Keep the last bandwidth as an exponential moving average in an attemp…

…t to smooth out the actual numbers a bit.

src/controller/abr-controller.js

@@ -22,6 +22,9 @@ class AbrController extends EventHandler {
     this._nextAutoLevel = -1;
     this.hls = hls;
     this.onCheck = this.abandonRulesCheck.bind(this);
+
+    // This factor weights the last bandwidth measurement as an exponential moving average.
+    this.exponentialWeighting = 0.8;
   }
 
   destroy() {
@@ -43,7 +46,11 @@ class AbrController extends EventHandler {
     // and leading to wrong bw estimation
     if (stats.aborted === undefined && data.frag.loadCounter === 1) {
       this.lastfetchduration = (performance.now() - stats.trequest) / 1000;
-      this.lastbw = (stats.loaded * 8) / this.lastfetchduration;
+      if (this.lastbw) {
+        this.lastbw = this.exponentialWeighting * ((stats.loaded * 8) / this.lastfetchduration) + (1 - this.exponentialWeighting) * this.lastbw;
+      } else {
+        this.lastbw = (stats.loaded * 8) / this.lastfetchduration;
+      }
       //console.log(`fetchDuration:${this.lastfetchduration},bw:${(this.lastbw/1000).toFixed(0)}/${stats.aborted}`);
     }
   }