C#

Module moduleVOX2WAV

    Dim WaveHeader() As Int32 = New Int32() {&H46464952, &HFFFFFFDB, &H45564157, &H20746D66, 16, &H10001, 6000, 12000, &H100002, &H61746164, -1}
    Dim IndexShift() As Int16 = New Int16() {-1, -1, -1, -1, 2, 4, 6, 8}
    Dim StepSize() As Int16 = New Int16() {16, 17, 19, 21, 23, 25, 28, 31, 34, 37, 41, 45, 50, 55, 60, 66, 73, 80, 88, 97, 107, 118, 130, 143, 157, 173, 190, 209, 230, 253, 279, 307, 337, 371, 408, 449, 494, 544, 598, 658, 724, 796, 876, 963, 1060, 1166, 1282, 1411, 1552, 1707, 1878, 2066, 2272, 2499, 2749, 3024, 3327, 3660, 4026, 4428, 4871, 5358, 5894, 6484, 7132, 7845, 8630, 9493, 10442, 11487, 12635, 13899, 15289, 16818, 18500, 20350, 22385, 24623, 27086, 29794}
    Dim Nibble2Bit(,) As Int16 = New Int16(,) {{0, 0, 0, 0}, {0, 0, 0, 1}, {0, 0, 1, 0}, {0, 0, 1, 1}, {0, 1, 0, 0}, {0, 1, 0, 1}, {0, 1, 1, 0}, {0, 1, 1, 1}, {1, 0, 0, 0}, {1, 0, 0, 1}, {1, 0, 1, 0}, {1, 0, 1, 1}, {1, 1, 0, 0}, {1, 1, 0, 1}, {1, 1, 1, 0}, {1, 1, 1, 1}}
    Dim SignTable() As Int16 = New Int16() {1, -1}
    Dim StepSizeIndex As Int16 = 0
    Dim Signal As Int16 = -2
    Dim AvgBuffer() As Int16 = New Int16() {0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0}
    Dim AvgIndex As Int16 = 0
    Dim Total As Int32 = 0
    Dim Length As Int32
    Dim Offset As Int32
    Dim nibble As Int16
    Dim ReadBuffer(4096) As Byte
    Dim WriteBuffer(8192) As Int16

    Public Sub Convert(ByVal srcVOXFile As String, ByVal destWAVFile As String)
        Dim strm As New IO.FileStream(srcVOXFile, IO.FileMode.Open, IO.FileAccess.Read)
        FileOpen(2, destWAVFile, OpenMode.Binary, OpenAccess.Write, OpenShare.LockWrite)
        FilePut(2, WaveHeader)
        Length = 4096
        While Length = 4096
            Length = strm.Read(ReadBuffer, 0, 4096)
            For Offset = 0 To Length - 1
                nibble = 0
                Signal += Decode(ReadBuffer(Offset) \ 16)
                If (Signal > 2047 Or Signal < -2047) Then Truncate()
                WriteBuffer(2 * Offset) = Signal
                nibble = 1
                Signal += Decode(ReadBuffer(Offset) Mod 16)
                If (Signal > 2047 Or Signal < -2047) Then Truncate()
                WriteBuffer(2 * Offset + 1) = Signal
            Next
            FilePut(2, WriteBuffer)
            Total += Length
        End While
        strm.Close() : strm = Nothing
        Total = 4 * Total
        Length = Total + 36
        FilePut(2, Length, 4 + 1)
        FilePut(2, Total, 40 + 1)
        FileClose(2)
    End Sub

    Public Function Decode(ByVal i As Byte) As Int16
        Dim diff As Int16
        Dim value As Int32
        value = 2 * Total + 2 * Offset + nibble
        diff = SignTable(Nibble2Bit(i, 0)) * (StepSize(StepSizeIndex) * Nibble2Bit(i, 1) + (StepSize(StepSizeIndex) / 2) * Nibble2Bit(i, 2) + (StepSize(StepSizeIndex) / 4) * Nibble2Bit(i, 3) + (StepSize(StepSizeIndex) / 8))
        StepSizeIndex = StepSizeIndex + IndexShift(i Mod 8)
        If StepSizeIndex < 0 Then StepSizeIndex = 0
        If StepSizeIndex > 48 Then
            StepSizeIndex = 48
        End If
        Return diff
    End Function

    Public Sub Truncate()
        Dim value As Int32
        value = 2 * Total + 2 * Offset + nibble
        If Signal > 2047 Then Signal = 2047
        If Signal < -2047 Then Signal = -2047
    End Sub

End Module