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/* |
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* Copyright (c) 2018-2019 Rafael da Silva Rocha. |
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* |
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* Permission is hereby granted, free of charge, to any person obtaining |
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* a copy of this software and associated documentation files (the |
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* "Software"), to deal in the Software without restriction, including |
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* without limitation the rights to use, copy, modify, merge, publish, |
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* distribute, sublicense, and/or sell copies of the Software, and to |
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* permit persons to whom the Software is furnished to do so, subject to |
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* the following conditions: |
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* |
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* The above copyright notice and this permission notice shall be |
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* included in all copies or substantial portions of the Software. |
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* |
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* THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, |
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* EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF |
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* MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND |
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* NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE |
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* LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION |
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* OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION |
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* WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE. |
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* |
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*/ |
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/** |
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* @fileoverview Function to create multi-stage frequency sweeps. |
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* @see https://github.com/rochars/frequency-sweep |
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*/ |
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/** |
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* Waveform functions. |
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* @private |
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*/ |
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const WAVES = { |
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noise: function(t, delta, phase, start, end, phi0) { |
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return Math.random() * (1 - (-1)) + (-1); |
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}, |
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sine: function(t, delta, phase, start, end, phi0) { |
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phase = 2 * Math.PI * t * (start + (end - start) * delta / 2); |
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return Math.sin(phase + phi0); |
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}, |
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triangle: function(t, delta, phase, start, end, phi0) { |
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phase = 2 * Math.PI * t * (start + (end - start) * delta / 2); |
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return (2 / Math.PI) * Math.asin(Math.sin(phase + phi0)); |
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}, |
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sawtooth: function(t, delta, phase, start, end, phi0) { |
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phase = 2 * Math.PI * t * (start + (end - start) * (delta / 2)) / 2; |
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return (2 / Math.PI) * Math.atan(Math.tan(phase + phi0)); |
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}, |
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square: function(t, delta, phase, start, end, phi0) { |
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phase = 2 * Math.PI * t * (start + (end - start) * delta / 2); |
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return Math.sign(Math.sin(phase + phi0)); |
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} |
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}; |
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/** |
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* Return the samples of a frequency sweep. The sweep may be divided |
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* in segments, each using a different waveform (or noise), and each with |
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* a start and end frequency. |
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* @param {!Array<Object<string, string|number>>} sequence The sequence. |
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* Each item in the array must have the properties: |
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* start: Integer value, the start frequency of the segment. |
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* end: Integer value, the end frequency of the segment. |
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* time: Float value, the duration of the segment. 1 = 1 second. |
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* wave: String, "sine", "square", "triangle", "sawtooth" or "noise". |
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* @param {number} sampleRate The sample rate. |
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* @return {!Array<number>} |
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*/ |
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export function sweep(sequence, sampleRate) { |
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let phi0 = 0; |
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let phase = 0; |
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let numSamples = 0; |
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let duration = 0; |
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let delta = 0; |
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let samples = []; |
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for (let i = 0; i < sequence.length; i++) { |
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numSamples = Math.round(sampleRate * sequence[i].time); |
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duration = numSamples / sampleRate; |
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for (let x = 0; x < numSamples; x++) { |
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delta = x / numSamples; |
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samples.push( |
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WAVES[sequence[i].wave]( |
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duration * delta, |
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delta, phase, |
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sequence[i].start, |
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sequence[i].end, |
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phi0)); |
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} |
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phase = 2 * Math.PI * duration * |
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(sequence[i].start + (sequence[i].end - sequence[i].start) / 2); |
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phi0 = phi0 + phase; |
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} |
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return samples; |
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} |
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rochars /
frequency-sweep
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