How to find difference between two fast fourier transform (fft) as presantage (%) in C# or in VB.NET

Question

1.00/5 (2 votes)

See more:

how to find difference between two Fast Fourier transform (fft) as presantage(%)

in c# or in vb.net

What I have tried:

find difference between two Fast Fourier transform (fft)

it is an array of single so i want compare two result of two .wav sound and know the different between it in %

Posted 10-Jun-17 13:04pm

giant18

Updated 11-Jun-20 22:09pm

v2

Add a Solution

Comments

Patrice T 10-Jun-17 19:41pm

find the maths

Ralf Meier 11-Jun-17 14:47pm

And ... what have you tried ...?
What is the result of your FFT ? An Array of Single ? A Curve (which is represented by an Array of Single) ?
If you want to get help you should be much more specific ... !!!

giant18 11-Jun-17 21:48pm

an array of single so i want compare two result of two .wav sound and know the different between it in %

Ralf Meier 12-Jun-17 3:15am

Have you tried to subtract the Contents from both Array-Elemets and build a new Array which only contains the difference ?
This could be the first step to get an Algorhytm ...

giant18 12-Jun-17 17:06pm

yes i try it but i did not find good result

Ralf Meier 13-Jun-17 2:33am

OK ... then you should improve this question with your code, which shows what you have tried and how you have done it and perhaps we find together a Solution for you ...

giant18 13-Jun-17 17:43pm

comparing 2 audio files result fft in c# or in vb.net i have result fft for each audio in double array i want to know from the result of fft the percentage of similarity or differences between two audio

Dim fft1new As Double() = FftAlgorithm.Calculate(GetSamplesForMonoWav("C:\Users\e1.wav", h2)) Dim fft2new As Double() = FftAlgorithm.Calculate(GetSamplesForMonoWav("C:\Users\e2.wav", h2))

Ralf Meier 14-Jun-17 5:24am

OK ... that's the code which shows how you get the FFT-Data into your System.
Each of those Array-Elements should now represent a frequency and it's amount inside the audio-signal.
Now you shoud build a 3rd Array with the size of the greatest Source-Array which contents the differents from both Source-Array's.
This difference could be build with a loop.
If both Source-Array's have the same FFT-Result your Result-Array should have mostly the content of '0'. In this case you have a good match. In other cases you should find your own rating.

I would suggest you give it a try ...

giant18 14-Jun-17 13:55pm

i try this code but dont work well

Dim f1 As Double = Nothing
For Each f As Double In fft1new
f1 += f
Next

Dim f2 As Double = Nothing
For Each f As Double In fft2new
f2 += f
Next

Dim f5 As Double
Dim f4 As Double = (((f2 - f1) / f2) * 100).ToString("#0.0")
If f1 = f2 Then
f5 = 0
Else

If f1 > f2 Then
f5 = ((f1 / f2)).ToString("#0.00")
Else
f5 = ((f2 / f1)).ToString("#0.00")
End If
End If

MsgBox(f5)

Ralf Meier 14-Jun-17 16:34pm

That has NOTHING in common with the description I suggested to you ...
So ... if your code "don't work well" - why don't you try my sugesstion ?

giant18 15-Jun-17 11:55am

i dont understand can you give me example

Ralf Meier 16-Jun-17 6:16am

I mean it like this :

Dim FFTResult(1) As Double

Private Sub FFT_Test()
Dim maxArray = Math.Max(FFT1new.Count, FFT2new.Count) - 1
ReDim FFTResult(maxArray)
Dim w1, w2 As Double

For i As Integer = 0 To maxArray
w1 = 0
If i < FFT1new.Count Then w1 = FFT1new(i)
w2 = 0
If i < FFT2new.Count Then w2 = FFT2new(i)

FFTResult(i) = Math.Abs(w1 - w2)
Next
End Sub

Now you should display the FFTResult-Array into a Chart to see what you have.
After this (perhaps) you could decide how to go further.

giant18 17-Jun-17 21:18pm

i try it but it not give me something that i want thank you for help

Ralf Meier 19-Jun-17 2:15am

As I described before :
- I don't know how the Contents of your Data-Arrays look like.
- so I don't know how the possible Result could look like.
- so it's impossible for me to decide which criteria must be fullfilled for "match" or "not match"
But if you do it like descibed by me YOU could ...

1 solution

Add a Solution

Add your solution here

Treat my content as plain text, not as HTML

Preview 0

…

Existing Members

Sign in to your account

...or Join us

Download, Vote, Comment, Publish.

Your Email
Password
Forgot your password?

Your Email
This email is in use. Do you need your password?
Optional Password

I have read and agree to the Terms of Service and Privacy Policy
Please subscribe me to the CodeProject newsletters

When answering a question please:

Read the question carefully.
Understand that English isn't everyone's first language so be lenient of bad spelling and grammar.
If a question is poorly phrased then either ask for clarification, ignore it, or edit the question and fix the problem. Insults are not welcome.
Don't tell someone to read the manual. Chances are they have and don't get it. Provide an answer or move on to the next question.

Let's work to help developers, not make them feel stupid.

This content, along with any associated source code and files, is licensed under The Code Project Open License (CPOL)

Anks007 · Answer 1 · 2020-06-11T22:09:00

Hii giant18,

I wanted to do the same and for that I used following method.
First array of data is X and second array of data is Y. I performed mean square error method on it, as I am working in C++.

C++

double meanSquareError(double *X,double *Y,uint16_t sizeOfArray)
{
	double sumOfSquare=0;

	for(uint16_t i=0;i<(Tempsamples/2);i++)
	{
		sumOfSquare = sumOfSquare + pow((X[i]-Y[i]),2);
	}

	return sqrt(sumOfSquare);
}

I am getting a big number for small difference, I applied this on FFT results.
If you have any solution better than me then please share it with me.

You can visit this link for more http://biomedicalsignalandimage.blogspot.com/2016/03/the-method-of-comparing-two-audio-files.html

Thank you