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tckmntckmn
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minimal working tuner
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‎.gitignore

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build
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.gradle

‎LICENSE

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‎build.gradle

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buildscript {
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repositories {
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google()
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jcenter()
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}
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dependencies {
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classpath 'com.android.tools.build:gradle:3.4.0'
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}
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}
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apply plugin: 'com.android.application'
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repositories {
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mavenCentral()
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maven {
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url "https://maven.google.com"
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}
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}
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dependencies {
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}
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android {
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compileSdkVersion 28
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buildToolsVersion "28.0.2"
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lintOptions {
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disable "GoogleAppIndexingWarning"
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}
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defaultConfig {
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applicationId "mn.tck.semitone"
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}
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}
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gradle.projectsEvaluated {
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tasks.withType(JavaCompile) {
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options.compilerArgs << "-Xlint:unchecked" << "-Xlint:deprecation"
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}
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}

‎src/main/AndroidManifest.xml

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<manifest xmlns:android="http://schemas.android.com/apk/res/android"
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package="mn.tck.semitone">
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<uses-permission android:name="android.permission.RECORD_AUDIO" />
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<uses-sdk android:minSdkVersion="16" />
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<application android:label="@string/app_name"
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android:allowBackup="true">
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<activity android:name=".MainActivity"
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android:label="@string/app_name">
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<intent-filter>
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<action android:name="android.intent.action.MAIN" />
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<category android:name="android.intent.category.LAUNCHER" />
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</intent-filter>
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</activity>
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</application>
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</manifest>

‎src/main/java/mn.tck.semitone/CentErrorView.java

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/*
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* Semitone - tuner, metronome, and piano for Android
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* Copyright (C) 2019 Andy Tockman <[email protected]>
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*
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* This program is free software: you can redistribute it and/or modify
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* it under the terms of the GNU General Public License as published by
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* the Free Software Foundation, either version 3 of the License, or
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* (at your option) any later version.
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*
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* This program is distributed in the hope that it will be useful,
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* but WITHOUT ANY WARRANTY; without even the implied warranty of
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* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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* GNU General Public License for more details.
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*
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* You should have received a copy of the GNU General Public License
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* along with this program. If not, see <http://www.gnu.org/licenses/>.
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*/
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package mn.tck.semitone;
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import android.app.*;
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import android.content.*;
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import android.graphics.*;
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import android.os.*;
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import android.util.*;
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import android.view.*;
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import android.widget.*;
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public class CentErrorView extends TextView {
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private Paint centerPaint, linePaint;
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double error;
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public CentErrorView(Context context, AttributeSet attrs) {
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super(context, attrs);
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centerPaint = new Paint();
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centerPaint.setColor(Color.WHITE);
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centerPaint.setStrokeWidth(1);
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linePaint = new Paint();
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linePaint.setColor(Color.RED);
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linePaint.setStrokeWidth(2);
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error = 0;
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}
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public void setError(double error) {
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this.error = error;
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setText(String.format("%+.2f cents", error*100));
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}
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@Override protected void onDraw(Canvas canvas) {
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super.onDraw(canvas);
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int width = getWidth(), height = getHeight(), middle = width / 2;
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// draw middle indicator
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canvas.drawLine(middle, 0, middle, height/4, centerPaint);
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canvas.drawLine(middle, height*3/4, middle, height, centerPaint);
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// draw error position
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int xpos = middle + (int)(error*width);
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canvas.drawLine(xpos, 0, xpos, height, linePaint);
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}
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}

‎src/main/java/mn.tck.semitone/DSP.java

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/*
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* Semitone - tuner, metronome, and piano for Android
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* Copyright (C) 2019 Andy Tockman <[email protected]>
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*
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* This program is free software: you can redistribute it and/or modify
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* it under the terms of the GNU General Public License as published by
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* the Free Software Foundation, either version 3 of the License, or
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* (at your option) any later version.
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*
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* This program is distributed in the hope that it will be useful,
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* but WITHOUT ANY WARRANTY; without even the implied warranty of
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* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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* GNU General Public License for more details.
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*
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* You should have received a copy of the GNU General Public License
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* along with this program. If not, see <http://www.gnu.org/licenses/>.
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*/
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package mn.tck.semitone;
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public class DSP {
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public static int fftlen, fftpow;
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static double[] cos;
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static double[] sin;
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public static void init(int bufsize) {
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fftpow = 31 - Integer.numberOfLeadingZeros(bufsize);
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fftlen = 1 << fftpow;
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cos = new double[fftlen/2];
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sin = new double[fftlen/2];
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for (int i = 0; i < fftlen/2; ++i) {
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cos[i] = Math.cos(-2*Math.PI*i/fftlen);
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sin[i] = Math.sin(-2*Math.PI*i/fftlen);
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}
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}
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// in-place Cooley-Tukey algorithm
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private static void fft(double[] re, double[] im) {
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// bit reversal
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{
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int j = 0;
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int n2 = fftlen/2;
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for (int i = 1; i < fftlen-1; ++i) {
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int n1 = n2;
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while (j >= n1) {
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j -= n1;
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n1 /= 2;
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}
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j += n1;
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double tmp;
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if (i < j) {
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tmp = re[i]; re[i] = re[j]; re[j] = tmp;
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tmp = im[i]; im[i] = im[j]; im[j] = tmp;
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}
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}
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}
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int n1 = 0, n2 = 1;
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for (int i = 0; i < fftpow; ++i) {
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n1 = n2;
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n2 *= 2;
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int a = 0;
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for (int j = 0; j < n1; ++j) {
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for (int k = j; k < fftlen; k += n2) {
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double tre = cos[a] * re[k+n1] - sin[a] * im[k+n1],
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tim = sin[a] * re[k+n1] + cos[a] * im[k+n1];
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re[k+n1] = re[k] - tre;
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im[k+n1] = im[k] - tim;
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re[k] += tre;
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im[k] += tim;
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}
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a += 1 << (fftpow - i - 1);
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}
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}
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}
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// in-place autocorrelation (scaled by N, but that doesn't matter for us)
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private static void autocorr(double[] are) {
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double[] aim = new double[fftlen];
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fft(are, aim);
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for (int i = 0; i < fftlen; ++i) {
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// corr(a, a) = ifft(fft(a) * conj(fft(a)))
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are[i] = are[i] * are[i] + aim[i] * aim[i];
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aim[i] = 0;
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}
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fft(aim, are); // inverse fft
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}
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// get frequency from mic data (buf must have length fftlen)
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public static double freq(double[] buf, int sr) {
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// TODO check buf length
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// TODO clone buf if necessary
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autocorr(buf);
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// look for the maximum value after the first local minimum
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// (only look halfway through cause it's symmetric)
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boolean looking = false;
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double maxval = 0;
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int j = -1; // maxidx
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for (int i = 0; i < fftlen/2; ++i) {
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if (looking) {
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double weighted = buf[i] * 1; // naive weighting
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if (weighted > maxval) {
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maxval = weighted;
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j = i;
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}
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} else {
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// looking = buf[i] < buf[i+1];
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looking = buf[i] < 0;
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}
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}
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// TODO handle this better
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if (j == -1) return 440;
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// quadratic interpolation
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double interp = 0.5 * (buf[j-1] - buf[j+1]) / (buf[j-1] - 2*buf[j] + buf[j+1]);
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return (double)sr / (j + interp);
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}
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}

‎src/main/java/mn.tck.semitone/MainActivity.java

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/*
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* Semitone - tuner, metronome, and piano for Android
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* Copyright (C) 2019 Andy Tockman <[email protected]>
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*
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* This program is free software: you can redistribute it and/or modify
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* it under the terms of the GNU General Public License as published by
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* the Free Software Foundation, either version 3 of the License, or
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* (at your option) any later version.
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*
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* This program is distributed in the hope that it will be useful,
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* but WITHOUT ANY WARRANTY; without even the implied warranty of
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* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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* GNU General Public License for more details.
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*
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* You should have received a copy of the GNU General Public License
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* along with this program. If not, see <http://www.gnu.org/licenses/>.
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*/
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package mn.tck.semitone;
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import android.app.*;
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import android.content.*;
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import android.graphics.*;
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import android.os.*;
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import android.util.*;
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import android.view.*;
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import android.widget.*;
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import android.media.AudioFormat;
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import android.media.AudioRecord;
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import android.media.MediaRecorder.AudioSource;
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import java.util.Arrays;
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public class MainActivity extends Activity {
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final static String[] notenames = {"A", "A#", "B", "C", "C#", "D", "D#", "E", "F", "F#", "G", "G#"};
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final static int SAMPLE_RATE = 44100;
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final static int HIST_SIZE = 16;
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static int bufsize;
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static AudioRecord ar;
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static DSP dsp;
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TextView notename;
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CentErrorView centerror;
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@Override protected void onCreate(Bundle state) {
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super.onCreate(state);
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requestWindowFeature(Window.FEATURE_NO_TITLE);
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setContentView(R.layout.activity_main);
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notename = (TextView) findViewById(R.id.notename);
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notename.getViewTreeObserver().addOnGlobalLayoutListener(new ViewTreeObserver.OnGlobalLayoutListener() {
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@Override public void onGlobalLayout() {
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notename.getViewTreeObserver().removeOnGlobalLayoutListener(this);
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notename.setTextSize(TypedValue.COMPLEX_UNIT_PX,
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Util.maxTextSize("G#000", notename.getWidth()));
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}
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});
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centerror = (CentErrorView) findViewById(R.id.centerror);
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bufsize = AudioRecord.getMinBufferSize(SAMPLE_RATE,
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AudioFormat.CHANNEL_IN_MONO, AudioFormat.ENCODING_PCM_16BIT);
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ar = new AudioRecord(AudioSource.MIC, SAMPLE_RATE,
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AudioFormat.CHANNEL_IN_MONO, AudioFormat.ENCODING_PCM_16BIT,
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bufsize);
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ar.startRecording();
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DSP.init(bufsize);
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new Thread(new TunerThread()).start();
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}
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class TunerThread implements Runnable {
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@Override public void run() {
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short[] buf = new short[bufsize];
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double[] dbuf = new double[DSP.fftlen];
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double[] hist = new double[HIST_SIZE];
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double[] sorted = new double[HIST_SIZE];
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for (;;) {
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// copy data to fft buffer - scale down to avoid huge numbers
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ar.read(buf, 0, bufsize);
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for (int i = 0; i < DSP.fftlen; ++i) dbuf[i] = buf[i] / 1024.0;
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// calculate frequency and note
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double freq = DSP.freq(dbuf, SAMPLE_RATE),
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semitone = 12 * Math.log(freq/440)/Math.log(2);
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// insert into moving average history
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for (int i = 1; i < HIST_SIZE; ++i) sorted[i-1] = hist[i-1] = hist[i];
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sorted[HIST_SIZE-1] = hist[HIST_SIZE-1] = semitone;
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// find median
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Arrays.sort(sorted);
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final double median = (sorted[HIST_SIZE/2-1]+sorted[HIST_SIZE/2])/2;
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final int rounded = (int)Math.round(median);
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final int note = Math.floorMod(rounded, 12);
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runOnUiThread(new Runnable() {
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@Override public void run() {
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notename.setText(notenames[note] +
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(Math.floorDiv(rounded, 12) + 5 - (note <= 2 ? 1 : 0)));
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centerror.setError(median - rounded);
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}
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});
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}
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}
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}
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}

‎src/main/java/mn.tck.semitone/Util.java

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/*
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* Semitone - tuner, metronome, and piano for Android
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* Copyright (C) 2019 Andy Tockman <[email protected]>
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*
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* This program is free software: you can redistribute it and/or modify
6+
* it under the terms of the GNU General Public License as published by
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* the Free Software Foundation, either version 3 of the License, or
8+
* (at your option) any later version.
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*
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* This program is distributed in the hope that it will be useful,
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* but WITHOUT ANY WARRANTY; without even the implied warranty of
12+
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
13+
* GNU General Public License for more details.
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*
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* You should have received a copy of the GNU General Public License
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* along with this program. If not, see <http://www.gnu.org/licenses/>.
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*/
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package mn.tck.semitone;
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import android.text.TextPaint;
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public class Util {
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public static int maxTextSize(String text, int maxWidth) {
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TextPaint paint = new TextPaint();
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for (int textSize = 10;; ++textSize) {
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paint.setTextSize(textSize);
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if (paint.measureText(text) > maxWidth) return textSize - 1;
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}
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}
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}

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