Fix chopped playback in MS Edge

Fudge the append window end to fix a playback bug in Edge.

Because Edge does not seem to implement MP4 edit lists correctly, we
may end up with some audio truncation and a gap.  If we fudge the end
of the append window a bit, we avoid this truncation and we get a
continuous buffered range and smooth playback.

Fixes #1597
Fixed #1435

Change-Id: If28f3f5499dbf5ad9d33ee4859f95ebd91ad3e59

lib/media/gap_jumping_controller.js

@@ -227,7 +227,7 @@ shaka.media.GapJumpingController.prototype.onPollGapJump_ = function() {
     if (this.config_.jumpLargeGaps && !event.defaultPrevented) {
       jumpLargeGap = true;
     } else {
-      shaka.log.info('Ignoring large gap at', currentTime);
+      shaka.log.info('Ignoring large gap at', currentTime, 'size', jumpSize);
     }
   }
 

lib/media/streaming_engine.js

@@ -294,9 +294,9 @@ shaka.media.StreamingEngine.MediaState_;
 
 
 /**
- * The fudge factor for the appendWindowStart.  By adjusting the window
- * backward, we avoid rounding errors that could cause us to remove the keyframe
- * at the start of the Period.
+ * The fudge factor for appendWindowStart.  By adjusting the window backward, we
+ * avoid rounding errors that could cause us to remove the keyframe at the start
+ * of the Period.
  *
  * NOTE: This was increased as part of the solution to
  * https://github.com/google/shaka-player/issues/1281
@@ -307,6 +307,20 @@ shaka.media.StreamingEngine.MediaState_;
 shaka.media.StreamingEngine.APPEND_WINDOW_START_FUDGE_ = 0.1;
 
 
+/**
+ * The fudge factor for appendWindowEnd.  By adjusting the window backward, we
+ * avoid rounding errors that could cause us to remove the last few samples of
+ * the Period.  This rounding error could then create an artificial gap and a
+ * stutter when the gap-jumping logic takes over.
+ *
+ * https://github.com/google/shaka-player/issues/1597
+ *
+ * @const {number}
+ * @private
+ */
+shaka.media.StreamingEngine.APPEND_WINDOW_END_FUDGE_ = 0.01;
+
+
 /**
  * The maximum number of segments by which a stream can get ahead of other
  * streams.
@@ -1482,9 +1496,10 @@ shaka.media.StreamingEngine.prototype.getSegmentReferenceIfAvailable_ =
  */
 shaka.media.StreamingEngine.prototype.fetchAndAppend_ = function(
     mediaState, playheadTime, currentPeriodIndex, reference) {
-  let logPrefix = shaka.media.StreamingEngine.logPrefix_(mediaState);
   const ContentType = shaka.util.ManifestParserUtils.ContentType;
-  let currentPeriod = this.manifest_.periods[currentPeriodIndex];
+  const StreamingEngine = shaka.media.StreamingEngine;
+  const logPrefix = StreamingEngine.logPrefix_(mediaState);
+  const currentPeriod = this.manifest_.periods[currentPeriodIndex];
 
   shaka.log.v1(logPrefix,
                'fetchAndAppend_:',
@@ -1504,11 +1519,15 @@ shaka.media.StreamingEngine.prototype.fetchAndAppend_ = function(
   // Compute the append window.
   let duration = this.manifest_.presentationTimeline.getDuration();
   let followingPeriod = this.manifest_.periods[currentPeriodIndex + 1];
+
   // Rounding issues can cause us to remove the first frame of the Period, so
   // reduce the start time slightly.
-  let windowFudge = shaka.media.StreamingEngine.APPEND_WINDOW_START_FUDGE_;
-  let appendWindowStart = Math.max(0, currentPeriod.startTime - windowFudge);
-  let appendWindowEnd = followingPeriod ? followingPeriod.startTime : duration;
+  const appendWindowStart = Math.max(0,
+      currentPeriod.startTime - StreamingEngine.APPEND_WINDOW_START_FUDGE_);
+  const appendWindowEnd = followingPeriod ?
+      followingPeriod.startTime + StreamingEngine.APPEND_WINDOW_END_FUDGE_ :
+      duration;
+
   goog.asserts.assert(
       reference.startTime <= appendWindowEnd,
       logPrefix + ' segment should start before append window end');
@@ -1709,7 +1728,7 @@ shaka.media.StreamingEngine.prototype.initSourceBuffer_ = function(
       currentPeriod.startTime - mediaState.stream.presentationTimeOffset;
   shaka.log.v1(logPrefix, 'setting timestamp offset to ' + timestampOffset);
   shaka.log.v1(logPrefix,
-               'setting appstart window start to ' + appendWindowStart);
+               'setting append window start to ' + appendWindowStart);
   shaka.log.v1(logPrefix, 'setting append window end to ' + appendWindowEnd);
   let setStreamProperties =
       this.playerInterface_.mediaSourceEngine.setStreamProperties(
@@ -2187,7 +2206,7 @@ shaka.media.StreamingEngine.prototype.fetch_ = function(reference) {
     if (reference.endByte != null) range += reference.endByte;
     request.headers['Range'] = range;
   }
-  shaka.log.v2('fetching: reference=' + reference);
+  shaka.log.v2('fetching: reference=', reference);
   let op = this.playerInterface_.netEngine.request(requestType, request);
   return op.promise.then(function(response) {
     return response.data;