added offset compensation for presentationTimeOffset

Telefonica · Nov 24, 2023 · 031dc5f · 031dc5f
1 parent 8104f8e
commit 031dc5f
Showing 1 changed file with 56 additions and 1 deletion.
diff --git a/lib/media/streaming_engine.js b/lib/media/streaming_engine.js
@@ -1194,7 +1194,7 @@ shaka.media.StreamingEngine = class {
     mediaState.performingUpdate = true;
 
     try {
-      await this.initSourceBuffer_(mediaState, reference);
+      const timescale = await this.initSourceBuffer_(mediaState, reference);
       this.destroyer_.ensureNotDestroyed();
       if (this.fatalError_) {
         return;
@@ -1261,6 +1261,39 @@ shaka.media.StreamingEngine = class {
           this.scheduleUpdate_(mediaState, 0);
           return;
         }
+        if (timescale) {
+          new shaka.util.Mp4Parser()
+              .box('moof', shaka.util.Mp4Parser.children)
+              .box('traf', shaka.util.Mp4Parser.children)
+              .fullBox('tfdt', async (box) => {
+                goog.asserts.assert(
+                    box.version != null,
+                    'TFDT is a full box and should have a valid version.');
+
+                const parsedTFDT = shaka.util.Mp4BoxParsers.parseTFDT(
+                    box.reader, box.version);
+
+                const baseMediaDecodeTime = parsedTFDT.baseMediaDecodeTime;
+                const scaledMediaDecodeTime = baseMediaDecodeTime / timescale;
+
+                if (Math.abs(mediaState.lastTimestampOffset) >
+                    scaledMediaDecodeTime) {
+                  const lastAppendWindowEnd = 0 +
+                      mediaState.lastAppendWindowEnd;
+                  const lastAppendWindowStart = 0 +
+                      mediaState.lastAppendWindowStart;
+                  shaka.log.v1(logPrefix,
+                      'setting timestamp offset to ' + -scaledMediaDecodeTime);
+                  await this.playerInterface_.mediaSourceEngine
+                      .setStreamProperties(
+                          mediaState.type, -scaledMediaDecodeTime,
+                          lastAppendWindowStart,
+                          lastAppendWindowEnd);
+                }
+              })
+              .parse(result, /* partialOkay= */ false,
+              /* isChunkedData= */ true);
+        }
         await this.append_(
             mediaState, presentationTime, stream, reference, result);
       }
@@ -1509,18 +1542,39 @@ shaka.media.StreamingEngine = class {
       operations.push(setProperties());
     }
 
+    let timescale;
+
     if (!shaka.media.InitSegmentReference.equal(
         reference.initSegmentReference, mediaState.lastInitSegmentReference)) {
       mediaState.lastInitSegmentReference = reference.initSegmentReference;
 
       if (reference.initSegmentReference) {
         shaka.log.v1(logPrefix, 'fetching init segment');
 
+        const setTimeScale = (data) => {
+          new shaka.util.Mp4Parser()
+              .box('moov', shaka.util.Mp4Parser.children)
+              .box('mvhd', (box) => {
+                const version = box.reader.readUint8();
+                if (version === 1) {
+                  // skip according the standard
+                  box.reader.skip(19);
+                } else {
+                  box.reader.skip(11);
+                }
+                timescale = box.reader.readUint32();
+                shaka.log.v2('mvhd', 'timescale', timescale);
+              })
+              .parse(data, /* partialOkay= */ false,
+                  /* isChunkedData= */ true);
+        };
+
         const fetchInit =
             this.fetch_(mediaState, reference.initSegmentReference);
         const append = async () => {
           try {
             const initSegment = await fetchInit;
+            mediaState.type === 'video' && setTimeScale(initSegment);
             this.destroyer_.ensureNotDestroyed();
             shaka.log.v1(logPrefix, 'appending init segment');
             const hasClosedCaptions = mediaState.stream.closedCaptions &&
@@ -1538,6 +1592,7 @@ shaka.media.StreamingEngine = class {
     }
 
     await Promise.all(operations);
+    return timescale;
   }