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/*
* 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.
*----------------------------------------------------------------------
*/
package javazoom.jl.decoder;
/**
* The <code>Equalizer</code> class can be used to specify
* equalization settings for the MPEG audio decoder.
* <p>
* 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 <code>Equalizer</code> 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];
for (int i=0, maxCount=BANDS; 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;
}
}
}
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