/*

 * Copyright (c) 2007, 2013, Oracle and/or its affiliates. All rights reserved.

 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.

 *

 * This code is free software; you can redistribute it and/or modify it

 * under the terms of the GNU General Public License version 2 only, as

 * published by the Free Software Foundation.  Oracle designates this

 * particular file as subject to the "Classpath" exception as provided

 * by Oracle in the LICENSE file that accompanied this code.

 *

 * This code 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

 * version 2 for more details (a copy is included in the LICENSE file that

 * accompanied this code).

 *

 * You should have received a copy of the GNU General Public License version

 * 2 along with this work; if not, write to the Free Software Foundation,

 * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.

 *

 * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA

 * or visit www.oracle.com if you need additional information or have any

 * questions.

 */

package com.sun.media.sound;

/**

 * Infinite impulse response (IIR) filter class.

 *

 * The filters where implemented and adapted using algorithms from musicdsp.org

 * archive: 1-RC and C filter, Simple 2-pole LP LP and HP filter, biquad,

 * tweaked butterworth RBJ Audio-EQ-Cookbook, EQ filter kookbook

 *

 * @author Karl Helgason

 */

public final class SoftFilter {

    public final static int FILTERTYPE_LP6 = 0x00;

    public final static int FILTERTYPE_LP12 = 0x01;

    public final static int FILTERTYPE_HP12 = 0x11;

    public final static int FILTERTYPE_BP12 = 0x21;

    public final static int FILTERTYPE_NP12 = 0x31;

    public final static int FILTERTYPE_LP24 = 0x03;

    public final static int FILTERTYPE_HP24 = 0x13;

    //

    // 0x0 = 1st-order, 6 dB/oct

    // 0x1 = 2nd-order, 12 dB/oct

    // 0x2 = 3rd-order, 18 dB/oct

    // 0x3 = 4th-order, 24 db/oct

    //

    // 0x00 = LP, Low Pass Filter

    // 0x10 = HP, High Pass Filter

    // 0x20 = BP, Band Pass Filter

    // 0x30 = NP, Notch or Band Elimination Filter

    //

    private int filtertype = FILTERTYPE_LP6;

    private final float samplerate;

    private float x1;

    private float x2;

    private float y1;

    private float y2;

    private float xx1;

    private float xx2;

    private float yy1;

    private float yy2;

    private float a0;

    private float a1;

    private float a2;

    private float b1;

    private float b2;

    private float q;

    private float gain = 1;

    private float wet = 0;

    private float last_wet = 0;

    private float last_a0;

    private float last_a1;

    private float last_a2;

    private float last_b1;

    private float last_b2;

    private float last_q;

    private float last_gain;

    private boolean last_set = false;

    private double cutoff = 44100;

    private double resonancedB = 0;

    private boolean dirty = true;

    public SoftFilter(float samplerate) {

        this.samplerate = samplerate;

        dirty = true;

    }

    public void setFrequency(double cent) {

        if (cutoff == cent)

            return;

        cutoff = cent;

        dirty = true;

    }

    public void setResonance(double db) {

        if (resonancedB == db)

            return;

        resonancedB = db;

        dirty = true;

    }

    public void reset() {

        dirty = true;

        last_set = false;

        x1 = 0;

        x2 = 0;

        y1 = 0;

        y2 = 0;

        xx1 = 0;

        xx2 = 0;

        yy1 = 0;

        yy2 = 0;

        wet = 0.0f;

        gain = 1.0f;

        a0 = 0;

        a1 = 0;

        a2 = 0;

        b1 = 0;

        b2 = 0;

    }

    public void setFilterType(int filtertype) {

        this.filtertype = filtertype;

    }

    public void processAudio(SoftAudioBuffer sbuffer) {

        if (filtertype == FILTERTYPE_LP6)

            filter1(sbuffer);

        if (filtertype == FILTERTYPE_LP12)

            filter2(sbuffer);

        if (filtertype == FILTERTYPE_HP12)

            filter2(sbuffer);

        if (filtertype == FILTERTYPE_BP12)

            filter2(sbuffer);

        if (filtertype == FILTERTYPE_NP12)

            filter2(sbuffer);

        if (filtertype == FILTERTYPE_LP24)

            filter4(sbuffer);

        if (filtertype == FILTERTYPE_HP24)

            filter4(sbuffer);

    }

    public void filter4(SoftAudioBuffer sbuffer) {

        float[] buffer = sbuffer.array();

        if (dirty) {

            filter2calc();

            dirty = false;

        }

        if (!last_set) {

            last_a0 = a0;

            last_a1 = a1;

            last_a2 = a2;

            last_b1 = b1;

            last_b2 = b2;

            last_gain = gain;

            last_wet = wet;

            last_set = true;

        }

        if (wet > 0 || last_wet > 0) {

            int len = buffer.length;

            float a0 = this.last_a0;

            float a1 = this.last_a1;

            float a2 = this.last_a2;

            float b1 = this.last_b1;

            float b2 = this.last_b2;

            float gain = this.last_gain;

            float wet = this.last_wet;

            float a0_delta = (this.a0 - this.last_a0) / len;

            float a1_delta = (this.a1 - this.last_a1) / len;

            float a2_delta = (this.a2 - this.last_a2) / len;

            float b1_delta = (this.b1 - this.last_b1) / len;

            float b2_delta = (this.b2 - this.last_b2) / len;

            float gain_delta = (this.gain - this.last_gain) / len;

            float wet_delta = (this.wet - this.last_wet) / len;

            float x1 = this.x1;

            float x2 = this.x2;

            float y1 = this.y1;

            float y2 = this.y2;

            float xx1 = this.xx1;

            float xx2 = this.xx2;

            float yy1 = this.yy1;

            float yy2 = this.yy2;

            if (wet_delta != 0) {

                for (int i = 0; i < len; i++) {

                    a0 += a0_delta;

                    a1 += a1_delta;

                    a2 += a2_delta;

                    b1 += b1_delta;

                    b2 += b2_delta;

                    gain += gain_delta;

                    wet += wet_delta;

                    float x = buffer[i];

                    float y = (a0*x + a1*x1 + a2*x2 - b1*y1 - b2*y2);

                    float xx = (y * gain) * wet + (x) * (1 - wet);

                    x2 = x1;

                    x1 = x;

                    y2 = y1;

                    y1 = y;

                    float yy = (a0*xx + a1*xx1 + a2*xx2 - b1*yy1 - b2*yy2);

                    buffer[i] = (yy * gain) * wet + (xx) * (1 - wet);

                    xx2 = xx1;

                    xx1 = xx;

                    yy2 = yy1;

                    yy1 = yy;

                }

            } else if (a0_delta == 0 && a1_delta == 0 && a2_delta == 0

                    && b1_delta == 0 && b2_delta == 0) {

                for (int i = 0; i < len; i++) {

                    float x = buffer[i];

                    float y = (a0*x + a1*x1 + a2*x2 - b1*y1 - b2*y2);

                    float xx = (y * gain) * wet + (x) * (1 - wet);

                    x2 = x1;

                    x1 = x;

                    y2 = y1;

                    y1 = y;

                    float yy = (a0*xx + a1*xx1 + a2*xx2 - b1*yy1 - b2*yy2);

                    buffer[i] = (yy * gain) * wet + (xx) * (1 - wet);

                    xx2 = xx1;

                    xx1 = xx;

                    yy2 = yy1;

                    yy1 = yy;

                }

            } else {

                for (int i = 0; i < len; i++) {

                    a0 += a0_delta;

                    a1 += a1_delta;

                    a2 += a2_delta;

                    b1 += b1_delta;

                    b2 += b2_delta;

                    gain += gain_delta;

                    float x = buffer[i];

                    float y = (a0*x + a1*x1 + a2*x2 - b1*y1 - b2*y2);

                    float xx = (y * gain) * wet + (x) * (1 - wet);

                    x2 = x1;

                    x1 = x;

                    y2 = y1;

                    y1 = y;

                    float yy = (a0*xx + a1*xx1 + a2*xx2 - b1*yy1 - b2*yy2);

                    buffer[i] = (yy * gain) * wet + (xx) * (1 - wet);

                    xx2 = xx1;

                    xx1 = xx;

                    yy2 = yy1;

                    yy1 = yy;

                }

            }

            if (Math.abs(x1) < 1.0E-8)

                x1 = 0;

            if (Math.abs(x2) < 1.0E-8)

                x2 = 0;

            if (Math.abs(y1) < 1.0E-8)

                y1 = 0;

            if (Math.abs(y2) < 1.0E-8)

                y2 = 0;

            this.x1 = x1;

            this.x2 = x2;

            this.y1 = y1;

            this.y2 = y2;

            this.xx1 = xx1;

            this.xx2 = xx2;

            this.yy1 = yy1;

            this.yy2 = yy2;

        }

        this.last_a0 = this.a0;

        this.last_a1 = this.a1;

        this.last_a2 = this.a2;

        this.last_b1 = this.b1;

        this.last_b2 = this.b2;

        this.last_gain = this.gain;

        this.last_wet = this.wet;

    }

    private double sinh(double x) {

        return (Math.exp(x) - Math.exp(-x)) * 0.5;

    }

    public void filter2calc() {

        double resonancedB = this.resonancedB;

        if (resonancedB < 0)

            resonancedB = 0;    // Negative dB are illegal.

        if (resonancedB > 30)

            resonancedB = 30;   // At least 22.5 dB is needed.

        if (filtertype == FILTERTYPE_LP24 || filtertype == FILTERTYPE_HP24)

            resonancedB *= 0.6;

        if (filtertype == FILTERTYPE_BP12) {

            wet = 1;

            double r = (cutoff / samplerate);

            if (r > 0.45)

                r = 0.45;

            double bandwidth = Math.PI * Math.pow(10.0, -(resonancedB / 20));

            double omega = 2 * Math.PI * r;

            double cs = Math.cos(omega);

            double sn = Math.sin(omega);

            double alpha = sn * sinh((Math.log(2)*bandwidth*omega) / (sn * 2));

            double b0 = alpha;

            double b1 = 0;

            double b2 = -alpha;

            double a0 = 1 + alpha;

            double a1 = -2 * cs;

            double a2 = 1 - alpha;

            double cf = 1.0 / a0;

            this.b1 = (float) (a1 * cf);

            this.b2 = (float) (a2 * cf);

            this.a0 = (float) (b0 * cf);

            this.a1 = (float) (b1 * cf);

            this.a2 = (float) (b2 * cf);

        }

        if (filtertype == FILTERTYPE_NP12) {

            wet = 1;

            double r = (cutoff / samplerate);

            if (r > 0.45)

                r = 0.45;

            double bandwidth = Math.PI * Math.pow(10.0, -(resonancedB / 20));

            double omega = 2 * Math.PI * r;

            double cs = Math.cos(omega);

            double sn = Math.sin(omega);

            double alpha = sn * sinh((Math.log(2)*bandwidth*omega) / (sn*2));

            double b0 = 1;

            double b1 = -2 * cs;

            double b2 = 1;

            double a0 = 1 + alpha;

            double a1 = -2 * cs;

            double a2 = 1 - alpha;

            double cf = 1.0 / a0;

            this.b1 = (float)(a1 * cf);

            this.b2 = (float)(a2 * cf);

            this.a0 = (float)(b0 * cf);

            this.a1 = (float)(b1 * cf);

            this.a2 = (float)(b2 * cf);

        }

        if (filtertype == FILTERTYPE_LP12 || filtertype == FILTERTYPE_LP24) {

            double r = (cutoff / samplerate);

            if (r > 0.45) {

                if (wet == 0) {

                    if (resonancedB < 0.00001)

                        wet = 0.0f;

                    else

                        wet = 1.0f;

                }

                r = 0.45;

            } else

                wet = 1.0f;

            double c = 1.0 / (Math.tan(Math.PI * r));

            double csq = c * c;

            double resonance = Math.pow(10.0, -(resonancedB / 20));

            double q = Math.sqrt(2.0f) * resonance;

            double a0 = 1.0 / (1.0 + (q * c) + (csq));

            double a1 = 2.0 * a0;

            double a2 = a0;

            double b1 = (2.0 * a0) * (1.0 - csq);

            double b2 = a0 * (1.0 - (q * c) + csq);

            this.a0 = (float)a0;

            this.a1 = (float)a1;

            this.a2 = (float)a2;

            this.b1 = (float)b1;

            this.b2 = (float)b2;

        }

        if (filtertype == FILTERTYPE_HP12 || filtertype == FILTERTYPE_HP24) {

            double r = (cutoff / samplerate);

            if (r > 0.45)

                r = 0.45;

            if (r < 0.0001)

                r = 0.0001;

            wet = 1.0f;

            double c = (Math.tan(Math.PI * (r)));

            double csq = c * c;

            double resonance = Math.pow(10.0, -(resonancedB / 20));

            double q = Math.sqrt(2.0f) * resonance;

            double a0 = 1.0 / (1.0 + (q * c) + (csq));

            double a1 = -2.0 * a0;

            double a2 = a0;

            double b1 = (2.0 * a0) * (csq - 1.0);

            double b2 = a0 * (1.0 - (q * c) + csq);

            this.a0 = (float)a0;

            this.a1 = (float)a1;

            this.a2 = (float)a2;

            this.b1 = (float)b1;

            this.b2 = (float)b2;

        }

    }

    public void filter2(SoftAudioBuffer sbuffer) {

        float[] buffer = sbuffer.array();

        if (dirty) {

            filter2calc();

            dirty = false;

        }

        if (!last_set) {

            last_a0 = a0;

            last_a1 = a1;

            last_a2 = a2;

            last_b1 = b1;

            last_b2 = b2;

            last_q = q;

            last_gain = gain;

            last_wet = wet;

            last_set = true;

        }

        if (wet > 0 || last_wet > 0) {

            int len = buffer.length;

            float a0 = this.last_a0;

            float a1 = this.last_a1;

            float a2 = this.last_a2;

            float b1 = this.last_b1;

            float b2 = this.last_b2;

            float gain = this.last_gain;

            float wet = this.last_wet;

            float a0_delta = (this.a0 - this.last_a0) / len;

            float a1_delta = (this.a1 - this.last_a1) / len;

            float a2_delta = (this.a2 - this.last_a2) / len;

            float b1_delta = (this.b1 - this.last_b1) / len;

            float b2_delta = (this.b2 - this.last_b2) / len;

            float gain_delta = (this.gain - this.last_gain) / len;

            float wet_delta = (this.wet - this.last_wet) / len;

            float x1 = this.x1;

            float x2 = this.x2;

            float y1 = this.y1;

            float y2 = this.y2;

            if (wet_delta != 0) {

                for (int i = 0; i < len; i++) {

                    a0 += a0_delta;

                    a1 += a1_delta;

                    a2 += a2_delta;

                    b1 += b1_delta;

                    b2 += b2_delta;

                    gain += gain_delta;

                    wet += wet_delta;

                    float x = buffer[i];

                    float y = (a0*x + a1*x1 + a2*x2 - b1*y1 - b2*y2);

                    buffer[i] = (y * gain) * wet + (x) * (1 - wet);

                    x2 = x1;

                    x1 = x;

                    y2 = y1;

                    y1 = y;

                }

            } else if (a0_delta == 0 && a1_delta == 0 && a2_delta == 0

                    && b1_delta == 0 && b2_delta == 0) {

                for (int i = 0; i < len; i++) {

                    float x = buffer[i];

                    float y = (a0*x + a1*x1 + a2*x2 - b1*y1 - b2*y2);

                    buffer[i] = y * gain;

                    x2 = x1;

                    x1 = x;

                    y2 = y1;

                    y1 = y;

                }

            } else {

                for (int i = 0; i < len; i++) {

                    a0 += a0_delta;

                    a1 += a1_delta;

                    a2 += a2_delta;

                    b1 += b1_delta;

                    b2 += b2_delta;

                    gain += gain_delta;

                    float x = buffer[i];

                    float y = (a0*x + a1*x1 + a2*x2 - b1*y1 - b2*y2);

                    buffer[i] = y * gain;

                    x2 = x1;

                    x1 = x;

                    y2 = y1;

                    y1 = y;

                }

            }

            if (Math.abs(x1) < 1.0E-8)

                x1 = 0;

            if (Math.abs(x2) < 1.0E-8)

                x2 = 0;

            if (Math.abs(y1) < 1.0E-8)

                y1 = 0;

            if (Math.abs(y2) < 1.0E-8)

                y2 = 0;

            this.x1 = x1;

            this.x2 = x2;

            this.y1 = y1;

            this.y2 = y2;

        }

        this.last_a0 = this.a0;

        this.last_a1 = this.a1;

        this.last_a2 = this.a2;

        this.last_b1 = this.b1;

        this.last_b2 = this.b2;

        this.last_q = this.q;

        this.last_gain = this.gain;

        this.last_wet = this.wet;

    }

    public void filter1calc() {

        if (cutoff < 120)

            cutoff = 120;

        double c = (7.0 / 6.0) * Math.PI * 2 * cutoff / samplerate;

        if (c > 1)

            c = 1;

        a0 = (float)(Math.sqrt(1 - Math.cos(c)) * Math.sqrt(0.5 * Math.PI));

        if (resonancedB < 0)

            resonancedB = 0;

        if (resonancedB > 20)

            resonancedB = 20;

        q = (float)(Math.sqrt(0.5) * Math.pow(10.0, -(resonancedB / 20)));

        gain = (float)Math.pow(10, -((resonancedB)) / 40.0);

        if (wet == 0.0f)

            if (resonancedB > 0.00001 || c < 0.9999999)

                wet = 1.0f;

    }

    public void filter1(SoftAudioBuffer sbuffer) {

        if (dirty) {

            filter1calc();

            dirty = false;

        }

        if (!last_set) {

            last_a0 = a0;

            last_q = q;

            last_gain = gain;

            last_wet = wet;

            last_set = true;

        }

        if (wet > 0 || last_wet > 0) {

            float[] buffer = sbuffer.array();

            int len = buffer.length;

            float a0 = this.last_a0;

            float q = this.last_q;

            float gain = this.last_gain;

            float wet = this.last_wet;

            float a0_delta = (this.a0 - this.last_a0) / len;

            float q_delta = (this.q - this.last_q) / len;

            float gain_delta = (this.gain - this.last_gain) / len;

            float wet_delta = (this.wet - this.last_wet) / len;

            float y2 = this.y2;

            float y1 = this.y1;

            if (wet_delta != 0) {

                for (int i = 0; i < len; i++) {

                    a0 += a0_delta;

                    q += q_delta;

                    gain += gain_delta;

                    wet += wet_delta;

                    float ga0 = (1 - q * a0);

                    y1 = ga0 * y1 + (a0) * (buffer[i] - y2);

                    y2 = ga0 * y2 + (a0) * y1;

                    buffer[i] = y2 * gain * wet + buffer[i] * (1 - wet);

                }

            } else if (a0_delta == 0 && q_delta == 0) {

                float ga0 = (1 - q * a0);

                for (int i = 0; i < len; i++) {

                    y1 = ga0 * y1 + (a0) * (buffer[i] - y2);

                    y2 = ga0 * y2 + (a0) * y1;

                    buffer[i] = y2 * gain;

                }

            } else {

                for (int i = 0; i < len; i++) {

                    a0 += a0_delta;

                    q += q_delta;

                    gain += gain_delta;

                    float ga0 = (1 - q * a0);

                    y1 = ga0 * y1 + (a0) * (buffer[i] - y2);

                    y2 = ga0 * y2 + (a0) * y1;

                    buffer[i] = y2 * gain;

                }

            }

            if (Math.abs(y2) < 1.0E-8)

                y2 = 0;

            if (Math.abs(y1) < 1.0E-8)

                y1 = 0;

            this.y2 = y2;

            this.y1 = y1;

        }

        this.last_a0 = this.a0;

        this.last_q = this.q;

        this.last_gain = this.gain;

        this.last_wet = this.wet;

    }

}