我的音頻規範化碼是否正確？

Question

我想將音頻文件規格化爲最大值。

爲了做到這一點，我用這個代碼：

Dim iHighestDataValue As Integer 
Dim iLowestDataValue As Integer 

Dim i& 
For i = 1 To dc.wavedatasize/2 
    Get #iFile, , DataValue(i) ' reads data value into array 

    If DataValue(i) > iHighestDataValue Then 
     iHighestDataValue = DataValue(i) 
    End If 

    If DataValue(i) < iLowestDataValue Then 
     iLowestDataValue = DataValue(i) 
    End If 
Next 

Dim sngVolumeLevel As Single 
sngVolumeLevel = ((iHighestDataValue + (iLowestDataValue * -1))/2)/32767 

它工作得很好，幾乎所有的文件，但對於一個文件，最後一行將失敗。

iHighestDataValue是13445，iLowestDataValue是-21940。

我想最後一行有些問題。 這只是VB6發生的一個錯誤，因爲它不能處理這個（正確的）計算，還是我引入了任何錯誤？

當我把最後一行到單獨的計算，它工作正常：

Dim sngHighest As Single 
If iHighestDataValue > 32767 Then 
    sngHighest = 32767 
Else 
    sngHighest = iHighestDataValue 
End If 

Dim sngLowest As Single 
If iLowestDataValue < -32767 Then 
    sngLowest = -32767 
Else 
    sngLowest = iLowestDataValue 
End If 
sngLowest = sngLowest * -1 

Dim sngVolumeLevel As Single 
sngVolumeLevel = (sngHighest + sngLowest)/2 
sngVolumeLevel = (sngVolumeLevel/32767) 

謝謝！

PS： 下面是函數的最後，歸一化部：

Dim tem As Long 

For i = 1 To dc.wavedatasize/2 
    tem = CLng(DataValue(i) * 1/sngVolumeLevel) 
    If tem > 32767 Then 
     tem = 32767 ' prevents integer overflow error 
    End If 
    If tem < -32767 Then 
     tem = -32767 ' prevents integer overflow error 
    End If 
    DataValue(i) = CInt(tem) ' changes data value 
Next i 

wh.riffdatasize = dc.wavedatasize + Len(wh) + Len(wf) 'Riff chunk size may be different 
' beacause some input wave files may contain information chunk which is not written in output file 

iFile = FreeFile 

Kill uPath 'Delete the original/source file. We will overwrite it with the normalized version of this file 

Open uPath For Binary As #iFile 
Put #iFile, , wh ' writes the wave header 
Put #iFile, , wf ' writes wave format 
Put #iFile, , dc ' writes the 8 byte string "data" and wave dataa size 

For i = 1 To dc.wavedatasize/2 
    Put #iFile, , DataValue(i) ' writes data value in ouput file 
Next i 

Close #iFile 

Answer 1

，因爲它產生削波的顯著量這是不正確的。

相反的：

sngVolumeLevel = ((iHighestDataValue + (iLowestDataValue * -1))/2)/32767 

更好地做到這一點：

If iHighestDataValue >= -iLowestDataValue Then 
    sngVolumeLevel = iHighestDataValue/32767. 
Else 
    sngVolumeLevel = iLowestDataValue/-32768. 
End If