mirror of https://github.com/ShaYmez/xlxd.git
95 lines
3.3 KiB
C++
95 lines
3.3 KiB
C++
//
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// cagc.cpp
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// ambed
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//
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// Created by Jean-Luc Deltombe (LX3JL) on 28/04/2017.
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// Copyright © 2015 Jean-Luc Deltombe (LX3JL). All rights reserved.
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//
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// ----------------------------------------------------------------------------
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// This file is part of ambed.
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//
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// xlxd is free software: you can redistribute it and/or modify
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// it under the terms of the GNU General Public License as published by
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// the Free Software Foundation, either version 3 of the License, or
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// (at your option) any later version.
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//
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// xlxd is distributed in the hope that it will be useful,
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// but WITHOUT ANY WARRANTY; without even the implied warranty of
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// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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// GNU General Public License for more details.
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//
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// You should have received a copy of the GNU General Public License
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// along with Foobar. If not, see <http://www.gnu.org/licenses/>.
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// ----------------------------------------------------------------------------
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// Geoffrey Merck F4FXL / KC3FRA AGC code borrowed from Liquid DSP
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// Only took the parts we need qnd recoeded it to be close the XLX coding style
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// https://github.com/jgaeddert/liquid-dsp/blob/master/src/agc/src/agc.c
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#include <math.h>
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#include "cagc.h"
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#include "main.h"
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////////////////////////////////////////////////////////////////////////////////////////
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// constructor
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CAGC::CAGC(float initialLeveldB)
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{
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// set internal gain appropriately
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m_Gain = pow(10.0f, initialLeveldB/20.0f);
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//+- 10dB Margin, TODO Move margin to constant
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m_GainMax = pow(10.0f, (initialLeveldB + AGC_CLAMPING)/20.0f);
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m_GainMin = pow(10.0f, (initialLeveldB - AGC_CLAMPING)/20.0f);
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m_EnergyPrime = 1.0f;
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// We do not target full scale to avoid stauration
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m_targetEnergy = 32767.0f * pow(10.0f, (initialLeveldB - 25.0)/20.0f);//25 dB below saturation as stated in docs
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//we also substract our target gain
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//this is the time constant of our AGC...
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m_Bandwidth = 1e-2f;//TODO : Move to parameter ?
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m_Alpha = m_Bandwidth;
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}
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////////////////////////////////////////////////////////////////////////////////////////
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// get
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float CAGC::GetGain()
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{
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return 20.0f*log10(m_Gain);
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}
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////////////////////////////////////////////////////////////////////////////////////////
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// process
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inline void CAGC::ProcessSampleBlock(uint8* voice, int length)
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{
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for(int i = 0; i < length; i += 2)
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{
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float input = (float)(short)MAKEWORD(voice[i+1], voice[i]);
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//apply AGC
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// apply gain to input sample
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float output = input * m_Gain;
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// compute output signal energy, scaled to 0 to 1
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float instantEnergy = abs(output) / m_targetEnergy;
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// smooth energy estimate using single-pole low-pass filter
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m_EnergyPrime = (1.0f - m_Alpha) * m_EnergyPrime + m_Alpha * instantEnergy;
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// update gain according to output energy
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if (m_EnergyPrime > 1e-6f)
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m_Gain *= exp( -0.5f * m_Alpha * log(m_EnergyPrime) );
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// clamp gain
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if (m_Gain > m_GainMax)
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m_Gain = m_GainMax;
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else if(m_Gain < m_GainMin)
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m_Gain = m_GainMin;
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//write processed sample back
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voice[i] = HIBYTE((short)output);
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voice[i+1] = LOBYTE((short)output);
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}
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}
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