diff --git a/libraries/transformer/src/androidTest/java/androidx/media3/transformer/mh/performance/CompositionPlaybackTest.java b/libraries/transformer/src/androidTest/java/androidx/media3/transformer/mh/performance/CompositionPlaybackTest.java
index a1ebb5d4f8..f0d51e5f6b 100644
--- a/libraries/transformer/src/androidTest/java/androidx/media3/transformer/mh/performance/CompositionPlaybackTest.java
+++ b/libraries/transformer/src/androidTest/java/androidx/media3/transformer/mh/performance/CompositionPlaybackTest.java
@@ -62,6 +62,9 @@ import org.junit.rules.TestName;
 import org.junit.runner.RunWith;
 
 /** Playback tests for {@link CompositionPlayer} */
+// These tests are in the performance package even though they are not performance tests so that
+// they are not run on all devices. This is because they use ImageReader, which has a tendency to
+// drop frames.
 @RunWith(AndroidJUnit4.class)
 public class CompositionPlaybackTest {
 
diff --git a/libraries/transformer/src/androidTest/java/androidx/media3/transformer/mh/performance/EffectPlaybackTest.java b/libraries/transformer/src/androidTest/java/androidx/media3/transformer/mh/performance/EffectPlaybackTest.java
index 96e079cd00..6a4c50421c 100644
--- a/libraries/transformer/src/androidTest/java/androidx/media3/transformer/mh/performance/EffectPlaybackTest.java
+++ b/libraries/transformer/src/androidTest/java/androidx/media3/transformer/mh/performance/EffectPlaybackTest.java
@@ -71,6 +71,9 @@ import org.junit.runners.Parameterized.Parameter;
 import org.junit.runners.Parameterized.Parameters;
 
 /** Test for {@link ExoPlayer#setVideoEffects}. */
+// These tests are in the performance package even though they are not performance tests so that
+// they are not run on all devices. This is because they use ImageReader, which has a tendency to
+// drop frames.
 @RunWith(Enclosed.class)
 public class EffectPlaybackTest {