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SoundPlayer: Implement the Fast Fourier Transform algorithm

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Cesar Torres 2021-03-21 12:48:31 +01:00 committed by Andreas Kling
parent f4f5a1c0e7
commit 809f1d984d
Notes: sideshowbarker 2024-07-18 21:03:18 +09:00 
Author: https://github.com/ngc6302h
Commit: https://github.com/SerenityOS/serenity/commit/809f1d984d6
Pull-request: https://github.com/SerenityOS/serenity/pull/5878
Reviewed-by: https://github.com/Dexesttp
Reviewed-by: https://github.com/RealKC
Reviewed-by: https://github.com/alimpfard
2 changed files with 110 additions and 0 deletions
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78
Userland/Applications/SoundPlayer/AudioAlgorithms.cpp Normal file
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/*
* Copyright (c) 2021, Cesar Torres <shortanemoia@protonmail.com>
* All rights reserved.
*
* Redistribution and use in source and binary forms, with or without
* modification, are permitted provided that the following conditions are met:
*
* 1. Redistributions of source code must retain the above copyright notice, this
* list of conditions and the following disclaimer.
*
* 2. Redistributions in binary form must reproduce the above copyright notice,
* this list of conditions and the following disclaimer in the documentation
* and/or other materials provided with the distribution.
*
* THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
* AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
* IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
* DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT HOLDER OR CONTRIBUTORS BE LIABLE
* FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
* DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR
* SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER
* CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY,
* OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
* OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
*/
#include "AudioAlgorithms.h"
#include <AK/Complex.h>
#include <math.h>
// This function uses the input vector as output too. therefore, if you wish to
// leave it intact, pass a copy to this function
//
// The sampling frequency must be more than twice the frequency to resolve.
// The sample window must be at least large enough to reflect the periodicity
// of the smallest frequency to be resolved.
//
// For example, to resolve a 10 KHz and a 2 Hz sine waves we need at least
// a samplerate of 20 KHz and a window of 0.5 seconds
//
// If invert is true, this function computes the inverse discrete fourier transform.
//
// The data vector must be a power of 2
// Adapted from https://cp-algorithms.com/algebra/fft.html
void fft(Vector<Complex<double>>& sample_data, bool invert)
{
int n = sample_data.size();
auto data = sample_data.data();
for (int i = 1, j = 0; i < n; i++) {
int bit = n >> 1;
for (; j & bit; bit >>= 1)
j ^= bit;
j ^= bit;
if (i < j)
swap(data[i], data[j]);
}
for (int len = 2; len <= n; len <<= 1) {
double ang = 2 * M_PI / len * (invert ? -1 : 1);
Complex<double> wlen(cos(ang), sin(ang));
for (int i = 0; i < n; i += len) {
Complex<double> w = { 1., 0. };
for (int j = 0; j < len / 2; j++) {
Complex<double> u = data[i + j], v = data[i + j + len / 2] * w;
data[i + j] = u + v;
data[i + j + len / 2] = u - v;
w *= wlen;
}
}
}
if (invert) {
for (int i = 0; i < n; i++)
data[i] /= n;
}
}

32
Userland/Applications/SoundPlayer/AudioAlgorithms.h Normal file
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/*
* Copyright (c) 2021, Cesar Torres <shortanemoia@protonmail.com>
* All rights reserved.
*
* Redistribution and use in source and binary forms, with or without
* modification, are permitted provided that the following conditions are met:
*
* 1. Redistributions of source code must retain the above copyright notice, this
* list of conditions and the following disclaimer.
*
* 2. Redistributions in binary form must reproduce the above copyright notice,
* this list of conditions and the following disclaimer in the documentation
* and/or other materials provided with the distribution.
*
* THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
* AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
* IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
* DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT HOLDER OR CONTRIBUTORS BE LIABLE
* FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
* DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR
* SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER
* CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY,
* OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
* OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
*/
#pragma once
#include <AK/Complex.h>
#include <AK/Vector.h>
void fft(Vector<Complex<double>>& sample_data, bool invert);