feat: Use ManagedMediaSource when available (#5683)

The spec can be seen at w3c/media-source#320

Closes #5271

externs/managedmediasource.js

@@ -0,0 +1,24 @@
+/*! @license
+ * Shaka Player
+ * Copyright 2016 Google LLC
+ * SPDX-License-Identifier: Apache-2.0
+ */
+
+/**
+ * @fileoverview Externs for ManagedMediaSource which were missing in the
+ * Closure compiler.
+ *
+ * @externs
+ */
+
+/**
+ * @constructor
+ * @extends {MediaSource}
+ */
+function ManagedMediaSource() {}
+
+/**
+ * @param {string} type
+ * @return {boolean}
+ */
+ManagedMediaSource.isTypeSupported = function(type) {};

lib/media/media_source_capabilities.js

@@ -23,9 +23,16 @@ shaka.media.Capabilities = class {
     if (supportMap.has(type)) {
       return supportMap.get(type);
     }
-    const currentSupport = MediaSource.isTypeSupported(type);
-    supportMap.set(type, currentSupport);
-    return currentSupport;
+    if (window.ManagedMediaSource) {
+      const currentSupport = ManagedMediaSource.isTypeSupported(type);
+      supportMap.set(type, currentSupport);
+      return currentSupport;
+    } else if (window.MediaSource) {
+      const currentSupport = MediaSource.isTypeSupported(type);
+      supportMap.set(type, currentSupport);
+      return currentSupport;
+    }
+    return false;
   }
 
   /**

lib/media/media_source_engine.js

@@ -119,7 +119,7 @@ shaka.media.MediaSourceEngine = class {
     /** @private {boolean} */
     this.playbackHasBegun_ = false;
 
-    /** @private {MediaSource} */
+    /** @private {(MediaSource|ManagedMediaSource)} */
     this.mediaSource_ = this.createMediaSource(this.mediaSourceOpen_);
 
     /** @private {boolean} */
@@ -145,6 +145,9 @@ shaka.media.MediaSourceEngine = class {
 
     /** @private {boolean} */
     this.needSplitMuxedContent_ = false;
+
+    /** @private {boolean} */
+    this.streamingAllowed_ = true;
   }
 
   /**
@@ -154,30 +157,60 @@ shaka.media.MediaSourceEngine = class {
    * Replaced by unit tests.
    *
    * @param {!shaka.util.PublicPromise} p
-   * @return {!MediaSource}
+   * @return {!(MediaSource|ManagedMediaSource)}
    */
   createMediaSource(p) {
-    const mediaSource = new MediaSource();
+    if (window.ManagedMediaSource) {
+      this.video_.disableRemotePlayback = true;
 
-    // Set up MediaSource on the video element.
-    this.eventManager_.listenOnce(
-        mediaSource, 'sourceopen', () => this.onSourceOpen_(p));
+      const mediaSource = new ManagedMediaSource();
 
-    // Correctly set when playback has begun.
-    this.eventManager_.listenOnce(this.video_, 'playing', () => {
-      this.playbackHasBegun_ = true;
-    });
+      this.eventManager_.listenOnce(
+          mediaSource, 'sourceopen', () => this.onSourceOpen_(p));
+
+      this.eventManager_.listen(
+          mediaSource, 'startstreaming', () => {
+            this.streamingAllowed_ = true;
+          });
+
+      this.eventManager_.listen(
+          mediaSource, 'endstreaming', () => {
+            this.streamingAllowed_ = false;
+          });
+
+      // Correctly set when playback has begun.
+      this.eventManager_.listenOnce(this.video_, 'playing', () => {
+        this.playbackHasBegun_ = true;
+      });
+
+      this.url_ = shaka.media.MediaSourceEngine.createObjectURL(mediaSource);
+
+      this.video_.src = this.url_;
+
+      return mediaSource;
+    } else {
+      const mediaSource = new MediaSource();
+
+      // Set up MediaSource on the video element.
+      this.eventManager_.listenOnce(
+          mediaSource, 'sourceopen', () => this.onSourceOpen_(p));
+
+      // Correctly set when playback has begun.
+      this.eventManager_.listenOnce(this.video_, 'playing', () => {
+        this.playbackHasBegun_ = true;
+      });
 
-    // Store the object URL for releasing it later.
-    this.url_ = shaka.media.MediaSourceEngine.createObjectURL(mediaSource);
+      // Store the object URL for releasing it later.
+      this.url_ = shaka.media.MediaSourceEngine.createObjectURL(mediaSource);
 
-    this.video_.src = this.url_;
+      this.video_.src = this.url_;
 
-    return mediaSource;
+      return mediaSource;
+    }
   }
 
   /**
-   * @param {!shaka.util.PublicPromise} p
+   * @param {shaka.util.PublicPromise} p
    * @private
    */
   onSourceOpen_(p) {
@@ -511,6 +544,16 @@ shaka.media.MediaSourceEngine = class {
     this.config_ = config;
   }
 
+  /**
+   * Indicate if the streaming is allowed by MediaSourceEngine.
+   * If we using MediaSource we allways returns true.
+   *
+   * @return {boolean}
+   */
+  isStreamingAllowed() {
+    return this.streamingAllowed_;
+  }
+
   /**
    * Reinitialize the TextEngine for a new text type.
    * @param {string} mimeType

lib/media/streaming_engine.js

@@ -1054,6 +1054,14 @@ shaka.media.StreamingEngine = class {
       this.playerInterface_.mediaSourceEngine.clearSelectedClosedCaptionId();
     }
 
+    if (!this.playerInterface_.mediaSourceEngine.isStreamingAllowed() &&
+        mediaState.type != ContentType.TEXT) {
+      // It is not allowed to add segments yet, so we schedule an update to
+      // check again later. So any prediction we make now could be terribly
+      // invalid soon.
+      return this.config_.updateIntervalSeconds / 2;
+    }
+
     const logPrefix = shaka.media.StreamingEngine.logPrefix_(mediaState);
 
     // Compute how far we've buffered ahead of the playhead.

lib/util/platform.js

@@ -23,15 +23,16 @@ shaka.util.Platform = class {
    * @return {boolean}
    */
   static supportsMediaSource() {
+    const mediaSource = window.ManagedMediaSource || window.MediaSource;
     // Browsers that lack a media source implementation will have no reference
     // to |window.MediaSource|. Platforms that we see having problematic media
     // source implementations will have this reference removed via a polyfill.
-    if (!window.MediaSource) {
+    if (!mediaSource) {
       return false;
     }
 
     // Some very old MediaSource implementations didn't have isTypeSupported.
-    if (!MediaSource.isTypeSupported) {
+    if (!mediaSource.isTypeSupported) {
       return false;
     }
 

test/test/util/fake_media_source_engine.js

@@ -147,6 +147,11 @@ shaka.test.FakeMediaSourceEngine = class {
     return Promise.resolve();
   }
 
+  /** @override */
+  isStreamingAllowed() {
+    return true;
+  }
+
   /**
    * @param {string} type
    * @return {?number}