fix: Content reload starttime with HLS on iOS (#4575)

A new method `shaka.media.Playhead.ready` has been added for start time
operations.

Fixes #4244

Author: alexandercerutti

lib/media/playhead.js

@@ -33,6 +33,14 @@ goog.requireType('shaka.media.PresentationTimeline');
  * @interface
  */
 shaka.media.Playhead = class {
+  /**
+   * Called when the Player is ready to begin playback. Anything that depends
+   * on setStartTime() should be done here, not in the constructor.
+   *
+   * @see https://github.com/shaka-project/shaka-player/issues/4244
+   */
+  ready() {}
+
   /**
    * Set the start time. If the content has already started playback, this will
    * be ignored.
@@ -90,6 +98,14 @@ shaka.media.SrcEqualsPlayhead = class {
 
     /** @private {shaka.util.EventManager} */
     this.eventManager_ = new shaka.util.EventManager();
+  }
+
+  /** @override */
+  ready() {
+    goog.asserts.assert(
+        this.mediaElement_ != null,
+        'Playhead should not be released before calling ready()',
+    );
 
     // We listen for the loaded-data-event so that we know when we can
     // interact with |currentTime|.
@@ -102,6 +118,7 @@ shaka.media.SrcEqualsPlayhead = class {
         this.eventManager_.listenOnce(this.mediaElement_, 'seeking', () => {
           this.started_ = true;
         });
+
         const currentTime = this.mediaElement_.currentTime;
         // Using the currentTime allows using a negative number in Live HLS
         const newTime = Math.max(0, currentTime + this.startTime_);
@@ -239,7 +256,12 @@ shaka.media.MediaSourcePlayhead = class {
     /** @type {shaka.util.Timer} */
     this.checkWindowTimer_ = new shaka.util.Timer(() => {
       this.onPollWindow_();
-    }).tickEvery(/* seconds= */ 0.25);
+    });
+  }
+
+  /** @override */
+  ready() {
+    this.checkWindowTimer_.tickEvery(/* seconds= */ 0.25);
   }
 
   /** @override */

lib/player.js

@@ -2062,6 +2062,8 @@ shaka.Player = class extends shaka.util.FakeEventTarget {
           shaka.util.StreamUtils.variantToTrack(initialVariant));
     }
 
+    this.playhead_.ready();
+
     // Decide if text should be shown automatically.
     // similar to video/audio track, we would skip switch initial text track
     // if user already pick text track (via selectTextTrack api)
@@ -2399,6 +2401,7 @@ shaka.Player = class extends shaka.util.FakeEventTarget {
         HTMLMediaElement.HAVE_METADATA,
         this.loadEventManager_,
         () => {
+          this.playhead_.ready();
           fullyLoaded.resolve();
         });
 

test/media/playhead_unit.js

@@ -161,6 +161,8 @@ describe('Playhead', () => {
           Util.spyFunc(onSeek),
           Util.spyFunc(onEvent));
 
+      playhead.ready();
+
       expect(video.currentTime).toBe(5);
       expect(playhead.getTime()).toBe(5);
 
@@ -182,6 +184,8 @@ describe('Playhead', () => {
           Util.spyFunc(onSeek),
           Util.spyFunc(onEvent));
 
+      playhead.ready();
+
       expect(video.addEventListener).toHaveBeenCalledWith(
           'loadedmetadata', jasmine.any(Function), jasmine.anything());
       expect(video.addEventListener).not.toHaveBeenCalledWith(
@@ -223,6 +227,8 @@ describe('Playhead', () => {
           Util.spyFunc(onSeek),
           Util.spyFunc(onEvent));
 
+      playhead.ready();
+
       video.on['seeking']();
       expect(playhead.getTime()).toBe(5);
       expect(video.currentTime).toBe(5);
@@ -264,6 +270,8 @@ describe('Playhead', () => {
           Util.spyFunc(onSeek),
           Util.spyFunc(onEvent));
 
+      playhead.ready();
+
       expect(playhead.getTime()).toBe(59);  // duration - durationBackoff
       expect(video.currentTime).toBe(59);  // duration - durationBackoff
     });
@@ -302,6 +310,8 @@ describe('Playhead', () => {
           Util.spyFunc(onSeek),
           Util.spyFunc(onEvent));
 
+      playhead.ready();
+
       expect(playhead.getTime()).toBe(30);
     });
 
@@ -314,6 +324,8 @@ describe('Playhead', () => {
           Util.spyFunc(onSeek),
           Util.spyFunc(onEvent));
 
+      playhead.ready();
+
       expect(video.addEventListener).toHaveBeenCalledWith(
           'loadedmetadata', jasmine.any(Function), jasmine.anything());
 
@@ -347,6 +359,8 @@ describe('Playhead', () => {
           Util.spyFunc(onSeek),
           Util.spyFunc(onEvent));
 
+      playhead.ready();
+
       expect(video.addEventListener).toHaveBeenCalledWith(
           'loadedmetadata', jasmine.any(Function), jasmine.anything());
 
@@ -380,6 +394,8 @@ describe('Playhead', () => {
         Util.spyFunc(onSeek),
         Util.spyFunc(onEvent));
 
+    playhead.ready();
+
     // This has to periodically increment the mock date to allow the onSeeking_
     // handler to seek, if appropriate.
 
@@ -652,6 +668,8 @@ describe('Playhead', () => {
     expect(currentTime).toBe(1000);
     seekCount = 0;
 
+    playhead.ready();
+
     // The availability window slips ahead.
     timeline.getSeekRangeStart.and.returnValue(1030);
     timeline.getSeekRangeEnd.and.returnValue(1030);
@@ -696,6 +714,8 @@ describe('Playhead', () => {
           Util.spyFunc(onSeek),
           Util.spyFunc(onEvent));
 
+      playhead.ready();
+
       video.on['seeking']();
       expect(video.currentTime).toBe(5);
       expect(playhead.getTime()).toBe(5);
@@ -728,6 +748,8 @@ describe('Playhead', () => {
           Util.spyFunc(onSeek),
           Util.spyFunc(onEvent));
 
+      playhead.ready();
+
       video.on['seeking']();
       expect(video.currentTime).toBe(5);
       expect(playhead.getTime()).toBe(5);
@@ -765,6 +787,9 @@ describe('Playhead', () => {
 
     video.currentTime = 0;
     video.seeking = true;
+
+    playhead.ready();
+
     // "video.seeking" stays true until the buffered range intersects with
     // "video.currentTime".  Playhead should correct anyway.
     video.on['seeking']();
@@ -809,6 +834,8 @@ describe('Playhead', () => {
         Util.spyFunc(onSeek),
         Util.spyFunc(onEvent));
 
+    playhead.ready();
+
     /**
      * Prevent retries on the initial start time seek.  This will ensure that
      * only one call is made for the initial seek, and that any additional calls
@@ -933,6 +960,8 @@ describe('Playhead', () => {
               Util.spyFunc(onSeek),
               Util.spyFunc(onEvent));
 
+          playhead.ready();
+
           jasmine.clock().tick(500);
           for (let time = data.start; time < data.waitingAt; time++) {
             // We don't want to run tick() for 1 second because it will trigger
@@ -1142,6 +1171,8 @@ describe('Playhead', () => {
           Util.spyFunc(onSeek),
           Util.spyFunc(onEvent));
 
+      playhead.ready();
+
       jasmine.clock().tick(500);
       expect(onEvent).not.toHaveBeenCalled();
 
@@ -1190,6 +1221,8 @@ describe('Playhead', () => {
           Util.spyFunc(onSeek),
           Util.spyFunc(onEvent));
 
+      playhead.ready();
+
       playhead.notifyOfBufferingChange();
       jasmine.clock().tick(500);
 
@@ -1212,6 +1245,8 @@ describe('Playhead', () => {
           Util.spyFunc(onSeek),
           Util.spyFunc(onEvent));
 
+      playhead.ready();
+
       playhead.notifyOfBufferingChange();
       jasmine.clock().tick(500);
 
@@ -1236,6 +1271,8 @@ describe('Playhead', () => {
           Util.spyFunc(onSeek),
           Util.spyFunc(onEvent));
 
+      playhead.ready();
+
       playhead.notifyOfBufferingChange();
       jasmine.clock().tick(500);
 
@@ -1260,6 +1297,8 @@ describe('Playhead', () => {
           Util.spyFunc(onSeek),
           Util.spyFunc(onEvent));
 
+      playhead.ready();
+
       playhead.notifyOfBufferingChange();
       jasmine.clock().tick(500);
 
@@ -1287,6 +1326,8 @@ describe('Playhead', () => {
             Util.spyFunc(onSeek),
             Util.spyFunc(onEvent));
 
+        playhead.ready();
+
         jasmine.clock().tick(500);
         expect(onEvent).not.toHaveBeenCalled();
 

test/test/util/simple_fakes.js

@@ -339,6 +339,9 @@ shaka.test.FakePlayhead = class {
     /** @private {number} */
     this.stallsDetected_ = 0;
 
+    /** @type {!jasmine.Spy} */
+    this.ready = jasmine.createSpy('ready');
+
     /** @type {!jasmine.Spy} */
     this.setStartTime = jasmine.createSpy('setStartTime')
         .and.callFake((value) => {