Use Network Information API to get bandwidth estimate when possible.

Issue shaka-project#994

Change-Id: Id4a33ce7467c2e89613acb191fb304f02d10ed65

externs/networkinformation.js

@@ -0,0 +1,52 @@
+/**
+ * @license
+ * Copyright 2016 Google Inc.
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+/**
+ * @fileoverview Externs for NetworkInformation based on
+ * {@link http://goo.gl/Cr1L15 Network Information API
+ *  draft 07 September 2017}
+ *
+ * @externs
+ */
+
+
+/** @const {NetworkInformation} */
+Navigator.prototype.connection;
+
+
+
+/**
+ * @interface
+ * @extends {EventTarget}
+ */
+function NetworkInformation() {}
+
+
+/** @const {string} */
+NetworkInformation.prototype.effectiveType;
+
+
+/** @const {number} */
+NetworkInformation.prototype.downlink;
+
+
+/** @const {boolean} */
+NetworkInformation.prototype.saveData;
+
+
+/** @const {string} */
+NetworkInformation.prototype.type;

lib/abr/simple_abr_manager.js

@@ -56,6 +56,8 @@ shaka.abr.SimpleAbrManager = function() {
 
   /** @private {shaka.abr.EwmaBandwidthEstimator} */
   this.bandwidthEstimator_ = new shaka.abr.EwmaBandwidthEstimator();
+  // TODO: Consider using NetworkInformation's change event to throw out an old
+  // estimate based on changing network types, such as wifi => 3g.
 
   /**
    * A filtered list of Variants to choose from.

lib/player.js

@@ -1964,6 +1964,25 @@ shaka.Player.prototype.configOverrides_ = function() {
  * @private
  */
 shaka.Player.prototype.defaultConfig_ = function() {
+  // This is a relatively safe default, since 3G cell connections
+  // are faster than this.  For slower connections, such as 2G,
+  // the default estimate may be too high.
+  var bandwidthEstimate = 500e3; // 500kbps
+
+  // Some browsers implement the Network Information API, which allows
+  // retrieving information about a user's network connection.
+  //
+  // We are excluding connection.type == undefined to avoid getting bogus data
+  // on platforms where the implementation is incomplete.  Currently, desktop
+  // Chrome 61 returns connection type undefined and a bogus downlink value.
+  if (navigator.connection && navigator.connection.type) {
+    // If it's available, get the bandwidth estimate from the browser (in
+    // megabits per second) and use it as defaultBandwidthEstimate.
+    bandwidthEstimate = navigator.connection.downlink * 1e6;
+    // TODO: move this into AbrManager, where changes to the estimate can be
+    // observed and absorbed.
+  }
+
   return {
     drm: {
       retryParameters: shaka.net.NetworkingEngine.defaultRetryParameters(),
@@ -2009,10 +2028,7 @@ shaka.Player.prototype.defaultConfig_ = function() {
     }.bind(null, this.video_),
     abr: {
       enabled: true,
-      // This is a relatively safe default, since 3G cell connections
-      // are faster than this.  For slower connections, such as 2G,
-      // the default estimate may be too high.
-      defaultBandwidthEstimate: 500e3,  // 500kbps
+      defaultBandwidthEstimate: bandwidthEstimate,
       switchInterval: 8,
       bandwidthUpgradeTarget: 0.85,
       bandwidthDowngradeTarget: 0.95,