VB6获取音频时长，获取的不准确怎么回事？

Option Explicit
Private Declare Function mciSendString Lib "winmm.dll" Alias "mciSendStringA" (ByVal lpstrCommand As String, ByVal lpstrReturnString As String, ByVal uReturnLength As Long, ByVal hwndCallback As Long) As Long

Public Function GetMusicLengthString(FileName As String) As String
Dim RefStr As String * 80
mciSendString "status " & FileName & " length", RefStr, 80, 0
GetMusicLengthString = RefStr
End Function

Private Sub Form_Load()
MsgBox GetMusicLengthString("E:\1.mp3")
End Sub

Option Explicit
Private Declare Function mciSendString Lib "winmm.dll" Alias "mciSendStringA" (ByVal lpstrCommand As String, ByVal lpstrReturnString As String, ByVal uReturnLength As Long, ByVal hwndCallback As Long) As Long

Private Sub Form_Load()
Dim r As String
r = String(256, Chr(0))
Dim f As String
f = "E:\1.mp3" '文件名根据自己需要改
mciSendString "Status " & f & " length", r, 256, 0
Dim m As Long
m = Val(r) \ 1000 \ 60
Dim c As Double
c = Val(r) / 1000 - m * 60
MsgBox "长度" & m & "分" & c & "秒"
End Sub