fix(HLS): Fix audio and video out of sync (#5658)

Fixes #5584 Fixes #5013 Fixes #5397 timestampOffset calculation is no longer necessary in the HLS parser because we introduce recently some change in MediaSourceEngine to calculate the timestampOffset Backported to v4.4.x and v4.3.x
shaka-project · Oct 4, 2023 · cb9789e · cb9789e
1 parent ee898e9
commit cb9789e
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Showing 3 changed files with 6 additions and 80 deletions.
diff --git a/lib/hls/hls_parser.js b/lib/hls/hls_parser.js
@@ -2427,15 +2427,13 @@ shaka.hls.HlsParser = class {
    * @param {!Map.<string, string>} variables
    * @param {string} absoluteMediaPlaylistUri
    * @param {string} type
-   * @param {number} timestampOffset
    * @param {shaka.extern.HlsAes128Key=} hlsAes128Key
    * @return {shaka.media.SegmentReference}
    * @private
    */
   createSegmentReference_(
       initSegmentReference, previousReference, hlsSegment, startTime,
-      variables, absoluteMediaPlaylistUri, type, timestampOffset,
-      hlsAes128Key) {
+      variables, absoluteMediaPlaylistUri, type, hlsAes128Key) {
     const tags = hlsSegment.tags;
     const absoluteSegmentUri = this.variableSubstitution_(
         hlsSegment.absoluteUri, variables);
@@ -2539,7 +2537,7 @@ shaka.hls.HlsParser = class {
             pStartByte,
             pEndByte,
             initSegmentReference,
-            /* timestampOffset= */ 0, // This value is ignored in sequence mode.
+            /* timestampOffset= */ 0,
             /* appendWindowStart= */ 0,
             /* appendWindowEnd= */ Infinity,
             /* partialReferences= */ [],
@@ -2612,7 +2610,7 @@ shaka.hls.HlsParser = class {
         startByte,
         endByte,
         initSegmentReference,
-        timestampOffset, // This value is ignored in sequence mode.
+        /* timestampOffset= */ 0,
         /* appendWindowStart= */ 0,
         /* appendWindowEnd= */ Infinity,
         partialSegmentRefs,
@@ -2697,7 +2695,6 @@ shaka.hls.HlsParser = class {
     const references = [];
 
     let previousReference = null;
-    let lastDiscontinuityStartTime = firstStartTime;
 
     for (let i = 0; i < hlsSegments.length; i++) {
       const item = hlsSegments[i];
@@ -2709,7 +2706,6 @@ shaka.hls.HlsParser = class {
           item.tags, 'EXT-X-DISCONTINUITY');
       if (discontinuityTag) {
         discontinuitySequence++;
-        lastDiscontinuityStartTime = startTime;
       }
 
       // Apply new AES-128 tags as you see them, keeping a running total.
@@ -2748,7 +2744,6 @@ shaka.hls.HlsParser = class {
           variables,
           playlist.absoluteUri,
           type,
-          lastDiscontinuityStartTime,
           hlsAes128Key);
 
       if (reference) {

diff --git a/lib/media/streaming_engine.js b/lib/media/streaming_engine.js
@@ -1693,10 +1693,10 @@ shaka.media.StreamingEngine = class {
       }
     }
 
-    const lastDiscontinuitySequence =
-        mediaState.lastSegmentReference ?
-            mediaState.lastSegmentReference.discontinuitySequence : null;
     if (this.manifest_.sequenceMode) {
+      const lastDiscontinuitySequence =
+          mediaState.lastSegmentReference ?
+              mediaState.lastSegmentReference.discontinuitySequence : null;
       // Across discontinuity bounds, we should resync timestamps for
       // sequence mode playbacks.  The next segment appended should
       // land at its theoretical timestamp from the segment index.
@@ -1706,18 +1706,6 @@ shaka.media.StreamingEngine = class {
         operations.push(this.playerInterface_.mediaSourceEngine.resync(
             mediaState.type, reference.startTime));
       }
-    } else {
-      // In segments mode, we need to resync to set the timestampOffset
-      // to the start of the current discontinuity sequence. This is
-      // because individual discontinuity sequences may have internal
-      // timestamps that overlap, so we adjust the timestampOffset to avoid
-      // having the SourceBuffer get overwritten.
-      if (reference.discontinuitySequence != lastDiscontinuitySequence) {
-        operations.push(
-            this.playerInterface_.mediaSourceEngine.resync(
-                mediaState.type,
-                reference.timestampOffset));
-      }
     }
 
     await Promise.all(operations);

diff --git a/test/hls/hls_parser_unit.js b/test/hls/hls_parser_unit.js
@@ -1114,63 +1114,6 @@ describe('HlsParser', () => {
     expect(references[6].discontinuitySequence).toBe(3);
   });
 
-  it('sets reference timetampOffset based on discontinuity start time',
-      async () => {
-        const master = [
-          '#EXTM3U\n',
-          '#EXT-X-STREAM-INF:BANDWIDTH=2000000,CODECS="avc1"\n',
-          'video\n',
-        ].join('');
-
-        const media = [
-          '#EXTM3U\n',
-          '#EXT-X-VERSION:3\n',
-          '#EXT-X-TARGETDURATION:5\n',
-          '#EXT-X-MEDIA-SEQUENCE:0\n',
-          '#EXTINF:3,\n',
-          'clip0-video-0.ts\n',
-          '#EXTINF:1,\n',
-          'clip0-video-1.ts\n',
-          '#EXT-X-DISCONTINUITY\n',
-          '#EXTINF:2,\n',
-          'clip1-video-1.ts\n',
-          '#EXTINF:3,\n',
-          'clip1-video-2.ts\n',
-          '#EXT-X-DISCONTINUITY\n',
-          '#EXTINF:1,\n',
-          'media-clip2-video-0.ts\n',
-          '#EXTINF:1,\n',
-          'media-clip2-video-1.ts\n',
-          '#EXT-X-DISCONTINUITY\n',
-          '#EXTINF:4,\n',
-          'media-clip3-video-1.ts\n',
-          '#EXT-X-ENDLIST\n',
-        ].join('');
-
-        fakeNetEngine
-            .setResponseText('test:/master', master)
-            .setResponseText('test:/video', media);
-
-        const manifest = await parser.start('test:/master', playerInterface);
-        await manifest.variants[0].video.createSegmentIndex();
-
-        const segmentIndex = manifest.variants[0].video.segmentIndex;
-        const references = [];
-
-        for (let i = 0; i < 7; i++) {
-          references.push(segmentIndex.get(i));
-        }
-
-        expect(references[0].timestampOffset).toBe(0);
-        expect(references[1].timestampOffset).toBe(0);
-        expect(references[2].timestampOffset).toBe(4);
-        expect(references[3].timestampOffset).toBe(4);
-        expect(references[4].timestampOffset).toBe(9);
-        expect(references[5].timestampOffset).toBe(9);
-        expect(references[6].timestampOffset).toBe(11);
-      },
-  );
-
   it('parses characteristics from audio tags', async () => {
     const master = [
       '#EXTM3U\n',