[RESOLVED] DirectSound reading data from capture buffer

[paulg4ije]

Can anyone see where I'm going wrong with my circular DirectSound Capture buffer here? If I just capture sound into a big non-circular buffer it works fine, but with a 1 second (44100 bytes) buffer and a 100ms timer to poll the read position it goes haywire. No error messages, just long blocks of zeros with short bursts of valid data. I can't help thinking I'm doing something silly with my calculation of the number of bytes to read and/or the read position.

Here is the code. gBuffer is defined elsewhere as a big byte array. In this example I am just trying to copy the captured sound data from the small temporary byte array (tempBuffer) into the big gBuffer byte array. Obviously this must be done so that every byte is read and copied into the byte array with no gaps or duplication of values. Timer1 is set to 100mS:

    Dim McaptureBuffer As CaptureBuffer
    Dim MiLastReadPos As Integer
    Dim MiBufferOffset As Integer
    Dim MiBufferSize As Integer = 44100

    Private Sub cmdStart_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles cmdStart.Click

        Dim waveFormat As New WaveFormat
        waveFormat.SamplesPerSecond = 44100
        waveFormat.Channels = 1
        waveFormat.BitsPerSample = 8
        waveFormat.FormatTag = WaveFormatTag.Pcm
        waveFormat.AverageBytesPerSecond = 44100
        waveFormat.BlockAlign = 1

        Dim captureBufferDesc = New CaptureBufferDescription
        captureBufferDesc.BufferBytes = 44100
        captureBufferDesc.ControlEffects = False
        captureBufferDesc.WaveMapped = True
        captureBufferDesc.Format = waveFormat

        Dim capture As New Capture

        McaptureBuffer = New CaptureBuffer(captureBufferDesc, capture)
        McaptureBuffer.Start(True) ' True = looping

        MiBufferOffset = 0
        Timer1.Enabled = True

    End Sub

    Private Sub Timer1_Tick(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles Timer1.Tick

        Dim iCap As Integer
        Dim iRead As Integer
        Dim iBytes As Integer

        Try

            McaptureBuffer.GetCurrentPosition(iCap, iRead)

            If iRead < MiLastReadPos Then
                ' "wrap-around" of circular buffer has occurred
                iBytes = (MiBufferSize - MiLastReadPos) + iRead
            Else
                iBytes = iRead - MiLastReadPos
            End If

            Dim tempBuffer(iBytes) As Byte
            McaptureBuffer.Read(iRead, New IO.MemoryStream(tempBuffer), iBytes, LockFlag.None)
            MiLastReadPos = iRead

            lstData.Items.Add(iBytes & " : " & MiBufferOffset)

            For n As Integer = 0 To tempBuffer.Length - 1
                Gbuffer(MiBufferOffset) = tempBuffer(n)
                MiBufferOffset += 1
            Next n

        Catch ex As Exception
            MsgBox(ex.Message)
        End Try

    End Sub

Any help would be muich appreciated.

[paulg4ije]

I found the first obvious mistake - I should be starting my Read from the last read position, not the present one. It's still not quite right though (sorry to be vague - there's a "glitch" value getting into the buffer on every Timer1 timeout). I'll keep working on it.

[paulg4ije]

OK, got it sorted out. My tempBuffer array was one byte bigger than it needed to be so I was always copying a 0 from it to the global buffer (gBuffer). Sorry to have wasted your time ...