feat: Add LCEVC dual track rendering

lib/media/streaming_engine.js

@@ -660,6 +660,12 @@ shaka.media.StreamingEngine = class {
     mediaState.stream = stream;
     mediaState.segmentIterator = null;
     mediaState.adaptation = !!adaptation;
+    if (stream.dependencyStream) {
+      mediaState.dependencyMediaState =
+          this.createMediaState_(stream.dependencyStream);
+    } else {
+      mediaState.dependencyMediaState = null;
+    }
 
     const streamTag = shaka.media.StreamingEngine.logPrefix_(mediaState);
     shaka.log.debug('switch: switching to Stream ' + streamTag);
@@ -1042,16 +1048,20 @@ shaka.media.StreamingEngine = class {
    * @private
    */
   createMediaState_(stream) {
-    return /** @type {shaka.media.StreamingEngine.MediaState_} */ ({
+    /** @type {!shaka.media.StreamingEngine.MediaState_} */
+    const mediaState = {
       stream,
-      type: stream.type,
+      type: /** @type {shaka.util.ManifestParserUtils.ContentType} */(
+        stream.type),
       segmentIterator: null,
       segmentPrefetch: this.createSegmentPrefetch_(stream),
       lastSegmentReference: null,
       lastInitSegmentReference: null,
       lastTimestampOffset: null,
       lastAppendWindowStart: null,
       lastAppendWindowEnd: null,
+      lastCodecs: null,
+      lastMimeType: null,
       restoreStreamAfterTrickPlay: null,
       endOfStream: false,
       performingUpdate: false,
@@ -1063,10 +1073,17 @@ shaka.media.StreamingEngine = class {
       // The playhead might be seeking on startup, if a start time is set, so
       // start "seeked" as true.
       seeked: true,
+      adaptation: false,
       recovering: false,
       hasError: false,
       operation: null,
-    });
+      dependencyMediaState: null,
+    };
+    if (stream.dependencyStream) {
+      mediaState.dependencyMediaState =
+          this.createMediaState_(stream.dependencyStream);
+    }
+    return mediaState;
   }
 
   /**
@@ -1514,6 +1531,10 @@ shaka.media.StreamingEngine = class {
     const p = this.fetchAndAppend_(mediaState, presentationTime, reference,
         adaptation);
     p.catch(() => {});  // TODO(#1993): Handle asynchronous errors.
+    if (mediaState.dependencyMediaState) {
+      this.fetchAndAppendDependency_(
+          mediaState.dependencyMediaState, presentationTime);
+    }
     return null;
   }
 
@@ -1898,6 +1919,48 @@ shaka.media.StreamingEngine = class {
   }
 
 
+  /**
+   * Fetches and appends a dependency media state
+   *
+   * @param {!shaka.media.StreamingEngine.MediaState_} mediaState
+   * @param {number} presentationTime
+   * @private
+   */
+  async fetchAndAppendDependency_(mediaState, presentationTime) {
+    const dependencyStream = mediaState.stream;
+    const iterator =
+        dependencyStream.segmentIndex.getIteratorForTime(presentationTime);
+    const reference = iterator && iterator.next().value;
+    if (reference) {
+      const initSegmentReference = reference.initSegmentReference;
+      if (initSegmentReference && !shaka.media.InitSegmentReference.equal(
+          initSegmentReference, mediaState.lastInitSegmentReference)) {
+        mediaState.lastInitSegmentReference = initSegmentReference;
+        try {
+          const init = await this.fetch_(mediaState, initSegmentReference);
+          this.playerInterface_.mediaSourceEngine.appendDependency(
+              init, 0, dependencyStream);
+        } catch (e) {
+          mediaState.lastInitSegmentReference = null;
+          throw e;
+        }
+      }
+      if (!mediaState.lastSegmentReference ||
+          mediaState.lastSegmentReference != reference) {
+        mediaState.lastSegmentReference = reference;
+        try {
+          const result = await this.fetch_(mediaState, reference);
+          this.playerInterface_.mediaSourceEngine.appendDependency(
+              result, 0, dependencyStream);
+        } catch (e) {
+          mediaState.lastSegmentReference = null;
+          throw e;
+        }
+      }
+    }
+  }
+
+
   /**
    * Clear per-stream error states and retry any failed streams.
    * @param {number} delaySeconds
@@ -3003,7 +3066,8 @@ shaka.media.StreamingEngine.PlayerInterface;
  *   recovering: boolean,
  *   hasError: boolean,
  *   operation: shaka.net.NetworkingEngine.PendingRequest,
- *   segmentPrefetch: shaka.media.SegmentPrefetch
+ *   segmentPrefetch: shaka.media.SegmentPrefetch,
+ *   dependencyMediaState: ?shaka.media.StreamingEngine.MediaState_
  * }}
  *
  * @description
@@ -3064,6 +3128,8 @@ shaka.media.StreamingEngine.PlayerInterface;
  * @property {?shaka.media.SegmentPrefetch} segmentPrefetch
  *   A prefetch object for managing prefetching. Null if unneeded
  *   (if prefetching is disabled, etc).
+ * @property {?shaka.media.StreamingEngine.MediaState_} dependencyMediaState
+ *   A dependency media state.
  */
 shaka.media.StreamingEngine.MediaState_;