feat: Content Steering HLS Pathway Cloning

src/content-steering-controller.js

@@ -11,10 +11,12 @@ import videojs from 'video.js';
  * TTL: number in seconds (optional) until the next content steering manifest reload.
  * RELOAD-URI: string (optional) uri to fetch the next content steering manifest.
  * SERVICE-LOCATION-PRIORITY or PATHWAY-PRIORITY a non empty array of unique string values.
+ * PATHWAY-CLONES: array (optional) (HLS only) pathway clone objects to copy from other playlists.
  */
 class SteeringManifest {
   constructor() {
     this.priority_ = [];
+    this.pathwayClones_ = new Map();
   }
 
   set version(number) {
@@ -43,6 +45,13 @@ class SteeringManifest {
     }
   }
 
+  set pathwayClones(array) {
+    // pathwayClones must be non-empty.
+    if (array && array.length) {
+      this.pathwayClones_ = new Map(array.map((clone) => [clone.ID, clone]));
+    }
+  }
+
   get version() {
     return this.version_;
   }
@@ -58,6 +67,10 @@ class SteeringManifest {
   get priority() {
     return this.priority_;
   }
+
+  get pathwayClones() {
+    return this.pathwayClones_;
+  }
 }
 
 /**
@@ -77,12 +90,13 @@ export default class ContentSteeringController extends videojs.EventTarget {
     this.defaultPathway = null;
     this.queryBeforeStart = null;
     this.availablePathways_ = new Set();
-    this.excludedPathways_ = new Set();
     this.steeringManifest = new SteeringManifest();
     this.proxyServerUrl_ = null;
     this.manifestType_ = null;
     this.ttlTimeout_ = null;
     this.request_ = null;
+    this.currentPathwayClones = new Map();
+    this.nextPathwayClones = new Map();
     this.excludedSteeringManifestURLs = new Set();
     this.logger_ = logger('Content Steering');
     this.xhr_ = xhr;
@@ -269,7 +283,11 @@ export default class ContentSteeringController extends videojs.EventTarget {
     this.steeringManifest.reloadUri = steeringJson['RELOAD-URI'];
     // HLS = PATHWAY-PRIORITY required. DASH = SERVICE-LOCATION-PRIORITY optional
     this.steeringManifest.priority = steeringJson['PATHWAY-PRIORITY'] || steeringJson['SERVICE-LOCATION-PRIORITY'];
-    // TODO: HLS handle PATHWAY-CLONES. See section 7.2 https://datatracker.ietf.org/doc/draft-pantos-hls-rfc8216bis/
+
+    // Pathway clones to be created/updated in HLS.
+    // See section 7.2 https://datatracker.ietf.org/doc/draft-pantos-hls-rfc8216bis/
+    this.steeringManifest.pathwayClones = steeringJson['PATHWAY-CLONES'];
+    this.nextPathwayClones = this.steeringManifest.pathwayClones;
 
     // 1. apply first pathway from the array.
     // 2. if first pathway doesn't exist in manifest, try next pathway.
@@ -397,7 +415,6 @@ export default class ContentSteeringController extends videojs.EventTarget {
     this.request_ = null;
     this.excludedSteeringManifestURLs = new Set();
     this.availablePathways_ = new Set();
-    this.excludedPathways_ = new Set();
     this.steeringManifest = new SteeringManifest();
   }
 

src/manifest.js

@@ -11,7 +11,7 @@ export const createPlaylistID = (index, uri) => {
 };
 
 // default function for creating a group id
-const groupID = (type, group, label) => {
+export const groupID = (type, group, label) => {
   return `placeholder-uri-${type}-${group}-${label}`;
 };
 

src/playlist-controller.js

@@ -2162,6 +2162,15 @@
     if (!currentPathway) {
       return;
     }
+
+    const pastClones = this.contentSteeringController_.currentPathwayClones;
+    const nextClones = this.contentSteeringController_.nextPathwayClones;
+    const hasClones = (pastClones && pastClones.size) || (nextClones && nextClones.size);
+
+    if (hasClones) {
+      this.handlePathwayClones_();
+    }
+
     const main = this.main();
     const playlists = main.playlists;
     const ids = new Set();
@@ -2211,6 +2220,100 @@
     }
   }
 
+  /**
+   * Add, update, or delete playlists and media groups for
+   * the pathway clones for HLS Content Steering.
+   *
+   * See https://datatracker.ietf.org/doc/draft-pantos-hls-rfc8216bis/
+   *
+   * NOTE: Pathway cloning does not currently support the `PER_VARIANT_URIS` and
+   * `PER_RENDITION_URIS` as we do not handle `STABLE-VARIANT-ID` or
+   * `STABLE-RENDITION-ID` values.
+   */
+  handlePathwayClones_() {
+    const main = this.main();
+    const playlists = main.playlists;
+    const currentPathwayClones = this.contentSteeringController_.currentPathwayClones;
+    const nextPathwayClones = this.contentSteeringController_.nextPathwayClones;
+
+    for (const [id, clone] of currentPathwayClones.entries()) {
+      const newClone = nextPathwayClones.get(id);
+
+      // Delete the old pathway clone.
+      if (!newClone) {
+        this.mainPlaylistLoader_.updateOrDeleteClone(clone);
+        this.contentSteeringController_.excludePathway(id);
+      }
+    }
+
+    for (const [id, clone] of nextPathwayClones.entries()) {
+      const oldClone = currentPathwayClones.get(id);
+
+      // Create a new pathway if it is a new pathway clone object.
+      if (!oldClone) {
+        const playlistsToClone = playlists.filter(p => {
+          return p.attributes['PATHWAY-ID'] === clone['BASE-ID'];
+        });
+
+        playlistsToClone.forEach((p) => {
+          this.mainPlaylistLoader_.addClonePathway(clone, p);
+        });
+
+        this.contentSteeringController_.addAvailablePathway(id);
+        continue;
+      }
+
+      // There have not been changes to the pathway clone object, so skip.
+      if (this.equalPathwayClones_(oldClone, clone)) {
+        continue;
+      }
+
+      // Update a preexisting cloned pathway.
+      // True is set for the update flag.
+      this.mainPlaylistLoader_.updateOrDeleteClone(clone, true);
+      this.contentSteeringController_.addAvailablePathway(id);
+    }
+
+    // Deep copy contents of next to current pathways.
+    this.contentSteeringController_.currentPathwayClones = new Map(JSON.parse(JSON.stringify([...nextPathwayClones])));
+  }
+
+  /**
+   * Determines whether two pathway clone objects are equivalent.
+   *
+   * @param {Object} a The first pathway clone object.
+   * @param {Object} b The second pathway clone object.
+   * @return {boolean} True if the pathway clone objects are equal, false otherwise.
+   */
+  equalPathwayClones_(a, b) {
+    if (
+      a['BASE-ID'] !== b['BASE-ID'] ||
+      a.ID !== b.ID ||
+      a['URI-REPLACEMENT'].HOST !== b['URI-REPLACEMENT'].HOST
+    ) {
+      return false;
+    }
+
+    const aParams = a['URI-REPLACEMENT'].PARAMS;
+    const bParams = b['URI-REPLACEMENT'].PARAMS;
+
+    // We need to iterate through both lists of params because one could be
+    // missing a parameter that the other has.
+    for (const p in aParams) {
+      if (aParams[p] !== bParams[p]) {
+        return false;
+      }
+    }
+
+    for (const p in bParams) {
+      if (aParams[p] !== bParams[p]) {
+        return false;
+      }
+    }
+
+    return true;
+  }
+
   /**
    * Changes the current playlists for audio, video and subtitles after a new pathway
    * is chosen from content steering.