Graphical waveform representation?

I want to 'draw' a waveform from a file on a picturebox control.
I don't know exactly how to approach the problem and I want to ask here some questions.

In the first version of the program, I want to use only 8-bit, 1 channel audio files because they're the most easy ones.

I know to draw a point in the picturebox control I must use picture1.pset and I know that raw audio data starts usually in the byte #45. After that I don't know anything else. So I would like to know what to do next.

I'm reading some source codes also.

EDIT: the file is a *.wav

Is this what you want

Quote:

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Originally Posted by jmsrickland

Is this what you want

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Yes, that is what I want.

http://www.vbaccelerator.com/home/VB...er/article.asp

Quote:

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Originally Posted by VBClassicRocks

http://www.vbaccelerator.com/home/VB...er/article.asp

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Thank you, I've read it.

I've been reading the link that VBClassicRocks posted and I've a more clear idea.
In the code I'm writting, I use only 8bit-mono files because I think they're the easiest one.

After reading the channels, bits per sample, etc... the program starts reading the sound information in the byte #45. So the first byte of 'sound information' is the byte #45.

If the byte value is above 127 it corresponds to positive Y.
If the byte value is below 127 it corresponds to negative Y.
http://i59.tinypic.com/w2rlt.jpg

I use Picture1.Line to draw the values in the Picture1 control.
I've stopped here because I don't know how to follow.

I tried:

Code:

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Dim MinView As Long      'Byte where the program starts to read
Dim MaxView As Long    'Byte where the program ends to read

Dim MyByte1 As Byte    'Actual byte the program reads
Dim MyByte2 As Byte    'Following byte that the program uses to perform the caculations when drawing the line

Dim ValueY1 As Long      'Value in the Y axis calculated from the value of the read byte
Dim ValueY2 As Long

Open CommonDialog.FileName For Binary Access Read As #1    'The program opens the file
      Dim I As Long
      For I = MinView To MaxView     
          Get #1, I, MyByte1
          Get #1, I + 1, MyByte2
          CalculateYValue MyByte1, MyByte2
          Picture1.Line (I, Picture1.ScaleHeight - ValueY1) - (I + 1, Picture1.ScaleHeight - ValueY2)
      Next I


Private Sub CalculateYValue (FirstByte As Byte, SecondByte As Byte)         
' Calculate the position in the graph (Y axis) of the current byte read, depending the size of the picture1 control
   
    ValueY1 = (FirstByte * Picture1.ScaleHeight) / 255
    ValueY2 = (SecondByte * Picture1.ScaleHeight) / 255
End Sub

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Is that ok?

Not sure this is going to do you any good but it does display waveform however I noticed it takes a long time to load certain wave files. It's similar to the one VBClassicRocks posted except it plays the wave file and shows the waveform as it plays instead of displaying it all at one time

@VBClassicRocks

The exe works fine but the source code is all screwed up. I get Object variable or With block not set on below and there are many other places where that error occurs (too many to post)

I realize you just posted a link to the source code at vbAc.. so maybe you have no knowledge of the code

Code:

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Private Sub setScroll()
Dim lMax As Long

  m_bSetting = True

  If (m_lZoom <= 1) Then
      m_lSampleStep = 1
      m_lPixelStep = Abs(m_lZoom)
      m_lSamplePerPixelStep = 1
      lMax = m_cWAVRead.AudioLength
  '
  '
  '

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Code:

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Private Sub setScroll()
Dim lMax As Long

  m_bSetting = True

  If (m_lZoom <= 1) Then
      m_lSampleStep = 1
      m_lPixelStep = Abs(m_lZoom)
      m_lSamplePerPixelStep = 1
'      lMax = m_cWAVRead.AudioLength
  Else
      m_lSamplePerPixelStep = m_lZoom
      m_lSampleStep = m_lSamplePerPixelStep \ 32
      If (m_lSampleStep < 1) Then
        m_lSampleStep = 1
      End If
      m_lPixelStep = 1
      Debug.Print m_lSamplePerPixelStep, (m_cWAVRead.AudioLength \ m_lSamplePerPixelStep), UserControl.ScaleWidth
      lMax = (m_cWAVRead.AudioLength \ m_lSamplePerPixelStep) - UserControl.ScaleWidth
  End If

  If lMax <= 0 Then
      m_cScroll.Value(efsHorizontal) = 0
      m_cScroll.Visible(efsHorizontal) = False
  Else
      m_cScroll.SmallChange(efsHorizontal) = UserControl.ScaleWidth \ 32
      m_cScroll.LargeChange(efsHorizontal) = UserControl.ScaleWidth
      m_cScroll.Max(efsHorizontal) = lMax
      m_cScroll.Visible(efsHorizontal) = True
  End If

  '
  '

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Quote:

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Originally Posted by jmsrickland

Not sure this is going to do you any good but it does display waveform however I noticed it takes a long time to load certain wave files. It's similar to the one VBClassicRocks posted except it plays the wave file and shows the waveform as it plays instead of displaying it all at one time

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Yes, I'm testing the code and it's very helpful. Thanks!