用C＃预览视频文件（简略）

我的IR项目里要对视频文件进行预览，目前还没有解决，以下的方法是一个尝试。

在system32下，有一个qedit.dll文件，这是DirectShow的一个COM组件（DS大部份都是COM组件），就是说我们可以直接以COM的形式引用到C＃项目里。

我做了一个简单测试项目。先把qedit.dll找到，然后以COM注册到项目中。对MediaDet类进行了一个简单的封装，然后运行一个测试项目：
运行结果（从AVI中提取第10桢的内容）：


部份代码：仅供参考：

MediaDetector类
using System;
using System.IO;
using DexterLib;
using System.Drawing;
using System.Drawing.Imaging;

namespace PublicLibrary
{
    /**//// <summary>
    /// Summary description for MediaDetector.
    /// </summary>
    public class MediaDetector
    {
        //fields
        protected MediaDetClass _MediaDet;
        protected Image.GetThumbnailImageAbort _ImageCallback;
        //events
        public event ErrorHandler OnError;
        //properties
        protected MediaDetClass MediaDecteor
        {
            get
            {
                if(this._MediaDet==null)
                {
                    try
                    {
                        this._MediaDet = new MediaDetClass();
                    }
                    catch(Exception ex)
                    {
                        this.FileErrorEvent(ex);
                    }
                }
                return _MediaDet;
            }
        }
        protected Image.GetThumbnailImageAbort ImageCallback
        {
            get
            {
                if(this._ImageCallback == null)
                {
                    this._ImageCallback = new Image.GetThumbnailImageAbort(ThumbnailCallback);
                }
                return this._ImageCallback;
            }
        }

        //methods
        private void FileErrorEvent(Exception i_ex)
        {
            if(this.OnError!=null)
            {
                try
                {
                    this.OnError(this,i_ex);
                }
                catch(Exception ex)
                {
                    System.Diagnostics.Trace.WriteLine(ex.Message);
                }
            }
        }
        /**//// <summary>
        /// Method to get thumbinal image from media file.
        /// </summary>
        /// <param name="i_MediaFile">Media file full path and name.</param>
        /// <param name="i_Size">Image size.</param>
        /// <param name="i_type">Media type</param>
        /// <param name="i_Stream">If the media type is video, this parameter is the video's stream to grab and create image.</param>
        /// <returns></returns>
        public Image GetThumbnail(string i_MediaFile,Size i_Size,MediaTypes i_type,int i_Stream)
        {
            switch(i_type)
            {
                default:
                case MediaTypes.Unknow:
                    this.FileErrorEvent(new Exception("Unknow media type."));
                    return null;
                case MediaTypes.Audio:
                    this.FileErrorEvent(new Exception("This media type has not implemented to create an image."));
                    return null;
                case MediaTypes.Image:
                    return this.GetThumbnailFromImage(i_MediaFile,i_Size);
                case MediaTypes.Video:
                    return this.GetThumbnailFromVideo(i_MediaFile,i_Size,i_Stream);
            }
        }

        public Image GetThumbnailFromImage(string i_MediaFile,Size i_Size)
        {
            try
            {
                Image m_image = Image.FromFile(i_MediaFile);
                return m_image.GetThumbnailImage(i_Size.Width,i_Size.Height,this.ImageCallback,IntPtr.Zero);
            }
            catch(Exception ex)
            {
                this.FileErrorEvent(ex);
                return null;
            }
        }

        public Image GetThumbnailFromVideo(string i_MediaFile,Size i_Size,int i_Stream)
        {
            this.MediaDecteor.Filename = i_MediaFile;
            this.MediaDecteor.CurrentStream = 0;
            //int m_ImageSize = (int)this.MediaDecteor.StreamLength;
            try
            {
                this.MediaDecteor.WriteBitmapBits(i_Stream,i_Size.Width,i_Size.Height,"Temp.bmp");
                Stream m_stream = File.Open("Temp.bmp",FileMode.Open,FileAccess.Read,FileShare.None);
                byte[] m_bytes = new byte[m_stream.Length];
                m_stream.Read(m_bytes,0,m_bytes.Length);
                m_stream.Close();
                File.Delete("Temp.bmp");
                MemoryStream m_MemoStream = new MemoryStream(m_bytes.Length);
                m_MemoStream.Write(m_bytes,0,m_bytes.Length);
                return Image.FromStream(m_MemoStream);
            }
            catch(Exception ex)
            {
                this.FileErrorEvent(ex);
                return null;
            }
        }

        private bool ThumbnailCallback()
        {
            return false;
        }
        //ctor
        public MediaDetector()
        {            
        }
    }

    public class MediaHelper#region public class MediaHelper
    public class MediaHelper
    {
        static public MediaTypes ConvertToMediaType(int i_Type)
        {
            switch(i_Type)
            {
                default:
                case 0:
                    return MediaTypes.Unknow;
                case 1:
                    return MediaTypes.Image;
                case 2:
                    return MediaTypes.Video;
                case 3:
                    return MediaTypes.Audio;
            }
        }

        static public MediaTypes ConvertToMediaType(string i_Type)
        {
            switch(i_Type.ToLower())
            {
                default:
                case "unknow":
                    return MediaTypes.Unknow;
                case "image":
                    return MediaTypes.Image;
                case "video":
                    return MediaTypes.Video;
                case "audio":
                    return MediaTypes.Audio;
            }
        }
    }
    #endregion

    public delegate void ErrorHandler(object i_Sender,Exception i_ex);
    public enum MediaTypes
    {
        Image = 1,
        Video = 2,
        Audio = 3,
        Unknow = 0,
    }

}

测试Form代码：

Form类
using System;
using System.Drawing;
using System.Collections;
using System.ComponentModel;
using System.Windows.Forms;
//
using PublicLibrary;

namespace Country.Study
{
    /**//// <summary>
    /// Summary description for Thumbinal.
    /// </summary>
    public class Thumbnail : System.Windows.Forms.Form
    {
        private MediaDetector _MediaDetector;
        //
        private MediaDetector MediaDetector
        {
            get
            {                
                return this._MediaDetector;
            }
        }
        //
        private System.Windows.Forms.StatusBar statusBar1;
        private System.Windows.Forms.Panel panel1;
        private System.Windows.Forms.TextBox C_Path;
        private System.Windows.Forms.Button C_Browse;
        private System.Windows.Forms.Panel panel2;
        private System.Windows.Forms.Label C_LabWidth;
        private System.Windows.Forms.TextBox C_Width;
        private System.Windows.Forms.Label C_LabHeight;
        private System.Windows.Forms.TextBox C_Height;
        private System.Windows.Forms.Label C_LabType;
        private System.Windows.Forms.ComboBox C_MediaTypes;
        private System.Windows.Forms.Label C_LabStream;
        private System.Windows.Forms.Button C_Create;
        private System.Windows.Forms.OpenFileDialog C_OpenFileDialog;
        private System.Windows.Forms.TextBox C_Stream;
        private System.Windows.Forms.PictureBox C_PicBox;
        /**//// <summary>
        /// Required designer variable.
        /// </summary>
        private System.ComponentModel.Container components = null;

        public Thumbnail()
        {
            //
            // Required for Windows Form Designer support
            //
            InitializeComponent();

            //
            // TODO: Add any constructor code after InitializeComponent call
            //
            this._MediaDetector = new MediaDetector();
            this._MediaDetector.OnError += new ErrorHandler(MediaDetector_OnError);
        }

        /**//// <summary>
        /// Clean up any resources being used.
        /// </summary>
        protected override void Dispose( bool disposing )
        {
            if(this._MediaDetector!=null)
            {
                this._MediaDetector.OnError -= new ErrorHandler(MediaDetector_OnError);
                this._MediaDetector = null;
            }
            if( disposing )
            {
                if(components != null)
                {
                    components.Dispose();
                }
            }
            base.Dispose( disposing );
        }

        Windows Form Designer generated code#region Windows Form Designer generated code
        /**//// <summary>
        /// Required method for Designer support - do not modify
        /// the contents of this method with the code editor.
        /// </summary>
        private void InitializeComponent()
        {
            this.statusBar1 = new System.Windows.Forms.StatusBar();
            this.panel1 = new System.Windows.Forms.Panel();
            this.C_Browse = new System.Windows.Forms.Button();
            this.C_Path = new System.Windows.Forms.TextBox();
            this.panel2 = new System.Windows.Forms.Panel();
            this.C_Create = new System.Windows.Forms.Button();
            this.C_Stream = new System.Windows.Forms.TextBox();
            this.C_LabStream = new System.Windows.Forms.Label();
            this.C_MediaTypes = new System.Windows.Forms.ComboBox();
            this.C_LabType = new System.Windows.Forms.Label();
            this.C_Height = new System.Windows.Forms.TextBox();
            this.C_LabHeight = new System.Windows.Forms.Label();
            this.C_LabWidth = new System.Windows.Forms.Label();
            this.C_Width = new System.Windows.Forms.TextBox();
            this.C_PicBox = new System.Windows.Forms.PictureBox();
            this.C_OpenFileDialog = new System.Windows.Forms.OpenFileDialog();
            this.panel1.SuspendLayout();
            this.panel2.SuspendLayout();
            this.SuspendLayout();
            // 
            // statusBar1
            // 
            this.statusBar1.Location = new System.Drawing.Point(0, 391);
            this.statusBar1.Name = "statusBar1";
            this.statusBar1.Size = new System.Drawing.Size(568, 22);
            this.statusBar1.TabIndex = 0;
            this.statusBar1.Text = "statusBar1";
            // 
            // panel1
            // 
            this.panel1.Controls.Add(this.C_Browse);
            this.panel1.Controls.Add(this.C_Path);
            this.panel1.Dock = System.Windows.Forms.DockStyle.Top;
            this.panel1.Location = new System.Drawing.Point(0, 0);
            this.panel1.Name = "panel1";
            this.panel1.Size = new System.Drawing.Size(568, 40);
            this.panel1.TabIndex = 1;
            // 
            // C_Browse
            // 
            this.C_Browse.Location = new System.Drawing.Point(480, 8);
            this.C_Browse.Name = "C_Browse";
            this.C_Browse.TabIndex = 1;
            this.C_Browse.Text = "Browse";
            this.C_Browse.Click += new System.EventHandler(this.C_Browse_Click);
            // 
            // C_Path
            // 
            this.C_Path.Location = new System.Drawing.Point(8, 8);
            this.C_Path.Name = "C_Path";
            this.C_Path.ReadOnly = true;
            this.C_Path.Size = new System.Drawing.Size(464, 20);
            this.C_Path.TabIndex = 0;
            this.C_Path.Text = "textBox1";
            // 
            // panel2
            // 
            this.panel2.Controls.Add(this.C_Create);
            this.panel2.Controls.Add(this.C_Stream);
            this.panel2.Controls.Add(this.C_LabStream);
            this.panel2.Controls.Add(this.C_MediaTypes);
            this.panel2.Controls.Add(this.C_LabType);
            this.panel2.Controls.Add(this.C_Height);
            this.panel2.Controls.Add(this.C_LabHeight);
            this.panel2.Controls.Add(this.C_LabWidth);
            this.panel2.Controls.Add(this.C_Width);
            this.panel2.Dock = System.Windows.Forms.DockStyle.Left;
            this.panel2.Location = new System.Drawing.Point(0, 40);
            this.panel2.Name = "panel2";
            this.panel2.Size = new System.Drawing.Size(176, 351);
            this.panel2.TabIndex = 2;
            // 
            // C_Create
            // 
            this.C_Create.Location = new System.Drawing.Point(8, 136);
            this.C_Create.Name = "C_Create";
            this.C_Create.Size = new System.Drawing.Size(152, 23);
            this.C_Create.TabIndex = 10;
            this.C_Create.Text = "Create Thumbnail Image";
            this.C_Create.Click += new System.EventHandler(this.C_Create_Click);
            // 
            // C_Stream
            // 
            this.C_Stream.Location = new System.Drawing.Point(64, 104);
            this.C_Stream.Name = "C_Stream";
            this.C_Stream.TabIndex = 9;
            this.C_Stream.Text = "1";
            // 
            // C_LabStream
            // 
            this.C_LabStream.Location = new System.Drawing.Point(8, 104);
            this.C_LabStream.Name = "C_LabStream";
            this.C_LabStream.Size = new System.Drawing.Size(56, 16);
            this.C_LabStream.TabIndex = 8;
            this.C_LabStream.Text = "Stream";
            // 
            // C_MediaTypes
            // 
            this.C_MediaTypes.Items.AddRange(new object[] {
                                                              "Unknow",
                                                              "Image",
                                                              "Audio",
                                                              "Video"});
            this.C_MediaTypes.Location = new System.Drawing.Point(64, 72);
            this.C_MediaTypes.Name = "C_MediaTypes";
            this.C_MediaTypes.Size = new System.Drawing.Size(104, 21);
            this.C_MediaTypes.TabIndex = 7;
            // 
            // C_LabType
            // 
            this.C_LabType.Location = new System.Drawing.Point(8, 72);
            this.C_LabType.Name = "C_LabType";
            this.C_LabType.Size = new System.Drawing.Size(56, 16);
            this.C_LabType.TabIndex = 6;
            this.C_LabType.Text = "Type";
            // 
            // C_Height
            // 
            this.C_Height.Location = new System.Drawing.Point(64, 40);
            this.C_Height.Name = "C_Height";
            this.C_Height.TabIndex = 5;
            this.C_Height.Text = "300";
            // 
            // C_LabHeight
            // 
            this.C_LabHeight.Location = new System.Drawing.Point(8, 40);
            this.C_LabHeight.Name = "C_LabHeight";
            this.C_LabHeight.Size = new System.Drawing.Size(56, 16);
            this.C_LabHeight.TabIndex = 4;
            this.C_LabHeight.Text = "Height";
            // 
            // C_LabWidth
            // 
            this.C_LabWidth.Location = new System.Drawing.Point(8, 8);
            this.C_LabWidth.Name = "C_LabWidth";
            this.C_LabWidth.Size = new System.Drawing.Size(56, 16);
            this.C_LabWidth.TabIndex = 3;
            this.C_LabWidth.Text = "Width";
            // 
            // C_Width
            // 
            this.C_Width.Location = new System.Drawing.Point(64, 8);
            this.C_Width.Name = "C_Width";
            this.C_Width.TabIndex = 3;
            this.C_Width.Text = "300";
            // 
            // C_PicBox
            // 
            this.C_PicBox.Location = new System.Drawing.Point(176, 40);
            this.C_PicBox.Name = "C_PicBox";
            this.C_PicBox.Size = new System.Drawing.Size(392, 351);
            this.C_PicBox.SizeMode = System.Windows.Forms.PictureBoxSizeMode.StretchImage;
            this.C_PicBox.TabIndex = 3;
            this.C_PicBox.TabStop = false;
            // 
            // Thumbnail
            // 
            this.AutoScaleBaseSize = new System.Drawing.Size(5, 13);
            this.ClientSize = new System.Drawing.Size(568, 413);
            this.Controls.Add(this.C_PicBox);
            this.Controls.Add(this.panel2);
            this.Controls.Add(this.panel1);
            this.Controls.Add(this.statusBar1);
            this.Name = "Thumbnail";
            this.Text = "Thumbinal";
            this.panel1.ResumeLayout(false);
            this.panel2.ResumeLayout(false);
            this.ResumeLayout(false);

        }
        #endregion

        private void C_Create_Click(object sender, System.EventArgs e)
        {
            try
            {
                int m_width = Convert.ToInt32(this.C_Width.Text);
                int m_height = Convert.ToInt32(this.C_Height.Text);
                int m_stream = Convert.ToInt32(this.C_Stream.Text);
                MediaTypes m_MediaType = MediaHelper.ConvertToMediaType(this.C_MediaTypes.SelectedItem.ToString());
                Image m_image = this.MediaDetector.GetThumbnail(this.C_Path.Text,new Size(m_width,m_height),m_MediaType,m_stream);
                this.C_PicBox.Image = m_image;
                this.C_PicBox.Width = m_width;
                this.C_PicBox.Height = m_height;                
                this.C_PicBox.Refresh();
            }
            catch(Exception ex)
            {
                MessageBox.Show(string.Format("Error:{0}",ex.Message));
            }        
        }

        private void MediaDetector_OnError(object i_Sender, Exception i_ex)
        {
            MessageBox.Show(this,string.Format("Create thumbnail image error. Message:{0}",i_ex.Message));
        }

        private void C_Browse_Click(object sender, System.EventArgs e)
        {
            if(this.C_OpenFileDialog.ShowDialog(this)==DialogResult.OK)
            {
                this.C_Path.Text = this.C_OpenFileDialog.FileName;
            }
        }
    }
}

仅做参考！