diff --git a/library/transformer/src/main/java/com/google/android/exoplayer2/transformer/ExoPlayerAssetLoader.java b/library/transformer/src/main/java/com/google/android/exoplayer2/transformer/ExoPlayerAssetLoader.java
index 46e71b084c..94a0793bd7 100644
--- a/library/transformer/src/main/java/com/google/android/exoplayer2/transformer/ExoPlayerAssetLoader.java
+++ b/library/transformer/src/main/java/com/google/android/exoplayer2/transformer/ExoPlayerAssetLoader.java
@@ -49,7 +49,6 @@ import com.google.android.exoplayer2.text.TextOutput;
 import com.google.android.exoplayer2.trackselection.DefaultTrackSelector;
 import com.google.android.exoplayer2.util.Clock;
 import com.google.android.exoplayer2.video.VideoRendererEventListener;
-import org.checkerframework.checker.nullness.qual.MonotonicNonNull;
 
 /* package */ final class ExoPlayerAssetLoader {
 
@@ -57,6 +56,8 @@ import org.checkerframework.checker.nullness.qual.MonotonicNonNull;
 
     void onTrackRegistered();
 
+    void onAllTracksRegistered();
+
     SamplePipeline onTrackAdded(Format format, long streamStartPositionUs, long streamOffsetUs)
         throws TransformationException;
 
@@ -72,7 +73,6 @@ import org.checkerframework.checker.nullness.qual.MonotonicNonNull;
   private final Looper looper;
   private final Clock clock;
 
-  private @MonotonicNonNull MuxerWrapper muxerWrapper;
   @Nullable private ExoPlayer player;
   private @Transformer.ProgressState int progressState;
 
@@ -93,19 +93,14 @@ import org.checkerframework.checker.nullness.qual.MonotonicNonNull;
   }
 
   public void start(
-      MediaItem mediaItem,
-      MuxerWrapper muxerWrapper,
-      Listener listener,
-      Transformer.AsyncErrorListener asyncErrorListener) {
-    this.muxerWrapper = muxerWrapper;
-
+      MediaItem mediaItem, Listener listener, Transformer.AsyncErrorListener asyncErrorListener) {
     DefaultTrackSelector trackSelector = new DefaultTrackSelector(context);
     trackSelector.setParameters(
         new DefaultTrackSelector.Parameters.Builder(context)
             .setForceHighestSupportedBitrate(true)
             .build());
     // Arbitrarily decrease buffers for playback so that samples start being sent earlier to the
-    // muxer (rebuffers are less problematic for the transformation use case).
+    // pipelines (rebuffers are less problematic for the transformation use case).
     DefaultLoadControl loadControl =
         new DefaultLoadControl.Builder()
             .setBufferDurationsMs(
@@ -238,9 +233,7 @@ import org.checkerframework.checker.nullness.qual.MonotonicNonNull;
 
     @Override
     public void onTracksChanged(Tracks tracks) {
-      if (checkNotNull(muxerWrapper).getTrackCount() == 0) {
-        listener.onError(new IllegalStateException("The output does not contain any tracks."));
-      }
+      listener.onAllTracksRegistered();
     }
 
     @Override
diff --git a/library/transformer/src/main/java/com/google/android/exoplayer2/transformer/MuxerWrapper.java b/library/transformer/src/main/java/com/google/android/exoplayer2/transformer/MuxerWrapper.java
index cde1f20de0..71f86747c5 100644
--- a/library/transformer/src/main/java/com/google/android/exoplayer2/transformer/MuxerWrapper.java
+++ b/library/transformer/src/main/java/com/google/android/exoplayer2/transformer/MuxerWrapper.java
@@ -235,11 +235,6 @@ import org.checkerframework.checker.nullness.qual.RequiresNonNull;
     }
   }
 
-  /** Returns the number of {@link #registerTrack() registered} tracks. */
-  public int getTrackCount() {
-    return trackCount;
-  }
-
   /**
    * Returns the average bitrate of data written to the track of the provided {@code trackType}, or
    * {@link C#RATE_UNSET_INT} if there is no track data.
diff --git a/library/transformer/src/main/java/com/google/android/exoplayer2/transformer/TransformerInternal.java b/library/transformer/src/main/java/com/google/android/exoplayer2/transformer/TransformerInternal.java
index 3d0c03f12a..2c1e82f2ab 100644
--- a/library/transformer/src/main/java/com/google/android/exoplayer2/transformer/TransformerInternal.java
+++ b/library/transformer/src/main/java/com/google/android/exoplayer2/transformer/TransformerInternal.java
@@ -85,7 +85,7 @@ import com.google.common.collect.ImmutableList;
     ComponentListener componentListener =
         new ComponentListener(
             mediaItem, muxerWrapper, listener, fallbackListener, asyncErrorListener);
-    exoPlayerAssetLoader.start(mediaItem, muxerWrapper, componentListener, asyncErrorListener);
+    exoPlayerAssetLoader.start(mediaItem, componentListener, asyncErrorListener);
   }
 
   public @Transformer.ProgressState int getProgress(ProgressHolder progressHolder) {
@@ -104,6 +104,8 @@ import com.google.common.collect.ImmutableList;
     private final FallbackListener fallbackListener;
     private final Transformer.AsyncErrorListener asyncErrorListener;
 
+    private volatile boolean trackRegistered;
+
     public ComponentListener(
         MediaItem mediaItem,
         MuxerWrapper muxerWrapper,
@@ -119,10 +121,18 @@ import com.google.common.collect.ImmutableList;
 
     @Override
     public void onTrackRegistered() {
+      trackRegistered = true;
       muxerWrapper.registerTrack();
       fallbackListener.registerTrack();
     }
 
+    @Override
+    public void onAllTracksRegistered() {
+      if (!trackRegistered) {
+        onError(new IllegalStateException("The output does not contain any tracks."));
+      }
+    }
+
     @Override
     public SamplePipeline onTrackAdded(
         Format format, long streamStartPositionUs, long streamOffsetUs)