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/* |
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* Copyright (c) 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 The resample function. |
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* @see https://github.com/rochars/wavefile |
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*/ |
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import { Interpolator } from './interpolator'; |
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import { FIRLPF } from './fir-lpf'; |
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/** |
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* Change the sample rate of the samples to a new sample rate. |
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* @param {!Array|!TypedArray} samples The original samples. |
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* @param {number} oldSampleRate The original sample rate. |
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* @param {number} sampleRate The target sample rate. |
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* @param {?Object} details The extra configuration, if needed. |
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* @return {!Float64Array} the new samples. |
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*/ |
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export function resample(samples, oldSampleRate, sampleRate, details={}) { |
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// Make the new sample container |
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let rate = ((sampleRate - oldSampleRate) / oldSampleRate) + 1; |
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let newSamples = new Float64Array(samples.length * (rate)); |
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// Create the interpolator |
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let interpolator = new Interpolator( |
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samples.length, |
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newSamples.length, |
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{ |
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method: details.method || 'cubic', |
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tension: details.tension || 0, |
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sincFilterSize: details.sincFilterSize || 32, |
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sincWindow: details.sincWindow || undefined, |
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lanczosFilterSize: details.lanczosFilterSize || 16, |
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clip: details.clip || 'mirror' |
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}); |
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// Default config |
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details.LPF = details.LPF === undefined ? true : details.LPF; |
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// Resample + LPF |
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if (details.LPF) { |
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// Upsampling |
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if (sampleRate > oldSampleRate) { |
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let filter = new FIRLPF( |
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details.LPForder || 71, |
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sampleRate, |
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(oldSampleRate / 2)); |
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upsample_( |
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samples, newSamples, interpolator, filter); |
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// Downsampling |
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} else { |
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let filter = new FIRLPF( |
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details.LPForder || 71, |
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oldSampleRate, |
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sampleRate / 2); |
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downsample_( |
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samples, newSamples, interpolator, filter); |
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} |
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// Resample, no LPF |
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} else { |
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resample_(samples, newSamples, interpolator); |
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} |
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return newSamples; |
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} |
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/** |
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* Resample. |
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* @param {!Array|!TypedArray} samples The original samples. |
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* @param {!Float64Array} newSamples The container for the new samples. |
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* @param {Object} interpolator The interpolator. |
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* @private |
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*/ |
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function resample_(samples, newSamples, interpolator) { |
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// Resample |
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for (let i = 0, len = newSamples.length; i < len; i++) { |
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newSamples[i] = interpolator.interpolate(i, samples); |
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} |
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} |
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/** |
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* Upsample with LPF. |
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* @param {!Array|!TypedArray} samples The original samples. |
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* @param {!Float64Array} newSamples The container for the new samples. |
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* @param {Object} interpolator The interpolator. |
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* @param {Object} filter The LPF object. |
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* @private |
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*/ |
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function upsample_(samples, newSamples, interpolator, filter) { |
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// Resample and filter |
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for (let i = 0, len = newSamples.length; i < len; i++) { |
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newSamples[i] = filter.filter(interpolator.interpolate(i, samples)); |
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} |
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// Reverse filter |
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filter.reset(); |
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for (let i = newSamples.length - 1; i >= 0; i--) { |
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newSamples[i] = filter.filter(newSamples[i]); |
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} |
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} |
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/** |
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* Downsample with LPF. |
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* @param {!Array|!TypedArray} samples The original samples. |
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* @param {!Float64Array} newSamples The container for the new samples. |
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* @param {Object} interpolator The interpolator. |
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* @param {Object} filter The LPF object. |
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* @private |
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*/ |
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function downsample_(samples, newSamples, interpolator, filter) { |
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// Filter |
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for (let i = 0, len = samples.length; i < len; i++) { |
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samples[i] = filter.filter(samples[i]); |
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} |
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// Reverse filter |
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filter.reset(); |
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for (let i = samples.length - 1; i >= 0; i--) { |
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samples[i] = filter.filter(samples[i]); |
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} |
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// Resample |
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resample_(samples, newSamples, interpolator); |
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} |
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rochars /
wavefile
