是否可以使用Excel vba檢查文件內容類型（mime）？

Question

準確地說，是否可以使用Excel VBA檢查一個文件是否實際上是一個mp3文件（不是擴展名，而是內容）？

編輯：兩個嘗試，我把代碼添加：

嘗試1 - 基於微軟社區的投入。奇怪的是，這驗證所有文件爲MP3，不知道我錯過了什麼。

Sub mp3_test() 
Dim rng As Range 
Dim c As clsMP3Info ' name of the class module 
Dim nSecs As Long 

book1 = ThisWorkbook.Name 

MsgBox "Please select the folder that contains files to be checked.", vbExclamation 

'FILE_EXT = "xlsx" 
strFolderName = Get_Folder_Path() & "\" 

Set FSO = CreateObject("Scripting.FileSystemObject") 
Set FSO_FOLDER = FSO.GetFolder(strFolderName) 

i = 2 
If FSO_FOLDER.Files.Count > 0 Then 

For Each FSO_FILE In FSO_FOLDER.Files 
'pq = q 
sFile = strFolderName & FSO_FILE.Name 

     Set c = New clsMP3Info 
     With c 
      If Len(sFile) Then c.Filename = sFile 
      If Not c.ValidMP3 Then 
        Range("B" & i).Value = "Invalid" 
        Range("A" & i).Value = FSO_FILE.Name 
        i = i + 1 
      Else 
        Range("B" & i).Value = "Valid" 
        Range("A" & i).Value = FSO_FILE.Name 
        i = i + 1 
        End If 
     End With 
Next 
End If 

s = MsgBox("Done!", vbOKOnly)  
End Sub 

嘗試2 - 基於@Steven在此帖子/線程中共享的代碼。這會導致溢出錯誤，因爲變量似乎不接受超過32767字節的大小。

Sub mp3c() 

Dim intFileNum As Integer, bytTemp As Byte 
Dim bytes() As Byte 
intFileNum = FreeFile 

Open "D:\Users\adminx\Desktop\Test\Audioslave - Revelations - 07 - Somedays.mp3" For Binary Access Read As intFileNum 

Dim i As Long 

i = 0 

Do While Not EOF(intFileNum) 
    Get intFileNum, , bytTemp 
    ReDim Preserve bytes(i + 1) 
    bytes(i) = bytTemp 
    i = i + 1 
Loop 

Close intFileNum 

Dim headerSize, width, height As Long 

width = BytesToInt(bytes(WIDTH_OFFSET + 0), bytes(WIDTH_OFFSET + 1), bytes(WIDTH_OFFSET + 2), bytes(WIDTH_OFFSET + 3)) 
height = BytesToInt(bytes(HEIGHT_OFFSET + 0), bytes(HEIGHT_OFFSET + 1), bytes(HEIGHT_OFFSET + 2), bytes(HEIGHT_OFFSET + 3)) 
headerSize = BytesToInt(bytes(HEADERSIZE_OFFSET + 0), bytes(HEADERSIZE_OFFSET + 1), bytes(HEADERSIZE_OFFSET + 2), bytes(HEADERSIZE_OFFSET + 3)) 
End Sub 

Answer 1

當然，你可以打開文件進行二進制訪問並讀取文件頭。下面是我讀取位圖標題的項目片段，顯然，您需要更改偏移量以從MP3文件中獲取所需的信息。

Dim intFileNum As Integer, bytTemp As Byte 
Dim bytes() As Byte 
intFileNum = FreeFile 

Open filePath For Binary Access Read As intFileNum 

Dim i As Integer 

i = 0 

Do While Not EOF(intFileNum) 
    Get intFileNum, , bytTemp 

    ReDim Preserve bytes(i + 1) 

    bytes(i) = bytTemp 

    i = i + 1 
Loop 

Close intFileNum 

Dim headerSize, width, height As Long 

width = BytesToInt(bytes(WIDTH_OFFSET + 0), bytes(WIDTH_OFFSET + 1), bytes(WIDTH_OFFSET + 2), bytes(WIDTH_OFFSET + 3)) 
height = BytesToInt(bytes(HEIGHT_OFFSET + 0), bytes(HEIGHT_OFFSET + 1), bytes(HEIGHT_OFFSET + 2), bytes(HEIGHT_OFFSET + 3)) 
headerSize = BytesToInt(bytes(HEADERSIZE_OFFSET + 0), bytes(HEADERSIZE_OFFSET + 1), bytes(HEADERSIZE_OFFSET + 2), bytes(HEADERSIZE_OFFSET + 3)) 

編輯：大概應該包括我BytesToInt功能，一個DWORD轉換成整數：

Function BytesToInt(a As Byte, b As Byte, c As Byte, d As Byte) As Double 

    BytesToInt = (d * 256^3) + (c * 256^2) + (b * 256) + a 

End Function