cr

Author: brandonocasey

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, true);
+    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], true);
+      const playlistUpdate = updatePlaylist(update, properties.playlists[0], dashPlaylistUnchanged);
 
       if (playlistUpdate) {
         update = playlistUpdate;

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
@@ -69,69 +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, dash = false) => {
+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
-  let unchanged = playlist.segments &&
-    media.segments &&
-    playlist.segments.length === media.segments.length &&
-    playlist.endList === media.endList &&
-    playlist.mediaSequence === media.mediaSequence;
-
-  // for dash mediaSequence and segment lengths will often match as
-  // mediaSequence is almost always 1 and the number of segments generated for a
-  // given time is often the same. So we need to make sure that the underlying segments are
-  // different.
-  if (dash && unchanged) {
-    const oldSidx = playlist.sidx;
-    const newSidx = media.sidx;
-
-    // if sidx changed then the playlists are different.
-    if (oldSidx && newSidx && (oldSidx.offset !== newSidx.offset || oldSidx.length !== newSidx.length)) {
-      unchanged = false;
-    } else if ((!oldSidx && newSidx) || (oldSidx && !newSidx)) {
-      unchanged = false;
-    } else {
-      for (let i = 0; i < playlist.segments.length; i++) {
-        const oldSegment = playlist.segments[i];
-        const newSegment = media.segments[i];
-
-        // if uris are different between segments there was a change
-        if (oldSegment.uri !== newSegment.uri) {
-          unchanged = false;
-          continue;
-        }
-
-        // neither segment has a byternage, there will be no byterange change.
-        if (!oldSegment.byterange && !newSegment.byterange) {
-          continue;
-        }
-        const oldByterange = oldSegment.byterange;
-        const newByterange = newSegment.byterange;
-
-        // if byterange only exists on one of the segments, there was a change.
-        if ((oldByterange && !newByterange) || (!oldByterange && newByterange)) {
-          unchanged = false;
-          continue;
-        }
-
-        // if both segments have byterange with different offsets, there was a change.
-        if (oldByterange.offset !== newByterange.offset || oldByterange.length !== newByterange.length) {
-          unchanged = false;
-          continue;
-        }
-      }
-    }
-  }
-
-  if (unchanged) {
+  if (unchangedCheck(playlist, media)) {
     return null;
   }