feat(HLS): Add support to _HLS_part query param in LL streams

lib/hls/hls_parser.js

@@ -349,10 +349,16 @@ shaka.hls.HlsParser = class {
         // 'EXT-X-SKIP' tag in the media playlist.
         queryData.add('_HLS_skip', 'YES');
       }
-      if (streamInfo.lastMediaSequence >= 0) {
+      if (streamInfo.nextMediaSequence >= 0) {
         // Indicates that the server must hold the request until a Playlist
         // contains a Media Segment with Media Sequence
-        queryData.add('_HLS_msn', String(streamInfo.lastMediaSequence + 1));
+        queryData.add('_HLS_msn', String(streamInfo.nextMediaSequence));
+      }
+      if (streamInfo.nextPart >= 0) {
+        // Indicates, in combination with _HLS_msn, that the server must hold
+        // the request until a Playlist contains Partial Segment N of Media
+        // Sequence Number M or later.
+        queryData.add('_HLS_part', String(streamInfo.nextPart));
       }
       if (queryData.getCount()) {
         uriObj.setQueryData(queryData);
@@ -399,17 +405,19 @@ shaka.hls.HlsParser = class {
       this.playerInterface_.newDrmInfo(stream);
     }
 
-    const mediaSequenceNumber = shaka.hls.Utils.getFirstTagWithNameAsNumber(
-        playlist.tags, 'EXT-X-MEDIA-SEQUENCE', 0);
-    streamInfo.lastMediaSequence = mediaSequenceNumber;
-
     const segments = this.createSegments_(
         streamInfo.verbatimMediaPlaylistUri, playlist, stream.type,
         stream.mimeType, mediaSequenceToStartTime, mediaVariables);
 
     stream.segmentIndex.mergeAndEvict(
         segments, this.presentationTimeline_.getSegmentAvailabilityStart());
     if (segments.length) {
+      const mediaSequenceNumber = shaka.hls.Utils.getFirstTagWithNameAsNumber(
+          playlist.tags, 'EXT-X-MEDIA-SEQUENCE', 0);
+      const {nextMediaSequence, nextPart} =
+          this.getNextMediaSequenceAndPart_(mediaSequenceNumber, segments);
+      streamInfo.nextMediaSequence = nextMediaSequence;
+      streamInfo.nextPart = nextPart;
       const playlistStartTime = mediaSequenceToStartTime.get(
           mediaSequenceNumber);
       stream.segmentIndex.evict(playlistStartTime);
@@ -1954,7 +1962,8 @@ shaka.hls.HlsParser = class {
       canSkipSegments: false,
       hasEndList: false,
       firstSequenceNumber: -1,
-      lastMediaSequence: -1,
+      nextMediaSequence: -1,
+      nextPart: -1,
       loadedOnce: false,
     };
 
@@ -2001,7 +2010,8 @@ shaka.hls.HlsParser = class {
       streamInfo.hasEndList = realStreamInfo.hasEndList;
       streamInfo.mediaSequenceToStartTime =
           realStreamInfo.mediaSequenceToStartTime;
-      streamInfo.lastMediaSequence = realStreamInfo.lastMediaSequence;
+      streamInfo.nextMediaSequence = realStreamInfo.nextMediaSequence;
+      streamInfo.nextPart = realStreamInfo.nextPart;
       streamInfo.loadedOnce = true;
       stream.segmentIndex = realStream.segmentIndex;
       stream.encrypted = realStream.encrypted;
@@ -2278,7 +2288,8 @@ shaka.hls.HlsParser = class {
     }
 
     const firstStartTime = segments[0].startTime;
-    const lastEndTime = segments[segments.length - 1].endTime;
+    const lastSegment = segments[segments.length - 1];
+    const lastEndTime = lastSegment.endTime;
     /** @type {!shaka.media.SegmentIndex} */
     const segmentIndex = new shaka.media.SegmentIndex(segments);
 
@@ -2287,9 +2298,12 @@ shaka.hls.HlsParser = class {
     const canSkipSegments = serverControlTag ?
           serverControlTag.getAttribute('CAN-SKIP-UNTIL') != null : false;
 
-    const lastMediaSequence = shaka.hls.Utils.getFirstTagWithNameAsNumber(
+    const mediaSequenceNumber = shaka.hls.Utils.getFirstTagWithNameAsNumber(
         playlist.tags, 'EXT-X-MEDIA-SEQUENCE', 0);
 
+    const {nextMediaSequence, nextPart} =
+        this.getNextMediaSequenceAndPart_(mediaSequenceNumber, segments);
+
     const stream = this.makeStreamObject_(codecs, type, language, primary, name,
         channelsCount, closedCaptions, characteristics, forced, spatialAudio);
     stream.segmentIndex = segmentIndex;
@@ -2308,12 +2322,54 @@ shaka.hls.HlsParser = class {
       canSkipSegments,
       hasEndList: false,
       firstSequenceNumber: -1,
-      lastMediaSequence,
+      nextMediaSequence,
+      nextPart,
       mediaSequenceToStartTime,
       loadedOnce: false,
     };
   }
 
+  /**
+   * Get the next msn and part
+   *
+   * @param {number} mediaSequenceNumber
+   * @param {!Array.<!shaka.media.SegmentReference>} segments
+   * @return {{nextMediaSequence: number, nextPart:number}}}
+   * @private
+   */
+  getNextMediaSequenceAndPart_(mediaSequenceNumber, segments) {
+    const currentMediaSequence = mediaSequenceNumber + segments.length - 1;
+    let nextMediaSequence = currentMediaSequence;
+    let nextPart = -1;
+    if (!segments.length) {
+      nextMediaSequence++;
+      return {
+        nextMediaSequence,
+        nextPart,
+      };
+    }
+    const lastSegment = segments[segments.length - 1];
+    const partialReferences = lastSegment.partialReferences;
+    if (!lastSegment.partialReferences.length) {
+      nextMediaSequence++;
+      return {
+        nextMediaSequence,
+        nextPart,
+      };
+    }
+    nextPart = partialReferences.length - 1;
+    const lastPartialReference =
+        partialReferences[partialReferences.length - 1];
+    if (!lastPartialReference.isPreload()) {
+      nextMediaSequence++;
+      nextPart = 0;
+    }
+    return {
+      nextMediaSequence,
+      nextPart,
+    };
+  }
+
 
   /**
    * Creates a stream object with the given parameters.
@@ -2831,6 +2887,9 @@ shaka.hls.HlsParser = class {
             /* syncTime= */ null,
             partialStatus,
             hlsAes128Key);
+        if (item.name == 'EXT-X-PRELOAD-HINT') {
+          partial.markAsPreload();
+        }
         partialSegmentRefs.push(partial);
       } // for-loop of hlsSegment.partialSegments
     }
@@ -3622,7 +3681,8 @@ shaka.hls.HlsParser = class {
  *   canSkipSegments: boolean,
  *   hasEndList: boolean,
  *   firstSequenceNumber: number,
- *   lastMediaSequence: number,
+ *   nextMediaSequence: number,
+ *   nextPart: number,
  *   loadedOnce: boolean
  * }}
  *
@@ -3655,8 +3715,10 @@ shaka.hls.HlsParser = class {
  *   True if the stream has an EXT-X-ENDLIST tag.
  * @property {number} firstSequenceNumber
  *   The sequence number of the first reference. Only calculated if needed.
- * @property {number} lastMediaSequence
- *   The last media sequence seen.
+ * @property {number} nextMediaSequence
+ *   The next media sequence.
+ * @property {number} nextPart
+ *   The next part.
  * @property {boolean} loadedOnce
  *   True if the stream has been loaded at least once.
  */

lib/media/segment_reference.js

@@ -262,6 +262,9 @@ shaka.media.SegmentReference = class {
     /** @type {shaka.media.SegmentReference.Status} */
     this.status = status;
 
+    /** @type {boolean} */
+    this.preload = false;
+
     /** @type {?shaka.extern.HlsAes128Key} */
     this.hlsAes128Key = hlsAes128Key;
 
@@ -385,6 +388,25 @@ shaka.media.SegmentReference = class {
     this.status = shaka.media.SegmentReference.Status.UNAVAILABLE;
   }
 
+  /**
+   * Mark the reference as preload.
+   *
+   * @export
+   */
+  markAsPreload() {
+    this.preload = true;
+  }
+
+  /**
+   * Returns true if the segment is preloaded.
+   *
+   * @return {boolean}
+   * @export
+   */
+  isPreload() {
+    return this.preload;
+  }
+
   /**
    * Set the segment's thumbnail sprite.
    *

test/hls/hls_live_unit.js

@@ -666,6 +666,7 @@ describe('HlsParser live', () => {
       const preloadRef = makeReference(
           'test:/partial.mp4', 6, 7.5, /* syncTime= */ null,
           /* baseUri= */ '', /* startByte= */ 210, /* endByte= */ null);
+      preloadRef.markAsPreload();
 
       // ref2 is not fully published yet, so it doesn't have a segment uri.
       const ref2 = makeReference(
@@ -930,7 +931,7 @@ describe('HlsParser live', () => {
         ].join('');
 
         fakeNetEngine.setResponseText(
-            'test:/video?_HLS_skip=YES&_HLS_msn=1', mediaWithSkippedSegments);
+            'test:/video?_HLS_skip=YES&_HLS_msn=2', mediaWithSkippedSegments);
 
         playerInterface.isLowLatencyMode = () => true;
 
@@ -940,7 +941,7 @@ describe('HlsParser live', () => {
         await delayForUpdatePeriod();
 
         fakeNetEngine.expectRequest(
-            'test:/video?_HLS_skip=YES&_HLS_msn=1',
+            'test:/video?_HLS_skip=YES&_HLS_msn=2',
             shaka.net.NetworkingEngine.RequestType.MANIFEST,
             {type:
               shaka.net.NetworkingEngine.AdvancedRequestType.MEDIA_PLAYLIST});
@@ -974,7 +975,7 @@ describe('HlsParser live', () => {
         // and ref1 should be in the SegmentReferences list.
         // ref3 should be appended to the SegmentReferences list.
         await testUpdate(
-            manifest, mediaWithSkippedSegments, [ref1, ref2, ref3], 1);
+            manifest, mediaWithSkippedSegments, [ref1, ref2, ref3], 2);
       });
 
       it('skips older segments with discontinuity', async () => {
@@ -1039,7 +1040,7 @@ describe('HlsParser live', () => {
         // and ref1,ref2 should be in the SegmentReferences list.
         // ref3,ref4 should be appended to the SegmentReferences list.
         await testUpdate(
-            manifest, mediaWithSkippedSegments2, [ref1, ref2, ref3, ref4], 1);
+            manifest, mediaWithSkippedSegments2, [ref1, ref2, ref3, ref4], 3);
       });
 
       it('updates encryption keys', async () => {