From 16406fd7103236661951f4a704ee8c8a5cd123b5 Mon Sep 17 00:00:00 2001
From: Ahmet Inan <xdsopl@gmail.com>
Date: Sun, 14 Apr 2024 21:56:05 +0200
Subject: [PATCH] added complex and phasor classes

---
 app/src/main/java/xdsopl/robot36/Complex.java | 70 +++++++++++++++++++
 .../java/xdsopl/robot36/MainActivity.java     | 20 +++++-
 app/src/main/java/xdsopl/robot36/Phasor.java  | 21 ++++++
 3 files changed, 109 insertions(+), 2 deletions(-)
 create mode 100644 app/src/main/java/xdsopl/robot36/Complex.java
 create mode 100644 app/src/main/java/xdsopl/robot36/Phasor.java

diff --git a/app/src/main/java/xdsopl/robot36/Complex.java b/app/src/main/java/xdsopl/robot36/Complex.java
new file mode 100644
index 0000000..db9bb71
--- /dev/null
+++ b/app/src/main/java/xdsopl/robot36/Complex.java
@@ -0,0 +1,70 @@
+/*
+Complex math
+
+Copyright 2024 Ahmet Inan <xdsopl@gmail.com>
+*/
+
+package xdsopl.robot36;
+
+public class Complex {
+	public float real, imag;
+	Complex() {
+		real = 0;
+		imag = 0;
+	}
+	Complex(float real, float imag) {
+		this.real = real;
+		this.imag = imag;
+	}
+	float norm() {
+		return real * real + imag * imag;
+	}
+	float abs() {
+		return (float) Math.sqrt(norm());
+	}
+	float arg() {
+		return (float) Math.atan2(imag, real);
+	}
+	Complex polar(float a, float b) {
+		real = a * (float) Math.cos(b);
+		imag = a * (float) Math.sin(b);
+		return this;
+	}
+	Complex conj() {
+		imag = -imag;
+		return this;
+	}
+	Complex add(Complex other) {
+		real += other.real;
+		imag += other.imag;
+		return this;
+	}
+	Complex sub(Complex other) {
+		real -= other.real;
+		imag -= other.imag;
+		return this;
+	}
+	Complex mul(float value) {
+		real *= value;
+		imag *= value;
+		return this;
+	}
+	Complex mul(Complex other) {
+		float tmp = real * other.real - imag * other.imag;
+		imag = real * other.imag + imag * other.real;
+		real = tmp;
+		return this;
+	}
+	Complex div(float value) {
+		real /= value;
+		imag /= value;
+		return this;
+	}
+	Complex div(Complex other) {
+		float den = other.norm();
+		float tmp = (real * other.real + imag * other.imag) / den;
+		imag = (imag * other.real - real * other.imag) / den;
+		real = tmp;
+		return this;
+	}
+}
diff --git a/app/src/main/java/xdsopl/robot36/MainActivity.java b/app/src/main/java/xdsopl/robot36/MainActivity.java
index f8b88dc..4e320f9 100644
--- a/app/src/main/java/xdsopl/robot36/MainActivity.java
+++ b/app/src/main/java/xdsopl/robot36/MainActivity.java
@@ -38,6 +38,9 @@ public class MainActivity extends AppCompatActivity {
 	private AudioRecord audioRecord;
 	private TextView status;
 	private SimpleMovingAverage powerAvg;
+	private SimpleMovingAverage realSyncAvg, imagSyncAvg;
+	private Phasor osc_1200;
+	private Complex sad;
 	private int tint;
 	private int curLine;
 
@@ -59,7 +62,13 @@ public class MainActivity extends AppCompatActivity {
 
 	private void processSamples() {
 		for (float v : recordBuffer) {
-			int x = Math.min((int) (scopeWidth * powerAvg.avg(v * v)), scopeWidth);
+			sad.real = v;
+			sad.imag = 0;
+			sad.mul(osc_1200.rotate());
+			sad.real = realSyncAvg.avg(sad.real);
+			sad.imag = imagSyncAvg.avg(sad.imag);
+			float level = sad.norm() / powerAvg.avg(v * v);
+			int x = Math.min((int) (scopeWidth * level), scopeWidth);
 			for (int i = 0; i < x; ++i)
 				scopePixels[scopeWidth * curLine + i] = tint;
 			for (int i = x; i < scopeWidth; ++i)
@@ -74,7 +83,14 @@ public class MainActivity extends AppCompatActivity {
 
 	private void initTools(int sampleRate) {
 		double powerWindowSeconds = 0.5;
-		powerAvg = new SimpleMovingAverage((int) Math.round(powerWindowSeconds * sampleRate));
+		int powerWindowSamples = (int) Math.round(powerWindowSeconds * sampleRate);
+		powerAvg = new SimpleMovingAverage(powerWindowSamples);
+		double syncPulseSeconds = 0.01;
+		int syncPulseSamples = (int) Math.round(syncPulseSeconds * sampleRate);
+		realSyncAvg = new SimpleMovingAverage(syncPulseSamples);
+		imagSyncAvg = new SimpleMovingAverage(syncPulseSamples);
+		osc_1200 = new Phasor(-1200, sampleRate);
+		sad = new Complex();
 	}
 
 	private void initAudioRecord() {
diff --git a/app/src/main/java/xdsopl/robot36/Phasor.java b/app/src/main/java/xdsopl/robot36/Phasor.java
new file mode 100644
index 0000000..958a85b
--- /dev/null
+++ b/app/src/main/java/xdsopl/robot36/Phasor.java
@@ -0,0 +1,21 @@
+/*
+Numerically controlled oscillator
+
+Copyright 2024 Ahmet Inan <xdsopl@gmail.com>
+*/
+
+package xdsopl.robot36;
+
+public class Phasor {
+	private final Complex value;
+	private final Complex delta;
+	Phasor(float freq, float rate) {
+		value = new Complex(1, 0);
+		double omega = 2 * Math.PI * freq / rate;
+		delta = new Complex((float) Math.cos(omega), (float) Math.sin(omega));
+	}
+	Complex rotate() {
+		value.mul(delta);
+		return value.div(value.abs());
+	}
+}