diff --git a/RELEASENOTES.md b/RELEASENOTES.md
index 5d7ac43b6a..85f9aec835 100644
--- a/RELEASENOTES.md
+++ b/RELEASENOTES.md
@@ -67,6 +67,8 @@
         ([#2882](https://github.com/google/ExoPlayer/issues/2882)).
     *   Correctly populate `Format.label` for audio only HLS streams
         ([#9608](https://github.com/google/ExoPlayer/issues/9608)).
+    *   Timestamp adjuster initialization occurs after opening the `DataSource`
+        ([#9777](https://github.com/google/ExoPlayer/pull/9777)).
 *   UI:
     *   Fix the color of the numbers in `StyledPlayerView` rewind and
         fastforward buttons when using certain themes
diff --git a/library/hls/src/main/java/com/google/android/exoplayer2/source/hls/HlsMediaChunk.java b/library/hls/src/main/java/com/google/android/exoplayer2/source/hls/HlsMediaChunk.java
index d0711a6d27..9bdc2b9079 100644
--- a/library/hls/src/main/java/com/google/android/exoplayer2/source/hls/HlsMediaChunk.java
+++ b/library/hls/src/main/java/com/google/android/exoplayer2/source/hls/HlsMediaChunk.java
@@ -423,19 +423,19 @@ import org.checkerframework.checker.nullness.qual.RequiresNonNull;
     // initDataLoadRequired =>  initDataSource != null && initDataSpec != null
     Assertions.checkNotNull(initDataSource);
     Assertions.checkNotNull(initDataSpec);
-    feedDataToExtractor(initDataSource, initDataSpec, initSegmentEncrypted);
+    feedDataToExtractor(
+        initDataSource,
+        initDataSpec,
+        initSegmentEncrypted,
+        /* initializeTimestampAdjuster= */ false);
     nextLoadPosition = 0;
     initDataLoadRequired = false;
   }
 
   @RequiresNonNull("output")
   private void loadMedia() throws IOException {
-    try {
-      timestampAdjuster.sharedInitializeOrWait(isMasterTimestampSource, startTimeUs);
-    } catch (InterruptedException e) {
-      throw new InterruptedIOException();
-    }
-    feedDataToExtractor(dataSource, dataSpec, mediaSegmentEncrypted);
+    feedDataToExtractor(
+        dataSource, dataSpec, mediaSegmentEncrypted, /* initializeTimestampAdjuster= */ true);
   }
 
   /**
@@ -445,7 +445,11 @@ import org.checkerframework.checker.nullness.qual.RequiresNonNull;
    */
   @RequiresNonNull("output")
   private void feedDataToExtractor(
-      DataSource dataSource, DataSpec dataSpec, boolean dataIsEncrypted) throws IOException {
+      DataSource dataSource,
+      DataSpec dataSpec,
+      boolean dataIsEncrypted,
+      boolean initializeTimestampAdjuster)
+      throws IOException {
     // If we previously fed part of this chunk to the extractor, we need to skip it this time. For
     // encrypted content we need to skip the data by reading it through the source, so as to ensure
     // correct decryption of the remainder of the chunk. For clear content, we can request the
@@ -460,7 +464,8 @@ import org.checkerframework.checker.nullness.qual.RequiresNonNull;
       skipLoadedBytes = false;
     }
     try {
-      ExtractorInput input = prepareExtraction(dataSource, loadDataSpec);
+      ExtractorInput input =
+          prepareExtraction(dataSource, loadDataSpec, initializeTimestampAdjuster);
       if (skipLoadedBytes) {
         input.skipFully(nextLoadPosition);
       }
@@ -484,9 +489,17 @@ import org.checkerframework.checker.nullness.qual.RequiresNonNull;
 
   @RequiresNonNull("output")
   @EnsuresNonNull("extractor")
-  private DefaultExtractorInput prepareExtraction(DataSource dataSource, DataSpec dataSpec)
+  private DefaultExtractorInput prepareExtraction(
+      DataSource dataSource, DataSpec dataSpec, boolean initializeTimestampAdjuster)
       throws IOException {
     long bytesToRead = dataSource.open(dataSpec);
+    if (initializeTimestampAdjuster) {
+      try {
+        timestampAdjuster.sharedInitializeOrWait(isMasterTimestampSource, startTimeUs);
+      } catch (InterruptedException e) {
+        throw new InterruptedIOException();
+      }
+    }
     DefaultExtractorInput extractorInput =
         new DefaultExtractorInput(dataSource, dataSpec.position, bytesToRead);