Imports BasicDSP
Imports BasicDSP.Filter
Imports ZedGraph
Public Class dsp1ex3
    Dim iwv As New Signal
    Dim owv As New Signal
    Dim filt As LTISystemChain
    Dim gp As Graph

    Public Sub MakeFilter()
        Dim ftype As Integer = txtFilter.SelectedIndex
        Dim lofreq As Double = Double.Parse(txtLoFreq.Text) / iwv.Rate
        Dim hifreq As Double = Double.Parse(txtHiFreq.Text) / iwv.Rate
        If ftype = 0 Then
            filt = ButterworthLowPass(lofreq, 4)
        ElseIf ftype = 1 Then
            filt = ButterworthHighPass(hifreq, 4)
        Else
            filt = ButterworthBandPass(lofreq, hifreq, 4)
        End If
        Dim fr As New Spectrum(500, iwv.Rate() / 2)
        For i As Integer = 0 To 499
            fr(i) = filt.Response(i / 1000)
        Next
        gp.PlotClear(1)
        gp.PlotDbSpectrum(1, fr, "Frequency Response")
    End Sub
    
    Private Sub OpenToolStripMenuItem_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles OpenToolStripMenuItem.Click
        If OpenFileDialog.ShowDialog() = Windows.Forms.DialogResult.OK Then
            If iwv.LoadWaveFile(OpenFileDialog.FileName) Then
                MakeFilter()
            Else
                MsgBox("Failed to load audio file")
            End If
        End If
    End Sub

    Private Sub PlayInputToolStripMenuItem_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles PlayInputToolStripMenuItem.Click
        iwv.Replay()
    End Sub

    Private Sub PlayOutputToolStripMenuItem_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles PlayOutputToolStripMenuItem.Click
        MakeFilter()
        owv = filt.Filter(iwv)
        owv.Replay()
    End Sub

    Private Sub DSPEx3_Load(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles MyBase.Load
        gp = New Graph(Me.CreateGraphics(), zgc)
        txtFilter.SelectedIndex = 2
        txtLoFreq.Text = 1000
        txtHiFreq.Text = 3000
        MakeFilter()
    End Sub

    Private Sub txtFilter_SelectedIndexChanged(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles txtFilter.SelectedIndexChanged
        MakeFilter()
    End Sub
End Class