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#7 NXDN Decoder support. Redesigns tuner and channel frequency error management. (#2431)

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Closes #7 

NXDN Decoder

* Implements: NXDN4800, NXDN9600, Type-C and Type-D decoding and trunk tracking.
* Redesigns tuner and channel frequency error management.
This commit is contained in:
Denny Sheirer
2026-07-08 03:44:08 -04:00
committed by GitHub
parent a053315675
commit 7945f0ce63
445 changed files with 30854 additions and 2053 deletions
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40
src/main/java/io/github/dsheirer/dsp/symbol/Dibit.java
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@@ -1,6 +1,6 @@
/*
* *****************************************************************************
* Copyright (C) 2014-2025 Dennis Sheirer
* Copyright (C) 2014-2026 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
@@ -52,6 +52,44 @@ public enum Dibit
mPhase = phase;
}
private static final float SOFT_SYMBOL_QUADRANT_BOUNDARY = (float)(Math.PI / 2.0);
/**
* Decodes the sample value to determine the correct QPSK quadrant and maps the value to a Dibit symbol.
* @param sample in radians.
* @return symbol decision.
*/
public static Dibit fromSample(float sample)
{
if(sample > 0)
{
return sample > SOFT_SYMBOL_QUADRANT_BOUNDARY ? Dibit.D01_PLUS_3 : Dibit.D00_PLUS_1;
}
else
{
return sample < -SOFT_SYMBOL_QUADRANT_BOUNDARY ? Dibit.D11_MINUS_3 : Dibit.D10_MINUS_1;
}
}
/**
* Calculates the error from the sample by first mapping it to a symbol and the error is the difference from
* the ideal phase of that symbol.
* @param sample to process
* @return error from ideal
*/
public static float getError(float sample)
{
if(sample > 0)
{
return sample > SOFT_SYMBOL_QUADRANT_BOUNDARY ? Dibit.D01_PLUS_3.mPhase - sample : Dibit.D00_PLUS_1.mPhase - sample;
}
else
{
return sample < -SOFT_SYMBOL_QUADRANT_BOUNDARY ? Dibit.D11_MINUS_3.mPhase - sample : Dibit.D10_MINUS_1.mPhase - sample;
}
}
/**
* Binary value of the symbol
*/