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I’m looking for some guidance in how I can create a notch filter of custom parameters and then apply it to a stream or sound, what I want to do in the long term is to notch at a given frequency, and move the frequency up and down.

I’m totally new to audio work, so I’m not really sure what i’m doing. Any guidance would be much appreciated. So far I’ve just played with FMOD to playback sounds and work on an interface for the tool I’m trying to write, but I’m completely unsure as to how I make a custom DSP filter, I’ve played with the flange, echo, chorus FMOD dsp’s to try them out and I think that I’ve got the stick by the right end at least.

-Arch

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the ‘dsp_custom’ shows you how to use your own DSP code.
You can then simply add it to the global mix (System::addDSP) or a single channel (Channel::addDSP) or a group of channels (ChannelGroup::addDSP)

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I’m using VB.net (2005) and I’m at the point of trying to get the callback to work for the .createDSP()


    dsp = New FMOD.DSP
    desc = New FMOD.DSP_DESCRIPTION

    desc.channels = 0
    desc.name = "Custom DSP"
    desc.read = New FMOD.DSP_READCALLBACK(AddressOf CUSTOM_CALLBACK1)


    result = fmodsystem.createDSP(desc, dsp)
    If result <> FMOD.RESULT.OK Then
        MsgBox("DSP Create - FAILED")
    Else
        dsp.setBypass(False)
        dsp.setActive(True)

End If

which loads the callback:


Public Function CUSTOM_CALLBACK1(ByRef dsp_state As FMOD.DSP_STATE, ByVal inbuffer As System.IntPtr, ByVal outbuffer As System.IntPtr, ByVal length As UInteger, ByVal inchannels As Integer, ByVal outchannels As Integer) As FMOD.RESULT
    MsgBox("CALL_BACK1")
    Return FMOD.RESULT.OK

End Function

Problem is that when I call .createDSP I’m getting an Error: 34, Invalid Parameter. I’m close to getting it to work I think, (i hope)

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[quote="brett"]the ‘dsp_custom’ shows you how to use your own DSP code.[/quote]

dsp_custom?? I’m not sure I’ve seen that in my searching, where can I find that? Is it one of the tutorials? or in the CHM help file?

The biggest issue at this point is getting a working callback, once thats done I guess I can move on to the filter itself, as you can tell Audio stuff is completely not my field.

anyhow, thanks for the quick and helpful response, much appreciated.

-Arch

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My advice to anyone using FMOD and VB.net, dont bother, C# is not too much more difficult, and VB6 I found unbelievably difficult to use CALLBACKS, problem solved by moving to C#

Now investigating DSP filter theory in order to make the best of my time writing the filters themselves.

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as the language was not specified as the forum notes say to do, I assumed c++, that is where the dsp_custom example is.

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True enough, thanks

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