.net从MP3中提取歌曲信息

       一首MP3歌曲除了音乐信息外，还包含了如歌名、演唱者等信息，当我们用winamp软件听音乐时，播放清单就自动将这些信息读出来。大部分人都喜欢从网上下载音乐，但下载下来的MP3文件名都是文件上传系统自动取名的，和歌曲本身根本不相符，所以，给用户带来了很大的麻烦。但是，懒人有懒人的做法，我们何不自己写一个程序，将歌曲信息自动读出来并为MP3文件自动更名呢？

 

       下面我就以C#为工具，把开发过程写出来。

 

       一首MP3的额外信息存放在文件的最后面，共占128个字节，其中包括以下的内容（我们定义一个结构说明）：

       public struct Mp3Info

        {

            public string identify;//TAG，三个字节

            public string Title;//歌曲名,30个字节

            public string Artist;//歌手名,30个字节

            public string Album;//所属唱片,30个字节

            public string Year;//年,4个字符

            public string Comment;//注释,28个字节

 

            public char reserved1;//保留位，一个字节

            public char reserved2;//保留位，一个字节

            public char reserved3;//保留位，一个字节

        }

 

       所以，我们只要把MP3文件的最后128个字节分段读出来并保存到该结构里就可以了。函数定义如下：

              /// <summary>

        /// 获取MP3文件最后128个字节

        /// </summary>

        /// <param name="FileName">文件名</param>

        /// <returns>返回字节数组</returns>

        private byte[] getLast128(string FileName)

        {

            FileStream fs = new FileStream(FileName,FileMode.Open,FileAccess.Read);

            Stream stream = fs;

 

            stream.Seek(-128,SeekOrigin.End);

 

            const int seekPos = 128;

            int rl = 0;

            byte[] Info = new byte[seekPos];

            rl = stream.Read(Info,0,seekPos);

 

            fs.Close();

            stream.Close();

 

            return Info;

        }

 

       再对上面返回的字节数组分段取出，并保存到Mp3Info结构中返回。

              /// <summary>

        /// 获取MP3歌曲的相关信息

        /// </summary>

        /// <param name = "Info">从MP3文件中截取的二进制信息</param>

        /// <returns>返回一个Mp3Info结构</returns>

        private Mp3Info getMp3Info(byte[] Info)

        {

            Mp3Info mp3Info = new Mp3Info();

 

            string str = null;

            int i;

            int position = 0;//循环的起始值

            int currentIndex = 0;//Info的当前索引值

            //获取TAG标识

            for(i = currentIndex;i<currentIndex+3;i++)

            {

                str = str+(char)Info[i];

   

                position++;

            }

            currentIndex = position;

            mp3Info.identify = str;

 

            //获取歌名

            str = null;

            byte[] bytTitle = new byte[30];//将歌名部分读到一个单独的数组中

            int j = 0;

            for(i = currentIndex;i<currentIndex+30;i++)

            {

                bytTitle[j] = Info[i];   

                position++;

                j++;

            }

            currentIndex = position;

            mp3Info.Title = this.byteToString(bytTitle);

 

            //获取歌手名

            str = null;

            j = 0;

            byte[] bytArtist = new byte[30];//将歌手名部分读到一个单独的数组中

            for(i = currentIndex;i<currentIndex+30;i++)

            {

                bytArtist[j] = Info[i];   

                position++;

                j++;

            }

            currentIndex = position;

            mp3Info.Artist = this.byteToString(bytArtist);

 

            //获取唱片名

            str = null;

            j = 0;

            byte[] bytAlbum = new byte[30];//将唱片名部分读到一个单独的数组中

            for(i = currentIndex;i<currentIndex+30;i++)

            {

                bytAlbum[j] = Info[i];   

                position++;

                j++;

            }

            currentIndex = position;

            mp3Info.Album = this.byteToString(bytAlbum);

 

            //获取年

            str = null;

            j = 0;

            byte[] bytYear = new byte[4];//将年部分读到一个单独的数组中

            for(i = currentIndex;i<currentIndex+4;i++)

            {

                bytYear[j] = Info[i]; 

                position++;

                j++;

            }

            currentIndex = position;

            mp3Info.Year = this.byteToString(bytYear);

           

            //获取注释

            str = null;

            j = 0;

            byte[] bytComment = new byte[28];//将注释部分读到一个单独的数组中

            for(i = currentIndex;i<currentIndex+25;i++)

            {

                bytComment[j] = Info[i];   

                position++;

                j++;

            }

            currentIndex = position;

            mp3Info.Comment = this.byteToString(bytComment);

 

            //以下获取保留位

            mp3Info.reserved1 = (char)Info[++position];

            mp3Info.reserved2 = (char)Info[++position];

            mp3Info.reserved3 = (char)Info[++position];

 

            return mp3Info;

        }

       上面程序用到下面的方法：

              /// <summary>

        /// 将字节数组转换成字符串

        /// </summary>

        /// <param name = "b">字节数组</param>

        /// <returns>返回转换后的字符串</returns>

        private string byteToString(byte[] b)

        {

            Encoding enc = Encoding.GetEncoding("GB2312");

            string str = enc.GetString(b);

            str = str.Substring(0,str.IndexOf('/0') >= 0 ? str.IndexOf('/0') : str.Length);//去掉无用字符

 

            return str;

        }

 

       改名怎么办呢？我们按（演唱者）歌名 的格式对歌曲进行改名，程序如下：

       /// <summary>

        /// 更改文件名

        /// </summary>

        /// <param name="filePath">文件名</param>

        /// <returns></returns>

        private bool ReName(string filePath)

        {

            if(File.Exists(filePath))

            {

                Mp3Info mp3Info = new Mp3Info();

                mp3Info = this.getMp3Info(this.getLast128(filePath));//读出文件信息

 

                mp3Info.Artist = this.DeleteNotValue(mp3Info.Artist);

                mp3Info.Title = this.DeleteNotValue(mp3Info.Title);

 

                if(mp3Info.Artist.Trim().Length==0)

                {

                    mp3Info.Artist="未命名";

                }

 

                if(mp3Info.Title.Trim().Length==0)

                {

                    mp3Info.Title="未知名歌曲";

                }

 

                try

                {

                    //更名

                    File.Move(filePath,filePath.Substring(0,filePath.ToLower().LastIndexOf("//")).Trim() + "//" + "(" + mp3Info.Artist.Trim() + ")" +mp3Info.Title.Trim() + ".mp3");

                    return true;

                }

                catch(Exception)

                {

                    return false;

                }

            }

            else

            {

                return false;

            }

        }

 

呵，思路就是这样了，如果有问题或者需要源码请发邮件至：lifenote@21cn.com索取