103 lines
3.1 KiB
JavaScript
103 lines
3.1 KiB
JavaScript
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/*
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* This file is part of Toolkit.
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*
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* Toolkit is free software; you can redistribute it and/or
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* modify it under the terms of the GNU General Public
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* License as published by the Free Software Foundation; either
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* version 3 of the License, or (at your option) any later version.
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*
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* Toolkit is distributed in the hope that it will be useful,
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* but WITHOUT ANY WARRANTY; without even the implied warranty of
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* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
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* Lesser General Public License for more details.
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*
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* You should have received a copy of the GNU General
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* Public License along with this program; if not, write to the
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* Free Software Foundation, Inc., 51 Franklin Street, Fifth Floor,
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* Boston, MA 02110-1301 USA
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*/
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"use strict";
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(function(w, TK){
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var notes = [ "C", "C#", "D", "D#", "E", "F", "F#", "G", "G#", "A", "A#", "B" ];
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TK.Notes = TK.class({
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/**
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* TK.Notes converts between frequencies, MIDI notes
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* and note names.
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*
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* @mixin TK.Notes
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*/
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_class: "Notes",
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/**
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* Returns a note name for a MIDI note number.
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*
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* @method TK.Notes#midi2note
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*
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* @param {int} note - The MIDI note to translate.
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*
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* @returns {string} note - The name of the note.
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*/
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midi2note: function (num) {
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return notes[num % 12] + parseInt(num / 12);
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},
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/**
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* Returns a frequency of a MIDI note number.
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*
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* @method TK.Notes#midi2freq
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*
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* @param {int} note - The MIDI note to translate.
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*
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* @returns {number} frequency - The frequency of the MIDI number.
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*/
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midi2freq: function (num, base) {
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base |= 440;
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return Math.pow(2, (num - 69) / 12) * base;
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},
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/**
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* Returns a MIDI note number for a frequency.
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*
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* @method TK.Notes#freq2midi
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*
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* @param {number} frequency - The frequency to translate.
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* @param {number} [base] - The frequency of A440.
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*
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* @returns {int} number - The MIDI number of the frequency.
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*/
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freq2midi: function (freq, base) {
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base |= 440;
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var f2 = Math.log2(freq / base);
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return Math.max(0, Math.round(12 * f2 + 69));
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},
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/**
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* Returns the percents a frequency misses a real note by.
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*
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* @method TK.Notes#freq2cents
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*
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* @param {number} frequency - The frequency to translate.
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* @param {number} [base] - The frequency of A440.
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*
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* @returns {number} cents - The percent of the difference to the next full note.
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*/
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freq2cents: function (freq, base) {
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base |= 440;
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var f2 = Math.log2(freq / base);
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f2 *= 1200;
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f2 %= 100;
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return (f2 < -50) ? 100 + f2 : (f2 > 50) ? -(100 - f2) : f2;
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},
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/**
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* Returns a note name for a frequency.
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*
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* @method TK.Notes#freq2note
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*
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* @param {number} frequency - The frequency to translate.
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* @param {number} [base] - The frequency of A440.
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*
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* @returns {string} note - The name of the note.
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*/
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freq2note: function (freq, base) {
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base |= 440;
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return this.midi2note(this.freq2midi(freq, base));
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}
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});
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})(this, this.TK);
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