fix(hls): Fixed buffering issue with live HLS

HLS now appends segments in sequence mode. In order to handle seeks, we use the timestampOffset property to inform MediaSource where the new segment should go. However, we were still setting timestampOffset when the manifest was updated, which caused issues in live HLS; suddenly, MediaSource would start inserting segments near the start of the presentation, rather than at the live edge. This changes MediaSourceEngine to not apply timestampOffset during initialization when in sequence mode, to fix that problem.
shaka-project · Feb 24, 2022 · f04d314 · f04d314
1 parent 5894b8c
commit f04d314
Show file tree

Hide file tree

Showing 6 changed files with 47 additions and 13 deletions.
diff --git a/lib/media/media_source_engine.js b/lib/media/media_source_engine.js
@@ -691,13 +691,18 @@ shaka.media.MediaSourceEngine = class {
    * @param {number} appendWindowEnd The timestamp to set the append window end
    *   to.  For future appends, frames/samples with timestamps greater than this
    *   value will be dropped.
+   * @param {boolean} sequenceMode  If true, the timestampOffset will not be
+   *   applied in this step.
    * @return {!Promise}
    */
   async setStreamProperties(
-      contentType, timestampOffset, appendWindowStart, appendWindowEnd) {
+      contentType, timestampOffset, appendWindowStart, appendWindowEnd,
+      sequenceMode) {
     const ContentType = shaka.util.ManifestParserUtils.ContentType;
     if (contentType == ContentType.TEXT) {
-      this.textEngine_.setTimestampOffset(timestampOffset);
+      if (!sequenceMode) {
+        this.textEngine_.setTimestampOffset(timestampOffset);
+      }
       this.textEngine_.setAppendWindow(appendWindowStart, appendWindowEnd);
       return;
     }
@@ -714,7 +719,10 @@ shaka.media.MediaSourceEngine = class {
       this.enqueueOperation_(
           contentType,
           () => this.abort_(contentType)),
-      this.enqueueOperation_(
+      // Don't set the timestampOffset here when in sequenceMode, since we
+      // use timestampOffset for a different purpose in that mode (e.g. to
+      // indicate where the current segment is).
+      sequenceMode ? Promise.resolve() : this.enqueueOperation_(
           contentType,
           () => this.setTimestampOffset_(contentType, timestampOffset)),
       this.enqueueOperation_(

diff --git a/lib/media/streaming_engine.js b/lib/media/streaming_engine.js
@@ -1520,7 +1520,7 @@ shaka.media.StreamingEngine = class {
 
           await this.playerInterface_.mediaSourceEngine.setStreamProperties(
               mediaState.type, timestampOffset, appendWindowStart,
-              appendWindowEnd);
+              appendWindowEnd, this.manifest_.sequenceMode);
         } catch (error) {
           mediaState.lastAppendWindowStart = null;
           mediaState.lastAppendWindowEnd = null;

diff --git a/test/media/media_source_engine_integration.js b/test/media/media_source_engine_integration.js
@@ -295,7 +295,27 @@ describe('MediaSourceEngine', () => {
     await mediaSourceEngine.setStreamProperties(ContentType.VIDEO,
         /* timestampOffset= */ 0,
         /* appendWindowStart= */ 5,
-        /* appendWindowEnd= */ 18);
+        /* appendWindowEnd= */ 18,
+        /* sequenceMode= */ false);
+    expect(buffered(ContentType.VIDEO, 0)).toBe(0);
+    await append(ContentType.VIDEO, 0);
+    expect(bufferStart(ContentType.VIDEO)).toBeCloseTo(5, 1);
+    expect(buffered(ContentType.VIDEO, 5)).toBeCloseTo(5, 1);
+    await append(ContentType.VIDEO, 1);
+    expect(buffered(ContentType.VIDEO, 5)).toBeCloseTo(13, 1);
+  });
+
+  it('does not initialize timestamp offset in sequence mode', async () => {
+    const initObject = new Map();
+    initObject.set(ContentType.VIDEO, getFakeStream(metadata.video));
+    await mediaSourceEngine.init(initObject, false);
+    await mediaSourceEngine.setDuration(presentationDuration);
+    await appendInit(ContentType.VIDEO);
+    await mediaSourceEngine.setStreamProperties(ContentType.VIDEO,
+        /* timestampOffset= */ 100,
+        /* appendWindowStart= */ 5,
+        /* appendWindowEnd= */ 18,
+        /* sequenceMode= */ true);
     expect(buffered(ContentType.VIDEO, 0)).toBe(0);
     await append(ContentType.VIDEO, 0);
     expect(bufferStart(ContentType.VIDEO)).toBeCloseTo(5, 1);
@@ -314,7 +334,8 @@ describe('MediaSourceEngine', () => {
     await mediaSourceEngine.setStreamProperties(ContentType.VIDEO,
         /* timestampOffset= */ 0,
         /* appendWindowStart= */ 0,
-        /* appendWindowEnd= */ 20);
+        /* appendWindowEnd= */ 20,
+        /* sequenceMode= */ false);
     await append(ContentType.VIDEO, 0);
     await append(ContentType.VIDEO, 1);
     expect(bufferStart(ContentType.VIDEO)).toBeCloseTo(0, 1);
@@ -326,7 +347,8 @@ describe('MediaSourceEngine', () => {
     await mediaSourceEngine.setStreamProperties(ContentType.VIDEO,
         /* timestampOffset= */ 15,
         /* appendWindowStart= */ 20,
-        /* appendWindowEnd= */ 35);
+        /* appendWindowEnd= */ 35,
+        /* sequenceMode= */ false);
     await append(ContentType.VIDEO, 0);
     await append(ContentType.VIDEO, 1);
     expect(bufferStart(ContentType.VIDEO)).toBeCloseTo(0, 1);

diff --git a/test/media/media_source_engine_unit.js b/test/media/media_source_engine_unit.js
@@ -825,7 +825,8 @@ describe('MediaSourceEngine', () => {
       await mediaSourceEngine.setStreamProperties(ContentType.TEXT,
           /* timestampOffset= */ 10,
           /* appendWindowStart= */ 0,
-          /* appendWindowEnd= */ 20);
+          /* appendWindowEnd= */ 20,
+          /* sequenceMode= */ false);
       expect(mockTextEngine.setTimestampOffset).toHaveBeenCalledWith(10);
       expect(mockTextEngine.setAppendWindow).toHaveBeenCalledWith(0, 20);
     });

diff --git a/test/media/streaming_engine_unit.js b/test/media/streaming_engine_unit.js
@@ -826,7 +826,7 @@ describe('StreamingEngine', () => {
       asymmetricMatch: (val) => val > 40 && val <= 40.1,
     };
     expect(mediaSourceEngine.setStreamProperties)
-        .toHaveBeenCalledWith('video', 0, lt20, gt40);
+        .toHaveBeenCalledWith('video', 0, lt20, gt40, false);
   });
 
   // Regression test for https://github.com/google/shaka-player/issues/3717

diff --git a/test/test/util/fake_media_source_engine.js b/test/test/util/fake_media_source_engine.js
@@ -114,8 +114,8 @@ shaka.test.FakeMediaSourceEngine = class {
 
     /** @type {!jasmine.Spy} */
     this.setStreamProperties = jasmine.createSpy('setStreamProperties')
-        .and.callFake((type, offset, end) =>
-          this.setStreamPropertiesImpl_(type, offset, end));
+        .and.callFake((type, offset, end, sequenceMode) =>
+          this.setStreamPropertiesImpl_(type, offset, end, sequenceMode));
 
     /** @type {!jasmine.Spy} */
     this.remove = jasmine.createSpy('remove')
@@ -362,14 +362,17 @@ shaka.test.FakeMediaSourceEngine = class {
    * @param {string} type
    * @param {number} offset
    * @param {number} appendWindowEnd
+   * @param {boolean} sequenceMode
    * @return {!Promise}
    * @private
    */
-  setStreamPropertiesImpl_(type, offset, appendWindowEnd) {
+  setStreamPropertiesImpl_(type, offset, appendWindowEnd, sequenceMode) {
     if (!this.segments[type]) {
       throw new Error('unexpected type');
     }
-    this.timestampOffsets_[type] = offset;
+    if (!sequenceMode) {
+      this.timestampOffsets_[type] = offset;
+    }
     // Don't use |appendWindowEnd|.
     return Promise.resolve();
   }