得到MP3中隱藏的信息

    為了保護音樂者的版權，在MP3文件中有一段特意存儲版權說明的信息，眾多的MP3播放器軟件都提供了修改和讀取MP3文件中隱藏信息的功能，那么這些信息到底存儲在哪里呢？如何得到這些信息呢？本文將為大家提供得到MP3信息的模塊。

      首先，定義一個公共類型Mp3tag如下：

  Public Type Mp3tag
      Artist  As String        ’Artist 存儲歌手信息
      Album  As String         ’Album  存儲唱片專輯信息
      Title As String          ’Title  存儲標題信息     
      Year As String           ’Year   存儲年代信息
      Comments As String       ’Comments 存儲備注信息
      Genre As Integer         ’Genre   存儲音樂風格序列
  End Type

      然后，定義一個獲取MP3信息的函數，它將返回這些信息，代碼如下：

Public Function GetMp3Tag(FName As String) As Mp3tag
    Dim Artist As String
    Dim Album As String
    Dim Title As String
    Dim Year As String
    Dim Comments As String
    Dim Genre As Integer
    
    If FName = "" Then Exit Function

    If Dir(FName) = "" Then Exit Function
    
    Dim FileNum As Integer

    FileNum = FreeFile                            ’得到一個自由的文件號

    Dim strInput As String

    Open FName For Binary Aclearcase/" target="_blank" >ccess Read As FileNum  ’以二進制形式打開文件
    
    If LOF(FileNum) < 128 Then
        Close FileNum
        Exit Function
    End If
    
    Seek FileNum, LOF(FileNum) - 127             ’把文件指針移動到MP3信息處
    strInput = Space(3)
    Get FileNum, , strInput


    If strInput <> "TAG" Then                    ’如果沒有發現信息標識，就關閉文件
        Close FileNum
        GoTo Done:
    End If
    
    strInput = Space(30)
    Get FileNum, , strInput
    Title = Trim(strInput)
    
    strInput = Space(30)
    Get FileNum, , strInput
    Artist = Trim(strInput)
    
    strInput = Space(30)
    Get FileNum, , strInput
    Album = Trim(strInput)
    
    strInput = Space(4)
    Get FileNum, , strInput
    Year = Trim(strInput)
    
    strInput = Space(30)
    Get FileNum, , strInput
    Comments = Trim(strInput)
    
    strInput = Space(1)
    Get FileNum, , strInput
    Genre = Asc(strInput)

Done:
        GetMp3Tag.Title = Title
        GetMp3Tag.Artist = Artist
        GetMp3Tag.Album = Album
        GetMp3Tag.Year = Year
        GetMp3Tag.Year = Comments
        If Genre < 0 Or Genre > 254 Then Genre = 12
        GetMp3Tag.Genre = CInt(Genre)
        
    Close FileNum

End Function
   
   注意：MP3文件對音樂的風格進行了限制，共254種。Genre返回的只是MP3風格的序列號，具體還需要定位，在這里我把所有類型以常數形式列出，每個類型之間用"|"號隔開。

Private Const sGenreMatrix = "Blues|Classic Rock|Country|Dance|Disco|Funk|Grunge|" + _
    "Hip-Hop|Jazz|Metal|New Age|Oldies|Other|Pop|R&B|Rap|Reggae|Rock|Techno|" + _
    "Industrial|Alternative|Ska|Death Metal|Pranks|Soundtrack|Euro-Techno|" + _
    "Ambient|Trip Hop|Vocal|Jazz+Funk|Fusion|Trance|Classical|Instrumental|Acid|" + _
    "House|Game|Sound Clip|Gospel|Noise|Alt. Rock|Bass|Soul|Punk|Space|Meditative|" + _
    "Instrumental Pop|Instrumental Rock|Ethnic|Gothic|Darkwave|Techno-Industrial|Electronic|" + _
    "Pop-Folk|Eurodance|Dream|Southern Rock|Comedy|Cult|Gangsta Rap|Top 40|Christian Rap|" + _
    "Pop/Punk|Jungle|Native American|Cabaret|New Wave|Phychedelic|Rave|Showtunes|Trailer|" + _
    "Lo-Fi|Tribal|Acid Punk|Acid Jazz|Polka|Retro|Musical|Rock & Roll|Hard Rock|Folk|" + _
    "Folk/Rock|National Folk|Swing|Fast-Fusion|Bebob|Latin|Revival|Celtic|Blue Grass|" + _
    "Avantegarde|Gothic Rock|Progressive Rock|Psychedelic Rock|Symphonic Rock|Slow Rock|" + _
    "Big Band|Chorus|Easy Listening|Acoustic|Humour|Speech|Chanson|Opera|Chamber Music|" + _
    "Sonata|Symphony|Booty Bass|Primus|Porn Groove|Satire|Slow Jam|Club|Tango|Samba|Folklore|" + _
    "Ballad|power Ballad|Rhythmic Soul|Freestyle|Duet|Punk Rock|Drum Solo|A Capella|Euro-House|" + _
    "Dance Hall|Goa|Drum & Bass|Club-House|Hardcore|Terror|indie|Brit Pop|Negerpunk|Polsk Punk|" + _
    "Beat|Christian Gangsta Rap|Heavy Metal|Black Metal|Crossover|Comteporary Christian|" + _
    "Christian Rock|Merengue|Salsa|Trash Metal|Anime|JPop|Synth Pop"


    把以上代碼寫到一個模塊中（.Bas），然后在窗體上加入5個TextBox和1個ComboBox控件，其中5個TextBox控件分別用來顯示一首Mp3文件的以下信息：歌手、年代、唱片、評論、標題，ComboBox控件用來顯示歌曲的風格。再放一個Command控件，其標題為“顯示信息”，在它的Click事件中加入以下代碼：
            Private sub Command1_click()
            Dim mp3Tag as Mp3tag
            mp3tag = GetMp3Tag ("c:\Song.mp3")
            Text1.Text = mp3tag.Artist
            Text2.Text = mp3tag.Album
            Text3.Text = mp3tag.Title
            Text4.Text = mp3tag.Year
            Text5.Text = mp3tag.Comments
            Combo1.ListIndex = mp3tag.Genre
            End Sub
     在窗體的加載過程中加入如下代碼：
            Private Sub Form_Load()
            Dim i As Integer,GenreArray() As String
            GenreArray = Split(sGenreMatrix, "|")
            For i = LBound(GenreArray) To UBound(GenreArray)
            Combo1.AddItem GenreArray(i)
            Next i
            End Sub
  
     以上代碼在VB6 \Win2000中測試通過。

原文轉自：http://www.anti-gravitydesign.com