mirror of
https://github.com/shaka-project/shaka-player.git
synced 2026-06-17 16:26:39 +03:00
Joey Parrish
f539147d48
This fixes all the license headers in the main library, which corrects the appearance of the main license in the compiled output. It seems that the `!` in the header forces the compiler to keep it in the output. I believe older compiler releases did this purely based on `@license`. Issue #2638 Change-Id: I7f0e918caad10c9af689c9d07672b7fe9be7b2f3
63 lines
1.3 KiB
JavaScript
63 lines
1.3 KiB
JavaScript
/*! @license
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* Shaka Player
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* Copyright 2016 Google LLC
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* SPDX-License-Identifier: Apache-2.0
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*/
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goog.provide('shaka.abr.Ewma');
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goog.require('goog.asserts');
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/**
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* @summary
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* This class computes an exponentionally-weighted moving average.
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*/
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shaka.abr.Ewma = class {
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/**
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* @param {number} halfLife The quantity of prior samples (by weight) used
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* when creating a new estimate. Those prior samples make up half of the
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* new estimate.
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*/
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constructor(halfLife) {
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goog.asserts.assert(halfLife > 0, 'expected halfLife to be positive');
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/**
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* Larger values of alpha expire historical data more slowly.
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* @private {number}
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*/
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this.alpha_ = Math.exp(Math.log(0.5) / halfLife);
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/** @private {number} */
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this.estimate_ = 0;
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/** @private {number} */
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this.totalWeight_ = 0;
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}
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/**
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* Takes a sample.
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*
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* @param {number} weight
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* @param {number} value
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*/
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sample(weight, value) {
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const adjAlpha = Math.pow(this.alpha_, weight);
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const newEstimate = value * (1 - adjAlpha) + adjAlpha * this.estimate_;
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if (!isNaN(newEstimate)) {
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this.estimate_ = newEstimate;
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this.totalWeight_ += weight;
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}
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}
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/**
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* @return {number}
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*/
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getEstimate() {
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const zeroFactor = 1 - Math.pow(this.alpha_, this.totalWeight_);
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return this.estimate_ / zeroFactor;
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}
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};
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