摄像头视频采集----基于AviCap

         相对DirectShow，AviCap算是视频采集框架里面的老前辈了，虽然已经有点力不从心，但对一些要求不高的场合还是很实用的，网上一番搜索之后（借鉴了很多现成的轮子），实现了一个基于AviCap的摄像头采集程序（C sharp实现）：

先实现一个CapVideo的类，主要是引入avicap提供的接口，结构体及一些方法的定义

其中主要用到了Avicap32.dll中提供的以下三个函数：

capCreateCaptureWindowA：创建一个视频显示窗口

capGetDriverDescriptionA：获取视频设备描述符

capGetVideoFormat：获取视频格式

   public class CapVideo
    {
        #region DLL Import Method
        [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("avicap32.dll")]
        public static extern int capGetVideoFormat(IntPtr hWnd, IntPtr psVideoFormat, int wSize);
        [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);
        #endregion 

        #region public const Fields
        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_GRAB_FRAME_NOSTOP = WM_USER + 61;
        public const int WM_CAP_GRAB_FRAME = WM_USER + 60;
        public const int WM_CAP_FILE_SAVEDIBA = WM_USER + 25;
        #endregion

        #region 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;
        }
        #endregion

        #region Public Method
        public delegate void FrameEventHandler(IntPtr lwnd, IntPtr lpVHdr);

        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);
        }
        #endregion
    }

接着实现一个Camera类，主要实现摄像头采集开始，停止，截图等功能。

    public class Camera
    {
        
        public Camera(IntPtr handle, int width, int height)
        {
            mControlPtr = handle;
            mWidth = width;
            mHeight = height;
        }

        //定义委托
        public delegate void RecievedFrameEventHandler(byte[] data);
        public event RecievedFrameEventHandler RecievedFrame;

        private IntPtr lwndC; 
        private IntPtr mControlPtr; 
        private int mWidth;
        private int mHeight;

        private CapVideo.FrameEventHandler mFrameEventHandler;

        #region Camera Operation

        //开始采集
        public bool StartCamera()
        {
            byte[] lpszName = new byte[100];
            byte[] lpszVer = new byte[100];
            
            //获取设备信息
            CapVideo.capGetDriverDescriptionA(0, lpszName, 100, lpszVer, 100);
            //创建捕获窗口
            this.lwndC = CapVideo.capCreateCaptureWindowA(lpszName, CapVideo.WS_VISIBLE + CapVideo.WS_CHILD, 0, 0, mWidth, mHeight, mControlPtr, 0);

            //连接设备
            if (this.capDriverConnect(this.lwndC, 0))
            {
                //设置为预览模式，初始帧率为60
                this.capPreview(this.lwndC, true);
                this.capPreviewRate(this.lwndC, 60);
              
                //BitMap及其头信息
                CapVideo.BITMAPINFO bitmapinfo = new CapVideo.BITMAPINFO();
                bitmapinfo.bmiHeader.biSize = CapVideo.SizeOf(bitmapinfo.bmiHeader);
                bitmapinfo.bmiHeader.biWidth = 400;
                bitmapinfo.bmiHeader.biHeight = 200;
                bitmapinfo.bmiHeader.biPlanes = 1;
                bitmapinfo.bmiHeader.biBitCount = 24;

                //设置视频参数
                this.capSetVideoFormat(this.lwndC, ref bitmapinfo, CapVideo.SizeOf(bitmapinfo));

                //注册回调
                this.mFrameEventHandler = new CapVideo.FrameEventHandler(FrameCallBack);
                this.capSetCallbackOnFrame(this.lwndC, this.mFrameEventHandler);

                //设置窗口
                CapVideo.SetWindowPos(this.lwndC, 0, 0, 0, mWidth, mHeight, 6);
                return true;
            }
            else
            {
                return false;
            }
        }
       

        //停止采集
        public void CloseCamera()
        {
            this.capDriverDisconnect(this.lwndC);
        }

        //快照
        public bool SnapShot(string str)
        {
            bool blRes = CapVideo.SendMessage(this.lwndC, CapVideo.WM_CAP_GRAB_FRAME_NOSTOP, 0, 0);
            if ( !blRes )
            {
                return blRes;
            }
            IntPtr ptr = Marshal.StringToHGlobalAnsi(str);
            return CapVideo.SendMessage(this.lwndC,CapVideo.WM_CAP_FILE_SAVEDIBA,0,ptr.ToInt32());
            Marshal.FreeHGlobal(ptr);

        }

        //收到帧数据时会执行此回调函数
        private void FrameCallBack(IntPtr lwnd, IntPtr lpVHdr)
        {
            CapVideo.VIDEOHDR videoHeader = new CapVideo.VIDEOHDR();
            byte[] VideoData;
            //获取帧头信息图像数据地址
            videoHeader = (CapVideo.VIDEOHDR)CapVideo.GetStructure(lpVHdr, videoHeader);
            VideoData = new byte[videoHeader.dwBytesUsed];
            //复制图像数据
            CapVideo.Copy(videoHeader.lpData, VideoData);
            if (this.RecievedFrame != null)
                this.RecievedFrame(VideoData);
        }

        //连接设备
        private bool capDriverConnect(IntPtr lwnd, short i)
        {
            return CapVideo.SendMessage(lwnd, CapVideo.WM_CAP_DRIVER_CONNECT, i, 0);
        }

        //断开连接
        private bool capDriverDisconnect(IntPtr lwnd)
        {
            return CapVideo.SendMessage(lwnd, CapVideo.WM_CAP_DRIVER_DISCONNECT, 0, 0);
        }

        //设置为预览模式
        private bool capPreview(IntPtr lwnd, bool f)
        {
            return CapVideo.SendMessage(lwnd, CapVideo.WM_CAP_SET_PREVIEW, f, 0);
        }

        //设置预览帧率
        private bool capPreviewRate(IntPtr lwnd, short wMS)
        {
            return CapVideo.SendMessage(lwnd, CapVideo.WM_CAP_SET_PREVIEWRATE, wMS, 0);
        }

        //设置回调函数
        private bool capSetCallbackOnFrame(IntPtr lwnd, CapVideo.FrameEventHandler lpProc)
        {
            return CapVideo.SendMessage(lwnd, CapVideo.WM_CAP_SET_CALLBACK_FRAME, 0, lpProc);
        }

        //设置视频格式
        private bool capSetVideoFormat(IntPtr hCapWnd, ref CapVideo.BITMAPINFO BmpFormat, int CapFormatSize)
        {
            return CapVideo.SendMessage(hCapWnd, CapVideo.WM_CAP_SET_VIDEOFORMAT, CapFormatSize, ref BmpFormat);
        }
        #endregion

    }

接下来就是演示例子，编写一个简单的WPF程序，利用以上代码实现摄像头采集，运行结果如下，画质不是很清楚，比起摄像头自带的软件，完全下降了两个档次，具体原因有待调查，不过利用AviCap来实现还是很节省资源的，采集时看了下CPU使用率，不超过5%。整个工程已上传至我的资源里，需要参考的朋友可以点击这里下载，另外后续想将摄像头分辨率调节的功能添加进去。