From 18e631ff790e0e9b3630ea8e36efb468474d0877 Mon Sep 17 00:00:00 2001
From: tonihei <tonihei@google.com>
Date: Tue, 25 Jun 2024 04:35:32 -0700
Subject: [PATCH] Add guard against additional tracks reported by Extractors

Extractors should not report additional tracks once they called
ExtractorOutput.endTracks. This causes thread safety issues in
ProgressiveMediaPeriod where the array of sample queues is
extended while the playback thread accesses the arrays.

Detecting this problem early is beneficial to avoid unexplained
exceptions later one. In most cases where this may happen (namely
TS extractors finding new tracks), it's better to ignore the new
tracks instead of failing completely. So this change adds a
warning log message and assigns a placeholder output.

Note: The same workaround already exists in HlsSampleStreamWrapper
and MediaExtractorCompat.

Issue: androidx/media#1476
#cherrypick
PiperOrigin-RevId: 646427213
---
 RELEASENOTES.md                                           | 3 +++
 .../media3/exoplayer/source/ProgressiveMediaPeriod.java   | 8 ++++++++
 2 files changed, 11 insertions(+)

diff --git a/RELEASENOTES.md b/RELEASENOTES.md
index 02f888ed06..a0f121c8c8 100644
--- a/RELEASENOTES.md
+++ b/RELEASENOTES.md
@@ -9,6 +9,9 @@
     *   Fix some audio focus inconsistencies, e.g. not reporting full or
         transient focus loss while the player is paused
         ([#1436](https://github.com/androidx/media/issues/1436)).
+    *   Fix potential `IndexOutOfBoundsException` caused by extractors reporting
+        additional tracks after the initial preparation step
+        ([#1476](https://github.com/androidx/media/issues/1476)).
 *   Transformer:
 *   Track Selection:
 *   Extractors:
diff --git a/libraries/exoplayer/src/main/java/androidx/media3/exoplayer/source/ProgressiveMediaPeriod.java b/libraries/exoplayer/src/main/java/androidx/media3/exoplayer/source/ProgressiveMediaPeriod.java
index 444d2168d0..0ee2cc1f36 100644
--- a/libraries/exoplayer/src/main/java/androidx/media3/exoplayer/source/ProgressiveMediaPeriod.java
+++ b/libraries/exoplayer/src/main/java/androidx/media3/exoplayer/source/ProgressiveMediaPeriod.java
@@ -31,6 +31,7 @@ import androidx.media3.common.ParserException;
 import androidx.media3.common.TrackGroup;
 import androidx.media3.common.util.Assertions;
 import androidx.media3.common.util.ConditionVariable;
+import androidx.media3.common.util.Log;
 import androidx.media3.common.util.NullableType;
 import androidx.media3.common.util.ParsableByteArray;
 import androidx.media3.common.util.Util;
@@ -53,6 +54,7 @@ import androidx.media3.exoplayer.upstream.LoadErrorHandlingPolicy.LoadErrorInfo;
 import androidx.media3.exoplayer.upstream.Loader;
 import androidx.media3.exoplayer.upstream.Loader.LoadErrorAction;
 import androidx.media3.exoplayer.upstream.Loader.Loadable;
+import androidx.media3.extractor.DummyTrackOutput;
 import androidx.media3.extractor.Extractor;
 import androidx.media3.extractor.ExtractorOutput;
 import androidx.media3.extractor.ForwardingSeekMap;
@@ -93,6 +95,8 @@ import org.checkerframework.checker.nullness.qual.MonotonicNonNull;
     void onSourceInfoRefreshed(long durationUs, boolean isSeekable, boolean isLive);
   }
 
+  private static final String TAG = "ProgressiveMediaPeriod";
+
   /**
    * When the source's duration is unknown, it is calculated by adding this value to the largest
    * sample timestamp seen when buffering completes.
@@ -733,6 +737,10 @@ import org.checkerframework.checker.nullness.qual.MonotonicNonNull;
         return sampleQueues[i];
       }
     }
+    if (sampleQueuesBuilt) {
+      Log.w(TAG, "Extractor added new track (id=" + id.id + ") after finishing tracks.");
+      return new DummyTrackOutput();
+    }
     SampleQueue trackOutput =
         SampleQueue.createWithDrm(allocator, drmSessionManager, drmEventDispatcher);
     trackOutput.setUpstreamFormatChangeListener(this);