前段时间，在局域网里面做一个小网站，其中有板块是涉及音乐的在线播放。考虑到以后维护的方便，决定把mp3文件都按专辑分不同的目录存放。然后使用一个程序监控存放mp3的目录，把每个mp3文件的信息都存入数据库中，用过ASP.NET页面将mp3文件的信息呈现给用户。其中使用.NET来读取mp3 文件的信息虽然不难，但也需要不少技巧，故将该过程整理与大家分享。
首先我们来看看mp3歌曲的信息所存放的位置。Mp3文件包含一个叫做ID3的标签。其实有两个标签，一个叫做ID3v1，另外一个叫做ID3v2。为了讲述的简单起见，我们这里只介绍ID3v1。
ID3V1结构比较简单，存放在MP3文件的末尾，大家可以用16进制的编辑器（例如：UltraEdit）打开一个MP3文件，注意其末尾的128个字节，数据结构定义如下：
名称 位置 长度 内容
Header 1-3 3 标签头
Title 4-33 30 标题
Artist 34-63 30 艺术家
Album 64-93 30 专辑
Year 94-97 4 出品年代
Comment 98-127 30 备注
Cenre 128 1 类型
注意：上述的标签头必须是”TAG”, 否则表示没有标签
ID3v1的各项信息是按顺序依次存放的，每项信息之后并没有任何的结束标志，如果某项信息长度小于标准长度，使用”\0”来补充。另外Genre是个例外，它用一个字节表示歌曲流派，其对应表如下(由于该内容太多，只列出前50项)：
0="Blues"
1="ClassicRock"
2="Country"
3="Dance"
4="Disco"
5="Funk"
6="Grunge"
7="Hip-Hop"
8="Jazz"
9="Metal"
10="NewAge"
11="Oldies"
12="Other"
13="Pop"
14="R&B"
15="Rap"
16="Reggae"
17="Rock"
18="Techno"
19="Industrial"
20="Alternative"
21="Ska"
22="DeathMetal"
23="Pranks"
24="Soundtrack"
25="Euro-Techno"
26="Ambient"
27="Trip-Hop"
28="Vocal"
29="Jazz Funk"
30="Fusion"
31="Trance"
32="Classical"
33="Instrumental"
34="Acid"
35="House"
36="Game"
37="SoundClip"
38="Gospel"
39="Noise"
40="AlternRock"
41="Bass"
42="Soul"
43="Punk"
44="Space"
45="Meditative"
46="InstrumentalPop"
47="InstrumentalRock"
48="Ethnic"
49="Gothic"
50="Darkwave"
知道了MP3歌曲信息存放的结构之后，我们就可以写出对应的代码。
首先定一个MP3Info类：
1 Public Class Mp3Info
2
3
4
5 Private Const TAGLEN As Integer = 128
6
7
8
9 Private _MP3Tag As String = String.Empty
10
11 Private _Artist As String = String.Empty
12
13 Private _Title As String = String.Empty
14
15 Private _Album As String = String.Empty
16
17 Private _Comment As String = String.Empty
18
19 Private _Year As String = String.Empty
20
21 Private _Genre As String = String.Empty
22
23 Private _GenreID As Byte
24
25
26
27 Private Genres() As String = {"Blues", "Classic Rock", "Country", "Dance", "Disco", "Funk", "Grunge", _
28
29 "Hip-Hop", "Jazz", "Metal", "New Age", "Oldies", "Other", "Pop", "R&B", "Rap", "Reggae", "Rock", _
30
31 "Techno", "Industrial", "Alternative", "Ska", "Death Metal", "Pranks", "Soundtrack", "Euro-Techno", _
32
33 "Ambient", "Trip-Hop", "Vocal", "Jazz Funk", "Fusion", "Trance", "Classical", "Instrumental", "Acid", _
34
35 "House", "Game", "Sound Clip", "Gospel", "Noise", "AlternRock", "Bass", "Soul", "Punk", "Space", _
36
37 "Meditative", "Instrumental Pop", "Instrumental Rock", "Ethnic", "Gothic", "Darkwave", "Techno-Industrial", _
38
39 "Electronic", "Pop-Folk", "Eurodance", "Dream", "Southern Rock", "Comedy", "Cult", "Gangsta", "Top 40", _
40
41 "Christian Rap", "Pop/Funk", "Jungle", "Native American", "Cabaret", "New Wave", "Psychedelic", "Rave", _
42
43 "Showtunes", "Trailer", "Lo-Fi", "Tribal", "Acid Punk", "Acid Jazz", "Polka", "Retro", "Musical", _
44
45 "Rock & Roll", "Hard Rock", "Folk", "Folk/Rock", "National Folk", "Swing", "Bebob", "Latin", "Revival", _
46
47 "Celtic", "Bluegrass", "Avantgarde", "Gothic Rock", "Progressive Rock", "Psychedelic Rock", "Symphonic Rock", _
48
49 "Slow Rock", "Big Band", "Chorus", "Easy Listening", "Acoustic", "Humour", "Speech", "Chanson", "Opera", _
50
51 "Chamber Music", "Sonata", "Symphony", "Booty Bass", "Primus", "Porn Groove", "Satire", "Slow Jam", "Club", _
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