mirror of
https://github.com/shaka-project/shaka-player.git
synced 2026-06-23 17:27:16 +03:00
Joey Parrish
4cc4e96dbd
* Updates all Copyright years to 2015. * Adds licenses annotations to all JS. * Makes all licenses identical to avoid repeated appearance in the compiled output. * Drops fileoverview annotations, which do not affect docs output. * The linter still requires fileoverview on externs. This patch required a newer closure compiler, since the previous version we used had a bug regarding license annotations that caused the license comment block to appear in the output once per file regardless of uniqueness. Change-Id: I2e9272db680cba7ecc4613d97f1d3a94ac2244cc
137 lines
3.4 KiB
JavaScript
137 lines
3.4 KiB
JavaScript
/**
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* @license
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* Copyright 2015 Google Inc.
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*
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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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goog.provide('shaka.util.EWMABandwidthEstimator');
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goog.require('shaka.util.EWMA');
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goog.require('shaka.util.FakeEvent');
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goog.require('shaka.util.FakeEventTarget');
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goog.require('shaka.util.IBandwidthEstimator');
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/**
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* Tracks bandwidth samples and estimates available bandwidth.
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* Based on the minimum of two exponentially-weighted moving averages with
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* different half-lives.
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*
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* @struct
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* @constructor
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* @extends {shaka.util.FakeEventTarget}
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* @implements {shaka.util.IBandwidthEstimator}
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* @export
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*/
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shaka.util.EWMABandwidthEstimator = function() {
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shaka.util.FakeEventTarget.call(this, null);
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/**
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* A fast-moving average.
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* Half of the estimate is based on the last 3 seconds of sample history.
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* @private {!shaka.util.EWMA}
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*/
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this.fast_ = new shaka.util.EWMA(3);
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/**
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* A slow-moving average.
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* Half of the estimate is based on the last 10 seconds of sample history.
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* @private {!shaka.util.EWMA}
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*/
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this.slow_ = new shaka.util.EWMA(10);
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/**
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* Prevents ultra-fast internal connections from causing crazy results.
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* @private {number}
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* @const
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*/
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this.minDelayMs_ = 50;
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/**
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* Initial estimate used when there is not enough data.
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* @private {number}
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* @const
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*/
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this.defaultEstimate_ = 5e5; // 500kbps
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/**
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* Minimum weight required to trust the estimate.
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* @private {number}
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* @const
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*/
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this.minWeight_ = 0.5;
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/**
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* Minimum number of bytes, under which samples are discarded.
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* @private {number}
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* @const
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*/
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this.minBytes_ = 65536;
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/**
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* The last time a sample was recorded, in milliseconds.
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* @private {number}
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*/
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this.lastSampleTime_ = 0;
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};
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goog.inherits(shaka.util.EWMABandwidthEstimator, shaka.util.FakeEventTarget);
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/** @override */
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shaka.util.EWMABandwidthEstimator.prototype.sample = function(delayMs, bytes) {
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if (bytes < this.minBytes_) {
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return;
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}
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delayMs = Math.max(delayMs, this.minDelayMs_);
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var bandwidth = 8000 * bytes / delayMs;
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var weight = delayMs / 1000;
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this.fast_.sample(weight, bandwidth);
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this.slow_.sample(weight, bandwidth);
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this.dispatchEvent(shaka.util.FakeEvent.create({
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'type': 'bandwidth'
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}));
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this.lastSampleTime_ = Date.now();
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};
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/** @override */
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shaka.util.EWMABandwidthEstimator.prototype.getBandwidth = function() {
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if (this.fast_.getTotalWeight() < this.minWeight_) {
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return this.defaultEstimate_;
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}
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// Take the minimum of these two estimates. This should have the effect of
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// adapting down quickly, but up more slowly.
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return Math.min(this.fast_.getEstimate(), this.slow_.getEstimate());
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};
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/** @override */
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shaka.util.EWMABandwidthEstimator.prototype.getDataAge = function() {
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return (Date.now() - this.lastSampleTime_) / 1000;
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};
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/** @override */
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shaka.util.EWMABandwidthEstimator.prototype.supportsCaching = function() {
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return false;
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};
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