fix: throttle final playlist reloads when using DASH (#277)

src/dash-playlist-loader.js

@@ -162,14 +162,26 @@ export default class DashPlaylistLoader extends EventTarget {
 
   pause() {
     this.stopRequest();
+    window.clearTimeout(this.mediaUpdateTimeout);
     if (this.state === 'HAVE_NOTHING') {
       // If we pause the loader before any data has been retrieved, its as if we never
       // started, so reset to an unstarted state.
       this.started = false;
     }
   }
 
-  load() {
+  load(isFinalRendition) {
+    window.clearTimeout(this.mediaUpdateTimeout);
+
+    const media = this.media();
+
+    if (isFinalRendition) {
+      const delay = media ? (media.targetDuration / 2) * 1000 : 5 * 1000;
+
+      this.mediaUpdateTimeout = window.setTimeout(() => this.load(), delay);
+      return;
+    }
+
     // because the playlists are internal to the manifest, load should either load the
     // main manifest, or do nothing but trigger an event
     if (!this.started) {

test/dash-playlist-loader.test.js

@@ -397,3 +397,42 @@ QUnit.test('media playlists "refresh" by re-parsing master xml', function(assert
 
   assert.equal(refreshes, 1, 'refreshed playlist after last segment duration');
 });
+
+QUnit.test('delays load when on final rendition', function(assert) {
+  let loader = new DashPlaylistLoader('dash.mpd', this.fakeHls);
+  let loadedplaylistEvents = 0;
+
+  loader.on('loadedplaylist', () => loadedplaylistEvents++);
+
+  // do an initial load to start the loader
+  loader.load();
+  standardXHRResponse(this.requests.shift());
+
+  // one for master, one for media on first selection
+  assert.equal(loadedplaylistEvents, 2, 'two loadedplaylist events after first load');
+
+  loader.load();
+
+  assert.equal(loadedplaylistEvents, 3, 'one more loadedplaylist event after load');
+
+  loader.load(false);
+
+  assert.equal(
+    loadedplaylistEvents,
+    4,
+    'one more loadedplaylist event after load with isFinalRendition false');
+
+  loader.load(true);
+
+  assert.equal(
+    loadedplaylistEvents,
+    4,
+    'no loadedplaylist event after load with isFinalRendition false');
+
+  this.clock.tick(loader.media().targetDuration / 2 * 1000);
+
+  assert.equal(
+    loadedplaylistEvents,
+    5,
+    'one more loadedplaylist event after final rendition delay');
+});