The source-code.biz Java DSP collection

A collection of Java classes for Digital Signal Processing

API documentation:	apidocs
Download JAR file:	dsp-collection.jar
Download full package:	dsp-collection.zip
Source code repository:	GitHub

Overview of the primary classes

Digital filtering

IirFilter	apidocs	source	IIR filter implementation.
IirFilterDesignFisher	apidocs	source	IIR filter design, Fisher method. Supports Butterworth, Chebyshev and Bessel filters.
IirFilterDesignExstrom	apidocs	source	IIR filter design, Exstrom method. For Butterworth filters.
BesselFilterDesign	apidocs	source	Computes Bessel filter poles and Bessel polynomials.
EchoFilter	apidocs	source	Adds an echo to a signal.

Java Sound integration of the filter modules

IirFilterAudioInputStreamFisher	apidocs	source	Provides an AudioInputStream for filtering. Fisher version.
IirFilterAudioInputStreamExstrom	apidocs	source	Provides an AudioInputStream for filtering. Exstrom version.
EchoFilterAudioInputStream	apidocs	source	Provides an AudioInputStream that adds an echo to a sound.

Signal analysis / generation / modification

ActivityDetector	apidocs	source	Activity detector
EnvelopeDetector	apidocs	source	Envelope detector
BrownNoiseGenerator	apidocs	source	Brown noise generator
RmsNormalizer	apidocs	source	A simple signal level normalizer.

Transforms

Dft

apidocs

source

DFT (discrete Fourier transform), including Goertzel

Math

PolynomialRootFinderJenkinsTraub	apidocs	source	Polynomial root-finder, Jenkins-Traub version.
PolynomialRootFinderLaguerre	apidocs	source	Polynomial root-finder, Laguerre version.
PolynomialUtils	apidocs	source	Some utility routines for polynomial math.
Complex	apidocs	source	Complex numbers

Visualization (Swing based)

FunctionPlot	apidocs	source	A simple function plot component.
SignalPlot	apidocs	source	A Swing component for plotting a sampled signal. (like a very simple "oscilloscope").
TransferFunctionPlot	apidocs	source	A component to display the transfer curve of a filter.

Overview of the test and utility programs

Filter visualization

Use the mouse to zoom and scroll within the plot area.

TestIirFilterTransferPlotFisher	source	Displays the transfer function (linear gain and phase) of an IIR filter, Fisher version.
TestIirFilterTransferPlotExstrom	source	Displays the transfer function (linear gain and phase) of an IIR filter, Exstrom version.
TestIirFilterResponsePlotFisher	source	Displays the impulse or step response of an IIR filter, Fisher version.
TestIirFilterResponsePlotExstrom	source	Displays the impulse or step response of an IIR filter, Exstrom version.

Test and utility programs that operate on WAV files

The WAV files may be mono or multi-channel and 16 or 24 bit. But some of the programs only process the first channel.

WavFilterFisher	source	Filters a WAV file. Fisher version. Supports multi-channel WAV files.
WavFilterExstrom	source	Filters a WAV file. Exstrom version. Supports multi-channel WAV files.
WavSplitter	source	Splits a WAV file into multiple WAV files, according to the silence gaps within the record.
TestSignalPlot	source	A simple test program to display the signal of a WAV file.
TestEnvelopeDetector	source	Generates the envelope of a signal in a WAV file and writes it into another WAV file.
TestBrownNoiseGenerator	source	Generates a WAV file with brown noise.
TestRmsNormalizer	source	Reads a WAV file, normalizes it's amplitude level and writes the result into another WAV file.

Simple test programs for individual classes

TestBesselFilterDesign	source	Prints bessel polynomial coeffcients, Bessel filter frequency scaling factors and Bessel filter poles.
TestIirFilterDesignExstrom	source	Designs an IIR filter using the Exstrom method and prints the IIR filter coefficients.
TestIirFilterDesignFisher	source	Designs an IIR filter using the Fisher method and prints the IIR filter coefficients.
TestFunctionPlot	source	Displays a sin(x)/x function using the `FunctionPlot` class. Use the mouse to zoom and scroll.
TestEchoFilter	source	Real-time test program for the echo filter (microphone in / speaker out).

Test programs for quality assurance (QA) for some classes in this collection

TestDft	source	QA tests for the DFT / IDFT routines.
TestIirFilterDesignExstromJavaC	source	Uses random numbers to test various filter designs with the Exstrom method and compares the computed filter coefficients with the output of the C programs from Exstrom.
TestIirFilterDesignRandom	source	Uses random numbers to design various filters and compares the results of the Exstrom and Fisher modules.
TestPolynomialRootFinder	source	QA test program for the polynomial root finder classes (Jenkins-Traub and Laguerre). It first verifies the results for some examples. Then it uses random numbers to generate various polynomials, find their roots (zeros) and verify that the roots are correct by computing the polonomial coefficients from the roots (expansion) and comparing the coefficients.
TestPolynomialUtils	source	Some simple QA tests for the `PolynomialUtils` routines.

Some examples of how to use the test programs

Filter a WAV file with a 4th order Chebyshev bandpass for 1000 - 2000 Hz and -0.5 dB ripple:

java -cp dsp-collection.jar WavFilterFisher in.wav bandpass chebyshev 4 -0.5 1000 2000 out.wav

Display the transfer function, the step response and the impulse response of a 9th order Chebyshev lowpass filter with -1 dB ripple. (Use the mouse to zoom and scroll within the plot areas)

java -cp dsp-collection.jar TestIirFilterTransferPlotFisher lowpass chebyshev 9 -1 0.25 0
java -cp dsp-collection.jar TestIirFilterResponsePlotFisher lowpass chebyshev 9 -1 0.25 0 step
java -cp dsp-collection.jar TestIirFilterResponsePlotFisher lowpass chebyshev 9 -1 0.25 0 impulse

And here an example of how the transfer curve looks like when an IIR filter is instable. Zoom in at the upper left edge of the gain curve. When you increase the filter order, e.g. from 5 to 6, the effect gets worse.

java -cp dsp-collection.jar TestIirFilterTransferPlotFisher bandpass butterworth 5 0 0.0025 0.025