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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
/** * 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; } }