#2226 DMR Decoder adds an equalizer to adjust symbol constellation balance/skew and gain to optimize symbol quadrant alignment/mapping. Reduces sync detectors from 3 to 2 and sets minimum objective channel sample rate to 19.2 kHz. (#2245)

Co-authored-by: denny <dennis.sheirer@gmail.com>

src/main/java/io/github/dsheirer/dsp/filter/decimate/DecimationFilterFactory.java

@@ -1,6 +1,6 @@
 /*
  * *****************************************************************************
- * Copyright (C) 2014-2022 Dennis Sheirer
+ * Copyright (C) 2014-2025 Dennis Sheirer
  *
  * This program is free software: you can redistribute it and/or modify
  * it under the terms of the GNU General Public License as published by
@@ -42,6 +42,7 @@ public class DecimationFilterFactory
         switch(decimationRate)
         {
             case 0:
+            case 1:
                 return new RealDecimateX0Filter();
             case 2:
                 return new RealDecimateX2Filter();

src/main/java/io/github/dsheirer/dsp/filter/interpolator/LinearInterpolator.java

@@ -1,6 +1,6 @@
 /*
  * *****************************************************************************
- * Copyright (C) 2014-2024 Dennis Sheirer
+ * Copyright (C) 2014-2025 Dennis Sheirer
  *
  * This program is free software: you can redistribute it and/or modify
  * it under the terms of the GNU General Public License as published by
@@ -20,13 +20,10 @@
 package io.github.dsheirer.dsp.filter.interpolator;
 
 /**
- * Linear interpolator for values in the range: -PI > 0 > PI with awareness of phase wrapping across the
- * (+/-) PI boundary.
+ * Linear interpolator.
  */
-public class PhaseAwareLinearInterpolator
+public class LinearInterpolator
 {
-    public static final float TWO_PI = (float)(Math.PI * 2.0);
-
     /**
      * Calculates an interpolated value between x1 and x2 at a linear position mu between 0.0 and 1.0
      * @param x1 first value
@@ -36,39 +33,16 @@ public class PhaseAwareLinearInterpolator
      */
     public static float calculate(float x1, float x2, float mu)
     {
-        //Detect phase wrap at the +PI/-PI boundary ... ignore opposite side of the unit circle at 0 axis
-        if(x1 * x2 < -Math.PI)
+        if(mu < 0 || mu > 1)
         {
-            if(x1 > 0)
-            {
-                float value = x1 + ((TWO_PI + x2 - x1) * mu);
-
-                if(value > Math.PI)
-                {
-                    return -TWO_PI + value;
-                }
-                else
-                {
-                    return value;
-                }
-            }
-            else
-            {
-                float value = x1 + ((-TWO_PI + x2 - x1) * mu);
-
-                if(value < -Math.PI)
-                {
-                    return TWO_PI + value;
-                }
-                else
-                {
-                    return value;
-                }
-            }
-        }
-        else
-        {
-            return x1 + ((x2 - x1) * mu);
+            throw new IllegalArgumentException("mu [" + mu + "] must be between 0 and 1");
         }
+
+        return x1 + ((x2 - x1) * mu);
+    }
+
+    public static float calculate(float x1, float x2, double mu)
+    {
+        return calculate(x1, x2, (float)mu);
     }
 }

src/main/java/io/github/dsheirer/dsp/psk/demod/DifferentialDemodulator.java

@@ -1,6 +1,6 @@
 /*
  * *****************************************************************************
- * Copyright (C) 2014-2024 Dennis Sheirer
+ * Copyright (C) 2014-2025 Dennis Sheirer
  *
  * This program is free software: you can redistribute it and/or modify
  * it under the terms of the GNU General Public License as published by
@@ -17,16 +17,16 @@
  * ****************************************************************************
  */
 
-package io.github.dsheirer.dsp.psk.dqpsk;
+package io.github.dsheirer.dsp.psk.demod;
 
 import io.github.dsheirer.dsp.filter.interpolator.Interpolator;
 import io.github.dsheirer.dsp.filter.interpolator.InterpolatorFactory;
 import io.github.dsheirer.dsp.fm.IDemodulator;
 
 /**
- * DQPSK demodulator base class
+ * Differential demodulator base class
  */
-public abstract class DQPSKDemodulator implements IDemodulator
+public abstract class DifferentialDemodulator implements IDemodulator
 {
     private int mSymbolRate;
     private float mSampleRate;
@@ -43,7 +43,7 @@ public abstract class DQPSKDemodulator implements IDemodulator
      * @param sampleRate in Hertz
      * @param symbolRate symbols per second
      */
-    public DQPSKDemodulator(double sampleRate, int symbolRate)
+    public DifferentialDemodulator(double sampleRate, int symbolRate)
     {
         mSampleRate = (float) sampleRate;
         mSymbolRate = symbolRate;
@@ -51,6 +51,12 @@ public abstract class DQPSKDemodulator implements IDemodulator
         mMu = mSamplesPerSymbol % 1; //Fractional part of the samples per symbol rate
         mInterpolationOffset = (int) Math.floor(mSamplesPerSymbol) - 4; //Interpolate at the middle of 8x samples
         mBufferOverlap = (int) Math.floor(mSamplesPerSymbol) + 4;
+
+        while(mInterpolationOffset < 0)
+        {
+            mInterpolationOffset++;
+            mBufferOverlap++;
+        }
     }
 
     /**

src/main/java/io/github/dsheirer/dsp/psk/demod/DifferentialDemodulatorFactory.java

@@ -1,6 +1,6 @@
 /*
  * *****************************************************************************
- * Copyright (C) 2014-2024 Dennis Sheirer
+ * Copyright (C) 2014-2025 Dennis Sheirer
  *
  * This program is free software: you can redistribute it and/or modify
  * it under the terms of the GNU General Public License as published by
@@ -17,7 +17,7 @@
  * ****************************************************************************
  */
 
-package io.github.dsheirer.dsp.psk.dqpsk;
+package io.github.dsheirer.dsp.psk.demod;
 
 import io.github.dsheirer.vector.calibrate.CalibrationManager;
 import io.github.dsheirer.vector.calibrate.CalibrationType;
@@ -26,11 +26,11 @@ import org.slf4j.Logger;
 import org.slf4j.LoggerFactory;
 
 /**
- * Factory for creating DQPSK demodulators
+ * Factory for creating PSK differential demodulators
  */
-public class DQPSKDemodulatorFactory
+public class DifferentialDemodulatorFactory
 {
-    private static final Logger mLog = LoggerFactory.getLogger(DQPSKDemodulatorFactory.class);
+    private static final Logger mLog = LoggerFactory.getLogger(DifferentialDemodulatorFactory.class);
 
     /**
      * Creates the optimal demodulator using calibration data to select the optimal implementation from scalar and
@@ -39,17 +39,17 @@ public class DQPSKDemodulatorFactory
      * @param symbolRate in Hertz
      * @return demodulator instance
      */
-    public static DQPSKDemodulator getDemodulator(double sampleRate, int symbolRate)
+    public static DifferentialDemodulator getDemodulator(double sampleRate, int symbolRate)
     {
-        Implementation implementation = CalibrationManager.getInstance().getImplementation(CalibrationType.DQPSK_DEMODULATOR);
+        Implementation implementation = CalibrationManager.getInstance().getImplementation(CalibrationType.DIFFERENTIAL_DEMODULATOR);
 
         return switch(implementation)
         {
-            case VECTOR_SIMD_64 -> new DQPSKDemodulatorVector64(sampleRate, symbolRate);
-            case VECTOR_SIMD_128 -> new DQPSKDemodulatorVector128(sampleRate, symbolRate);
-            case VECTOR_SIMD_256 -> new DQPSKDemodulatorVector256(sampleRate, symbolRate);
-            case VECTOR_SIMD_512 -> new DQPSKDemodulatorVector512(sampleRate, symbolRate);
-            default -> new DQPSKDemodulatorScalar(sampleRate, symbolRate); //Includes SCALAR case
+            case VECTOR_SIMD_64 -> new DifferentialDemodulatorVector64(sampleRate, symbolRate);
+            case VECTOR_SIMD_128 -> new DifferentialDemodulatorVector128(sampleRate, symbolRate);
+            case VECTOR_SIMD_256 -> new DifferentialDemodulatorVector256(sampleRate, symbolRate);
+            case VECTOR_SIMD_512 -> new DifferentialDemodulatorVector512(sampleRate, symbolRate);
+            default -> new DifferentialDemodulatorScalar(sampleRate, symbolRate); //Includes SCALAR case
         };
     }
 }

src/main/java/io/github/dsheirer/dsp/psk/demod/DifferentialDemodulatorScalar.java

@@ -1,6 +1,6 @@
 /*
  * *****************************************************************************
- * Copyright (C) 2014-2024 Dennis Sheirer
+ * Copyright (C) 2014-2025 Dennis Sheirer
  *
  * This program is free software: you can redistribute it and/or modify
  * it under the terms of the GNU General Public License as published by
@@ -17,25 +17,25 @@
  * ****************************************************************************
  */
 
-package io.github.dsheirer.dsp.psk.dqpsk;
+package io.github.dsheirer.dsp.psk.demod;
 
 import java.util.Arrays;
 import org.slf4j.Logger;
 import org.slf4j.LoggerFactory;
 
 /**
- * DQPSK demodulator that uses scalar calculations for demodulating the sample stream.
+ * Differential demodulator that uses scalar calculations for demodulating the sample stream.
  */
-public class DQPSKDemodulatorScalar extends DQPSKDemodulator
+public class DifferentialDemodulatorScalar extends DifferentialDemodulator
 {
-    private static final Logger LOGGER = LoggerFactory.getLogger(DQPSKDemodulatorScalar.class);
+    private static final Logger LOGGER = LoggerFactory.getLogger(DifferentialDemodulatorScalar.class);
 
     /**
      * Constructor
      *
      * @param symbolRate symbols per second
      */
-    public DQPSKDemodulatorScalar(double sampleRate, int symbolRate)
+    public DifferentialDemodulatorScalar(double sampleRate, int symbolRate)
     {
         super(sampleRate, symbolRate);
     }

src/main/java/io/github/dsheirer/dsp/psk/demod/DifferentialDemodulatorVector128.java

@@ -1,6 +1,6 @@
 /*
  * *****************************************************************************
- * Copyright (C) 2014-2024 Dennis Sheirer
+ * Copyright (C) 2014-2025 Dennis Sheirer
  *
  * This program is free software: you can redistribute it and/or modify
  * it under the terms of the GNU General Public License as published by
@@ -17,7 +17,7 @@
  * ****************************************************************************
  */
 
-package io.github.dsheirer.dsp.psk.dqpsk;
+package io.github.dsheirer.dsp.psk.demod;
 
 import java.util.Arrays;
 import jdk.incubator.vector.FloatVector;
@@ -27,11 +27,11 @@ import org.slf4j.Logger;
 import org.slf4j.LoggerFactory;
 
 /**
- * DQPSK demodulator that uses Vector SIMD 128 calculations for demodulating the sample stream.
+ * Differential demodulator that uses Vector SIMD 128 calculations for demodulating the sample stream.
  */
-public class DQPSKDemodulatorVector128 extends DQPSKDemodulator
+public class DifferentialDemodulatorVector128 extends DifferentialDemodulator
 {
-    private static final Logger LOGGER = LoggerFactory.getLogger(DQPSKDemodulatorVector128.class);
+    private static final Logger LOGGER = LoggerFactory.getLogger(DifferentialDemodulatorVector128.class);
     private static final VectorSpecies<Float> VECTOR_SPECIES = FloatVector.SPECIES_128;
 
     /**
@@ -40,7 +40,7 @@ public class DQPSKDemodulatorVector128 extends DQPSKDemodulator
      * @param sampleRate in Hertz
      * @param symbolRate symbols per second
      */
-    public DQPSKDemodulatorVector128(double sampleRate, int symbolRate)
+    public DifferentialDemodulatorVector128(double sampleRate, int symbolRate)
     {
         super(sampleRate, symbolRate);
     }

src/main/java/io/github/dsheirer/dsp/psk/demod/DifferentialDemodulatorVector256.java

@@ -1,6 +1,6 @@
 /*
  * *****************************************************************************
- * Copyright (C) 2014-2024 Dennis Sheirer
+ * Copyright (C) 2014-2025 Dennis Sheirer
  *
  * This program is free software: you can redistribute it and/or modify
  * it under the terms of the GNU General Public License as published by
@@ -17,7 +17,7 @@
  * ****************************************************************************
  */
 
-package io.github.dsheirer.dsp.psk.dqpsk;
+package io.github.dsheirer.dsp.psk.demod;
 
 import java.util.Arrays;
 import jdk.incubator.vector.FloatVector;
@@ -25,9 +25,9 @@ import jdk.incubator.vector.VectorOperators;
 import jdk.incubator.vector.VectorSpecies;
 
 /**
- * DQPSK demodulator that uses Vector SIMD calculations for demodulating the sample stream.
+ * Differential demodulator that uses Vector SIMD calculations for demodulating the sample stream.
  */
-public class DQPSKDemodulatorVector256 extends DQPSKDemodulator
+public class DifferentialDemodulatorVector256 extends DifferentialDemodulator
 {
     private static final VectorSpecies<Float> VECTOR_SPECIES = FloatVector.SPECIES_256;
 
@@ -37,7 +37,7 @@ public class DQPSKDemodulatorVector256 extends DQPSKDemodulator
      * @param sampleRate in Hertz
      * @param symbolRate symbols per second
      */
-    public DQPSKDemodulatorVector256(double sampleRate, int symbolRate)
+    public DifferentialDemodulatorVector256(double sampleRate, int symbolRate)
     {
         super(sampleRate, symbolRate);
     }
@@ -68,7 +68,6 @@ public class DQPSKDemodulatorVector256 extends DQPSKDemodulator
         //Append new samples to the residual samples from the previous buffer.
         System.arraycopy(i, 0, mIBuffer, bufferOverlap, sampleLength);
         System.arraycopy(q, 0, mQBuffer, bufferOverlap, sampleLength);
-        //mIDecoded, mQDecoded and mPhase will be filled below during the decoding process.
 
         float[] interpolatedI = new float[VECTOR_SPECIES.length()];
         float[] interpolatedQ = new float[VECTOR_SPECIES.length()];

src/main/java/io/github/dsheirer/dsp/psk/demod/DifferentialDemodulatorVector512.java

@@ -1,6 +1,6 @@
 /*
  * *****************************************************************************
- * Copyright (C) 2014-2024 Dennis Sheirer
+ * Copyright (C) 2014-2025 Dennis Sheirer
  *
  * This program is free software: you can redistribute it and/or modify
  * it under the terms of the GNU General Public License as published by
@@ -17,7 +17,7 @@
  * ****************************************************************************
  */
 
-package io.github.dsheirer.dsp.psk.dqpsk;
+package io.github.dsheirer.dsp.psk.demod;
 
 import java.util.Arrays;
 import jdk.incubator.vector.FloatVector;
@@ -27,11 +27,11 @@ import org.slf4j.Logger;
 import org.slf4j.LoggerFactory;
 
 /**
- * DQPSK demodulator that uses Vector SIMD 512 calculations for demodulating the sample stream.
+ * Differential demodulator that uses Vector SIMD 512 calculations for demodulating the sample stream.
  */
-public class DQPSKDemodulatorVector512 extends DQPSKDemodulator
+public class DifferentialDemodulatorVector512 extends DifferentialDemodulator
 {
-    private static final Logger LOGGER = LoggerFactory.getLogger(DQPSKDemodulatorVector512.class);
+    private static final Logger LOGGER = LoggerFactory.getLogger(DifferentialDemodulatorVector512.class);
     private static final VectorSpecies<Float> VECTOR_SPECIES = FloatVector.SPECIES_512;
 
     /**
@@ -39,7 +39,7 @@ public class DQPSKDemodulatorVector512 extends DQPSKDemodulator
      *
      * @param symbolRate symbols per second
      */
-    public DQPSKDemodulatorVector512(double sampleRate, int symbolRate)
+    public DifferentialDemodulatorVector512(double sampleRate, int symbolRate)
     {
         super(sampleRate, symbolRate);
     }

src/main/java/io/github/dsheirer/dsp/psk/demod/DifferentialDemodulatorVector64.java

@@ -1,6 +1,6 @@
 /*
  * *****************************************************************************
- * Copyright (C) 2014-2024 Dennis Sheirer
+ * Copyright (C) 2014-2025 Dennis Sheirer
  *
  * This program is free software: you can redistribute it and/or modify
  * it under the terms of the GNU General Public License as published by
@@ -17,7 +17,7 @@
  * ****************************************************************************
  */
 
-package io.github.dsheirer.dsp.psk.dqpsk;
+package io.github.dsheirer.dsp.psk.demod;
 
 import java.util.Arrays;
 import jdk.incubator.vector.FloatVector;
@@ -27,11 +27,11 @@ import org.slf4j.Logger;
 import org.slf4j.LoggerFactory;
 
 /**
- * DQPSK demodulator that uses Vector SIMD 64 calculations for demodulating the sample stream.
+ * Differential demodulator that uses Vector SIMD 64 calculations for demodulating the sample stream.
  */
-public class DQPSKDemodulatorVector64 extends DQPSKDemodulator
+public class DifferentialDemodulatorVector64 extends DifferentialDemodulator
 {
-    private static final Logger LOGGER = LoggerFactory.getLogger(DQPSKDemodulatorVector64.class);
+    private static final Logger LOGGER = LoggerFactory.getLogger(DifferentialDemodulatorVector64.class);
     private static final VectorSpecies<Float> VECTOR_SPECIES = FloatVector.SPECIES_64;
 
     /**
@@ -40,7 +40,7 @@ public class DQPSKDemodulatorVector64 extends DQPSKDemodulator
      * @param sampleRate in Hertz
      * @param symbolRate symbols per second
      */
-    public DQPSKDemodulatorVector64(double sampleRate, int symbolRate)
+    public DifferentialDemodulatorVector64(double sampleRate, int symbolRate)
     {
         super(sampleRate, symbolRate);
     }

src/main/java/io/github/dsheirer/dsp/symbol/Dibit.java

@@ -1,6 +1,6 @@
 /*
  * *****************************************************************************
- * Copyright (C) 2014-2024 Dennis Sheirer
+ * Copyright (C) 2014-2025 Dennis Sheirer
  *
  * This program is free software: you can redistribute it and/or modify
  * it under the terms of the GNU General Public License as published by
@@ -21,10 +21,10 @@ package io.github.dsheirer.dsp.symbol;
 
 public enum Dibit
 {
-    D01_PLUS_3(false, true, 1, 4, 1, (float)(Math.PI / 4 * 3), (float)-Math.sin(Math.toRadians(45)), (float)Math.sin(Math.toRadians(45))),
-    D00_PLUS_1(false, false, 0, 0, 0, (float)(Math.PI / 4.0), (float)Math.sin(Math.toRadians(45)), (float)Math.sin(Math.toRadians(45))),
-    D10_MINUS_1(true, false, 2, 8, 2, (float)(Math.PI / -4.0), (float)Math.sin(Math.toRadians(45)), (float)-Math.sin(Math.toRadians(45))),
-    D11_MINUS_3(true, true, 3, 12, 3, (float)(Math.PI / 4 * -3), (float)-Math.sin(Math.toRadians(45)), (float)-Math.sin(Math.toRadians(45)));
+    D01_PLUS_3(false, true, 1, 4, 1, (float)((Math.PI / 4) * 3)),
+    D00_PLUS_1(false, false, 0, 0, 0, (float)(Math.PI / 4)),
+    D10_MINUS_1(true, false, 2, 8, 2, (float)(Math.PI / -4)),
+    D11_MINUS_3(true, true, 3, 12, 3, (float)((Math.PI / 4) * -3));
 
     private boolean mBit1;
     private boolean mBit2;
@@ -32,8 +32,6 @@ public enum Dibit
     private int mHighValue;
     private int mValue;
     private float mPhase;
-    private float mIdealI;
-    private float mIdealQ;
 
     /**
      * Dibit constructor.
@@ -43,10 +41,8 @@ public enum Dibit
      * @param highValue integer value of the high order bit
      * @param value integer value combined of both bits.
      * @param phase optimal phase value for this symbol when transmitted.
-     * @param idealI ideal inphase value for this symbol when transmitted.
-     * @param idealQ ideal quadrature value for this symbol when transmitted.
      */
-    Dibit(boolean bit1, boolean bit2, int lowValue, int highValue, int value, float phase, float idealI, float idealQ)
+    Dibit(boolean bit1, boolean bit2, int lowValue, int highValue, int value, float phase)
     {
         mBit1 = bit1;
         mBit2 = bit2;
@@ -54,8 +50,6 @@ public enum Dibit
         mHighValue = highValue;
         mValue = value;
         mPhase = phase;
-        mIdealI = idealI;
-        mIdealQ = idealQ;
     }
 
     /**
@@ -75,24 +69,6 @@ public enum Dibit
         return mPhase;
     }
 
-    /**
-     * Ideal inphase value when this symbol is transmitted.
-     * @return ideal I
-     */
-    public float getIdealI()
-    {
-        return mIdealI;
-    }
-
-    /**
-     * Ideal quadrature value when this symbol is transmitted.
-     * @return ideal Q
-     */
-    public float getIdealQ()
-    {
-        return mIdealQ;
-    }
-
     /**
      * Allowable transition state 1 for trellis coded modulation.  Indicates
      * the dibit that differs from this dibit in the LSB bit position.