Add option to select lowest rendition available on startup

src/master-playlist-controller.js

@@ -12,6 +12,7 @@ import { translateLegacyCodecs } from 'videojs-contrib-media-sources/es5/codec-u
 import worker from 'webworkify';
 import Decrypter from './decrypter-worker';
 import Config from './config';
+import { parseCodecs } from './util/codecs.js';
 
 let Hls;
 
@@ -65,36 +66,6 @@ const objectChanged = function(a, b) {
   return false;
 };
 
-/**
- * Parses a codec string to retrieve the number of codecs specified,
- * the video codec and object type indicator, and the audio profile.
- *
- * @private
- */
-const parseCodecs = function(codecs) {
-  let result = {
-    codecCount: 0
-  };
-  let parsed;
-
-  result.codecCount = codecs.split(',').length;
-  result.codecCount = result.codecCount || 2;
-
-  // parse the video codec
-  parsed = (/(^|\s|,)+(avc1)([^ ,]*)/i).exec(codecs);
-  if (parsed) {
-    result.videoCodec = parsed[2];
-    result.videoObjectTypeIndicator = parsed[3];
-  }
-
-  // parse the last field of the audio codec
-  result.audioProfile =
-    (/(^|\s|,)+mp4a.[0-9A-Fa-f]+\.([0-9A-Fa-f]+)/i).exec(codecs);
-  result.audioProfile = result.audioProfile && result.audioProfile[2];
-
-  return result;
-};
-
 /**
  * Replace codecs in the codec string with the old apple-style `avc1.<dd>.<dd>` to the
  * standard `avc1.<hhhhhh>`.
@@ -283,7 +254,8 @@ export class MasterPlaylistController extends videojs.EventTarget {
       bandwidth,
       externHls,
       useCueTags,
-      blacklistDuration
+      blacklistDuration,
+      enableLowInitialPlaylist
     } = options;
 
     if (!url) {
@@ -298,6 +270,7 @@ export class MasterPlaylistController extends videojs.EventTarget {
     this.mode_ = mode;
     this.useCueTags_ = useCueTags;
     this.blacklistDuration = blacklistDuration;
+    this.enableLowInitialPlaylist = enableLowInitialPlaylist;
     if (this.useCueTags_) {
       this.cueTagsTrack_ = this.tech_.addTextTrack('metadata',
         'ad-cues');
@@ -430,7 +403,11 @@ export class MasterPlaylistController extends videojs.EventTarget {
 
       if (!updatedPlaylist) {
         // select the initial variant
-        this.initialMedia_ = this.selectPlaylist();
+        const initialPlaylistSelector =
+          this.enableLowInitialPlaylist ?
+            this.selectInitialPlaylist : this.selectPlaylist;
+
+        this.initialMedia_ = initialPlaylistSelector();
         this.masterPlaylistLoader_.media(this.initialMedia_);
         return;
       }

src/playlist-selectors.js

@@ -1,5 +1,6 @@
 import Config from './config';
 import Playlist from './playlist';
+import { parseCodecs } from './util/codecs.js';
 
 // Utilities
 
@@ -356,3 +357,27 @@ export const minRebufferMaxBandwidthSelector = function(settings) {
 
   return rebufferingEstimates[0] || null;
 };
+
+/**
+ * Chooses the appropriate media playlist, which in this case is the lowest bitrate
+ * one with video.  If no renditions with video exist, return the lowest audio rendition.
+ *
+ * @return {Object|null}
+ *         {Object} return.playlist
+ *         The lowest bitrate playlist that contains a video codec.  If no such rendition
+ *         exists pick the lowest audio rendition.
+ */
+export const lowestBitrateCompatibleVariantSelector = function() {
+  const { playlists } = this.playlists.master;
+
+  // Sort ascending by bitrate
+  stableSort(playlists,
+    (a, b) => comparePlaylistBandwidth(a, b));
+
+  const playlistsWithVideo =
+    playlists.filter(playlist => parseCodecs(playlist.attributes.CODECS).videoCodec);
+
+  const selectedPlaylists = playlistsWithVideo.length !== 0 ? playlistsWithVideo : playlists;
+
+  return selectedPlaylists[0] || null;
+};

src/util/codecs.js

@@ -0,0 +1,34 @@
+
+/**
+ * @file - codecs.js - Handles tasks regarding codec strings such as translating them to
+ * codec strings, or translating codec strings into objects that can be examined.
+ */
+
+/**
+ * Parses a codec string to retrieve the number of codecs specified,
+ * the video codec and object type indicator, and the audio profile.
+ */
+
+export const parseCodecs = function(codecs = '') {
+  let result = {
+    codecCount: 0
+  };
+  let parsed;
+
+  result.codecCount = codecs.split(',').length;
+  result.codecCount = result.codecCount || 2;
+
+  // parse the video codec
+  parsed = (/(^|\s|,)+(avc1)([^ ,]*)/i).exec(codecs);
+  if (parsed) {
+    result.videoCodec = parsed[2];
+    result.videoObjectTypeIndicator = parsed[3];
+  }
+
+  // parse the last field of the audio codec
+  result.audioProfile =
+    (/(^|\s|,)+mp4a.[0-9A-Fa-f]+\.([0-9A-Fa-f]+)/i).exec(codecs);
+  result.audioProfile = result.audioProfile && result.audioProfile[2];
+
+  return result;
+};

src/videojs-contrib-hls.js

@@ -21,6 +21,7 @@ import PlaybackWatcher from './playback-watcher';
 import reloadSourceOnError from './reload-source-on-error';
 import {
   lastBandwidthSelector,
+  lowestBitrateCompatibleVariantSelector,
   comparePlaylistBandwidth,
   comparePlaylistResolution
 } from './playlist-selectors.js';
@@ -39,6 +40,7 @@ const Hls = {
   utils,
 
   STANDARD_PLAYLIST_SELECTOR: lastBandwidthSelector,
+  INITIAL_PLAYLIST_SELECTOR: lowestBitrateCompatibleVariantSelector,
   comparePlaylistBandwidth,
   comparePlaylistResolution,
 
@@ -271,6 +273,7 @@ class HlsHandler extends Component {
   setOptions_() {
     // defaults
     this.options_.withCredentials = this.options_.withCredentials || false;
+    this.options_.enableLowInitialPlaylist = this.options_.enableLowInitialPlaylist || false;
 
     if (typeof this.options_.blacklistDuration !== 'number') {
       this.options_.blacklistDuration = 5 * 60;
@@ -328,6 +331,10 @@ class HlsHandler extends Component {
       this.selectPlaylist ?
         this.selectPlaylist.bind(this) : Hls.STANDARD_PLAYLIST_SELECTOR.bind(this);
 
+    this.masterPlaylistController_.selectInitialPlaylist =
+      this.selectInitialPlaylist ?
+        this.selectInitialPlaylist.bind(this) : Hls.INITIAL_PLAYLIST_SELECTOR.bind(this);
+
     // re-expose some internal objects for backwards compatibility with < v2
     this.playlists = this.masterPlaylistController_.masterPlaylistLoader_;
     this.mediaSource = this.masterPlaylistController_.mediaSource;

test/master-playlist-controller.test.js

@@ -212,6 +212,50 @@ QUnit.test('resets SegmentLoader when seeking in flash for both in and out of bu
 
   });
 
+QUnit.only('selects lowest bitrate rendition when enableLowInitialPlaylist is set',
+  function(assert) {
+    this.player = createPlayer({ html5: { hls: { enableLowInitialPlaylist: true } } });
+
+    this.player.src({
+      src: 'manifest/master.m3u8',
+      type: 'application/vnd.apple.mpegurl'
+    });
+
+    this.clock.tick(1);
+
+    const masterPlaylistController = this.player.tech_.hls.masterPlaylistController_;
+    const masterPlaylistLoader = masterPlaylistController.masterPlaylistLoader_;
+
+    let numCallsToSelectInitialPlaylistCalls = 0;
+    let numCallsToSelectPlaylist = 0;
+
+    // master
+    this.standardXHRResponse(this.requests.shift());
+    // media
+    this.standardXHRResponse(this.requests.shift());
+
+    // This shouldn't get called, but if it does we should track it so that
+    // we can catch this failure case.
+    masterPlaylistController.selectPlaylist = () => {
+      numCallsToSelectPlaylist++;
+      return masterPlaylistController.master().playlists[0];
+    };
+
+    masterPlaylistController.selectInitialPlaylist = () => {
+      numCallsToSelectInitialPlaylistCalls++;
+      return masterPlaylistController.master().playlists[0];
+    };
+
+    masterPlaylistController.mediaSource.trigger('sourceopen');
+
+    // Trigger playlist event which should utilize selectInitialPlaylist and
+    // not selectPlaylist
+    masterPlaylistLoader.trigger('loadedplaylist');
+
+    assert.equal(numCallsToSelectInitialPlaylistCalls, 1, 'selectInitialPlaylist');
+    assert.equal(numCallsToSelectPlaylist, 0, 'selectPlaylist');
+  });
+
 QUnit.test('resyncs SegmentLoader for a fast quality change', function(assert) {
   let resyncs = 0;