MP3中提取歌曲信息(转)

Posted on 2008-04-20 15:43  少林  阅读(308)  评论(0编辑  收藏
2007-03-27 14:50

转自:http://dev.csdn.net/article/30/30624.shtm
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("file://%20%20%22)).trim/() + "\\" + "(" + mp3Info.Artist.Trim() + ")" +mp3Info.Title.Trim() + ".mp3");
                     return true;
                 }
                 catch(Exception)
                 {
                     return false;
                 }
             }
             else
             {
                 return false;
             }
         }

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