public struct BitMapInfoHeader
        {
            [MarshalAs(UnmanagedType.I4)]
            public Int32 biSize;
            [MarshalAs(UnmanagedType.I4)]
            public Int32 biWidth;
            [MarshalAs(UnmanagedType.I4)]
            public Int32 biHeight;
            [MarshalAs(UnmanagedType.I2)]
            public short biPlanes;
            [MarshalAs(UnmanagedType.I2)]
            public short biBitCount;
            [MarshalAs(UnmanagedType.I4)]
            public Int32 biCompression;
            [MarshalAs(UnmanagedType.I4)]
            public Int32 biSizeImage;
            [MarshalAs(UnmanagedType.I4)]
            public Int32 biXPelsPerMeter;
            [MarshalAs(UnmanagedType.I4)]
            public Int32 biYPelsPerMeter;
            [MarshalAs(UnmanagedType.I4)]
            public Int32 biClrUsed;
            [MarshalAs(UnmanagedType.I4)]
            public Int32 biClrImportant;
        }

        [StructLayout(LayoutKind.Sequential)]
        public struct BitMapInfo
        {
            [MarshalAs(UnmanagedType.Struct, SizeConst = 40)]
            public BitMapInfoHeader bmiHeader;
            [MarshalAs(UnmanagedType.ByValArray, SizeConst = 1024)]
            public Int32[] bmiColors;
        }

        public delegate void FrameEventHandler(IntPtr lwnd, IntPtr lpVHdr);

        //  Public  methods
        public static object GetStructure(IntPtr ptr, ValueType structure)
        {
            return Marshal.PtrToStructure(ptr, structure.GetType());
        }

        public static object GetStructure(int ptr, ValueType structure)
        {
            return GetStructure(new IntPtr(ptr), structure);
        }

        public static void Copy(IntPtr ptr, byte[] data)
        {
            Marshal.Copy(ptr, data, 0, data.Length);
        }

        public static void Copy(int ptr, byte[] data)
        {
            Copy(new IntPtr(ptr), data);
        }

        public static int SizeOf(object structure)
        {
            return Marshal.SizeOf(structure);
        }
    }

 

但是使用的例子却没有，特别关于视频流的问题。因此我特地查看了msdn。现在把研究过程写下来：

http://msdn.microsoft.com/en-us/library/ms713477(VS.85).aspx

 

在c#里面的例子，实际上使用了AVICap这个c++的类库。 他的功能包括：

1. 捕捉视频音频到avi文件

2. 动态链接、断开捕捉设备

3. 查看实时的视频信号

4. 设置捕捉率

5. 显示设置对话框、palettes

6. 拷贝图像到剪贴板

7. 对单个图像进行截图+保存为DIB

8.  Specify a file to use when capturing and copy the contents of the capture file to another file.（这个没太理解）

 

 

现在对avicap所有方法进行说明：

1.  建立一个捕捉窗口：

代码

hWndC = capCreateCaptureWindow (
    (LPSTR) "My Capture Window", // window name if pop-up 
    WS_CHILD | WS_VISIBLE,       // window style 
    0, 0, 160, 120,              // window position and dimensions
    (HWND) hwndParent, 
    (int) nID /* child ID *

 

2. 链接捕捉设备

代码

fOK = SendMessage (hWndC, WM_CAP_DRIVER_CONNECT, 0, 0L); 
// 
// Or, use the macro to connect to the MSVIDEO driver: 
// fOK = capDriverConnect(hWndC, 0); 
// 
// Place code to set up and capture video here. 
// 
capDriverDisconnect (hWndC); 

 

 

3. 枚举可以使用的捕捉设备：

char szDeviceName[80];
char szDeviceVersion[80];

for (wIndex = 0; wIndex < 10; wIndex++) 
{
    if (capGetDriverDescription(
            wIndex, 
            szDeviceName, 
            sizeof (szDeviceName), 
            szDeviceVersion, 
            sizeof (szDeviceVersion)
        )) 
    {
        // Append name to list of installed capture drivers
        // and then let the user select a driver to use.
    }
} 

 

4. 获取捕捉设备的能力

CAPDRIVERCAPS CapDrvCaps; 

SendMessage (hWndC, WM_CAP_DRIVER_GET_CAPS, 
    sizeof (CAPDRIVERCAPS), (LONG) (LPVOID) &CapDrvCaps); 

// Or, use the macro to retrieve the driver capabilities. 
// capDriverGetCaps(hWndC, &CapDrvCaps, sizeof (CAPDRIVERCAPS));