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/* |
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* Copyright (c) 2017-2018 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 A module to change the bit depth of PCM samples. |
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* @see https://github.com/rochars/wavefile |
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* @see https://github.com/rochars/bitdepth |
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*/ |
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/** |
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* Change the bit depth of PCM samples. |
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* @param {!Array|!TypedArray} samples The original samples. |
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* @param {string} bithDepth The original bit depth. |
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* @param {!TypedArray} newSamples The output array. |
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* @param {string} targetBitDepth The target bit depth. |
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* @throws {Error} If original or target bit depths are not valid. |
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*/ |
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export function changeBitDepth(samples, bithDepth, newSamples, targetBitDepth) { |
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// float to float, just copy the values |
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if (["32f","64"].indexOf(bithDepth) > -1 && |
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["32f","64"].indexOf(targetBitDepth) > -1) { |
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newSamples.set(samples); |
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return; |
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} |
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validateBitDepth_(bithDepth); |
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validateBitDepth_(targetBitDepth); |
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/** @type {!Function} */ |
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let toFunction = getBitDepthFunction_(bithDepth, targetBitDepth); |
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/** @type {!Object<string, number>} */ |
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let options = { |
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oldMin: Math.pow(2, parseInt(bithDepth, 10)) / 2, |
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newMin: Math.pow(2, parseInt(targetBitDepth, 10)) / 2, |
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oldMax: (Math.pow(2, parseInt(bithDepth, 10)) / 2) - 1, |
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newMax: (Math.pow(2, parseInt(targetBitDepth, 10)) / 2) - 1, |
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}; |
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// sign the samples if original is 8-bit |
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sign8Bit_(bithDepth, samples, true); |
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// change the resolution of the samples |
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for (let i = 0, len = samples.length; i < len; i++) { |
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newSamples[i] = toFunction(samples[i], options); |
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} |
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// unsign the samples if target is 8-bit |
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sign8Bit_(targetBitDepth, newSamples, false); |
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} |
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/** |
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* Change the bit depth from int to int. |
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* @param {number} sample The sample. |
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* @param {!Object<string, number>} args Data about the bit depths. |
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* @return {number} |
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* @private |
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*/ |
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function intToInt_(sample, args) { |
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if (sample > 0) { |
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sample = parseInt((sample / args.oldMax) * args.newMax, 10); |
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} else { |
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sample = parseInt((sample / args.oldMin) * args.newMin, 10); |
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} |
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return sample; |
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} |
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/** |
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* Change the bit depth from float to int. |
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* @param {number} sample The sample. |
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* @param {!Object<string, number>} args Data about the bit depths. |
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* @return {number} |
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* @private |
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*/ |
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function floatToInt_(sample, args) { |
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return parseInt( |
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sample > 0 ? sample * args.newMax : sample * args.newMin, 10); |
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} |
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/** |
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* Change the bit depth from int to float. |
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* @param {number} sample The sample. |
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* @param {!Object<string, number>} args Data about the bit depths. |
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* @return {number} |
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* @private |
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*/ |
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function intToFloat_(sample, args) { |
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return sample > 0 ? sample / args.oldMax : sample / args.oldMin; |
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} |
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/** |
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* Return the function to change the bit depth of a sample. |
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* @param {string} original The original bit depth of the data. |
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* @param {string} target The new bit depth of the data. |
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* @return {!Function} |
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* @private |
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*/ |
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function getBitDepthFunction_(original, target) { |
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/** @type {!Function} */ |
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let func = function(x) {return x;}; |
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if (original != target) { |
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if (["32f", "64"].includes(original)) { |
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func = floatToInt_; |
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} else { |
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if (["32f", "64"].includes(target)) { |
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func = intToFloat_; |
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} else { |
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func = intToInt_; |
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} |
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} |
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} |
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return func; |
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} |
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/** |
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* Validate the bit depth. |
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* @param {string} bitDepth The original bit depth. |
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* @throws {Error} If bit depth is not valid. |
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* @private |
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*/ |
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function validateBitDepth_(bitDepth) { |
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if ((bitDepth != "32f" && bitDepth != "64") && |
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(parseInt(bitDepth, 10) < "8" || parseInt(bitDepth, 10) > "53")) { |
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throw new Error("Invalid bit depth."); |
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} |
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} |
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/** |
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* Sign samples if they are 8-bit. |
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* @param {string} bitDepth The bit depth code. |
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* @param {!Array|!TypedArray} samples The samples. |
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* @param {boolean} sign True to sign, false to unsign. |
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* @private |
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*/ |
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function sign8Bit_(bitDepth, samples, sign) { |
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if (bitDepth == "8") { |
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let factor = sign ? -128 : 128; |
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for (let i = 0, len = samples.length; i < len; i++) { |
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samples[i] = samples[i] += factor; |
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} |
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} |
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} |
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rochars /
wavefile
