fix: live dash segment changes should be considered a playlist update (…

…#1065) Currently dash content goes off of the number attribute for segments to determine the mediaSequence. This is problematic as the first segment is almost always listed as 1. So in essence when we request the playlist again the media sequence will be the same, and likely the amount of segments will be the same, so we will determine that this playlist update didn't update anything at all.
videojs · Feb 19, 2021 · 1ce7838 · 1ce7838
1 parent cf2efcb
commit 1ce7838
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Showing 4 changed files with 291 additions and 11 deletions.
diff --git a/src/dash-playlist-loader.js b/src/dash-playlist-loader.js
@@ -6,7 +6,8 @@ import {
 } from 'mpd-parser';
 import {
   refreshDelay,
-  updateMaster as updatePlaylist
+  updateMaster as updatePlaylist,
+  isPlaylistUnchanged
 } from './playlist-loader';
 import { resolveUrl, resolveManifestRedirect } from './resolve-url';
 import parseSidx from 'mux.js/lib/tools/parse-sidx';
@@ -21,6 +22,67 @@ import {toUint8} from '@videojs/vhs-utils/es/byte-helpers';
 
 const { EventTarget, mergeOptions } = videojs;
 
+const dashPlaylistUnchanged = function(a, b) {
+  if (!isPlaylistUnchanged(a, b)) {
+    return false;
+  }
+
+  // for dash the above check will often return true in scenarios where
+  // the playlist actually has changed because mediaSequence isn't a
+  // dash thing, and we often set it to 1. So if the playlists have the same amount
+  // of segments we return true.
+  // So for dash we need to make sure that the underlying segments are different.
+
+  // if sidx changed then the playlists are different.
+  if (a.sidx && b.sidx && (a.sidx.offset !== b.sidx.offset || a.sidx.length !== b.sidx.length)) {
+    return false;
+  } else if ((!a.sidx && b.sidx) || (a.sidx && !b.sidx)) {
+    return false;
+  }
+
+  // one or the other does not have segments
+  // there was a change.
+  if (a.segments && !b.segments || !a.segments && b.segments) {
+    return false;
+  }
+
+  // neither has segments nothing changed
+  if (!a.segments && !b.segments) {
+    return true;
+  }
+
+  // check segments themselves
+  for (let i = 0; i < a.segments.length; i++) {
+    const aSegment = a.segments[i];
+    const bSegment = b.segments[i];
+
+    // if uris are different between segments there was a change
+    if (aSegment.uri !== bSegment.uri) {
+      return false;
+    }
+
+    // neither segment has a byterange, there will be no byterange change.
+    if (!aSegment.byterange && !bSegment.byterange) {
+      continue;
+    }
+    const aByterange = aSegment.byterange;
+    const bByterange = bSegment.byterange;
+
+    // if byterange only exists on one of the segments, there was a change.
+    if ((aByterange && !bByterange) || (!aByterange && bByterange)) {
+      return false;
+    }
+
+    // if both segments have byterange with different offsets, there was a change.
+    if (aByterange.offset !== bByterange.offset || aByterange.length !== bByterange.length) {
+      return false;
+    }
+  }
+
+  // if everything was the same with segments, this is the same playlist.
+  return true;
+};
+
 /**
  * Parses the master XML string and updates playlist URI references.
  *
@@ -92,7 +154,7 @@ export const updateMaster = (oldMaster, newMaster, sidxMapping) => {
         addSidxSegmentsToPlaylist(playlist, sidxMapping[sidxKey].sidx, playlist.sidx.resolvedUri);
       }
     }
-    const playlistUpdate = updatePlaylist(update, playlist);
+    const playlistUpdate = updatePlaylist(update, playlist, dashPlaylistUnchanged);
 
     if (playlistUpdate) {
       update = playlistUpdate;
@@ -104,7 +166,7 @@ export const updateMaster = (oldMaster, newMaster, sidxMapping) => {
   forEachMediaGroup(newMaster, (properties, type, group, label) => {
     if (properties.playlists && properties.playlists.length) {
       const id = properties.playlists[0].id;
-      const playlistUpdate = updatePlaylist(update, properties.playlists[0]);
+      const playlistUpdate = updatePlaylist(update, properties.playlists[0], dashPlaylistUnchanged);
 
       if (playlistUpdate) {
         update = playlistUpdate;

diff --git a/src/playlist-loader.js b/src/playlist-loader.js
@@ -57,6 +57,14 @@ export const resolveSegmentUris = (segment, baseUri) => {
   }
 };
 
+// consider the playlist unchanged if the playlist object is the same or
+// the number of segments is equal, the media sequence number is unchanged,
+// and this playlist hasn't become the end of the playlist
+export const isPlaylistUnchanged = (a, b) => a === b ||
+  (a.segments && b.segments && a.segments.length === b.segments.length &&
+   a.endList === b.endList &&
+   a.mediaSequence === b.mediaSequence);
+
 /**
   * Returns a new master playlist that is the result of merging an
   * updated media playlist into the original version. If the
@@ -69,21 +77,15 @@ export const resolveSegmentUris = (segment, baseUri) => {
   * master playlist with the updated media playlist merged in, or
   * null if the merge produced no change.
   */
-export const updateMaster = (master, media) => {
+export const updateMaster = (master, media, unchangedCheck = isPlaylistUnchanged) => {
   const result = mergeOptions(master, {});
   const playlist = result.playlists[media.id];
 
   if (!playlist) {
     return null;
   }
 
-  // consider the playlist unchanged if the number of segments is equal, the media
-  // sequence number is unchanged, and this playlist hasn't become the end of the playlist
-  if (playlist.segments &&
-      media.segments &&
-      playlist.segments.length === media.segments.length &&
-      playlist.endList === media.endList &&
-      playlist.mediaSequence === media.mediaSequence) {
+  if (unchangedCheck(playlist, media)) {
     return null;
   }
 

diff --git a/test/dash-playlist-loader.test.js b/test/dash-playlist-loader.test.js
@@ -1684,6 +1684,164 @@ QUnit.test('refreshXml_: updates media playlist reference if master changed', fu
   );
 });
 
+QUnit.test('refreshXml_: updates playlists if segment uri changed, but media sequence did not', 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();
+
+  // change segment uris
+  const newMasterXml = loader.masterXml_
+    .replace(/\$RepresentationID\$/g, '$RepresentationID$-foo')
+    .replace('media="segment-$Number$.mp4"', 'media="segment-foo$Number$.mp4"');
+
+  loader.refreshXml_();
+
+  assert.strictEqual(this.requests.length, 1, 'manifest is being requested');
+
+  this.requests.shift().respond(200, null, newMasterXml);
+
+  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'
+  );
+});
+
+QUnit.test('refreshXml_: updates playlists if sidx changed', function(assert) {
+  const loader = new DashPlaylistLoader('dash-sidx.mpd', this.fakeVhs);
+
+  loader.load();
+  this.standardXHRResponse(this.requests.shift());
+  this.standardXHRResponse(this.requests.shift(), mp4VideoInitSegment().subarray(0, 10));
+  this.standardXHRResponse(this.requests.shift(), sidxResponse());
+
+  const oldMaster = loader.master;
+  const oldMedia = loader.media();
+
+  const newMasterXml = loader.masterXml_
+    .replace(/indexRange="200-399"/g, 'indexRange="500-699"');
+
+  loader.refreshXml_();
+
+  assert.strictEqual(this.requests.length, 1, 'manifest is being requested');
+
+  this.standardXHRResponse(this.requests.shift(), newMasterXml);
+
+  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'
+  );
+});
+
+QUnit.test('refreshXml_: updates playlists if sidx removed', function(assert) {
+  const loader = new DashPlaylistLoader('dash-sidx.mpd', this.fakeVhs);
+
+  loader.load();
+  this.standardXHRResponse(this.requests.shift());
+  this.standardXHRResponse(this.requests.shift(), mp4VideoInitSegment().subarray(0, 10));
+  this.standardXHRResponse(this.requests.shift(), sidxResponse());
+
+  const oldMaster = loader.master;
+  const oldMedia = loader.media();
+
+  const newMasterXml = loader.masterXml_
+    .replace(/indexRange="200-399"/g, '');
+
+  loader.refreshXml_();
+
+  assert.strictEqual(this.requests.length, 1, 'manifest is being requested');
+
+  this.standardXHRResponse(this.requests.shift(), newMasterXml);
+
+  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'
+  );
+});
+
+QUnit.test('refreshXml_: updates playlists if only segment byteranges change', function(assert) {
+  const loader = new DashPlaylistLoader('dashByterange.mpd', this.fakeVhs);
+
+  loader.load();
+  this.standardXHRResponse(this.requests.shift());
+
+  const oldMaster = loader.master;
+  const oldMedia = loader.media();
+
+  const newMasterXml = loader.masterXml_
+    .replace('mediaRange="12883295-13124492"', 'mediaRange="12883296-13124492"');
+
+  loader.refreshXml_();
+
+  assert.strictEqual(this.requests.length, 1, 'manifest is being requested');
+
+  this.standardXHRResponse(this.requests.shift(), newMasterXml);
+
+  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'
+  );
+});
+
+QUnit.test('refreshXml_: updates playlists if sidx removed', function(assert) {
+  const loader = new DashPlaylistLoader('dash-sidx.mpd', this.fakeVhs);
+
+  loader.load();
+  this.standardXHRResponse(this.requests.shift());
+  this.standardXHRResponse(this.requests.shift(), mp4VideoInitSegment().subarray(0, 10));
+  this.standardXHRResponse(this.requests.shift(), sidxResponse());
+
+  const oldMaster = loader.master;
+  const oldMedia = loader.media();
+
+  const newMasterXml = loader.masterXml_
+    .replace(/indexRange="200-399"/g, '');
+
+  loader.refreshXml_();
+
+  assert.strictEqual(this.requests.length, 1, 'manifest is being requested');
+
+  this.standardXHRResponse(this.requests.shift(), newMasterXml);
+
+  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'
+  );
+});
+
 QUnit.test('addSidxSegments_: updates master with sidx information', function(assert) {
   const loader = new DashPlaylistLoader('dash.mpd', this.fakeVhs);
   const sidxData = sidxResponse();

diff --git a/test/manifests/dashByterange.mpd b/test/manifests/dashByterange.mpd
@@ -0,0 +1,58 @@
+<?xml version="1.0" encoding="UTF-8"?>
+<MPD xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
+    xmlns="urn:mpeg:DASH:schema:MPD:2011"
+    xsi:schemaLocation="urn:mpeg:DASH:schema:MPD:2011"
+    profiles="urn:mpeg:dash:profile:isoff-main:2011"
+    type="static"
+    mediaPresentationDuration="PT0H9M56.46S"
+    minBufferTime="PT15.0S">
+<BaseURL>http://www-itec.uni-klu.ac.at/ftp/datasets/mmsys12/BigBuckBunny/bunny_15s/</BaseURL>
+<Period start="PT0S">
+    <AdaptationSet bitstreamSwitching="true">
+        <Representation id="3" codecs="avc1" mimeType="video/mp4" width="480" height="360" startWithSAP="1" bandwidth="176031">
+            <SegmentList duration="15">
+                <SegmentURL media="bunny_15s_200kbit/bunny_200kbit_dashNonSeg.mp4" mediaRange="868-347185" />
+                <SegmentURL media="bunny_15s_200kbit/bunny_200kbit_dashNonSeg.mp4" mediaRange="347186-664464" />
+                <SegmentURL media="bunny_15s_200kbit/bunny_200kbit_dashNonSeg.mp4" mediaRange="664465-1027685" />
+                <SegmentURL media="bunny_15s_200kbit/bunny_200kbit_dashNonSeg.mp4" mediaRange="1027686-1367784" />
+                <SegmentURL media="bunny_15s_200kbit/bunny_200kbit_dashNonSeg.mp4" mediaRange="1367785-1677710" />
+                <SegmentURL media="bunny_15s_200kbit/bunny_200kbit_dashNonSeg.mp4" mediaRange="1677711-2001517" />
+                <SegmentURL media="bunny_15s_200kbit/bunny_200kbit_dashNonSeg.mp4" mediaRange="2001518-2290173" />
+                <SegmentURL media="bunny_15s_200kbit/bunny_200kbit_dashNonSeg.mp4" mediaRange="2290174-2634238" />
+                <SegmentURL media="bunny_15s_200kbit/bunny_200kbit_dashNonSeg.mp4" mediaRange="2634239-2985994" />
+                <SegmentURL media="bunny_15s_200kbit/bunny_200kbit_dashNonSeg.mp4" mediaRange="2985995-3323725" />
+                <SegmentURL media="bunny_15s_200kbit/bunny_200kbit_dashNonSeg.mp4" mediaRange="3323726-3650264" />
+                <SegmentURL media="bunny_15s_200kbit/bunny_200kbit_dashNonSeg.mp4" mediaRange="3650265-3978004" />
+                <SegmentURL media="bunny_15s_200kbit/bunny_200kbit_dashNonSeg.mp4" mediaRange="3978005-4304349" />
+                <SegmentURL media="bunny_15s_200kbit/bunny_200kbit_dashNonSeg.mp4" mediaRange="4304350-4629741" />
+                <SegmentURL media="bunny_15s_200kbit/bunny_200kbit_dashNonSeg.mp4" mediaRange="4629742-4951671" />
+                <SegmentURL media="bunny_15s_200kbit/bunny_200kbit_dashNonSeg.mp4" mediaRange="4951672-5282910" />
+                <SegmentURL media="bunny_15s_200kbit/bunny_200kbit_dashNonSeg.mp4" mediaRange="5282911-5629211" />
+                <SegmentURL media="bunny_15s_200kbit/bunny_200kbit_dashNonSeg.mp4" mediaRange="5629212-5963914" />
+                <SegmentURL media="bunny_15s_200kbit/bunny_200kbit_dashNonSeg.mp4" mediaRange="5963915-6312646" />
+                <SegmentURL media="bunny_15s_200kbit/bunny_200kbit_dashNonSeg.mp4" mediaRange="6312647-6612703" />
+                <SegmentURL media="bunny_15s_200kbit/bunny_200kbit_dashNonSeg.mp4" mediaRange="6612704-6923786" />
+                <SegmentURL media="bunny_15s_200kbit/bunny_200kbit_dashNonSeg.mp4" mediaRange="6923787-7272547" />
+                <SegmentURL media="bunny_15s_200kbit/bunny_200kbit_dashNonSeg.mp4" mediaRange="7272548-7590097" />
+                <SegmentURL media="bunny_15s_200kbit/bunny_200kbit_dashNonSeg.mp4" mediaRange="7590098-7947017" />
+                <SegmentURL media="bunny_15s_200kbit/bunny_200kbit_dashNonSeg.mp4" mediaRange="7947018-8276044" />
+                <SegmentURL media="bunny_15s_200kbit/bunny_200kbit_dashNonSeg.mp4" mediaRange="8276045-8551338" />
+                <SegmentURL media="bunny_15s_200kbit/bunny_200kbit_dashNonSeg.mp4" mediaRange="8551339-8866104" />
+                <SegmentURL media="bunny_15s_200kbit/bunny_200kbit_dashNonSeg.mp4" mediaRange="8866105-9171839" />
+                <SegmentURL media="bunny_15s_200kbit/bunny_200kbit_dashNonSeg.mp4" mediaRange="9171840-9515898" />
+                <SegmentURL media="bunny_15s_200kbit/bunny_200kbit_dashNonSeg.mp4" mediaRange="9515899-9849503" />
+                <SegmentURL media="bunny_15s_200kbit/bunny_200kbit_dashNonSeg.mp4" mediaRange="9849504-10161047" />
+                <SegmentURL media="bunny_15s_200kbit/bunny_200kbit_dashNonSeg.mp4" mediaRange="10161048-10494887" />
+                <SegmentURL media="bunny_15s_200kbit/bunny_200kbit_dashNonSeg.mp4" mediaRange="10494888-10786011" />
+                <SegmentURL media="bunny_15s_200kbit/bunny_200kbit_dashNonSeg.mp4" mediaRange="10786012-11142570" />
+                <SegmentURL media="bunny_15s_200kbit/bunny_200kbit_dashNonSeg.mp4" mediaRange="11142571-11503643" />
+                <SegmentURL media="bunny_15s_200kbit/bunny_200kbit_dashNonSeg.mp4" mediaRange="11503644-11859498" />
+                <SegmentURL media="bunny_15s_200kbit/bunny_200kbit_dashNonSeg.mp4" mediaRange="11859499-12213313" />
+                <SegmentURL media="bunny_15s_200kbit/bunny_200kbit_dashNonSeg.mp4" mediaRange="12213314-12578158" />
+                <SegmentURL media="bunny_15s_200kbit/bunny_200kbit_dashNonSeg.mp4" mediaRange="12578159-12883294" />
+                <SegmentURL media="bunny_15s_200kbit/bunny_200kbit_dashNonSeg.mp4" mediaRange="12883295-13124492" />
+            </SegmentList>
+        </Representation>
+    </AdaptationSet>
+</Period>
+</MPD>