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205 lines
3.8 KiB
C++
205 lines
3.8 KiB
C++
/*
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* ctcssdetector.cpp
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*
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* Created on: Jun 16, 2015
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* Author: f4exb
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*/
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#include <cmath>
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#include "dsp/ctcssdetector.h"
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CTCSSDetector::CTCSSDetector() :
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N(0),
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sampleRate(0),
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samplesProcessed(0),
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maxPowerIndex(0),
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toneDetected(false),
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maxPower(0.0)
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{
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nTones = 32;
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k = new Real[nTones];
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coef = new Real[nTones];
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toneSet = new Real[nTones];
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u0 = new Real[nTones];
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u1 = new Real[nTones];
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power = new Real[nTones];
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// The 32 EIA standard tones
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toneSet[0] = 67.0;
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toneSet[1] = 71.9;
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toneSet[2] = 74.4;
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toneSet[3] = 77.0;
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toneSet[4] = 79.7;
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toneSet[5] = 82.5;
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toneSet[6] = 85.4;
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toneSet[7] = 88.5;
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toneSet[8] = 91.5;
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toneSet[9] = 94.8;
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toneSet[10] = 97.4;
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toneSet[11] = 100.0;
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toneSet[12] = 103.5;
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toneSet[13] = 107.2;
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toneSet[14] = 110.9;
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toneSet[15] = 114.8;
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toneSet[16] = 118.8;
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toneSet[17] = 123.0;
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toneSet[18] = 127.3;
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toneSet[19] = 131.8;
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toneSet[20] = 136.5;
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toneSet[21] = 141.3;
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toneSet[22] = 146.2;
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toneSet[23] = 151.4;
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toneSet[24] = 156.7;
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toneSet[25] = 162.2;
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toneSet[26] = 167.9;
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toneSet[27] = 173.8;
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toneSet[28] = 179.9;
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toneSet[29] = 186.2;
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toneSet[30] = 192.8;
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toneSet[31] = 203.5;
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}
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CTCSSDetector::CTCSSDetector(int _nTones, Real *tones) :
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N(0),
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sampleRate(0),
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samplesProcessed(0),
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maxPowerIndex(0),
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toneDetected(false),
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maxPower(0.0)
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{
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nTones = _nTones;
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k = new Real[nTones];
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coef = new Real[nTones];
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toneSet = new Real[nTones];
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u0 = new Real[nTones];
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u1 = new Real[nTones];
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power = new Real[nTones];
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for (int j = 0; j < nTones; ++j)
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{
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toneSet[j] = tones[j];
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}
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}
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CTCSSDetector::~CTCSSDetector()
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{
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delete[] k;
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delete[] coef;
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delete[] toneSet;
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delete[] u0;
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delete[] u1;
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delete[] power;
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}
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void CTCSSDetector::setCoefficients(int zN, int _samplerate )
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{
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N = zN; // save the basic parameters for use during analysis
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sampleRate = _samplerate;
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// for each of the frequencies (tones) of interest calculate
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// k and the associated filter coefficient as per the Goertzel
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// algorithm. Note: we are using a real value (as apposed to
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// an integer as described in some references. k is retained
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// for later display. The tone set is specified in the
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// constructor. Notice that the resulting coefficients are
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// independent of N.
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for (int j = 0; j < nTones; ++j)
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{
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k[j] = ((double)N * toneSet[j]) / (double)sampleRate;
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coef[j] = 2.0 * cos((2.0 * M_PI * toneSet[j])/(double)sampleRate);
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}
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}
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// Analyze an input signal for the presence of CTCSS tones.
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bool CTCSSDetector::analyze(Real *sample)
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{
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feedback(*sample); // Goertzel feedback
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samplesProcessed += 1;
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if (samplesProcessed == N) // completed a block of N
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{
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feedForward(); // calculate the power at each tone
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samplesProcessed = 0;
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return true; // have a result
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}
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else
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{
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return false;
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}
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}
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void CTCSSDetector::feedback(Real in)
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{
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Real t;
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// feedback for each tone
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for (int j = 0; j < nTones; ++j)
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{
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t = u0[j];
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u0[j] = in + (coef[j] * u0[j]) - u1[j];
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u1[j] = t;
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}
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}
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void CTCSSDetector::feedForward()
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{
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initializePower();
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for (int j = 0; j < nTones; ++j)
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{
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power[j] = (u0[j] * u0[j]) + (u1[j] * u1[j]) - (coef[j] * u0[j] * u1[j]);
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u0[j] = u1[j] = 0.0; // reset for next block.
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}
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evaluatePower();
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}
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void CTCSSDetector::reset()
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{
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for (int j = 0; j < nTones; ++j)
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{
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power[j] = u0[j] = u1[j] = 0.0; // reset
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}
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samplesProcessed = 0;
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maxPower = 0.0;
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maxPowerIndex = 0;
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toneDetected = false;
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}
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void CTCSSDetector::initializePower()
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{
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for (int j = 0; j < nTones; ++j)
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{
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power[j] = 0.0; // reset
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}
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}
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void CTCSSDetector::evaluatePower()
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{
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Real sumPower = 0.0;
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Real aboveAvg = 2.0; // Arbitrary max power above average threshold
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maxPower = 0.0;
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for (int j = 0; j < nTones; ++j)
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{
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sumPower += power[j];
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if (power[j] > maxPower)
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{
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maxPower = power[j];
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maxPowerIndex = j;
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}
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}
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toneDetected = (maxPower > (sumPower/nTones) + aboveAvg);
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}
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