everything

.gitignore

@@ -0,0 +1,7 @@
+out
+bin
+.vs
+__pycache__
+
+*.json
+res

CMakeLists.txt

@@ -0,0 +1,14 @@
+cmake_minimum_required(VERSION 3.14)
+set(CMAKE_CXX_STANDARD 17)
+set(CMAKE_CXX_STANDARD_REQUIRED ON)
+
+project(spectralyze)
+
+add_executable(spectralyze
+	"src/main.cpp"
+ "src/FFT.hpp")
+
+target_include_directories(spectralyze PRIVATE
+	"lib/AudioFile"
+	"lib/json"
+)

src/FFT.hpp

@@ -0,0 +1,75 @@
+#pragma once
+#define _USE_MATH_DEFINES
+#include <math.h>
+#include <vector>
+#include <complex>
+
+#define TWO_PI (double)6.28318530718f
+#define POW_OF_TWO(x) (x && !(x & (x - 1)))
+
+using namespace std::complex_literals;
+
+std::vector<std::complex<double>> radix2dit(const std::vector<double>::const_iterator& begin, size_t N, size_t s)
+{
+	std::vector<std::complex<double>> output(N);
+	if (N == 1) 
+	{
+		output[0] = *begin;
+	}
+	else
+	{
+		size_t halfN = N >> 1;
+		std::vector<std::complex<double>> first = radix2dit(begin, halfN, s << 1);
+		std::vector<std::complex<double>> second = radix2dit(begin + s, halfN, s << 1);
+
+		/*if (s == 1) {
+			std::future<std::vector<std::complex<double>>> firstFuture = std::async(&radix2dit, begin, halfN, s << 1);
+			std::future<std::vector<std::complex<double>>> secondFuture = std::async(&radix2dit, begin + s, halfN, s << 1);
+
+			first = firstFuture.get();
+			second = secondFuture.get();
+		}
+		else {
+			first = radix2dit(begin, halfN, s << 1);
+			second = radix2dit(begin + 1, halfN, s << 1);
+		}*/
+
+		std::complex<double> coeff = -M_PI * 1.0i / (double)halfN;
+
+		for (int k = 0; k < N >> 1; k++)
+		{
+			std::complex<double> p = first[k];
+			std::complex<double> q = std::exp(coeff * (double)k) * second[k];
+
+			output[k] = p + q;
+			output[halfN + k] = p - q;
+		}
+	}
+
+	return output;
+}
+
+std::vector<std::pair<double, double>> FFT(std::vector<double> signal, size_t sampleRate)
+{
+	size_t N = signal.size();
+	while (!POW_OF_TWO(N))
+	{
+		// Pad with zeros
+		signal.push_back(0.0f);
+		N++;
+	}
+
+	std::vector<std::complex<double>> spectrum = radix2dit(signal.cbegin(), N, 1);
+	double freqRes = (double)sampleRate / (double)N;
+	double nyquistLimit = (double)sampleRate / 2.0f;
+
+	std::vector<std::pair<double, double>> output;
+	double freq = 0.0f;
+	for (int k = 0; freq < nyquistLimit; k++) 
+	{
+		output.push_back(std::make_pair(freq, 2.0f * std::abs(spectrum[k]) / (double)N));
+		freq += freqRes;
+	}
+
+	return output;
+}

src/main.cpp

@@ -0,0 +1,53 @@
+#include <iostream>
+#include <fstream>
+#include <iomanip>
+#include <filesystem>
+
+#include "AudioFile.h"
+#include "json.hpp"
+#include "FFT.hpp"
+
+void PrintUsage();
+
+int main(int argc, char** argv)
+{
+	if (argc < 2) {
+		PrintUsage();
+		return 1;
+	}
+
+	int numFiles = argc - 1;
+	for (int i = 1; i < argc; i++) {
+		AudioFile<double> audioFile;
+		audioFile.load(argv[i]);
+
+		std::string filename = std::filesystem::path(argv[i]).filename().string();
+
+		int sampleRate = audioFile.getSampleRate();
+		int numChannels = audioFile.getNumChannels();
+
+		nlohmann::json output;
+		for (int c = 1; c <= numChannels; c++) {
+			std::cout << "\rAnalyzing " << filename << "... Channel " << c << "/" << numChannels << "            ";
+			std::vector<std::pair<double, double>> spectrum = FFT(audioFile.samples[c-1], sampleRate);
+
+			std::string chName = "channel_" + std::to_string(c);
+			output[chName] = nlohmann::json::array();
+			for (const std::pair<double, double>& pair : spectrum) {
+				output[chName].push_back({ {"freq", pair.first}, {"mag", pair.second } });
+			}
+		}
+
+		std::ofstream ofs(std::filesystem::path(argv[i]).replace_extension("json"));
+		ofs << std::setw(4) << output << std::endl;
+		ofs.close();
+		std::cout << "\rAnalyzing " << filename << "... Done!        " << std::endl;
+	}
+
+	return 0;
+}
+
+void PrintUsage()
+{
+	std::cerr << "Usage: spectralyze file1 [file2...]" << std::endl;
+}