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325 lines
12 KiB
C++
325 lines
12 KiB
C++
///////////////////////////////////////////////////////////////////////////////////
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// Copyright (C) 2019 F4EXB //
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// written by Edouard Griffiths //
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// //
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// Audio compressor based on sndfilter by Sean Connelly (@voidqk) //
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// https://github.com/voidqk/sndfilter //
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// //
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// Sample by sample interface to facilitate integration in SDRangel modulators. //
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// Uses mono samples (just floats) //
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// //
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// This program 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 as version 3 of the License, or //
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// (at your option) any later version. //
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// //
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// This program 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 V3 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 this program. If not, see <http://www.gnu.org/licenses/>. //
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///////////////////////////////////////////////////////////////////////////////////
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#include <algorithm>
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#include "audiocompressorsnd.h"
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AudioCompressorSnd::AudioCompressorSnd()
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{
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m_sampleIndex = 0;
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std::fill(m_processedBuffer, m_processedBuffer+AUDIOCOMPRESSORSND_SF_COMPRESSOR_CHUNKSIZE, 0.0f);
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}
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AudioCompressorSnd::~AudioCompressorSnd()
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{}
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void AudioCompressorSnd::initState()
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{
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m_compressorState.sf_advancecomp(
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m_rate,
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m_pregain,
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m_threshold,
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m_knee,
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m_ratio,
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m_attack,
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m_release,
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m_predelay,
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m_releasezone1,
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m_releasezone2,
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m_releasezone3,
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m_releasezone4,
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m_postgain,
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m_wet
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);
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}
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float AudioCompressorSnd::compress(float sample)
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{
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float compressedSample;
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if (m_sampleIndex >= AUDIOCOMPRESSORSND_SF_COMPRESSOR_CHUNKSIZE)
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{
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sf_compressor_process(&m_compressorState, AUDIOCOMPRESSORSND_SF_COMPRESSOR_CHUNKSIZE, m_storageBuffer, m_processedBuffer);
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m_sampleIndex = 0;
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}
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compressedSample = m_processedBuffer[m_sampleIndex];
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m_storageBuffer[m_sampleIndex] = sample;
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m_sampleIndex++;
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return compressedSample;
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}
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// populate the compressor state with advanced parameters
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void AudioCompressorSnd::CompressorState::sf_advancecomp(
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// these parameters are the same as the simple version above:
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int rate, float pregain, float threshold, float knee, float ratio, float attack, float release,
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// these are the advanced parameters:
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float predelay, // seconds, length of the predelay buffer [0 to 1]
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float releasezone1, // release zones should be increasing between 0 and 1, and are a fraction
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float releasezone2, // of the release time depending on the input dB -- these parameters define
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float releasezone3, // the adaptive release curve, which is discussed in further detail in the
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float releasezone4, // demo: adaptive-release-curve.html
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float postgain, // dB, amount of gain to apply after compression [0 to 100]
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float wet) // amount to apply the effect [0 completely dry to 1 completely wet]
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{
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// setup the predelay buffer
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int delaybufsize = rate * predelay;
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if (delaybufsize < 1)
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{
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delaybufsize = 1;
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}
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else if (delaybufsize > AUDIOCOMPRESSORSND_SF_COMPRESSOR_MAXDELAY)
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{
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delaybufsize = AUDIOCOMPRESSORSND_SF_COMPRESSOR_MAXDELAY;
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std::fill(delaybuf, delaybuf+delaybufsize, 0.0f);
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}
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// useful values
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float linearpregain = db2lin(pregain);
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float linearthreshold = db2lin(threshold);
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float slope = 1.0f / ratio;
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float attacksamples = rate * attack;
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float attacksamplesinv = 1.0f / attacksamples;
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float releasesamples = rate * release;
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float satrelease = 0.0025f; // seconds
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float satreleasesamplesinv = 1.0f / ((float)rate * satrelease);
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float dry = 1.0f - wet;
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// metering values (not used in core algorithm, but used to output a meter if desired)
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float meterfalloff = 0.325f; // seconds
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float meterrelease = 1.0f - expf(-1.0f / ((float)rate * meterfalloff));
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// calculate knee curve parameters
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float k = 5.0f; // initial guess
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float kneedboffset = 0.0f;
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float linearthresholdknee = 0.0f;
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if (knee > 0.0f) // if a knee exists, search for a good k value
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{
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float xknee = db2lin(threshold + knee);
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float mink = 0.1f;
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float maxk = 10000.0f;
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// search by comparing the knee slope at the current k guess, to the ideal slope
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for (int i = 0; i < 15; i++)
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{
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if (kneeslope(xknee, k, linearthreshold) < slope) {
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maxk = k;
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} else {
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mink = k;
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}
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k = sqrtf(mink * maxk);
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}
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kneedboffset = lin2db(kneecurve(xknee, k, linearthreshold));
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linearthresholdknee = db2lin(threshold + knee);
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}
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// calculate a master gain based on what sounds good
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float fulllevel = compcurve(1.0f, k, slope, linearthreshold, linearthresholdknee, threshold, knee, kneedboffset);
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float mastergain = db2lin(postgain) * powf(1.0f / fulllevel, 0.6f);
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// calculate the adaptive release curve parameters
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// solve a,b,c,d in `y = a*x^3 + b*x^2 + c*x + d`
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// interescting points (0, y1), (1, y2), (2, y3), (3, y4)
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float y1 = releasesamples * releasezone1;
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float y2 = releasesamples * releasezone2;
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float y3 = releasesamples * releasezone3;
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float y4 = releasesamples * releasezone4;
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float a = (-y1 + 3.0f * y2 - 3.0f * y3 + y4) / 6.0f;
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float b = y1 - 2.5f * y2 + 2.0f * y3 - 0.5f * y4;
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float c = (-11.0f * y1 + 18.0f * y2 - 9.0f * y3 + 2.0f * y4) / 6.0f;
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float d = y1;
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// save everything
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this->metergain = 1.0f; // large value overwritten immediately since it's always < 0
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this->meterrelease = meterrelease;
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this->threshold = threshold;
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this->knee = knee;
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this->wet = wet;
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this->linearpregain = linearpregain;
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this->linearthreshold = linearthreshold;
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this->slope = slope;
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this->attacksamplesinv = attacksamplesinv;
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this->satreleasesamplesinv = satreleasesamplesinv;
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this->dry = dry;
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this->k = k;
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this->kneedboffset = kneedboffset;
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this->linearthresholdknee = linearthresholdknee;
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this->mastergain = mastergain;
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this->a = a;
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this->b = b;
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this->c = c;
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this->d = d;
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this->detectoravg = 0.0f;
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this->compgain = 1.0f;
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this->maxcompdiffdb = -1.0f;
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this->delaybufsize = delaybufsize;
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this->delaywritepos = 0;
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this->delayreadpos = delaybufsize > 1 ? 1 : 0;
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}
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void AudioCompressorSnd::sf_compressor_process(AudioCompressorSnd::CompressorState *state, int size, float *input, float *output)
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{
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// pull out the state into local variables
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float metergain = state->metergain;
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float meterrelease = state->meterrelease;
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float threshold = state->threshold;
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float knee = state->knee;
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float linearpregain = state->linearpregain;
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float linearthreshold = state->linearthreshold;
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float slope = state->slope;
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float attacksamplesinv = state->attacksamplesinv;
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float satreleasesamplesinv = state->satreleasesamplesinv;
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float wet = state->wet;
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float dry = state->dry;
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float k = state->k;
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float kneedboffset = state->kneedboffset;
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float linearthresholdknee = state->linearthresholdknee;
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float mastergain = state->mastergain;
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float a = state->a;
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float b = state->b;
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float c = state->c;
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float d = state->d;
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float detectoravg = state->detectoravg;
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float compgain = state->compgain;
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float maxcompdiffdb = state->maxcompdiffdb;
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int delaybufsize = state->delaybufsize;
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int delaywritepos = state->delaywritepos;
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int delayreadpos = state->delayreadpos;
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float *delaybuf = state->delaybuf;
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int samplesperchunk = AUDIOCOMPRESSORSND_SF_COMPRESSOR_SPU;
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int chunks = size / samplesperchunk;
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float ang90 = (float)M_PI * 0.5f;
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float ang90inv = 2.0f / (float)M_PI;
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int samplepos = 0;
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float spacingdb = AUDIOCOMPRESSORSND_SF_COMPRESSOR_SPACINGDB;
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for (int ch = 0; ch < chunks; ch++)
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{
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detectoravg = fixf(detectoravg, 1.0f);
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float desiredgain = detectoravg;
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float scaleddesiredgain = asinf(desiredgain) * ang90inv;
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float compdiffdb = lin2db(compgain / scaleddesiredgain);
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// calculate envelope rate based on whether we're attacking or releasing
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float enveloperate;
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if (compdiffdb < 0.0f)
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{ // compgain < scaleddesiredgain, so we're releasing
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compdiffdb = fixf(compdiffdb, -1.0f);
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maxcompdiffdb = -1; // reset for a future attack mode
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// apply the adaptive release curve
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// scale compdiffdb between 0-3
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float x = (clampf(compdiffdb, -12.0f, 0.0f) + 12.0f) * 0.25f;
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float releasesamples = adaptivereleasecurve(x, a, b, c, d);
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enveloperate = db2lin(spacingdb / releasesamples);
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}
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else
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{ // compresorgain > scaleddesiredgain, so we're attacking
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compdiffdb = fixf(compdiffdb, 1.0f);
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if (maxcompdiffdb == -1 || maxcompdiffdb < compdiffdb)
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maxcompdiffdb = compdiffdb;
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float attenuate = maxcompdiffdb;
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if (attenuate < 0.5f)
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attenuate = 0.5f;
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enveloperate = 1.0f - powf(0.25f / attenuate, attacksamplesinv);
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}
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// process the chunk
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for (int chi = 0; chi < samplesperchunk; chi++, samplepos++,
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delayreadpos = (delayreadpos + 1) % delaybufsize,
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delaywritepos = (delaywritepos + 1) % delaybufsize)
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{
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float inputL = input[samplepos] * linearpregain;
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delaybuf[delaywritepos] = inputL;
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inputL = absf(inputL);
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float inputmax = inputL;
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float attenuation;
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if (inputmax < 0.0001f)
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attenuation = 1.0f;
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else
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{
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float inputcomp = compcurve(inputmax, k, slope, linearthreshold,
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linearthresholdknee, threshold, knee, kneedboffset);
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attenuation = inputcomp / inputmax;
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}
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float rate;
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if (attenuation > detectoravg)
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{ // if releasing
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float attenuationdb = -lin2db(attenuation);
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if (attenuationdb < 2.0f)
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attenuationdb = 2.0f;
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float dbpersample = attenuationdb * satreleasesamplesinv;
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rate = db2lin(dbpersample) - 1.0f;
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}
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else
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rate = 1.0f;
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detectoravg += (attenuation - detectoravg) * rate;
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if (detectoravg > 1.0f)
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detectoravg = 1.0f;
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detectoravg = fixf(detectoravg, 1.0f);
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if (enveloperate < 1) // attack, reduce gain
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compgain += (scaleddesiredgain - compgain) * enveloperate;
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else
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{ // release, increase gain
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compgain *= enveloperate;
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if (compgain > 1.0f)
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compgain = 1.0f;
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}
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// the final gain value!
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float premixgain = sinf(ang90 * compgain);
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float gain = dry + wet * mastergain * premixgain;
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// calculate metering (not used in core algo, but used to output a meter if desired)
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float premixgaindb = lin2db(premixgain);
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if (premixgaindb < metergain)
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metergain = premixgaindb; // spike immediately
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else
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metergain += (premixgaindb - metergain) * meterrelease; // fall slowly
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// apply the gain
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output[samplepos] = delaybuf[delayreadpos] * gain;
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}
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}
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state->metergain = metergain;
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state->detectoravg = detectoravg;
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state->compgain = compgain;
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state->maxcompdiffdb = maxcompdiffdb;
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state->delaywritepos = delaywritepos;
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state->delayreadpos = delayreadpos;
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}
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