118 lines
4.6 KiB
JavaScript
118 lines
4.6 KiB
JavaScript
/**
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* @license
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* Copyright 2017 Google Inc. All Rights Reserved.
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* Licensed under the Apache License, Version 2.0 (the "License");
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* you may not use this file except in compliance with the License.
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* You may obtain a copy of the License at
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*
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* http://www.apache.org/licenses/LICENSE-2.0
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*
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* Unless required by applicable law or agreed to in writing, software
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* distributed under the License is distributed on an "AS IS" BASIS,
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* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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* See the License for the specific language governing permissions and
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* limitations under the License.
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*/
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/**
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* @file Directivity/occlusion filter.
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* @author Andrew Allen <bitllama@google.com>
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*/
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'use strict';
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// Internal dependencies.
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import Utils from './utils.js';
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/**
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* @class Directivity
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* @description Directivity/occlusion filter.
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* @param {AudioContext} context
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* Associated {@link
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https://developer.mozilla.org/en-US/docs/Web/API/AudioContext AudioContext}.
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* @param {Object} options
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* @param {Number} options.alpha
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* Determines directivity pattern (0 to 1). See
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* {@link Directivity#setPattern setPattern} for more details. Defaults to
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* {@linkcode Utils.DEFAULT_DIRECTIVITY_ALPHA DEFAULT_DIRECTIVITY_ALPHA}.
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* @param {Number} options.sharpness
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* Determines the sharpness of the directivity pattern (1 to Inf). See
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* {@link Directivity#setPattern setPattern} for more details. Defaults to
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* {@linkcode Utils.DEFAULT_DIRECTIVITY_SHARPNESS
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* DEFAULT_DIRECTIVITY_SHARPNESS}.
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*/
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class Directivity {
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constructor(context, options) {
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// Public variables.
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/**
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* Mono (1-channel) input {@link
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* https://developer.mozilla.org/en-US/docs/Web/API/AudioNode AudioNode}.
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* @member {AudioNode} input
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* @memberof Directivity
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* @instance
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*/
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/**
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* Mono (1-channel) output {@link
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* https://developer.mozilla.org/en-US/docs/Web/API/AudioNode AudioNode}.
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* @member {AudioNode} output
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* @memberof Directivity
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* @instance
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*/
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// Use defaults for undefined arguments.
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if (options == undefined) {
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options = {};
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}
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if (options.alpha == undefined) {
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options.alpha = Utils.DEFAULT_DIRECTIVITY_ALPHA;
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}
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if (options.sharpness == undefined) {
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options.sharpness = Utils.DEFAULT_DIRECTIVITY_SHARPNESS;
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}
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// Create audio node.
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this._context = context;
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this._lowpass = context.createBiquadFilter();
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// Initialize filter coefficients.
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this._lowpass.type = 'lowpass';
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this._lowpass.Q.value = 0;
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this._lowpass.frequency.value = context.sampleRate * 0.5;
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this._cosTheta = 0;
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this.setPattern(options.alpha, options.sharpness);
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// Input/Output proxy.
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this.input = this._lowpass;
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this.output = this._lowpass;
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}
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/**
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* Compute the filter using the source's forward orientation and the listener's
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* position.
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* @param {Float32Array} forward The source's forward vector.
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* @param {Float32Array} direction The direction from the source to the
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* listener.
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*/
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computeAngle(forward, direction) {
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let forwardNorm = Utils.normalizeVector(forward);
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let directionNorm = Utils.normalizeVector(direction);
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let coeff = 1;
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if (this._alpha > Utils.EPSILON_FLOAT) {
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let cosTheta = forwardNorm[0] * directionNorm[0] +
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forwardNorm[1] * directionNorm[1] + forwardNorm[2] * directionNorm[2];
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coeff = (1 - this._alpha) + this._alpha * cosTheta;
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coeff = Math.pow(Math.abs(coeff), this._sharpness);
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}
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this._lowpass.frequency.value = this._context.sampleRate * 0.5 * coeff;
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}
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/**
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* Set source's directivity pattern (defined by alpha), where 0 is an
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* omnidirectional pattern, 1 is a bidirectional pattern, 0.5 is a cardiod
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* pattern. The sharpness of the pattern is increased exponenentially.
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* @param {Number} alpha
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* Determines directivity pattern (0 to 1).
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* @param {Number} sharpness
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* Determines the sharpness of the directivity pattern (1 to Inf).
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* DEFAULT_DIRECTIVITY_SHARPNESS}.
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*/
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setPattern(alpha, sharpness) {
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// Clamp and set values.
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this._alpha = Math.min(1, Math.max(0, alpha));
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this._sharpness = Math.max(1, sharpness);
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// Update angle calculation using new values.
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this.computeAngle([this._cosTheta * this._cosTheta, 0, 0], [1, 0, 0]);
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}
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}
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export default Directivity;
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