fix(FEC-11586): [Player, Safari] The 'FF' (Fast forward) seek button …

…is flashing time to time in player due to getting different values from 'isOnLiveEdge' parameter (#611)

Description of the Changes
issue: The live indicator depends on the isOnLiveEdge flag and the isOnLiveEdge flag is calculated by the following formula: liveDuration - currentTime <= segmentDuration × 2.

and the segmentDuration is calculated by the gap between last updated Video.seekable, and Video.bufferd. (and on the assumption that the bufferd is bigger than seekable at any point)

but in practice bufferd Unlike Video.currentTime (which is always progresses), is sometimes reverses which brings the segmentDuration to become a negative number, and hence although that current time is close enough to seekable to be considered on live, the condition returns false since the liveDuration - currentTime would always be a positive number

fix: The solution is to not rely on the bufferd to determine the liveDuration but on the gap between the seekables themself.

solves FEC-11586

src/engines/html5/media-source/adapters/native-adapter.js

@@ -1118,7 +1118,7 @@ export default class NativeAdapter extends BaseMediaSourceAdapter {
   }
 
   get liveDuration() {
-    return this._getLiveEdge() + this.getSegmentDuration();
+    return this._getLiveEdge();
   }
 
   /**
@@ -1157,16 +1157,33 @@ export default class NativeAdapter extends BaseMediaSourceAdapter {
    */
   _handleLiveDurationChange(): void {
     this._liveDurationChangeInterval = setInterval(() => {
+      this._calculateSegmentDuration();
       const liveEdge = this._getLiveEdge();
       if (this._liveEdge !== liveEdge) {
         this._liveEdge = liveEdge;
         this._videoElement.dispatchEvent(new window.Event(Html5EventType.DURATION_CHANGE));
       }
+    }, LIVE_DURATION_INTERVAL_MS);
+  }
+
+  /**
+   * Calculate the segment duration
+   * @function _calculateSegmentDuration
+   * @returns {void}
+   * @private
+   */
+  _calculateSegmentDuration() {
+    if (this._videoElement.seekable.start(0) === 0) {
       const {buffered, seekable} = this._videoElement;
       if (buffered.length && seekable.length) {
         this._segmentDuration = (buffered.end(buffered.length - 1) - seekable.end(seekable.length - 1)) / SAFARI_BUFFERED_SEGMENTS_COUNT;
       }
-    }, LIVE_DURATION_INTERVAL_MS);
+    } else {
+      const liveEdge = this._getLiveEdge();
+      if (this._liveEdge !== liveEdge) {
+        this._segmentDuration = liveEdge - this._liveEdge;
+      }
+    }
   }
 
   /**