feat: Add isLowLatency to shaka.extern.Manifest (#6842)

externs/shaka/manifest.js

@@ -24,7 +24,8 @@
  *   serviceDescription: ?shaka.extern.ServiceDescription,
  *   nextUrl: ?string,
  *   periodCount: number,
- *   gapCount: number
+ *   gapCount: number,
+ *   isLowLatency: boolean
  * }}
  *
  * @description
@@ -108,6 +109,8 @@
  *   discontinuities found between periods. For HLS, it is a number of EXT-X-GAP
  *   and GAP=YES occurrences. For MSS, it is always set to 0.
  *   If in src= mode or nothing is loaded, NaN.
+ * @property {bolean} isLowLatency
+ *   If true, the manifest is Low Latency.
  *
  * @exportDoc
  */

lib/dash/dash_parser.js

@@ -155,6 +155,9 @@ shaka.dash.DashParser = class {
 
     /** @private {number} */
     this.gapCount_ = 0;
+
+    /** @private {boolean} */
+    this.isLowLatency_ = false;
   }
 
   /**
@@ -709,7 +712,7 @@ shaka.dash.DashParser = class {
     // lowLatencyMode, but if it has been configured to activate the
     // lowLatencyMode if a stream of this type is detected, we automatically
     // activate the lowLatencyMode.
-    if (this.minTotalAvailabilityTimeOffset_ && !this.lowLatencyMode_) {
+    if (this.isLowLatency_ && !this.lowLatencyMode_) {
       const autoLowLatencyMode = this.playerInterface_.isAutoLowLatencyMode();
       if (autoLowLatencyMode) {
         this.playerInterface_.enableLowLatencyMode();
@@ -720,14 +723,6 @@ shaka.dash.DashParser = class {
     if (this.lowLatencyMode_) {
       presentationTimeline.setAvailabilityTimeOffset(
           this.minTotalAvailabilityTimeOffset_);
-    } else if (this.minTotalAvailabilityTimeOffset_) {
-      // If the playlist contains AvailabilityTimeOffset value, the
-      // streaming.lowLatencyMode value should be set to true to stream with low
-      // latency mode.
-      shaka.log.alwaysWarn('Low-latency DASH live stream detected, but ' +
-        'low-latency streaming mode is not enabled in Shaka Player. ' +
-        'Set streaming.lowLatencyMode configuration to true, and see ' +
-        'https://bit.ly/3clctcj for details.');
     }
 
     // Use @maxSegmentDuration to override smaller, derived values.
@@ -765,6 +760,7 @@ shaka.dash.DashParser = class {
         nextUrl: this.parseMpdChaining_(mpd),
         periodCount: periods.length,
         gapCount: this.gapCount_,
+        isLowLatency: this.isLowLatency_,
       };
 
       // We only need to do clock sync when we're using presentation start
@@ -1918,6 +1914,8 @@ shaka.dash.DashParser = class {
         Math.min(this.minTotalAvailabilityTimeOffset_,
             context.representation.availabilityTimeOffset);
 
+    this.isLowLatency_ = this.minTotalAvailabilityTimeOffset_ > 0;
+
     if (!this.verifyRepresentation_(context.representation)) {
       shaka.log.warning('Skipping Representation', context.representation);
       return null;

lib/hls/hls_parser.js

@@ -925,6 +925,7 @@ shaka.hls.HlsParser = class {
       nextUrl: null,
       periodCount: 1,
       gapCount: 0,
+      isLowLatency: false,
     };
 
     // If there is no 'CODECS' attribute in the manifest and codec guessing is
@@ -3353,11 +3354,8 @@ shaka.hls.HlsParser = class {
     let startByte = 0;
     let endByte = null;
 
-    if (hlsSegment.partialSegments.length && !this.lowLatencyMode_) {
-      shaka.log.alwaysWarn('Low-latency HLS live stream detected, but ' +
-                'low-latency streaming mode is not enabled in Shaka ' +
-                'Player. Set streaming.lowLatencyMode configuration to ' +
-                'true, and see https://bit.ly/3clctcj for details.');
+    if (hlsSegment.partialSegments.length) {
+      this.manifest_.isLowLatency = true;
     }
 
     let syncTime = null;

lib/media/streaming_engine.js

@@ -1529,9 +1529,11 @@ shaka.media.StreamingEngine = class {
       const isMP4 = stream.mimeType == 'video/mp4' ||
               stream.mimeType == 'audio/mp4';
       const isReadableStreamSupported = window.ReadableStream;
+      const lowLatencyMode = this.config_.lowLatencyMode &&
+          this.manifest_.isLowLatency;
       // Enable MP4 low latency streaming with ReadableStream chunked data.
       // And only for DASH and HLS with byterange optimization.
-      if (this.config_.lowLatencyMode && isReadableStreamSupported && isMP4 &&
+      if (lowLatencyMode && isReadableStreamSupported && isMP4 &&
           (this.manifest_.type != shaka.media.ManifestParser.HLS ||
           reference.hasByterangeOptimization())) {
         let remaining = new Uint8Array(0);
@@ -1622,7 +1624,7 @@ shaka.media.StreamingEngine = class {
               reference.startTime, /* skipFirst= */ true);
         }
       } else {
-        if (this.config_.lowLatencyMode && !isReadableStreamSupported) {
+        if (lowLatencyMode && !isReadableStreamSupported) {
           shaka.log.warning('Low latency streaming mode is enabled, but ' +
             'ReadableStream is not supported by the browser.');
         }

lib/mss/mss_parser.js

@@ -422,6 +422,7 @@ shaka.mss.MssParser = class {
         nextUrl: null,
         periodCount: 1,
         gapCount: 0,
+        isLowLatency: false,
       };
 
       // This is the first point where we have a meaningful presentation start

lib/offline/manifest_converter.js

@@ -96,6 +96,7 @@ shaka.offline.ManifestConverter = class {
       nextUrl: null,
       periodCount: 1,
       gapCount: 0,
+      isLowLatency: false,
     };
   }
 

lib/player.js

@@ -2446,6 +2446,13 @@ shaka.Player = class extends shaka.util.FakeEventTarget {
       this.parser_.onInitialVariantChosen(toLazyLoad);
     }
 
+    if (this.manifest_.isLowLatency && !this.config_.streaming.lowLatencyMode) {
+      shaka.log.alwaysWarn('Low-latency live stream detected, but ' +
+          'low-latency streaming mode is not enabled in Shaka Player. ' +
+          'Set streaming.lowLatencyMode configuration to true, and see ' +
+          'https://bit.ly/3clctcj for details.');
+    }
+
     shaka.Player.applyPlayRange_(this.manifest_.presentationTimeline,
         this.config_.playRangeStart,
         this.config_.playRangeEnd);

test/hls/hls_parser_unit.js

@@ -2923,8 +2923,10 @@ describe('HlsParser', () => {
      * @param {!Array.<number>} startTimes
      * @param {number} syncTimeOffset
      * @param {(function(!shaka.media.SegmentReference))=} modifyFn
+     * @param {boolean=} isLowLatency
      */
-    async function test(media, startTimes, syncTimeOffset, modifyFn) {
+    async function test(media, startTimes, syncTimeOffset, modifyFn,
+        isLowLatency = false) {
       const master = [
         '#EXTM3U\n',
         '#EXT-X-STREAM-INF:BANDWIDTH=200,CODECS="avc1.4d401f,vtt",',
@@ -2953,6 +2955,7 @@ describe('HlsParser', () => {
         });
         manifest.sequenceMode = sequenceMode;
         manifest.type = shaka.media.ManifestParser.HLS;
+        manifest.isLowLatency = !!isLowLatency;
       });
 
       fakeNetEngine
@@ -3073,7 +3076,7 @@ describe('HlsParser', () => {
           reference.partialReferences = [partialRef, partialRef2];
           reference.allPartialSegments = true;
         }
-      });
+      }, /* isLowLatency= */ true);
     });
   });
 

test/media/playhead_unit.js

@@ -140,6 +140,7 @@ describe('Playhead', () => {
       nextUrl: null,
       periodCount: 1,
       gapCount: 0,
+      isLowLatency: false,
     };
 
     config = shaka.util.PlayerConfiguration.createDefault().streaming;

test/media/streaming_engine_integration.js

@@ -608,6 +608,7 @@ describe('StreamingEngine', () => {
         nextUrl: null,
         periodCount: 1,
         gapCount: 0,
+        isLowLatency: false,
         variants: [{
           id: 1,
           video: {

test/media/streaming_engine_unit.js

@@ -686,6 +686,7 @@ describe('StreamingEngine', () => {
     // Use the VOD manifests to test the streamDataCallback function in the low
     // latency mode.
     setupVod();
+    manifest.isLowLatency = true;
 
     const config = shaka.util.PlayerConfiguration.createDefault().streaming;
     config.lowLatencyMode = true;

test/test/util/manifest_generator.js

@@ -109,6 +109,8 @@ shaka.test.ManifestGenerator.Manifest = class {
     this.periodCount = 1;
     /** @type {number} */
     this.gapCount = 0;
+    /** @type {boolean} */
+    this.isLowLatency = false;
 
 
     /** @type {shaka.extern.Manifest} */

test/test/util/streaming_engine_util.js

@@ -323,6 +323,7 @@ shaka.test.StreamingEngineUtil = class {
       nextUrl: null,
       periodCount: 1,
       gapCount: 0,
+      isLowLatency: false,
     };
 
     /** @type {shaka.extern.Variant} */