feat: Support Parallel Segment Fetching

demo/locales/source.json

@@ -1044,7 +1044,7 @@
     "message": "Filters for assets that have [JARGON:XLINK] tags in their manifests, so that they can be broken into multiple files."
   },
   "DEMO_SEGMENT_PREFETCH_LIMIT": {
-    "description": "Segment Prefetch Limit configuration used by StreamingEngine.",
+    "description": "Max number of segments to be prefetched ahead of current time position.",
     "message": "Segment Prefetch Limit."
   }
 }

externs/shaka/player.js

@@ -1076,8 +1076,7 @@ shaka.extern.ManifestConfiguration;
  * @property {boolean} segmentPrefetchLimit
  *   The maximum number of segments for each active stream to be prefetched
  *   ahead of playhead in parallel.
- *   If <code>0</code>, the segments will be fetched
- *   sequentially.
+ *   If <code>0</code>, the segments will be fetched sequentially.
  *   Defaults to <code>0</code>.
  * @exportDoc
  */

lib/media/segment_prefetch.js

@@ -4,6 +4,7 @@
  * SPDX-License-Identifier: Apache-2.0
  */
 
+goog.require('goog.asserts');
 goog.require('shaka.net.NetworkingEngine');
 goog.require('shaka.media.InitSegmentReference');
 goog.require('shaka.media.SegmentReference');
@@ -20,15 +21,10 @@ shaka.media.SegmentPrefetch = class {
   /**
    * @param {number} prefetchLimit
    * @param {shaka.extern.Stream} stream
-   * @param {function(
-   *  !(shaka.media.InitSegmentReference|shaka.media.SegmentReference),
-   *  shaka.extern.Stream
-   * ):!shaka.net.NetworkingEngine.PendingRequest} fetchDispatcher
+   * @param {shaka.media.SegmentPrefetch.fetchDispatcher} fetchDispatcher
    */
   constructor(prefetchLimit, stream, fetchDispatcher) {
-    /**
-     * @private {number}
-     */
+    /** @private {number} */
     this.prefetchLimit_ = prefetchLimit;
 
     /** @private {shaka.extern.Stream} */
@@ -37,15 +33,12 @@ shaka.media.SegmentPrefetch = class {
     /** @private {number} */
     this.prefetchPosTime_ = 0;
 
-    /** @private {function(
-     * !(shaka.media.InitSegmentReference|shaka.media.SegmentReference),
-     * shaka.extern.Stream
-     * ):!shaka.net.NetworkingEngine.PendingRequest} */
+    /** @private {shaka.media.SegmentPrefetch.fetchDispatcher} */
     this.fetchDispatcher_ = fetchDispatcher;
 
     /**
      * @private {!Map.<shaka.media.SegmentReference,
-                 !shaka.net.NetworkingEngine.PendingRequest>}
+     *           !shaka.net.NetworkingEngine.PendingRequest>}
      */
     this.segmentPrefetchMap_ = new Map();
   }
@@ -57,9 +50,9 @@ shaka.media.SegmentPrefetch = class {
    * @public
    */
   prefetchSegments(startReference) {
-    if (!(this.prefetchLimit_ > 0)) {
-      return;
-    }
+    goog.asserts.assert(this.prefetchLimit_ > 0,
+        'SegmentPrefetch can not be used when prefetchLimit <= 0.');
+
     const logPrefix = shaka.media.SegmentPrefetch.logPrefix_(
         this.stream_,
     );
@@ -93,11 +86,11 @@ shaka.media.SegmentPrefetch = class {
    * @public
    */
   getPrefetchedSegment(reference) {
+    goog.asserts.assert(this.prefetchLimit_ > 0,
+        'SegmentPrefetch can not be used when prefetchLimit <= 0.');
+
     let op = null;
-    if (
-      !(reference instanceof shaka.media.SegmentReference) ||
-      !(this.prefetchLimit_ > 0)
-    ) {
+    if (!(reference instanceof shaka.media.SegmentReference)) {
       return null;
     }
 
@@ -171,3 +164,15 @@ shaka.media.SegmentPrefetch = class {
     return 'SegmentPrefetch(' + stream.type + ':' + stream.id + ')';
   }
 };
+
+/**
+ * @typedef {function(
+ *  !(shaka.media.InitSegmentReference|shaka.media.SegmentReference),
+ *  shaka.extern.Stream
+ * ):!shaka.net.NetworkingEngine.PendingRequest}
+ *
+ * @description
+ * A callback function that fetches a segment.
+ * @export
+ */
+shaka.media.SegmentPrefetch.fetchDispatcher;

lib/media/streaming_engine.js

@@ -2100,7 +2100,7 @@ shaka.media.StreamingEngine = class {
 
     shaka.log.v2('fetching: reference=', reference);
     let duration = 0;
-    if ((reference instanceof shaka.media.SegmentReference)) {
+    if (reference instanceof shaka.media.SegmentReference) {
       // start and endTime are not defined in InitSegmentReference
       duration = reference.endTime - reference.startTime;
     }
@@ -2164,10 +2164,6 @@ shaka.media.StreamingEngine = class {
       }
     }
 
-    if (mediaState.segmentPrefetch) {
-      mediaState.segmentPrefetch.clearAll();
-    }
-
     this.destroyer_.ensureNotDestroyed();
 
     shaka.log.debug(logPrefix, 'cleared buffer');
@@ -2414,8 +2410,9 @@ shaka.media.StreamingEngine.PlayerInterface;
  *   updating.
  * @property {shaka.net.NetworkingEngine.PendingRequest} operation
  *   Operation with the number of bytes to be downloaded.
- * @property {shaka.media.SegmentPrefetch} segmentPrefetch
- *   segmentPrefetch.
+ * @property {?shaka.media.SegmentPrefetch} segmentPrefetch
+ *   A prefetch object for managing prefetching. Null if unneeded
+ *   (if prefetching is disabled, etc).
  */
 shaka.media.StreamingEngine.MediaState_;
 

test/test/util/fake_segment_prefetch.js

@@ -20,9 +20,9 @@ shaka.test.FakeSegmentPrefetch = class {
     /** @private {shaka.extern.Stream} */
     this.streamObj_ = stream;
 
-    /** @private {
-     * !Object.<string, shaka.test.FakeMediaSourceEngine.SegmentData>
-     * } */
+    /**
+    * @private {!Object.<string, shaka.test.FakeMediaSourceEngine.SegmentData>}
+    */
     this.segmentData_ = segmentData;
   }