fix: cache source buffer params on codec switch reload (#7630)

Caches source buffer parameters on codec switch with the RELOAD
configuration

Fixes #7555

AUTHORS

@@ -32,6 +32,7 @@ Cristian Atehortua <[email protected]>
 Damien Deis <[email protected]>
 Dany L'Hébreux <[email protected]>
 Dave Nicholas <[email protected]>
+David Pfister <[email protected]>
 Davide Zordan <[email protected]>
 Dl Dador <[email protected]>
 Edgeware AB <*@edgeware.tv>

CONTRIBUTORS

@@ -48,6 +48,7 @@ Cristian Atehortua <[email protected]>
 Damien Deis <[email protected]>
 Dany L'Hébreux <[email protected]>
 Dave Nicholas <[email protected]>
+David Pfister <[email protected]>
 Davide Zordan <[email protected]>
 Dl Dador <[email protected]>
 Donato Borrello <[email protected]>

lib/media/media_source_engine.js

@@ -2100,6 +2100,48 @@ shaka.media.MediaSourceEngine = class {
         null);
   }
 
+  /**
+   * Returns the source buffer parameters
+   * @param {shaka.util.ManifestParserUtils.ContentType} contentType
+   * @return {?shaka.media.MediaSourceEngine.SourceBufferParams}
+   * @private
+   */
+  getSourceBufferParams_(contentType) {
+    if (!this.sourceBuffers_[contentType]) {
+      return null;
+    }
+    return {
+      timestampOffset: this.sourceBuffers_[contentType].timestampOffset,
+      appendWindowStart: this.sourceBuffers_[contentType].appendWindowStart,
+      appendWindowEnd: this.sourceBuffers_[contentType].appendWindowEnd,
+    };
+  }
+
+  /**
+   * Restore source buffer parameters
+   * @param {shaka.util.ManifestParserUtils.ContentType} contentType
+   * @param {?shaka.media.MediaSourceEngine.SourceBufferParams} params
+   * @private
+   */
+  restoreSourceBufferParams_(contentType, params) {
+    if (!params) {
+      return;
+    }
+
+    if (!this.sourceBuffers_[contentType]) {
+      shaka.log.warning('Attempted to restore a non-existent source buffer');
+      return;
+    }
+
+    this.sourceBuffers_[contentType].timestampOffset =
+      params.timestampOffset;
+    // `end` needs to be set before `start`
+    this.sourceBuffers_[contentType].appendWindowEnd =
+      params.appendWindowEnd;
+    this.sourceBuffers_[contentType].appendWindowStart =
+      params.appendWindowStart;
+  }
+
   /**
    * Resets the MediaSource and re-adds source buffers due to codec mismatch
    *
@@ -2160,7 +2202,6 @@ shaka.media.MediaSourceEngine = class {
       }
       await Promise.all(cleanup);
       this.transmuxers_ = {};
-      this.sourceBuffers_ = {};
 
       const previousDuration = this.mediaSource_.duration;
       this.mediaSourceOpen_ = new shaka.util.PublicPromise();
@@ -2191,6 +2232,7 @@ shaka.media.MediaSourceEngine = class {
           onSourceBufferAdded);
 
       for (const contentType of streamsByType.keys()) {
+        const previousParams = this.getSourceBufferParams_(contentType);
         const stream = streamsByType.get(contentType);
         // eslint-disable-next-line no-await-in-loop
         await this.initSourceBuffer_(contentType, stream, stream.codecs);
@@ -2200,6 +2242,8 @@ shaka.media.MediaSourceEngine = class {
         } else {
           this.queues_[contentType] = [];
         }
+
+        this.restoreSourceBufferParams_(contentType, previousParams);
       }
       const audio = streamsByType.get(ContentType.AUDIO);
       if (audio && audio.isAudioMuxedInVideo) {
@@ -2497,3 +2541,12 @@ shaka.media.MediaSourceEngine.SourceBufferMode_ = {
  *   Called when an embedded 'emsg' box should trigger a manifest update.
  */
 shaka.media.MediaSourceEngine.PlayerInterface;
+
+/**
+ * @typedef {{
+ *   timestampOffset: number,
+ *   appendWindowStart: number,
+ *   appendWindowEnd: number
+ * }}
+ */
+shaka.media.MediaSourceEngine.SourceBufferParams;