The aim of this article is to show an efficient algorithm of signal processing which will allow one to have a competent system of sound fingerprinting and signal recognition. I'll try to come with some explanations of the article's algorithm, and also speak about how it can be implemented using the C# programming language. Additionally, I'll try to cover topics of digital signal processing that are used in the algorithm, thus you'll be able to get a clearer image of the entire system. And as a proof of concept, I'll show you how to develop a simple WPF MVVM application.
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// Sound Fingerprinting framework
// git://github.com/AddictedCS/soundfingerprinting.git
// Code license: CPOL v.1.02
// ciumac.sergiu@gmail.com
using System;
using Soundfingerprinting.Fingerprinting.FFT;
namespace Soundfingerprinting.Fingerprinting.Windows
{
/// <summary>
/// Hanning window function
/// </summary>
public class HanningWindow : IWindowFunction
{
#region IWindowFunction Members
/// <summary>
/// Window the outer space by Hanning window function
/// </summary>
/// <param name = "outerspace">Array to be windowed</param>
/// <param name = "length">Window length</param>
/// <remarks>
/// For additional explanation please consult http://en.wikipedia.org/wiki/Hann_function
/// </remarks>
public void WindowInPlace(float[] outerspace, int length)
{
#if SAFE
if (outerspace == null)
throw new ArgumentNullException("outerspace");
if (outerspace.Length <= 1)
throw new ArgumentException("Length of outer space parameter should be bigger than 1, otherwise division by zero will occur");
if (outerspace.Length < length)
throw new ArgumentException("Length of the outer space parameter should be bigger of equal to window length");
#endif
//Hanning window of the whole signal
for (int i = 0, n = length; i < n; i++)
outerspace[i] *= (float) (0.5*(1 - Math.Cos(2*Math.PI*i/(n - 1))));
}
/// <summary>
/// Window the outer space by Hanning window function
/// </summary>
/// <param name = "outerspace">Array to be windowed</param>
/// <param name = "length">Window length</param>
/// <remarks>
/// For additional explanation please consult http://en.wikipedia.org/wiki/Hann_function
/// </remarks>
public void WindowInPlace(Complex[] outerspace, int length)
{
#if SAFE
if (outerspace == null)
throw new ArgumentNullException("outerspace");
if (outerspace.Length <= 1)
throw new ArgumentException("Length of outer space parameter should be bigger than 1, otherwise division by zero will occur");
if (outerspace.Length < length)
throw new ArgumentException("Length of the outer space parameter should be bigger of equal to window length");
#endif
//Hanning window of the whole signal
for (int i = 0, n = length; i < n; i++)
outerspace[i] *= 0.5*(1 - Math.Cos(2*Math.PI*i/(n - 1)));
}
/// <summary>
/// Gets the corresponding window function
/// </summary>
/// <param name = "length">Length of the window</param>
/// <returns>Window function</returns>
public double[] GetWindow(int length)
{
double[] array = new double[length];
//Hanning window of the whole signal
for (int i = 0; i < length; i++)
array[i] = 0.5*(1 - Math.Cos(2*Math.PI*i/(length - 1)));
return array;
}
#endregion
}
}
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Interested in computer science, math, research, and everything that relates to innovation. Fan of agnostic programming, don't mind developing under any platform/framework if it explores interesting topics. In search of a better programming paradigm.
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