Package com.tino1b2be.dtmf

Enum Class WindowFunction

java.lang.Object

java.lang.Enum<WindowFunction>

com.tino1b2be.dtmf.WindowFunction

All Implemented Interfaces:

Serializable, Comparable<WindowFunction>, Constable

public enum WindowFunction
extends Enum<WindowFunction>

Window function applied to each analysis block before the Goertzel bank computes magnitudes.

DTMF detection at a bin width of 40–60 Hz already separates the eight DTMF frequencies by at least 100 Hz, so windowing is a precision knob rather than a necessity. The production defaults (defaults, forTelephony, forVoip, forNoisyAudio) all use RECTANGULAR; the advanced builder can override to HAMMING or HANN when sidelobe leakage from a nearby non-DTMF tone is a concern.

Formulas (for a window of length N, n = 0..N-1):

• RECTANGULAR — identity; leaves samples unchanged.
• HAMMING — 0.54 - 0.46 · cos(2π · n / (N - 1)).
• HANN — 0.5 · (1 - cos(2π · n / (N - 1))). At the endpoints the coefficient is exactly 0.

The single-sample window (N == 1) is treated as a pass-through for every shape: the textbook formulas have a zero-width denominator in that case, and the only sensible coefficient is 1.0.

Since:

2.0.0

Nested Class Summary

Nested classes/interfaces inherited from class java.lang.Enum

Enum.EnumDesc<E extends Enum<E>>

Enum Constant Summary

Enum Constants

Enum Constant	Description
HAMMING	Hamming window: 0.54 - 0.46 · cos(2π · n / (N - 1)).
HANN	Hann window: 0.5 · (1 - cos(2π · n / (N - 1))).
RECTANGULAR	No window; samples pass through unchanged.

Method Summary

Modifier and Type	Method	Description
abstract void	applyInPlace(double[] samples, int offset, int length)	Multiply each sample in samples[offset .. offset + length) by the corresponding window coefficient, in place.
static WindowFunction	valueOf(String name)	Returns the enum constant of this class with the specified name.
static WindowFunction[]	values()	Returns an array containing the constants of this enum class, in the order they are declared.

Methods inherited from class java.lang.Enum

clone, compareTo, describeConstable, equals, finalize, getDeclaringClass, hashCode, name, ordinal, toString, valueOf

Methods inherited from class java.lang.Object

getClass, notify, notifyAll, wait, wait, wait

Enum Constant Details

RECTANGULAR

public static final WindowFunction RECTANGULAR

No window; samples pass through unchanged.

HAMMING

public static final WindowFunction HAMMING

Hamming window: 0.54 - 0.46 · cos(2π · n / (N - 1)).

HANN

public static final WindowFunction HANN

Hann window: 0.5 · (1 - cos(2π · n / (N - 1))).

Method Details

values

public static WindowFunction[] values()

Returns an array containing the constants of this enum class, in the order they are declared.

Returns:

an array containing the constants of this enum class, in the order they are declared

valueOf

public static WindowFunction valueOf(String name)

Returns the enum constant of this class with the specified name. The string must match exactly an identifier used to declare an enum constant in this class. (Extraneous whitespace characters are not permitted.)

Parameters:

name - the name of the enum constant to be returned.

Returns:

the enum constant with the specified name

Throws:

IllegalArgumentException - if this enum class has no constant with the specified name

NullPointerException - if the argument is null

applyInPlace

public abstract void applyInPlace(double[] samples,
 int offset,
 int length)

Multiply each sample in samples[offset .. offset + length) by the corresponding window coefficient, in place.

Parameters:

samples - destination buffer; must be non-null

offset - index of the first sample to window; must be non-negative

length - number of samples to window; the window length

Throws:

NullPointerException - if samples is null

IndexOutOfBoundsException - if offset or length describes a range outside samples