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-rw-r--r--src/com/softsynth/math/AudioMath.java84
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diff --git a/src/com/softsynth/math/AudioMath.java b/src/com/softsynth/math/AudioMath.java
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-/*
- * Copyright 1998 Phil Burk, Mobileer Inc
- *
- * Licensed under the Apache License, Version 2.0 (the "License");
- * you may not use this file except in compliance with the License.
- * You may obtain a copy of the License at
- *
- * http://www.apache.org/licenses/LICENSE-2.0
- *
- * Unless required by applicable law or agreed to in writing, software
- * distributed under the License is distributed on an "AS IS" BASIS,
- * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
- * See the License for the specific language governing permissions and
- * limitations under the License.
- */
-
-package com.softsynth.math;
-
-/**
- * Miscellaneous math functions useful in Audio
- *
- * @author (C) 1998 Phil Burk
- */
-public class AudioMath {
- // use scalar to convert natural log to log_base_10
- private final static double a2dScalar = 20.0 / Math.log(10.0);
- public static final int CONCERT_A_PITCH = 69;
- public static final double CONCERT_A_FREQUENCY = 440.0;
- private static double mConcertAFrequency = CONCERT_A_FREQUENCY;
-
- /**
- * Convert amplitude to decibels. 1.0 is zero dB. 0.5 is -6.02 dB.
- */
- public static double amplitudeToDecibels(double amplitude) {
- double db = Math.log(amplitude) * a2dScalar;
- return db;
- }
-
- /**
- * Convert decibels to amplitude. Zero dB is 1.0 and -6.02 dB is 0.5.
- */
- public static double decibelsToAmplitude(double decibels) {
- double amp = Math.pow(10.0, decibels / 20.0);
- return amp;
- }
-
- /**
- * Calculate MIDI pitch based on frequency in Hertz. Middle C is 60.0.
- */
- public static double frequencyToPitch(double frequency) {
- return CONCERT_A_PITCH + 12 * Math.log(frequency / mConcertAFrequency) / Math.log(2.0);
- }
-
- /**
- * Calculate frequency in Hertz based on MIDI pitch. Middle C is 60.0. You can use fractional
- * pitches so 60.5 would give you a pitch half way between C and C#.
- */
- public static double pitchToFrequency(double pitch) {
- return mConcertAFrequency * Math.pow(2.0, ((pitch - CONCERT_A_PITCH) * (1.0 / 12.0)));
- }
-
- /**
- * This can be used to globally adjust the tuning in JSyn from Concert A at 440.0 Hz to
- * a slightly different frequency. Some orchestras use a higher frequency, eg. 441.0.
- * This value will be used by pitchToFrequency() and frequencyToPitch().
- *
- * @param concertAFrequency
- */
- public static void setConcertAFrequency(double concertAFrequency) {
- mConcertAFrequency = concertAFrequency;
- }
-
- public static double getConcertAFrequency() {
- return mConcertAFrequency;
- }
-
- /** Convert a delta value in semitones to a frequency multiplier.
- * @param semitones
- * @return scaler For example 2.0 for an input of 12.0 semitones.
- */
- public static double semitonesToFrequencyScaler(double semitones) {
- return Math.pow(2.0, semitones / 12.0);
- }
-}