fix: Avoid rebuffering when using big trick play rates (#7988)

Author: avelad

lib/media/streaming_engine.js

@@ -1368,12 +1368,17 @@ shaka.media.StreamingEngine = class {
       return null;
     }
 
+    // Update updateIntervalSeconds according to our current playbackrate,
+    // and always considering a minimum of 1.
+    const updateIntervalSeconds = this.config_.updateIntervalSeconds /
+        Math.max(1, Math.abs(this.playerInterface_.getPlaybackRate()));
+
     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;
+      return updateIntervalSeconds / 2;
     }
 
     const logPrefix = shaka.media.StreamingEngine.logPrefix_(mediaState);
@@ -1445,9 +1450,8 @@ shaka.media.StreamingEngine = class {
       shaka.log.v2(logPrefix, 'buffering goal met');
 
       // Do not try to predict the next update.  Just poll according to
-      // configuration (seconds). The playback rate can change at any time, so
-      // any prediction we make now could be terribly invalid soon.
-      return this.config_.updateIntervalSeconds / 2;
+      // configuration (seconds).
+      return updateIntervalSeconds / 2;
     }
 
     // Lack of segment iterator is the best indicator stream has changed.
@@ -1459,7 +1463,7 @@ shaka.media.StreamingEngine = class {
       // In any case just try again... if the manifest is incomplete or is not
       // being updated then we'll idle forever; otherwise, we'll end up getting
       // a SegmentReference eventually.
-      return this.config_.updateIntervalSeconds;
+      return updateIntervalSeconds;
     }
     // Get media state adaptation and reset this value. By guarding it during
     // actual stream change we ensure it won't be cleaned by accident on regular
@@ -1498,7 +1502,7 @@ shaka.media.StreamingEngine = class {
       // For example, let video buffering catch up to audio buffering before
       // fetching another audio segment.
       shaka.log.v2(logPrefix, 'waiting for other streams to buffer');
-      return this.config_.updateIntervalSeconds;
+      return updateIntervalSeconds;
     }
 
     if (mediaState.segmentPrefetch && mediaState.segmentIterator &&