LMMS/plugins/Compressor/Compressor.cpp

/*
 * Compressor.cpp
 *
 * Copyright (c) 2020 Lost Robot <r94231@gmail.com>
 *
 * This file is part of LMMS - https://lmms.io
 *
 * 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; either
 * version 2 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 for more details.
 *
 * You should have received a copy of the GNU General Public
 * License along with this program (see COPYING); if not, write to the
 * Free Software Foundation, Inc., 51 Franklin Street, Fifth Floor,
 * Boston, MA 02110-1301 USA.
 *
 */

#include "Compressor.h"

#include "embed.h"
#include "interpolation.h"
#include "lmms_math.h"
#include "plugin_export.h"

extern "C"
{

Plugin::Descriptor PLUGIN_EXPORT compressor_plugin_descriptor =
{
	STRINGIFY(PLUGIN_NAME),
	"Compressor",
	QT_TRANSLATE_NOOP("PluginBrowser", "A dynamic range compressor."),
	"Lost Robot <r94231@gmail.com>",
	0x0100,
	Plugin::Effect,
	new PluginPixmapLoader("logo"),
	NULL,
	NULL
} ;

}


CompressorEffect::CompressorEffect(Model* parent, const Descriptor::SubPluginFeatures::Key* key) :
	Effect(&compressor_plugin_descriptor, parent, key),
	m_compressorControls(this)
{
	m_sampleRate = Engine::mixer()->processingSampleRate();

	m_yL[0] = m_yL[1] = COMP_NOISE_FLOOR;

	m_maxLookaheadVal[0] = 0;
	m_maxLookaheadVal[1] = 0;

	// 200 ms
	m_crestTimeConst = exp(-1.f / (0.2f * m_sampleRate));

	connect(&m_compressorControls.m_attackModel, SIGNAL(dataChanged()), this, SLOT(calcAttack()), Qt::DirectConnection);
	connect(&m_compressorControls.m_releaseModel, SIGNAL(dataChanged()), this, SLOT(calcRelease()), Qt::DirectConnection);
	connect(&m_compressorControls.m_holdModel, SIGNAL(dataChanged()), this, SLOT(calcHold()), Qt::DirectConnection);
	connect(&m_compressorControls.m_ratioModel, SIGNAL(dataChanged()), this, SLOT(calcRatio()), Qt::DirectConnection);
	connect(&m_compressorControls.m_rangeModel, SIGNAL(dataChanged()), this, SLOT(calcRange()), Qt::DirectConnection);
	connect(&m_compressorControls.m_rmsModel, SIGNAL(dataChanged()), this, SLOT(resizeRMS()), Qt::DirectConnection);
	connect(&m_compressorControls.m_lookaheadLengthModel, SIGNAL(dataChanged()), this, SLOT(calcLookaheadLength()), Qt::DirectConnection);
	connect(&m_compressorControls.m_thresholdModel, SIGNAL(dataChanged()), this, SLOT(calcThreshold()), Qt::DirectConnection);
	connect(&m_compressorControls.m_kneeModel, SIGNAL(dataChanged()), this, SLOT(calcKnee()), Qt::DirectConnection);
	connect(&m_compressorControls.m_outGainModel, SIGNAL(dataChanged()), this, SLOT(calcOutGain()), Qt::DirectConnection);
	connect(&m_compressorControls.m_inGainModel, SIGNAL(dataChanged()), this, SLOT(calcInGain()), Qt::DirectConnection);
	connect(&m_compressorControls.m_tiltModel, SIGNAL(dataChanged()), this, SLOT(calcTiltCoeffs()), Qt::DirectConnection);
	connect(&m_compressorControls.m_tiltFreqModel, SIGNAL(dataChanged()), this, SLOT(calcTiltCoeffs()), Qt::DirectConnection);
	connect(&m_compressorControls.m_limiterModel, SIGNAL(dataChanged()), this, SLOT(redrawKnee()), Qt::DirectConnection);
	connect(&m_compressorControls.m_mixModel, SIGNAL(dataChanged()), this, SLOT(calcMix()), Qt::DirectConnection);

	connect(&m_compressorControls.m_autoAttackModel, SIGNAL(dataChanged()), this, SLOT(calcAutoAttack()), Qt::DirectConnection);
	connect(&m_compressorControls.m_autoReleaseModel, SIGNAL(dataChanged()), this, SLOT(calcAutoRelease()), Qt::DirectConnection);

	connect(&m_compressorControls.m_thresholdModel, SIGNAL(dataChanged()), this, SLOT(calcAutoMakeup()), Qt::DirectConnection);
	connect(&m_compressorControls.m_ratioModel, SIGNAL(dataChanged()), this, SLOT(calcAutoMakeup()), Qt::DirectConnection);
	connect(&m_compressorControls.m_kneeModel, SIGNAL(dataChanged()), this, SLOT(calcAutoMakeup()), Qt::DirectConnection);
	connect(&m_compressorControls.m_autoMakeupModel, SIGNAL(dataChanged()), this, SLOT(calcAutoMakeup()), Qt::DirectConnection);

	connect(Engine::mixer(), SIGNAL(sampleRateChanged()), this, SLOT(changeSampleRate()));
	changeSampleRate();
}




CompressorEffect::~CompressorEffect()
{
}


float CompressorEffect::msToCoeff(float ms)
{
	// Convert time in milliseconds to applicable lowpass coefficient
	return exp(m_coeffPrecalc / ms);
}



void CompressorEffect::calcAutoMakeup()
{
	// Formulas using the compressor's Threshold, Ratio, and Knee values to estimate a good makeup gain value

	float tempGainResult;
	if (-m_thresholdVal < m_kneeVal)
	{
		const float temp = -m_thresholdVal + m_kneeVal;
		tempGainResult = ((m_compressorControls.m_limiterModel.value() ? 0 : m_ratioVal) - 1) * temp * temp / (4 * m_kneeVal);
	}
	else// Above knee
	{
		tempGainResult = m_compressorControls.m_limiterModel.value()
			? m_thresholdVal
			: m_thresholdVal - m_thresholdVal * m_ratioVal;
	}

	m_autoMakeupVal = 1.f / dbfsToAmp(tempGainResult);
}



void CompressorEffect::calcAttack()
{
	m_attCoeff = msToCoeff(m_compressorControls.m_attackModel.value());
}

void CompressorEffect::calcRelease()
{
	m_relCoeff = msToCoeff(m_compressorControls.m_releaseModel.value());
}

void CompressorEffect::calcAutoAttack()
{
	m_autoAttVal = m_compressorControls.m_autoAttackModel.value() * 0.01f;
}

void CompressorEffect::calcAutoRelease()
{
	m_autoRelVal = m_compressorControls.m_autoReleaseModel.value() * 0.01f;
}

void CompressorEffect::calcHold()
{
	m_holdLength = m_compressorControls.m_holdModel.value() * 0.001f * m_sampleRate;
	m_holdTimer[0] = 0;
	m_holdTimer[1] = 0;
}

void CompressorEffect::calcOutGain()
{
	// 0.999 is needed to keep the values from crossing the threshold all the time
	// (most commonly for limiters specifically), and is kept across all modes for consistency.
	m_outGainVal = dbfsToAmp(m_compressorControls.m_outGainModel.value()) * 0.999;
}

void CompressorEffect::calcRatio()
{
	m_ratioVal = 1.f / m_compressorControls.m_ratioModel.value();
	m_redrawKnee = true;
}

void CompressorEffect::calcRange()
{
	// Range is inactive when turned all the way down
	m_rangeVal = (m_compressorControls.m_rangeModel.value() > m_compressorControls.m_rangeModel.minValue())
			? dbfsToAmp(m_compressorControls.m_rangeModel.value())
			: 0;
}

void CompressorEffect::resizeRMS()
{
	m_rmsTimeConst = exp(-1.f / (m_compressorControls.m_rmsModel.value() * 0.001f * m_sampleRate));
}

void CompressorEffect::calcLookaheadLength()
{
	m_lookaheadLength = qMax(m_compressorControls.m_lookaheadLengthModel.value() * 0.001f * m_sampleRate, 1.f);

	m_preLookaheadLength = ceil(m_lookaheadDelayLength - m_lookaheadLength);
}

void CompressorEffect::calcThreshold()
{
	m_thresholdVal = m_compressorControls.m_thresholdModel.value();
	m_thresholdAmpVal = dbfsToAmp(m_thresholdVal);
	m_redrawKnee = true;
	m_redrawThreshold = true;
}

void CompressorEffect::calcKnee()
{
	m_kneeVal = m_compressorControls.m_kneeModel.value() * 0.5f;
	m_redrawKnee = true;
}

void CompressorEffect::calcInGain()
{
	m_inGainVal = dbfsToAmp(m_compressorControls.m_inGainModel.value());
}

void CompressorEffect::redrawKnee()
{
	m_redrawKnee = true;
}

void CompressorEffect::calcTiltCoeffs()
{
	m_tiltVal = m_compressorControls.m_tiltModel.value();

	const float amp = 6 / log(2);

	const float gfactor = 5;
	const float g1 = m_tiltVal > 0 ? -gfactor * m_tiltVal : -m_tiltVal;
	const float g2 = m_tiltVal > 0 ? m_tiltVal : gfactor * m_tiltVal;

	m_lgain = exp(g1 / amp) - 1;
	m_hgain = exp(g2 / amp) - 1;

	const float omega = 2 * F_PI * m_compressorControls.m_tiltFreqModel.value();
	const float n = 1 / (m_sampleRate * 3 + omega);
	m_a0 = 2 * omega * n;
	m_b1 = (m_sampleRate * 3 - omega) * n;
}

void CompressorEffect::calcMix()
{
	m_mixVal = m_compressorControls.m_mixModel.value() * 0.01;
}



bool CompressorEffect::processAudioBuffer(sampleFrame* buf, const fpp_t frames)
{
	if (!isEnabled() || !isRunning())
	{
		// Clear lookahead buffers and other values when needed
		if (!m_cleanedBuffers)
		{
			m_yL[0] = m_yL[1] = COMP_NOISE_FLOOR;
			m_gainResult[0] = m_gainResult[1] = 1;
			m_displayPeak[0] = m_displayPeak[1] = COMP_NOISE_FLOOR;
			m_displayGain[0] = m_displayGain[1] = COMP_NOISE_FLOOR;
			std::fill(std::begin(m_lookaheadBuf[0]), std::end(m_lookaheadBuf[0]), 0);
			std::fill(std::begin(m_lookaheadBuf[1]), std::end(m_lookaheadBuf[1]), 0);
			m_lookaheadBufLoc[0] = 0;
			m_lookaheadBufLoc[1] = 0;
			std::fill(std::begin(m_preLookaheadBuf[0]), std::end(m_preLookaheadBuf[0]), 0);
			std::fill(std::begin(m_preLookaheadBuf[1]), std::end(m_preLookaheadBuf[1]), 0);
			m_preLookaheadBufLoc[0] = 0;
			m_preLookaheadBufLoc[1] = 0;
			std::fill(std::begin(m_inputBuf[0]), std::end(m_inputBuf[0]), 0);
			std::fill(std::begin(m_inputBuf[1]), std::end(m_inputBuf[1]), 0);
			m_inputBufLoc = 0;
			m_cleanedBuffers = true;
		}
		return false;
	}
	else
	{
		m_cleanedBuffers = false;
	}

	float outSum = 0.0;
	const float d = dryLevel();
	const float w = wetLevel();

	float lOutPeak = 0.0;
	float rOutPeak = 0.0;
	float lInPeak = 0.0;
	float rInPeak = 0.0;
	
	const bool midside = m_compressorControls.m_midsideModel.value();
	const bool peakmode = m_compressorControls.m_peakmodeModel.value();
	const float inBalance = m_compressorControls.m_inBalanceModel.value();
	const float outBalance = m_compressorControls.m_outBalanceModel.value();
	const bool limiter = m_compressorControls.m_limiterModel.value();
	const float blend = m_compressorControls.m_blendModel.value();
	const float stereoBalance = m_compressorControls.m_stereoBalanceModel.value();
	const bool autoMakeup = m_compressorControls.m_autoMakeupModel.value();
	const int stereoLink = m_compressorControls.m_stereoLinkModel.value();
	const bool audition = m_compressorControls.m_auditionModel.value();
	const bool feedback = m_compressorControls.m_feedbackModel.value();
	const bool lookahead = m_compressorControls.m_lookaheadModel.value();

	for(fpp_t f = 0; f < frames; ++f)
	{
		sample_t drySignal[2] = {buf[f][0], buf[f][1]};
		sample_t s[2] = {drySignal[0] * m_inGainVal, drySignal[1] * m_inGainVal};

		// Calculate tilt filters, to bias the sidechain to the low or high frequencies
		if (m_tiltVal)
		{
			calcTiltFilter(s[0], s[0], 0);
			calcTiltFilter(s[1], s[1], 1);
		}

		if (midside)// Convert left/right to mid/side
		{
			const float temp = s[0];
			s[0] = (temp + s[1]) * 0.5;
			s[1] = temp - s[1];
		}

		s[0] *= inBalance > 0 ? 1 - inBalance : 1;
		s[1] *= inBalance < 0 ? 1 + inBalance : 1;

		m_gainResult[0] = 0;
		m_gainResult[1] = 0;

		for (int i = 0; i < 2; i++)
		{
			float inputValue = feedback ? m_prevOut[i] : s[i];

			// Calculate the crest factor of the audio by diving the peak by the RMS
			m_crestPeakVal[i] = qMax(inputValue * inputValue, m_crestTimeConst * m_crestPeakVal[i] + (1 - m_crestTimeConst) * (inputValue * inputValue));
			m_crestRmsVal[i] = m_crestTimeConst * m_crestRmsVal[i] + ((1 - m_crestTimeConst) * (inputValue * inputValue));
			m_crestFactorVal[i] = m_crestPeakVal[i] / m_crestRmsVal[i];

			m_rmsVal[i] = m_rmsTimeConst * m_rmsVal[i] + ((1 - m_rmsTimeConst) * (inputValue * inputValue));

			// Grab the peak or RMS value
			inputValue = qMax(COMP_NOISE_FLOOR, peakmode ? abs(inputValue) : sqrt(m_rmsVal[i]));

			// The following code uses math magic to semi-efficiently
			// find the largest value in the lookahead buffer.
			// This can probably be improved.
			if (lookahead)
			{
				// Pre-lookahead delay, so the total delay always matches 20 ms
				++m_preLookaheadBufLoc[i];
				if (m_preLookaheadBufLoc[i] >= m_preLookaheadLength)
				{
					m_preLookaheadBufLoc[i] = 0;
				}
				const float tempInputValue = inputValue;
				inputValue = m_preLookaheadBuf[i][m_preLookaheadBufLoc[i]];
				m_preLookaheadBuf[i][m_preLookaheadBufLoc[i]] = tempInputValue;


				// Increment ring buffer location
				++m_lookaheadBufLoc[i];
				if (m_lookaheadBufLoc[i] >= m_lookaheadLength)
				{
					m_lookaheadBufLoc[i] = 0;
				}

				m_lookaheadBuf[i][m_lookaheadBufLoc[i]] = inputValue;

				// If the new input value is larger than the stored maximum,
				// store that as the maximum
				if (inputValue >= m_maxLookaheadVal[i])
				{
					m_maxLookaheadVal[i] = inputValue;
					m_maxLookaheadTimer[i] = m_lookaheadLength;
				}

				// Decrement timer.  When the timer reaches 0, that means the
				// stored maximum value has left the buffer and a new
				// maximum value must be found.
				if (--m_maxLookaheadTimer[i] <= 0)
				{
					m_maxLookaheadTimer[i] = std::distance(std::begin(m_lookaheadBuf[i]),
						std::max_element(std::begin(m_lookaheadBuf[i]), std::begin(m_lookaheadBuf[i]) + m_lookaheadLength));
					m_maxLookaheadVal[i] = m_lookaheadBuf[i][m_maxLookaheadTimer[i]];
					m_maxLookaheadTimer[i] = realmod(m_maxLookaheadTimer[i] - m_lookaheadBufLoc[i], m_lookaheadLength);
				}

				inputValue = m_maxLookaheadVal[i];
			}

			float t = inputValue;

			if (t > m_yL[i])// Attack phase
			{
				// We want the "resting value" of our crest factor to be with a sine wave,
				// which with this variable has a value of 2.
				// So, we pull this value down to 0, and multiply it by the percentage of
				// automatic attack control that is applied.  We then add 2 back to it.
				float crestFactorValTemp = ((m_crestFactorVal[i] - 2.f) * m_autoAttVal) + 2.f;

				// Calculate attack value depending on crest factor
				const float att = m_autoAttVal
					? msToCoeff(2.f * m_compressorControls.m_attackModel.value() / (crestFactorValTemp))
					: m_attCoeff;

				m_yL[i] = m_yL[i] * att + (1 - att) * t;
				m_holdTimer[i] = m_holdLength;// Reset hold timer
			}
			else// Release phase
			{
				float crestFactorValTemp = ((m_crestFactorVal[i] - 2.f) * m_autoRelVal) + 2.f;

				const float rel = m_autoRelVal
					? msToCoeff(2.f * m_compressorControls.m_releaseModel.value() / (crestFactorValTemp))
					: m_relCoeff;

				if (m_holdTimer[i])// Don't change peak if hold is being applied
				{
					--m_holdTimer[i];
				}
				else
				{
					m_yL[i] = m_yL[i] * rel + (1 - rel) * t;
				}
			}

			// Keep it above the noise floor
			m_yL[i] = qMax(COMP_NOISE_FLOOR, m_yL[i]);

			// For the visualizer
			m_displayPeak[i] = qMax(m_yL[i], m_displayPeak[i]);

			const float currentPeakDbfs = ampToDbfs(m_yL[i]);

			// Now find the gain change that should be applied,
			// depending on the measured input value.
			if (currentPeakDbfs - m_thresholdVal < -m_kneeVal)// Below knee
			{
				m_gainResult[i] = currentPeakDbfs;
			}
			else if (currentPeakDbfs - m_thresholdVal < m_kneeVal)// Within knee
			{
				const float temp = currentPeakDbfs - m_thresholdVal + m_kneeVal;
				m_gainResult[i] = currentPeakDbfs + ((limiter ? 0 : m_ratioVal) - 1) * temp * temp / (4 * m_kneeVal);
			}
			else// Above knee
			{
				m_gainResult[i] = limiter
					? m_thresholdVal
					: m_thresholdVal + (currentPeakDbfs - m_thresholdVal) * m_ratioVal;
			}

			m_gainResult[i] = dbfsToAmp(m_gainResult[i]) / m_yL[i];
			m_gainResult[i] = qMax(m_rangeVal, m_gainResult[i]);
		}

		switch (stereoLink)
		{
			case Unlinked:
			{
				break;
			}
			case Maximum:
			{
				m_gainResult[0] = m_gainResult[1] = qMin(m_gainResult[0], m_gainResult[1]);
				break;
			}
			case Average:
			{
				m_gainResult[0] = m_gainResult[1] = (m_gainResult[0] + m_gainResult[1]) * 0.5f;
				break;
			}
			case Minimum:
			{
				m_gainResult[0] = m_gainResult[1] = qMax(m_gainResult[0], m_gainResult[1]);
				break;
			}
			case Blend:
			{
				if (blend > 0)// 0 is unlinked
				{
					if (blend <= 1)// Blend to minimum volume
					{
						const float temp1 = qMin(m_gainResult[0], m_gainResult[1]);
						m_gainResult[0] = linearInterpolate(m_gainResult[0], temp1, blend);
						m_gainResult[1] = linearInterpolate(m_gainResult[1], temp1, blend);
					}
					else if (blend <= 2)// Blend to average volume
					{
						const float temp1 = qMin(m_gainResult[0], m_gainResult[1]);
						const float temp2 = (m_gainResult[0] + m_gainResult[1]) * 0.5f;
						m_gainResult[0] = linearInterpolate(temp1, temp2, blend - 1);
						m_gainResult[1] = m_gainResult[0];
					}
					else// Blend to maximum volume
					{
						const float temp1 = (m_gainResult[0] + m_gainResult[1]) * 0.5f;
						const float temp2 = qMax(m_gainResult[0], m_gainResult[1]);
						m_gainResult[0] = linearInterpolate(temp1, temp2, blend - 2);
						m_gainResult[1] = m_gainResult[0];
					}
				}
				break;
			}
		}

		// Bias compression to the left or right (or mid or side)
		if (stereoBalance != 0)
		{
			m_gainResult[0] = 1 - ((1 - m_gainResult[0]) * (stereoBalance > 0 ? 1 - stereoBalance : 1));
			m_gainResult[1] = 1 - ((1 - m_gainResult[1]) * (stereoBalance < 0 ? 1 + stereoBalance : 1));
		}

		// For visualizer
		m_displayGain[0] = qMax(m_gainResult[0], m_displayGain[0]);
		m_displayGain[1] = qMax(m_gainResult[1], m_displayGain[1]);

		// Delay the signal by 20 ms via ring buffer if lookahead is enabled
		if (lookahead)
		{
			++m_inputBufLoc;
			if (m_inputBufLoc >= m_lookaheadDelayLength)
			{
				m_inputBufLoc = 0;
			}

			const float temp[2] = {drySignal[0], drySignal[1]};
			s[0] = m_inputBuf[0][m_inputBufLoc];
			s[1] = m_inputBuf[1][m_inputBufLoc];

			m_inputBuf[0][m_inputBufLoc] = temp[0];
			m_inputBuf[1][m_inputBufLoc] = temp[1];
		}
		else
		{
			s[0] = drySignal[0];
			s[1] = drySignal[1];
		}

		float delayedDrySignal[2] = {s[0], s[1]};
		
		if (midside)// Convert left/right to mid/side
		{
			const float temp = s[0];
			s[0] = (temp + s[1]) * 0.5;
			s[1] = temp - s[1];
		}

		s[0] *= inBalance > 0 ? 1 - inBalance : 1;
		s[1] *= inBalance < 0 ? 1 + inBalance : 1;

		s[0] *= m_gainResult[0] * m_inGainVal * m_outGainVal * (outBalance > 0 ? 1 - outBalance : 1);
		s[1] *= m_gainResult[1] * m_inGainVal * m_outGainVal * (outBalance < 0 ? 1 + outBalance : 1);

		if (midside)// Convert mid/side back to left/right
		{
			const float temp1 = s[0];
			const float temp2 = s[1] * 0.5;
			s[0] = temp1 + temp2;
			s[1] = temp1 - temp2;
		}

		m_prevOut[0] = s[0];
		m_prevOut[1] = s[1];

		// Negate wet signal from dry signal
		if (audition)
		{
			s[0] = (-s[0] + delayedDrySignal[0] * m_outGainVal);
			s[1] = (-s[1] + delayedDrySignal[1] * m_outGainVal);
		}
		else if (autoMakeup)
		{
			s[0] *= m_autoMakeupVal;
			s[1] *= m_autoMakeupVal;
		}

		// Calculate wet/dry value results
		const float temp1 = delayedDrySignal[0];
		const float temp2 = delayedDrySignal[1];
		buf[f][0] = d * temp1 + w * s[0];
		buf[f][1] = d * temp2 + w * s[1];
		buf[f][0] = (1 - m_mixVal) * temp1 + m_mixVal * buf[f][0];
		buf[f][1] = (1 - m_mixVal) * temp2 + m_mixVal * buf[f][1];

		outSum += buf[f][0] * buf[f][0] + buf[f][1] * buf[f][1];

		lInPeak = drySignal[0] > lInPeak ? drySignal[0] : lInPeak;
		rInPeak = drySignal[1] > rInPeak ? drySignal[1] : rInPeak;
		lOutPeak = s[0] > lOutPeak ? s[0] : lOutPeak;
		rOutPeak = s[1] > rOutPeak ? s[1] : rOutPeak;
	}

	checkGate(outSum / frames);
	m_compressorControls.m_outPeakL = lOutPeak;
	m_compressorControls.m_outPeakR = rOutPeak;
	m_compressorControls.m_inPeakL = lInPeak;
	m_compressorControls.m_inPeakR = rInPeak;

	return isRunning();
}


// Regular modulo doesn't handle negative numbers correctly.  This does.
inline int CompressorEffect::realmod(int k, int n)
{
	return (k %= n) < 0 ? k+n : k;
}

// Regular fmod doesn't handle negative numbers correctly.  This does.
inline float CompressorEffect::realfmod(float k, float n)
{
	return (k = fmod(k, n)) < 0 ? k+n : k;
}



inline void CompressorEffect::calcTiltFilter(sample_t inputSample, sample_t &outputSample, int filtNum)
{
	m_tiltOut[filtNum] = m_a0 * inputSample + m_b1 * m_tiltOut[filtNum];
	outputSample = inputSample + m_lgain * m_tiltOut[filtNum] + m_hgain * (inputSample - m_tiltOut[filtNum]);
}



void CompressorEffect::changeSampleRate()
{
	m_sampleRate = Engine::mixer()->processingSampleRate();

	m_coeffPrecalc = COMP_LOG / (m_sampleRate * 0.001f);

	// 200 ms
	m_crestTimeConst = exp(-1.f / (0.2f * m_sampleRate));

	// 20 ms
	m_lookaheadDelayLength = 0.02 * m_sampleRate;
	m_inputBuf[0].resize(m_lookaheadDelayLength);
	m_inputBuf[1].resize(m_lookaheadDelayLength);

	m_lookaheadBuf[0].resize(m_lookaheadDelayLength);
	m_lookaheadBuf[1].resize(m_lookaheadDelayLength);

	m_preLookaheadBuf[0].resize(m_lookaheadDelayLength);
	m_preLookaheadBuf[1].resize(m_lookaheadDelayLength);

	calcThreshold();
	calcKnee();
	calcRatio();
	calcAutoMakeup();// This should be after Threshold, Knee, and Ratio

	calcAttack();
	calcRelease();
	calcRange();
	calcLookaheadLength();
	calcHold();
	resizeRMS();
	calcOutGain();
	calcInGain();
	calcTiltCoeffs();
	calcMix();
}



extern "C"
{

// necessary for getting instance out of shared lib
PLUGIN_EXPORT Plugin * lmms_plugin_main(Model* parent, void* data)
{
	return new CompressorEffect(parent, static_cast<const Plugin::Descriptor::SubPluginFeatures::Key *>(data));
}

}