fix: use playlist NAME when available as its ID

src/dash-playlist-loader.js

@@ -43,7 +43,7 @@ export const parseMasterXml = ({ masterXml, srcUrl, clientOffset, sidxMapping })
     sidxMapping
   });
 
-  addPropertiesToMaster(master, srcUrl);
+  addPropertiesToMaster(master, srcUrl, true);
 
   return master;
 };

src/manifest.js

@@ -99,18 +99,32 @@ export const setupMediaPlaylist = ({ playlist, uri, id }) => {
  *
  * @param {Object} master
  *        The master playlist
+ * @param {boolean} [useNameForId=false]
+ *        Whether we should use the NAME property for ID.
+ *        Generally only used for DASH and defaults to false.
  */
-export const setupMediaPlaylists = (master) => {
+export const setupMediaPlaylists = (master, useNameForId) => {
   let i = master.playlists.length;
 
   while (i--) {
     const playlist = master.playlists[i];
+    const createdId = createPlaylistID(i, playlist.uri);
+    let id = createdId;
+
+    // If useNameForId is set, use the NAME attribute for the ID.
+    // Generally, this will be used for DASH because
+    // DASH Representations can change order across refreshes which can make referring to them by index not work.
+    if (useNameForId) {
+      id = playlist.attributes && playlist.attributes.NAME || id;
+    }
 
     setupMediaPlaylist({
       playlist,
-      id: createPlaylistID(i, playlist.uri)
+      id
     });
     playlist.resolvedUri = resolveUrl(master.uri, playlist.uri);
+    // make sure that if a useNameForId is true, the old "createdId" id is also available
+    master.playlists[createdId] = playlist;
     master.playlists[playlist.id] = playlist;
     // URI reference added for backwards compatibility
     master.playlists[playlist.uri] = playlist;
@@ -187,8 +201,11 @@ export const masterForMedia = (media, uri) => {
  *        Master manifest object
  * @param {string} uri
  *        The source URI
+ * @param {boolean} [useNameForId=false]
+ *        Whether we should use the NAME property for ID.
+ *        Generally only used for DASH and defaults to false.
  */
-export const addPropertiesToMaster = (master, uri) => {
+export const addPropertiesToMaster = (master, uri, useNameForId = false) => {
   master.uri = uri;
 
   for (let i = 0; i < master.playlists.length; i++) {
@@ -221,6 +238,6 @@ export const addPropertiesToMaster = (master, uri) => {
     master.playlists[phonyUri] = properties.playlists[0];
   });
 
-  setupMediaPlaylists(master);
+  setupMediaPlaylists(master, useNameForId);
   resolveMediaGroupUris(master);
 };

test/dash-playlist-loader.test.js

@@ -1295,7 +1295,12 @@ QUnit.test('parseMasterXml: setup phony playlists and resolves uris', function(a
 
   assert.strictEqual(masterPlaylist.uri, loader.srcUrl, 'master playlist uri set correctly');
   assert.strictEqual(masterPlaylist.playlists[0].uri, 'placeholder-uri-0');
-  assert.strictEqual(masterPlaylist.playlists[0].id, '0-placeholder-uri-0');
+  assert.strictEqual(masterPlaylist.playlists[0].id, '1080p');
+  assert.strictEqual(
+    masterPlaylist.playlists['1080p'],
+    masterPlaylist.playlists['0-placeholder-uri-0'],
+    'available via old and new ids'
+  );
   assert.deepEqual(
     masterPlaylist.playlists['0-placeholder-uri-0'],
     masterPlaylist.playlists[0],
@@ -1621,6 +1626,43 @@ QUnit.test('refreshXml_: updates media playlist reference if master changed', fu
   );
 });
 
+QUnit.test('refreshXml_: keep reference to same playlist by id across mpd updates', function(assert) {
+  const loader = new DashPlaylistLoader('dash.mpd', this.fakeVhs);
+
+  loader.load();
+  this.standardXHRResponse(this.requests.shift());
+
+  const oldMaster = loader.master;
+  const oldMedia = loader.media();
+
+  loader.refreshXml_();
+
+  assert.strictEqual(this.requests.length, 1, 'manifest is being requested');
+
+  this.requests.shift().respond(200, null, testDataManifests['dash-swapped']);
+
+  const newMaster = loader.master;
+  const newMedia = loader.media();
+
+  assert.notEqual(newMaster, oldMaster, 'master changed');
+  assert.notEqual(newMedia, oldMedia, 'media changed');
+  assert.equal(
+    newMedia,
+    newMaster.playlists[newMedia.id],
+    'media from updated master'
+  );
+
+  // given that the only thing that changed in the new manifest is
+  // the mediaPresentationDuration and order of representations
+  // the old media and the new media should be equivalent.
+  // Comparing the attributes is an easy way to check.
+  assert.deepEqual(
+    newMedia.attributes,
+    oldMedia.attributes,
+    'old media and new media references by same id'
+  );
+});
+
 QUnit.test('sidxRequestFinished_: updates master with sidx information', function(assert) {
   const loader = new DashPlaylistLoader('dash.mpd', this.fakeVhs);
   const fakePlaylist = {
@@ -2258,9 +2300,14 @@ QUnit.test(
       'setup phony uri for media playlist'
     );
     assert.equal(
-      loader.master.playlists[0].id, '0-placeholder-uri-0',
+      loader.master.playlists[0].id, '1080p',
       'setup phony id for media playlist'
     );
+    assert.strictEqual(
+      loader.master.playlists['1080p'],
+      loader.master.playlists['0-placeholder-uri-0'],
+      'reference by NAME and old id'
+    );
     assert.strictEqual(
       loader.master.playlists['0-placeholder-uri-0'],
       loader.master.playlists[0], 'set reference by uri for easy access'
@@ -2270,9 +2317,14 @@ QUnit.test(
       'setup phony uri for media playlist'
     );
     assert.equal(
-      loader.master.playlists[1].id, '1-placeholder-uri-1',
+      loader.master.playlists[1].id, '720p',
       'setup phony id for media playlist'
     );
+    assert.strictEqual(
+      loader.master.playlists['720p'],
+      loader.master.playlists['1-placeholder-uri-1'],
+      'reference by NAME and old id'
+    );
     assert.strictEqual(
       loader.master.playlists['1-placeholder-uri-1'],
       loader.master.playlists[1], 'set reference by uri for easy access'

test/manifests/dash-swapped.mpd

@@ -0,0 +1,24 @@
+<?xml version="1.0"?>
+<MPD xmlns="urn:mpeg:dash:schema:mpd:2011" profiles="urn:mpeg:dash:profile:full:2011" minBufferTime="1.5" mediaPresentationDuration="PT5S">
+  <Period>
+    <BaseURL>main/</BaseURL>
+    <AdaptationSet mimeType="video/mp4">
+      <BaseURL>video/</BaseURL>
+      <Representation id="720p" bandwidth="2400000" width="1280" height="720" codecs="avc1.420015">
+        <BaseURL>720/</BaseURL>
+        <SegmentTemplate media="$RepresentationID$-segment-$Number$.mp4" initialization="$RepresentationID$-init.mp4" duration="10" timescale="10" startNumber="0" />
+      </Representation>
+      <Representation id="1080p" bandwidth="6800000" width="1920" height="1080" codecs="avc1.420015">
+        <BaseURL>1080/</BaseURL>
+        <SegmentTemplate media="$RepresentationID$-segment-$Number$.mp4" initialization="$RepresentationID$-init.mp4" duration="10" timescale="10" startNumber="0" />
+      </Representation>
+    </AdaptationSet>
+    <AdaptationSet mimeType="audio/mp4">
+      <BaseURL>audio/</BaseURL>
+      <Representation id="audio" bandwidth="128000" codecs="mp4a.40.2">
+        <BaseURL>720/</BaseURL>
+        <SegmentTemplate media="segment-$Number$.mp4" initialization="$RepresentationID$-init.mp4" duration="10" timescale="10" startNumber="0" />
+      </Representation>
+    </AdaptationSet>
+  </Period>
+</MPD>