/* * 11/19/04 1.0 moved to LGPL. * 12/12/99 Initial version. mdm@techie.com *----------------------------------------------------------------------- * This program is free software; you can redistribute it and/or modify * it under the terms of the GNU Library 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 Library General Public License for more details. * * You should have received a copy of the GNU Library General Public * License along with this program; if not, write to the Free Software * Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA. *---------------------------------------------------------------------- */ /** * The Equalizer class can be used to specify equalization settings * for the MPEG audio decoder. *

* The equalizer consists of 32 band-pass filters. Each band of the equalizer * can take on a fractional value between -1.0 and +1.0. At -1.0, the input * signal is attenuated by 6dB, at +1.0 the signal is amplified by 6dB. * * @see Decoder * * @author MDM */ public final class Equalizer { /** * Equalizer setting to denote that a given band will not be present in the * output signal. */ static public final float BAND_NOT_PRESENT = Float.NEGATIVE_INFINITY; static public final Equalizer PASS_THRU_EQ = new Equalizer(); private static final int BANDS = 32; private final float[] settings = new float[BANDS]; /** * Creates a new Equalizer instance. */ public Equalizer() { } // private Equalizer(float b1, float b2, float b3, float b4, float b5, // float b6, float b7, float b8, float b9, float b10, float b11, // float b12, float b13, float b14, float b15, float b16, // float b17, float b18, float b19, float b20); public Equalizer(float[] settings) { setFrom(settings); } public Equalizer(EQFunction eq) { setFrom(eq); } public void setFrom(float[] eq) { reset(); int max = (eq.length > BANDS) ? BANDS : eq.length; for (int i = 0; i < max; i++) { settings[i] = limit(eq[i]); } } public void setFrom(EQFunction eq) { reset(); int max = BANDS; for (int i = 0; i < max; i++) { settings[i] = limit(eq.getBand(i)); } } /** * Sets the bands of this equalizer to the value the bands of another * equalizer. Bands that are not present in both equalizers are ignored. */ public void setFrom(Equalizer eq) { if (eq != this) { setFrom(eq.settings); } } /** * Sets all bands to 0.0 */ public void reset() { for (int i = 0; i < BANDS; i++) { settings[i] = 0.0f; } } /** * Retrieves the number of bands present in this equalizer. */ public int getBandCount() { return settings.length; } public float setBand(int band, float neweq) { float eq = 0.0f; if ((band >= 0) && (band < BANDS)) { eq = settings[band]; settings[band] = limit(neweq); } return eq; } /** * Retrieves the eq setting for a given band. */ public float getBand(int band) { float eq = 0.0f; if ((band >= 0) && (band < BANDS)) { eq = settings[band]; } return eq; } private float limit(float eq) { if (eq == BAND_NOT_PRESENT) return eq; if (eq > 1.0f) return 1.0f; if (eq < -1.0f) return -1.0f; return eq; } /** * Retrieves an array of floats whose values represent a scaling factor that * can be applied to linear samples in each band to provide the equalization * represented by this instance. * * @return an array of factors that can be applied to the subbands. */ float[] getBandFactors() { float[] factors = new float[BANDS]; int maxCount = BANDS; for (int i = 0; i < maxCount; i++) { factors[i] = getBandFactor(settings[i]); } return factors; } /** * Converts an equalizer band setting to a sample factor. The factor is * determined by the function f = 2^n where n is the equalizer band setting in * the range [-1.0,1.0]. * */ float getBandFactor(float eq) { if (eq == BAND_NOT_PRESENT) return 0.0f; float f = (float) Math.pow(2.0, eq); return f; } static abstract public class EQFunction { /** * Returns the setting of a band in the equalizer. * * @param band * The index of the band to retrieve the setting for. * * @return the setting of the specified band. This is a value between -1 and * +1. */ public float getBand(int band) { return 0.0f; } } }