uk.co.modularaudio.util.audio.controlinterpolation.CDSpringAndDamperDouble12Interpolator.java Source code

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/**
 *
 * Copyright (C) 2015 - Daniel Hams, Modular Audio Limited
 *                      daniel.hams@gmail.com
 *
 * Mad 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 3 of the License, or
 * (at your option) any later version.
 *
 * Mad 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 Mad.  If not, see <http://www.gnu.org/licenses/>.
 *
 */

package uk.co.modularaudio.util.audio.controlinterpolation;

import java.util.Arrays;

import org.apache.commons.logging.Log;
import org.apache.commons.logging.LogFactory;

import uk.co.modularaudio.util.audio.format.DataRate;
import uk.co.modularaudio.util.audio.math.AudioMath;

public class CDSpringAndDamperDouble12Interpolator implements ControlValueInterpolator {
    @SuppressWarnings("unused")
    private static Log log = LogFactory.getLog(CDSpringAndDamperDouble12Interpolator.class.getName());

    // Vaguely close to low pass non 12
    private static final double FORCE_SCALE = 0.17;
    private static final double DAMPING_FACTOR = 2.0 * Math.sqrt(FORCE_SCALE);
    private static final double INTEGRATION_TIMESTEP_FOR_48K = 0.03;

    private static final double MIN_VALUE_DELTA_DB = -120.0;
    private static final double MIN_VALUE_DELTA = AudioMath.dbToLevel(MIN_VALUE_DELTA_DB);
    private static final double MIN_VELOCITY = 0.00001;

    private class State {
        double x;
        double v;
    };

    private class Derivative {
        double dx;
        double dv;
    };

    private double deltaTimestep;

    private final State curState = new State();
    private final State evaluateState = new State();

    private final Derivative a = new Derivative();
    private final Derivative b = new Derivative();
    private final Derivative c = new Derivative();
    private final Derivative d = new Derivative();

    private final Derivative integrationDerivative = new Derivative();

    private float lowerBound;
    private float upperBound;

    private double desPos = 0.0f;

    public CDSpringAndDamperDouble12Interpolator() {
        curState.x = 0.0;
        curState.v = 0.0;
        this.lowerBound = Float.NEGATIVE_INFINITY;
        this.upperBound = Float.POSITIVE_INFINITY;
        deltaTimestep = INTEGRATION_TIMESTEP_FOR_48K;
    }

    @Override
    public void resetLowerUpperBounds(final float lowerBound, final float upperBound) {
        this.lowerBound = lowerBound;
        this.upperBound = upperBound;
    }

    @Override
    public final void generateControlValues(final float[] output, final int outputIndex, final int length) {
        final int lastIndex = outputIndex + length;

        if (curState.v == 0.0 && curState.x == desPos) {
            //         log.debug("Filling as steady state");
            final float curStateFloat = (float) curState.x;
            Arrays.fill(output, outputIndex, lastIndex, curStateFloat);
        } else {
            //         final float delta = desPos - curState.x;
            //         log.debug("Performing integration desVal(" + desPos + ") delta(" + delta + ") - " + curState.x + " - " + curState.v );
            for (int curIndex = outputIndex; curIndex < lastIndex; ++curIndex) {
                integrate(curState, 0, deltaTimestep);
                final float curStateFloat = (float) curState.x;
                if (curStateFloat > upperBound) {
                    output[curIndex] = upperBound;
                } else if (curStateFloat < lowerBound) {
                    output[curIndex] = lowerBound;
                } else {
                    output[curIndex] = curStateFloat;
                }
            }
        }
    }

    @Override
    public final void notifyOfNewValue(final float value) {
        desPos = value;
    }

    @Override
    public final boolean checkForDenormal() {
        final double delta = desPos - curState.x;
        final double absX = (delta < 0.0 ? -delta : delta);
        final double absV = (curState.v < 0.0 ? -curState.v : curState.v);

        if (curState.x != desPos) {
            //         final float deltaInDb = AudioMath.levelToDbF( absX );
            //         log.debug("Not yet damped - pos(" + MathFormatter.slowFloatPrint( curState.x, 8, true ) +
            //               ") desPos(" + MathFormatter.slowFloatPrint( desPos, 8, true ) +
            //               ") delta(" + MathFormatter.slowFloatPrint( delta, 8, true ) +
            //               ") absV(" + MathFormatter.slowFloatPrint( absV, 8, true ) +
            //               ") deltaDb(" + MathFormatter.slowFloatPrint( deltaInDb, 8, true ) + ")");

            // Nudge by two bits towards desired value
            final int sigNum = (delta < 0 ? -2 : 2);
            curState.x = curState.x + sigNum * AudioMath.MIN_SIGNED_FLOATING_POINT_24BIT_VAL_D;
        }

        if (absX <= MIN_VALUE_DELTA && absV <= MIN_VELOCITY) {
            curState.x = desPos;
            curState.v = 0.0;
            //         log.debug("Damped to pos(" + MathFormatter.slowFloatPrint( desPos, 8, true ) +
            //               ") v=0");
            return true;
        } else {
            return false;
        }
        //      else
        //      {
        //         if( absX > MIN_VALUE_DELTA )
        //         {
        //            log.debug( "Not damping due to delta" );
        //         }
        //         if( absV > MIN_VELOCITY )
        //         {
        //            log.debug( "Not damping due to vel" );
        //         }
        //      }

    }

    @Override
    public final void hardSetValue(final float value) {
        curState.x = value;
        curState.v = 0.0;
        desPos = value;
    }

    private final void evaluate(final State initial, final double t, final double dt, final Derivative d,
            final Derivative o) {
        evaluateState.x = initial.x + d.dx * dt;
        evaluateState.v = initial.v + d.dv * dt;

        o.dx = evaluateState.v;
        o.dv = acceleration(evaluateState, t + dt);
        //      log.debug("Acceleration is " + output.dv );
    }

    private final double acceleration(final State state, final double t) {
        final double k = FORCE_SCALE;
        final double b = DAMPING_FACTOR;
        final double posDiff = state.x - desPos;
        //      log.debug("PosDiff is " + posDiff );
        return -k * posDiff - b * state.v;
    }

    private final void integrate(final State state, final double t, final double dt) {
        evaluate(state, t, 0.0, integrationDerivative, a);
        evaluate(state, t, dt * 0.5, a, b);
        evaluate(state, t, dt * 0.5, b, c);
        evaluate(state, t, dt, c, d);

        final double dxdt = 1.0 / 6.0 * (a.dx + 2.0 * (b.dx + c.dx) + d.dx);
        final double dvdt = 1.0 / 6.0 * (a.dv + 2.0 * (b.dv + c.dv) + d.dv);

        state.x = (state.x + dxdt * dt);
        state.v = (state.v + dvdt * dt);
    }

    @Override
    public void resetSampleRateAndPeriod(final int sampleRate, final int periodLengthFrames,
            final int interpolatorLengthFrames) {
        deltaTimestep = (DataRate.SR_48000.getValue() * INTEGRATION_TIMESTEP_FOR_48K) / sampleRate;
    }

    @Override
    public float getValue() {
        return (float) desPos;
    }
}