# dsp.getParameterData return ERR\_INVALID\_PARAM
**URL:** https://qa.fmod.com/t/dsp-getparameterdata-return-err-invalid-param/13376
**Category:** FMOD Engine
**Created:** [August 24, 2017, 12:49am UTC](https://qa.fmod.com/t/dsp-getparameterdata-return-err-invalid-param/13376 "2017-08-24T00:49:23Z")
**Posts on this page:** 5
**Page:** 1
### Author:  [@r\_emak\_e](https://qa.fmod.com/u/r_emak_e)
#### Post date: [August 24, 2017, 12:49am UTC](https://qa.fmod.com/t/dsp-getparameterdata-return-err-invalid-param/13376/1 "2017-08-24T00:49:23Z")
```
using System;
using System.Collections.Generic;
using System.ComponentModel;
using System.Data;
using System.Drawing;
using System.Linq;
using System.Text;
using System.Threading.Tasks;
using System.Windows.Forms;
using AudioSpectrumStudy.Fmod;
using System.Runtime.InteropServices;
namespace AudioSpectrumStudy
{
public partial class Form1 : Form
{
Fmod.System system;
Fmod.Channel channel;
Fmod.Sound sound;
Fmod.ChannelGroup channelGroup;
Fmod.DSP dsp;
Fmod.DSP_DESCRIPTION description;
Timer timer;
public Form1()
{
InitializeComponent();
textBox1.MouseDoubleClick += textBox1_MouseDoubleClick;
system = new Fmod.System(IntPtr.Zero);
system.init(32, INITFLAGS.NORMAL, IntPtr.Zero);
channel = new Channel(IntPtr.Zero);
sound = new Sound(IntPtr.Zero);
sound.setMusicSpeed(1.0f);
sound.setMode(MODE._2D);
description = new DSP_DESCRIPTION();
system.createDSP(ref description, out dsp);
channel.getChannelGroup(out channelGroup);
timer = new Timer();
timer.Tick += timer_Tick;
}
void textBox1_MouseDoubleClick(object sender, MouseEventArgs e)
{
OpenFileDialog ofd = new OpenFileDialog();
ofd.Filter = "File|*.*";
ofd.ShowDialog();
textBox1.Text = ofd.FileName;
}
void timer_Tick(object sender, EventArgs e)
{
system.update();
UpdateSpectrum();
progressBar1.Value = (int)_spectrum[0] > 100 ? 100 : (int)_spectrum[0];
}
private void Form1_Load(object sender, EventArgs e)
{
}
private const int SPECTRUM_SIZE = 512;
private float[][] _spectrumInfo;
public float[] _spectrum;
private void UpdateSpectrum()
{
if (_spectrum == null || _spectrumInfo == null)
{
if(_spectrum == null)
_spectrum = new float[SPECTRUM_SIZE];
if (_spectrumInfo == null)
{
_spectrumInfo = new float[2][];
_spectrumInfo[0] = new float[SPECTRUM_SIZE];
_spectrumInfo[1] = new float[SPECTRUM_SIZE];
}
}
System.IntPtr data = IntPtr.Zero;
uint length = 0;
dsp.getParameterData(3, out data, out length);
//Fmod.DSP_PARAMETER_FFT spectrumBuffer = new DSP_PARAMETER_FFT();
var spectrumBuffer = (Fmod.DSP_PARAMETER_FFT)Marshal.PtrToStructure(data, typeof(Fmod.DSP_PARAMETER_FFT));
_spectrumInfo = spectrumBuffer.spectrum;
for (int i = 0; i < SPECTRUM_SIZE; i++)
{
_spectrum[i] = (_spectrumInfo[0][i] + _spectrumInfo[1][i]) / 2f;
}
}
private void button1_Click(object sender, EventArgs e)
{
system.createSound(textBox1.Text, MODE._2D, out sound);
system.playSound(sound, channelGroup, false, out channel);
system.playDSP(dsp, channelGroup, false, out channel);
system.release();
system.close();
timer.Start();
}
}
}
```
this is my code
var spectrumBuffer = (Fmod.DSP\_PARAMETER\_FFT)Marshal.PtrToStructure(data, typeof(Fmod.DSP\_PARAMETER\_FFT));
this code raise exception ‘ArgumentNullException’ so, I traced with debug why the exception raise.
I found dsp.getParameterData() method was returned ‘ERR\_INVALID\_PARAM’
why working like that?
---
### Author:  [@cameron-fmod](https://qa.fmod.com/u/cameron-fmod)
#### Post date: [August 24, 2017, 4:31am UTC](https://qa.fmod.com/t/dsp-getparameterdata-return-err-invalid-param/13376/2 "2017-08-24T04:31:02Z")
It looks like you aren’t adding your dsp to anything.
You will need to use Channel/ChannelGroup::[addDSP()](https://www.fmod.org/docs/content/generated/FMOD_Channel_AddDSP.html).
Also a good idea to make sure the sound is playing before using getParameterData, otherwise you will just get back meaningless data.
---
### Author:  [@r\_emak\_e](https://qa.fmod.com/u/r_emak_e)
#### Post date: [August 24, 2017, 4:48am UTC](https://qa.fmod.com/t/dsp-getparameterdata-return-err-invalid-param/13376/3 "2017-08-24T04:48:29Z")
> [@](#):
>
> It looks like you aren’t adding your dsp to anything.
> You will need to use Channel/ChannelGroup::[addDSP()](https://www.fmod.org/docs/content/generated/FMOD_Channel_AddDSP.html).
>
> Also a good idea to make sure the sound is playing before using getParameterData, otherwise you will just get back meaningless data.
truly music was not played…
playSound Method also returned ERR\_INVALID\_PARAM too.
I’m so confused about use this api now 😑
---
### Author:  [@cameron-fmod](https://qa.fmod.com/u/cameron-fmod)
#### Post date: [August 24, 2017, 5:47am UTC](https://qa.fmod.com/t/dsp-getparameterdata-return-err-invalid-param/13376/4 "2017-08-24T05:47:42Z")
The channelgroup may not be valid, you are calling getChannelGroup on the channel before it has been assigned (in the playSound method). You don’t have to use a channelgroup when creating a sound, you can pass in null or even the master group using System::getMasterChannelGroup.
Also when creating the dsp, you need to specify the description going in to create it. Otherwise you can use createDSPByType(FMOD.DSP\_TYPE.FFT, out dsp).
---
### Author:  [@r\_emak\_e](https://qa.fmod.com/u/r_emak_e)
#### Post date: [August 24, 2017, 6:55am UTC](https://qa.fmod.com/t/dsp-getparameterdata-return-err-invalid-param/13376/5 "2017-08-24T06:55:30Z")
thx at all, I turned the other solution.
now have new issue
private void FmodERRCheck(Fmod.RESULT result){
if (result != RESULT.OK)
{
MessageBox.Show(Fmod.Error.String(result));
}
}
```
private void InitFmodSystems()
{
Fmod.Factory.System_Create(out system);
system = new Fmod.System(IntPtr.Zero);
system.init(3, INITFLAGS.NORMAL, IntPtr.Zero);
channelGroup = new ChannelGroup(IntPtr.Zero);
FmodERRCheck(system.createChannelGroup("", out channelGroup));
}
```
I fixed my code right that
FmodERRCheck(system.createChannelGroup("", out channelGroup));
this line message to me ERR\_INVALID\_PARAM again.
welp. I think that could be working 😕