sdrangel/sdrbase/dsp/agc.cpp

///////////////////////////////////////////////////////////////////////////////////////
// Copyright (C) 2015-2019 Edouard Griffiths, F4EXB <f4exb06@gmail.com>              //
//                                                                                   //
// 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              //
// the Free Software Foundation as version 3 of the License, or                      //
// (at your option) any later version.                                               //
//                                                                                   //
// This program is distributed in the hope that it will be useful,                   //
// but WITHOUT ANY WARRANTY; without even the implied warranty of                    //
// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the                      //
// GNU General Public License V3 for more details.                                   //
//                                                                                   //
// You should have received a copy of the GNU General Public License                 //
// along with this program. If not, see <http://www.gnu.org/licenses/>.              //
///////////////////////////////////////////////////////////////////////////////////////

#include <algorithm>
#include "dsp/agc.h"

#include "util/stepfunctions.h"

AGC::AGC(int historySize, double R) :
	m_u0(1.0),
	m_R(R),
	m_moving_average(historySize, m_R),
	m_historySize(historySize),
	m_count(0)
{}

AGC::~AGC()
{}

void AGC::resize(int historySize, double R)
{
	m_R = R;
	m_moving_average.resize(historySize, R);
	m_historySize = historySize;
	m_count = 0;
}

Real AGC::getValue()
{
	return m_u0;
}

Real AGC::getAverage()
{
	return m_moving_average.average();
}


MagAGC::MagAGC(int historySize, double R, double threshold) :
	AGC(historySize, R),
	m_squared(false),
	m_magsq(0.0),
	m_threshold(threshold),
	m_thresholdEnable(true),
	m_gate(0),
	m_stepLength(std::min(2400, historySize/2)), // max 50 ms (at 48 kHz)
    m_stepDelta(1.0/m_stepLength),
	m_stepUpCounter(0),
    m_stepDownCounter(0),
	m_gateCounter(0),
	m_stepDownDelay(historySize),
    m_hardLimiting(false)
{}

MagAGC::~MagAGC()
{}

void MagAGC::resize(int historySize, int stepLength, Real R)
{
    m_stepLength = stepLength;
    m_stepDelta = 1.0 / m_stepLength;
    m_stepUpCounter = 0;
    m_stepDownCounter = 0;
    AGC::resize(historySize, R);
    m_moving_average.fill(m_squared ? R : R*R);
}

void MagAGC::setOrder(double R)
{
    AGC::setOrder(R);
    m_moving_average.fill(m_squared ? R : R*R);
}

void MagAGC::setThresholdEnable(bool enable)
{
    if (m_thresholdEnable != enable)
    {
        m_stepUpCounter = 0;
        m_stepDownCounter = 0;
    }

    m_thresholdEnable = enable;
}

void MagAGC::feed(Complex& ci)
{
	ci *= feedAndGetValue(ci);
}

double MagAGC::hardLimiter(double multiplier, double magsq)
{
    if ((m_hardLimiting) && (multiplier*multiplier*magsq > 1.0)) {
        return 1.0 / (multiplier*sqrt(magsq));
    } else {
        return multiplier;
    }
}

double MagAGC::feedAndGetValue(const Complex& ci)
{
    m_magsq = ci.real()*ci.real() + ci.imag()*ci.imag();
    m_moving_average.feed(m_magsq);
    m_u0 = m_R / (m_squared ? m_moving_average.average() : sqrt(m_moving_average.average()));

    if (m_thresholdEnable)
    {
        bool open = false;

        if (m_magsq > m_threshold)
        {
            if (m_gateCounter < m_gate) {
                m_gateCounter++;
            } else {
                open = true;
            }
        }
        else
        {
            m_gateCounter = 0;
        }

        if (open)
        {
            m_count = m_stepDownDelay; // delay before step down (grace delay)
        }
        else
        {
            m_count--;
            m_gateCounter = m_gate; // keep gate open during grace
        }

        if (m_count > 0) // up phase
        {
            m_stepDownCounter = m_stepUpCounter; // prepare for step down

            if (m_stepUpCounter < m_stepLength) // step up
            {
                m_stepUpCounter++;
                return hardLimiter(m_u0 * StepFunctions::smootherstep(m_stepUpCounter * m_stepDelta), m_magsq);
            }
            else // steady open
            {
                return hardLimiter(m_u0, m_magsq);
            }
        }
        else // down phase
        {
            m_stepUpCounter = m_stepDownCounter; // prepare for step up

            if (m_stepDownCounter > 0) // step down
            {
                m_stepDownCounter--;
                return hardLimiter(m_u0 * StepFunctions::smootherstep(m_stepDownCounter * m_stepDelta), m_magsq);
            }
            else // steady closed
            {
                return 0.0;
            }
        }
    }
    else
    {
        return hardLimiter(m_u0, m_magsq);
    }
}

float MagAGC::getStepValue() const
{
    if (m_count > 0) // up phase
    {
        return StepFunctions::smootherstep(m_stepUpCounter * m_stepDelta); // step up
    }
    else // down phase
    {
        return StepFunctions::smootherstep(m_stepDownCounter * m_stepDelta); // step down
    }
}