mirror of https://github.com/ShaYmez/xlxd.git
82 lines
2.5 KiB
C++
82 lines
2.5 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 "main.h"
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#include <math.h>
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#include "cagc.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_g = powf(10.0f, -initialLeveldB/20.0f);
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// ensure resulting gain is not arbitrarily low
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if (m_g < 1e-16f)
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m_g = 1e-16f;
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m_scale = 1.0f;
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m_bandwidth = 1e-2f;
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m_y2_prime = 1.0f;
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}
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void CAGC::Apply(uint8 * voice, int size)
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{
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for (int i = 0; i < size; i+=2)
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{
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//Get the sample
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float _x = (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 _y = _x * m_g;
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// compute output signal energy
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float y2 = _y * _y;
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// smooth energy estimate using single-pole low-pass filter
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m_y2_prime = (1.0f - m_alpha) * m_y2_prime + m_alpha*y2;
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// update gain according to output energy
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if (m_y2_prime > 1e-6f)
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m_g *= exp( -0.5f * m_alpha * log(m_y2_prime) );
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// clamp to 120 dB gain
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if (m_g > 1e6f)
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m_g = 1e6f;
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// apply output scale
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_y *= m_scale;
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//write processed sample back to it
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voice[i] = HIBYTE((short)_y);
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voice[i+1] = LOBYTE((short)_y);
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}
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} |