Remove TrackToken and replace with int trackId

This is to make API simpler and to have parity with `MediaMuxer`

PiperOrigin-RevId: 712954669

RELEASENOTES.md

@@ -38,6 +38,8 @@
 *   Muxers:
     *   Renamed `setSampleCopyEnabled()` method to `setSampleCopyingEnabled()`
         in both `Mp4Muxer.Builder` and `FragmentedMp4Muxer.Builder`.
+    *   `Mp4Muxer.addTrack()` and `FragmentedMp4Muxer.addTrack()` now return an
+        `int` track id instead of a `TrackToken`.
 *   IMA extension:
 *   Session:
     *   Fix bug where calling a `Player` method on a `MediaController` connected

libraries/muxer/src/androidTest/java/androidx/media3/muxer/AndroidMuxerTestUtil.java

@@ -44,11 +44,11 @@ import java.util.List;
         context.getResources().getAssets().openFd(MP4_FILE_ASSET_DIRECTORY + inputFileName);
     extractor.setDataSource(fd);
 
-    List<Muxer.TrackToken> addedTracks = new ArrayList<>();
+    List<Integer> addedTracks = new ArrayList<>();
     for (int i = 0; i < extractor.getTrackCount(); i++) {
-      Muxer.TrackToken trackToken =
+      int trackId =
           muxer.addTrack(MediaFormatUtil.createFormatFromMediaFormat(extractor.getTrackFormat(i)));
-      addedTracks.add(trackToken);
+      addedTracks.add(trackId);
       extractor.selectTrack(i);
     }
 

libraries/muxer/src/main/java/androidx/media3/muxer/FragmentedMp4Muxer.java

@@ -19,6 +19,7 @@ import static androidx.media3.common.util.Assertions.checkArgument;
 import static androidx.media3.common.util.Assertions.checkNotNull;
 
 import android.media.MediaCodec.BufferInfo;
+import android.util.SparseArray;
 import androidx.media3.common.Format;
 import androidx.media3.common.Metadata;
 import androidx.media3.common.util.UnstableApi;
@@ -64,10 +65,9 @@ import java.nio.ByteBuffer;
  * <p>To create a fragmented MP4 file, the caller must:
  *
  * <ul>
- *   <li>Add tracks using {@link #addTrack(Format)} which will return a {@link Mp4Muxer.TrackToken}.
+ *   <li>Add tracks using {@link #addTrack(Format)} which will return a track id.
- *   <li>Use the associated {@link Mp4Muxer.TrackToken} when {@linkplain
+ *   <li>Use the associated track id when {@linkplain #writeSampleData(int, ByteBuffer, BufferInfo)
- *       #writeSampleData(Mp4Muxer.TrackToken, ByteBuffer, BufferInfo) writing samples} for that
+ *       writing samples} for that track.
- *       track.
  *   <li>{@link #close} the muxer when all data has been written.
  * </ul>
  *
@@ -76,8 +76,8 @@ import java.nio.ByteBuffer;
  * <ul>
  *   <li>All tracks must be added before writing any samples.
  *   <li>The caller is responsible for ensuring that samples of different track types are well
- *       interleaved by calling {@link #writeSampleData(Mp4Muxer.TrackToken, ByteBuffer,
+ *       interleaved by calling {@link #writeSampleData(int, ByteBuffer, BufferInfo)} in an order
- *       BufferInfo)} in an order that interleaves samples from different tracks.
+ *       that interleaves samples from different tracks.
  * </ul>
  */
 @UnstableApi
@@ -121,10 +121,10 @@ public final class FragmentedMp4Muxer implements Muxer {
     /**
      * Sets whether to enable the sample copy.
      *
-     * <p>If the sample copy is enabled, {@link #writeSampleData(TrackToken, ByteBuffer,
+     * <p>If the sample copy is enabled, {@link #writeSampleData(int, ByteBuffer, BufferInfo)}
-     * BufferInfo)} copies the input {@link ByteBuffer} and {@link BufferInfo} before it returns, so
+     * copies the input {@link ByteBuffer} and {@link BufferInfo} before it returns, so it is safe
-     * it is safe to reuse them immediately. Otherwise, the muxer takes ownership of the {@link
+     * to reuse them immediately. Otherwise, the muxer takes ownership of the {@link ByteBuffer} and
-     * ByteBuffer} and the {@link BufferInfo} and the caller must not modify them.
+     * the {@link BufferInfo} and the caller must not modify them.
      *
      * <p>The default value is {@code true}.
      */
@@ -142,6 +142,7 @@ public final class FragmentedMp4Muxer implements Muxer {
 
   private final FragmentedMp4Writer fragmentedMp4Writer;
   private final MetadataCollector metadataCollector;
+  private final SparseArray<Track> trackIdToTrack;
 
   private FragmentedMp4Muxer(
       OutputStream outputStream, long fragmentDurationMs, boolean sampleCopyEnabled) {
@@ -154,11 +155,14 @@ public final class FragmentedMp4Muxer implements Muxer {
             AnnexBToAvccConverter.DEFAULT,
             fragmentDurationMs,
             sampleCopyEnabled);
+    trackIdToTrack = new SparseArray<>();
   }
 
   @Override
-  public TrackToken addTrack(Format format) {
+  public int addTrack(Format format) {
-    return fragmentedMp4Writer.addTrack(/* sortKey= */ 1, format);
+    Track track = fragmentedMp4Writer.addTrack(/* sortKey= */ 1, format);
+    trackIdToTrack.append(track.id, track);
+    return track.id;
   }
 
   /**
@@ -171,7 +175,7 @@ public final class FragmentedMp4Muxer implements Muxer {
    *
    * <p>Note: Out of order B-frames are currently not supported.
    *
-   * @param trackToken The {@link TrackToken} for which this sample is being written.
+   * @param trackId The track id for which this sample is being written.
    * @param byteBuffer The encoded sample. The muxer takes ownership of the buffer if {@link
    *     Builder#setSampleCopyingEnabled(boolean) sample copying} is disabled. Otherwise, the
    *     position of the buffer is updated but the caller retains ownership.
@@ -179,10 +183,10 @@ public final class FragmentedMp4Muxer implements Muxer {
    * @throws MuxerException If there is any error while writing data to the disk.
    */
   @Override
-  public void writeSampleData(TrackToken trackToken, ByteBuffer byteBuffer, BufferInfo bufferInfo)
+  public void writeSampleData(int trackId, ByteBuffer byteBuffer, BufferInfo bufferInfo)
       throws MuxerException {
     try {
-      fragmentedMp4Writer.writeSampleData(trackToken, byteBuffer, bufferInfo);
+      fragmentedMp4Writer.writeSampleData(trackIdToTrack.get(trackId), byteBuffer, bufferInfo);
     } catch (IOException e) {
       throw new MuxerException(
           "Failed to write sample for presentationTimeUs="

libraries/muxer/src/main/java/androidx/media3/muxer/FragmentedMp4Writer.java

@@ -33,7 +33,6 @@ import android.media.MediaCodec.BufferInfo;
 import androidx.media3.common.Format;
 import androidx.media3.common.MimeTypes;
 import androidx.media3.common.util.Util;
-import androidx.media3.muxer.Muxer.TrackToken;
 import com.google.common.collect.ImmutableList;
 import java.io.IOException;
 import java.io.OutputStream;
@@ -122,6 +121,7 @@ import org.checkerframework.checker.nullness.qual.MonotonicNonNull;
   private boolean headerCreated;
   private long minInputPresentationTimeUs;
   private long maxTrackDurationUs;
+  private int nextTrackId;
 
   /**
    * Creates an instance.
@@ -153,8 +153,8 @@ import org.checkerframework.checker.nullness.qual.MonotonicNonNull;
     currentFragmentSequenceNumber = 1;
   }
 
-  public TrackToken addTrack(int sortKey, Format format) {
+  public Track addTrack(int sortKey, Format format) {
-    Track track = new Track(format, sampleCopyEnabled);
+    Track track = new Track(nextTrackId++, format, sampleCopyEnabled);
     tracks.add(track);
     if (MimeTypes.isVideo(format.sampleMimeType)) {
       videoTrack = track;
@@ -162,15 +162,12 @@ import org.checkerframework.checker.nullness.qual.MonotonicNonNull;
     return track;
   }
 
-  public void writeSampleData(
+  public void writeSampleData(Track track, ByteBuffer byteBuffer, MediaCodec.BufferInfo bufferInfo)
-      TrackToken token, ByteBuffer byteBuffer, MediaCodec.BufferInfo bufferInfo)
       throws IOException {
-    checkArgument(token instanceof Track);
     if (!headerCreated) {
       createHeader();
       headerCreated = true;
     }
-    Track track = (Track) token;
     if (shouldFlushPendingSamples(track, bufferInfo)) {
       createFragment();
     }

libraries/muxer/src/main/java/androidx/media3/muxer/Mp4Muxer.java

@@ -89,9 +89,9 @@ import org.checkerframework.checker.nullness.qual.EnsuresNonNull;
  * <p>To create an MP4 container file, the caller must:
  *
  * <ul>
- *   <li>Add tracks using {@link #addTrack(int, Format)} which will return a {@link TrackToken}.
+ *   <li>Add tracks using {@link #addTrack(int, Format)} which will return a track id.
- *   <li>Use the associated {@link TrackToken} when {@linkplain #writeSampleData(TrackToken,
+ *   <li>Use the associated track id when {@linkplain #writeSampleData(int, ByteBuffer, BufferInfo)
- *       ByteBuffer, BufferInfo) writing samples} for that track.
+ *       writing samples} for that track.
  *   <li>{@link #close} the muxer when all data has been written.
  * </ul>
  *
@@ -100,8 +100,8 @@ import org.checkerframework.checker.nullness.qual.EnsuresNonNull;
  * <ul>
  *   <li>Tracks can be added at any point, even after writing some samples to other tracks.
  *   <li>The caller is responsible for ensuring that samples of different track types are well
- *       interleaved by calling {@link #writeSampleData(TrackToken, ByteBuffer, BufferInfo)} in an
+ *       interleaved by calling {@link #writeSampleData(int, ByteBuffer, BufferInfo)} in an order
- *       order that interleaves samples from different tracks.
+ *       that interleaves samples from different tracks.
  *   <li>When writing a file, if an error occurs and the muxer is not closed, then the output MP4
  *       file may still have some partial data.
  * </ul>
@@ -252,10 +252,10 @@ public final class Mp4Muxer implements Muxer {
     /**
      * Sets whether to enable the sample copy.
      *
-     * <p>If the sample copy is enabled, {@link #writeSampleData(TrackToken, ByteBuffer,
+     * <p>If the sample copy is enabled, {@link #writeSampleData(int, ByteBuffer, BufferInfo)}
-     * BufferInfo)} copies the input {@link ByteBuffer} and {@link BufferInfo} before it returns, so
+     * copies the input {@link ByteBuffer} and {@link BufferInfo} before it returns, so it is safe
-     * it is safe to reuse them immediately. Otherwise, the muxer takes ownership of the {@link
+     * to reuse them immediately. Otherwise, the muxer takes ownership of the {@link ByteBuffer} and
-     * ByteBuffer} and the {@link BufferInfo} and the caller must not modify them.
+     * the {@link BufferInfo} and the caller must not modify them.
      *
      * <p>The default value is {@code true}.
      */
@@ -269,7 +269,7 @@ public final class Mp4Muxer implements Muxer {
      * Sets whether to enable sample batching.
      *
      * <p>If sample batching is enabled, samples are written in batches for each track, otherwise
-     * samples are written as they {@linkplain #writeSampleData(TrackToken, ByteBuffer, BufferInfo)
+     * samples are written as they {@linkplain #writeSampleData(int, ByteBuffer, BufferInfo)
      * arrive}.
      *
      * <p>The default value is {@code true}.
@@ -348,6 +348,7 @@ public final class Mp4Muxer implements Muxer {
   @Nullable private final Mp4AtFileParameters mp4AtFileParameters;
   private final MetadataCollector metadataCollector;
   private final Mp4Writer mp4Writer;
+  private final List<Track> trackIdToTrack;
   private final List<Track> auxiliaryTracks;
 
   @Nullable private String cacheFilePath;
@@ -355,6 +356,8 @@ public final class Mp4Muxer implements Muxer {
   @Nullable private MetadataCollector auxiliaryTracksMetadataCollector;
   @Nullable private Mp4Writer auxiliaryTracksMp4Writer;
 
+  private int nextTrackId;
+
   private Mp4Muxer(
       FileOutputStream outputStream,
       @LastSampleDurationBehavior int lastFrameDurationBehavior,
@@ -383,6 +386,7 @@ public final class Mp4Muxer implements Muxer {
             sampleCopyEnabled,
             sampleBatchingEnabled,
             attemptStreamableOutputEnabled);
+    trackIdToTrack = new ArrayList<>();
     auxiliaryTracks = new ArrayList<>();
   }
 
@@ -395,11 +399,12 @@ public final class Mp4Muxer implements Muxer {
    * <p>The order of tracks remains same in which they are added.
    *
    * @param format The {@link Format} for the track.
-   * @return A unique {@link TrackToken}. It should be used in {@link #writeSampleData}.
+   * @return A unique track id. The track id is non-negative. It should be used in {@link
+   *     #writeSampleData}.
    * @throws MuxerException If an error occurs while adding track.
    */
   @Override
-  public TrackToken addTrack(Format format) throws MuxerException {
+  public int addTrack(Format format) throws MuxerException {
     return addTrack(/* sortKey= */ 1, format);
   }
 
@@ -410,31 +415,37 @@ public final class Mp4Muxer implements Muxer {
    * other tracks.
    *
    * <p>The final order of tracks is determined by the provided sort key. Tracks with a lower sort
-   * key will always have a lower track id than tracks with a higher sort key. Ordering between
+   * key will be written before tracks with a higher sort key. Ordering between tracks with the same
-   * tracks with the same sort key is not specified.
+   * sort key is not specified.
    *
    * @param sortKey The key used for sorting the track list.
    * @param format The {@link Format} for the track.
-   * @return A unique {@link TrackToken}. It should be used in {@link #writeSampleData}.
+   * @return A unique track id. The track id is non-negative. It should be used in {@link
+   *     #writeSampleData}.
    * @throws MuxerException If an error occurs while adding track.
    */
-  public TrackToken addTrack(int sortKey, Format format) throws MuxerException {
+  public int addTrack(int sortKey, Format format) throws MuxerException {
+    Track track;
     if (outputFileFormat == FILE_FORMAT_MP4_WITH_AUXILIARY_TRACKS_EXTENSION
         && isAuxiliaryTrack(format)) {
       if (checkNotNull(mp4AtFileParameters).shouldInterleaveSamples) {
         // Auxiliary tracks are handled by the primary Mp4Writer.
-        return mp4Writer.addAuxiliaryTrack(sortKey, format);
+        track = mp4Writer.addAuxiliaryTrack(nextTrackId++, sortKey, format);
+      } else {
+        // Auxiliary tracks are handled by the auxiliary tracks Mp4Writer.
+        try {
+          ensureSetupForAuxiliaryTracks();
+        } catch (FileNotFoundException e) {
+          throw new MuxerException("Cache file not found", e);
+        }
+        track = auxiliaryTracksMp4Writer.addTrack(nextTrackId++, sortKey, format);
+        auxiliaryTracks.add(track);
       }
-      try {
+    } else {
-        ensureSetupForAuxiliaryTracks();
+      track = mp4Writer.addTrack(nextTrackId++, sortKey, format);
-      } catch (FileNotFoundException e) {
-        throw new MuxerException("Cache file not found", e);
-      }
-      Track track = auxiliaryTracksMp4Writer.addTrack(sortKey, format);
-      auxiliaryTracks.add(track);
-      return track;
     }
-    return mp4Writer.addTrack(sortKey, format);
+    trackIdToTrack.add(track);
+    return track.id;
   }
 
   /**
@@ -442,13 +453,13 @@ public final class Mp4Muxer implements Muxer {
    *
    * <p>When sample batching is {@linkplain Mp4Muxer.Builder#setSampleBatchingEnabled(boolean)
    * enabled}, provide sample data ({@link ByteBuffer}, {@link BufferInfo}) that won't be modified
-   * after calling the {@link #writeSampleData(TrackToken, ByteBuffer, BufferInfo)} method, unless
+   * after calling the {@link #writeSampleData(int, ByteBuffer, BufferInfo)} method, unless sample
-   * sample copying is also {@linkplain Mp4Muxer.Builder#setSampleCopyingEnabled(boolean) enabled}.
+   * copying is also {@linkplain Mp4Muxer.Builder#setSampleCopyingEnabled(boolean) enabled}. This
-   * This ensures data integrity within the batch. If sample copying is {@linkplain
+   * ensures data integrity within the batch. If sample copying is {@linkplain
    * Mp4Muxer.Builder#setSampleCopyingEnabled(boolean) enabled}, it's safe to modify the data after
    * the method returns, as the muxer internally creates a sample copy.
    *
-   * @param trackToken The {@link TrackToken} for which this sample is being written.
+   * @param trackId The track id for which this sample is being written.
    * @param byteBuffer The encoded sample. The muxer takes ownership of the buffer if {@link
    *     Builder#setSampleCopyingEnabled(boolean) sample copying} is disabled. Otherwise, the
    *     position of the buffer is updated but the caller retains ownership.
@@ -456,12 +467,11 @@ public final class Mp4Muxer implements Muxer {
    * @throws MuxerException If an error occurs while writing data to the output file.
    */
   @Override
-  public void writeSampleData(TrackToken trackToken, ByteBuffer byteBuffer, BufferInfo bufferInfo)
+  public void writeSampleData(int trackId, ByteBuffer byteBuffer, BufferInfo bufferInfo)
       throws MuxerException {
-    checkState(trackToken instanceof Track);
+    Track track = trackIdToTrack.get(trackId);
-    Track track = (Track) trackToken;
     try {
-      if (auxiliaryTracks.contains(trackToken)) {
+      if (auxiliaryTracks.contains(track)) {
         checkNotNull(auxiliaryTracksMp4Writer).writeSampleData(track, byteBuffer, bufferInfo);
       } else {
         mp4Writer.writeSampleData(track, byteBuffer, bufferInfo);

libraries/muxer/src/main/java/androidx/media3/muxer/Mp4Writer.java

@@ -111,12 +111,13 @@ import java.util.concurrent.atomic.AtomicBoolean;
   /**
    * Adds a track of the given {@link Format}.
    *
+   * @param trackId The track id for the track.
    * @param sortKey The key used for sorting the track list.
    * @param format The {@link Format} for the track.
    * @return A unique {@link Track}. It should be used in {@link #writeSampleData}.
    */
-  public Track addTrack(int sortKey, Format format) {
+  public Track addTrack(int trackId, int sortKey, Format format) {
-    Track track = new Track(format, sortKey, sampleCopyEnabled);
+    Track track = new Track(trackId, format, sortKey, sampleCopyEnabled);
     tracks.add(track);
     Collections.sort(tracks, (a, b) -> Integer.compare(a.sortKey, b.sortKey));
     return track;
@@ -127,12 +128,13 @@ import java.util.concurrent.atomic.AtomicBoolean;
    *
    * <p>See {@link MuxerUtil#isAuxiliaryTrack(Format)} for auxiliary tracks.
    *
+   * @param trackId The track id for the track.
    * @param sortKey The key used for sorting the track list.
    * @param format The {@link Format} for the track.
    * @return A unique {@link Track}. It should be used in {@link #writeSampleData}.
    */
-  public Track addAuxiliaryTrack(int sortKey, Format format) {
+  public Track addAuxiliaryTrack(int trackId, int sortKey, Format format) {
-    Track track = new Track(format, sortKey, sampleCopyEnabled);
+    Track track = new Track(trackId, format, sortKey, sampleCopyEnabled);
     auxiliaryTracks.add(track);
     Collections.sort(auxiliaryTracks, (a, b) -> Integer.compare(a.sortKey, b.sortKey));
     return track;

libraries/muxer/src/main/java/androidx/media3/muxer/Muxer.java

@@ -44,29 +44,24 @@ public interface Muxer {
     ImmutableList<String> getSupportedSampleMimeTypes(@C.TrackType int trackType);
   }
 
-  /** A token representing an added track. */
-  interface TrackToken {}
-
   /**
    * Adds a track of the given media format.
    *
    * @param format The {@link Format} of the track.
-   * @return The {@link TrackToken} for this track, which should be passed to {@link
+   * @return A track id for this track, which should be passed to {@link #writeSampleData}.
-   *     #writeSampleData}.
    * @throws MuxerException If the muxer encounters a problem while adding the track.
    */
-  TrackToken addTrack(Format format) throws MuxerException;
+  int addTrack(Format format) throws MuxerException;
 
   /**
    * Writes encoded sample data.
    *
-   * @param trackToken The {@link TrackToken} of the track, previously returned by {@link
+   * @param trackId The track id, previously returned by {@link #addTrack(Format)}.
-   *     #addTrack(Format)}.
    * @param byteBuffer A buffer containing the sample data to write to the container.
    * @param bufferInfo The {@link BufferInfo} of the sample.
    * @throws MuxerException If the muxer fails to write the sample.
    */
-  void writeSampleData(TrackToken trackToken, ByteBuffer byteBuffer, BufferInfo bufferInfo)
+  void writeSampleData(int trackId, ByteBuffer byteBuffer, BufferInfo bufferInfo)
       throws MuxerException;
 
   /** Adds {@linkplain Metadata.Entry metadata} about the output file. */

libraries/muxer/src/main/java/androidx/media3/muxer/Track.java

@@ -22,7 +22,6 @@ import android.media.MediaCodec.BufferInfo;
 import androidx.media3.common.C;
 import androidx.media3.common.Format;
 import androidx.media3.common.MimeTypes;
-import androidx.media3.muxer.Muxer.TrackToken;
 import java.nio.ByteBuffer;
 import java.util.ArrayDeque;
 import java.util.ArrayList;
@@ -30,7 +29,8 @@ import java.util.Deque;
 import java.util.List;
 
 /** Represents a single track (audio, video, metadata etc.). */
-/* package */ final class Track implements TrackToken {
+/* package */ final class Track {
+  public final int id;
   public final Format format;
   public final int sortKey;
   public final List<BufferInfo> writtenSamples;
@@ -44,18 +44,20 @@ import java.util.List;
   private final boolean sampleCopyEnabled;
 
   /** Creates an instance with {@code sortKey} set to 1. */
-  public Track(Format format, boolean sampleCopyEnabled) {
+  public Track(int trackId, Format format, boolean sampleCopyEnabled) {
-    this(format, /* sortKey= */ 1, sampleCopyEnabled);
+    this(trackId, format, /* sortKey= */ 1, sampleCopyEnabled);
   }
 
   /**
    * Creates an instance.
    *
+   * @param trackId A unique id for the track.
    * @param format The {@link Format} for the track.
    * @param sortKey The key used for sorting the track list.
    * @param sampleCopyEnabled Whether sample copying is enabled.
    */
-  public Track(Format format, int sortKey, boolean sampleCopyEnabled) {
+  public Track(int trackId, Format format, int sortKey, boolean sampleCopyEnabled) {
+    id = trackId;
     this.format = format;
     this.sortKey = sortKey;
     this.sampleCopyEnabled = sampleCopyEnabled;

libraries/muxer/src/test/java/androidx/media3/muxer/Mp4MuxerEndToEndTest.java

@@ -35,7 +35,6 @@ import androidx.media3.container.Mp4TimestampData;
 import androidx.media3.container.XmpData;
 import androidx.media3.extractor.mp4.Mp4Extractor;
 import androidx.media3.extractor.text.DefaultSubtitleParserFactory;
-import androidx.media3.muxer.Muxer.TrackToken;
 import androidx.media3.test.utils.DumpFileAsserts;
 import androidx.media3.test.utils.DumpableMp4Box;
 import androidx.media3.test.utils.FakeExtractorOutput;
@@ -83,8 +82,8 @@ public class Mp4MuxerEndToEndTest {
               /* value= */ Util.getUtf8Bytes("StringValue"),
               MdtaMetadataEntry.TYPE_INDICATOR_STRING));
       muxer.addMetadataEntry(new XmpData(xmpBytes));
-      TrackToken token = muxer.addTrack(FAKE_VIDEO_FORMAT);
+      int trackId = muxer.addTrack(FAKE_VIDEO_FORMAT);
-      muxer.writeSampleData(token, sampleAndSampleInfo.first, sampleAndSampleInfo.second);
+      muxer.writeSampleData(trackId, sampleAndSampleInfo.first, sampleAndSampleInfo.second);
     } finally {
       muxer.close();
     }
@@ -136,12 +135,12 @@ public class Mp4MuxerEndToEndTest {
         getFakeSampleAndSampleInfo(/* presentationTimeUs= */ 300L);
 
     try {
-      TrackToken track1 = mp4Muxer.addTrack(FAKE_VIDEO_FORMAT);
+      int track1 = mp4Muxer.addTrack(FAKE_VIDEO_FORMAT);
       mp4Muxer.writeSampleData(track1, track1Sample1.first, track1Sample1.second);
       mp4Muxer.writeSampleData(track1, track1Sample2.first, track1Sample2.second);
 
       // Add same track again but with different samples.
-      TrackToken track2 = mp4Muxer.addTrack(FAKE_VIDEO_FORMAT);
+      int track2 = mp4Muxer.addTrack(FAKE_VIDEO_FORMAT);
       mp4Muxer.writeSampleData(track2, track2Sample1.first, track2Sample1.second);
       mp4Muxer.writeSampleData(track2, track2Sample2.first, track2Sample2.second);
     } finally {
@@ -180,12 +179,12 @@ public class Mp4MuxerEndToEndTest {
         getFakeSampleAndSampleInfo(/* presentationTimeUs= */ 200L);
 
     try {
-      TrackToken track1 = mp4Muxer.addTrack(FAKE_VIDEO_FORMAT);
+      int track1 = mp4Muxer.addTrack(FAKE_VIDEO_FORMAT);
       mp4Muxer.writeSampleData(track1, track1Sample1.first, track1Sample1.second);
       mp4Muxer.writeSampleData(track1, track1Sample2.first, track1Sample2.second);
 
       // Add same track again but with different samples.
-      TrackToken track2 = mp4Muxer.addTrack(FAKE_VIDEO_FORMAT);
+      int track2 = mp4Muxer.addTrack(FAKE_VIDEO_FORMAT);
       mp4Muxer.writeSampleData(track2, track2Sample1.first, track2Sample1.second);
       mp4Muxer.writeSampleData(track2, track2Sample2.first, track2Sample2.second);
     } finally {
@@ -218,7 +217,7 @@ public class Mp4MuxerEndToEndTest {
         getFakeSampleAndSampleInfo(/* presentationTimeUs= */ 300L);
 
     try {
-      TrackToken track1 = mp4Muxer.addTrack(FAKE_VIDEO_FORMAT);
+      int track1 = mp4Muxer.addTrack(FAKE_VIDEO_FORMAT);
       mp4Muxer.writeSampleData(track1, track1Sample1.first, track1Sample1.second);
       mp4Muxer.writeSampleData(track1, track1Sample2.first, track1Sample2.second);
       mp4Muxer.writeSampleData(track1, track1Sample3.first, track1Sample3.second);
@@ -257,7 +256,7 @@ public class Mp4MuxerEndToEndTest {
         getFakeSampleAndSampleInfo(/* presentationTimeUs= */ 2_000L);
 
     try {
-      TrackToken track1 = mp4Muxer.addTrack(FAKE_VIDEO_FORMAT);
+      int track1 = mp4Muxer.addTrack(FAKE_VIDEO_FORMAT);
       mp4Muxer.writeSampleData(track1, track1Sample1.first, track1Sample1.second);
       mp4Muxer.writeSampleData(track1, track1Sample2.first, track1Sample2.second);
       mp4Muxer.writeSampleData(track1, track1Sample3.first, track1Sample3.second);
@@ -301,12 +300,12 @@ public class Mp4MuxerEndToEndTest {
         getFakeSampleAndSampleInfo(/* presentationTimeUs= */ 23_001_033_192L);
 
     try {
-      TrackToken track1 = mp4Muxer.addTrack(FAKE_VIDEO_FORMAT);
+      int track1 = mp4Muxer.addTrack(FAKE_VIDEO_FORMAT);
       mp4Muxer.writeSampleData(track1, track1Sample1.first, track1Sample1.second);
       mp4Muxer.writeSampleData(track1, track1Sample2.first, track1Sample2.second);
       mp4Muxer.writeSampleData(track1, track1Sample3.first, track1Sample3.second);
       mp4Muxer.writeSampleData(track1, track1Sample4.first, track1Sample4.second);
-      TrackToken track2 = mp4Muxer.addTrack(FAKE_VIDEO_FORMAT);
+      int track2 = mp4Muxer.addTrack(FAKE_VIDEO_FORMAT);
       mp4Muxer.writeSampleData(track2, track2Sample1.first, track2Sample1.second);
       mp4Muxer.writeSampleData(track2, track2Sample2.first, track2Sample2.second);
       mp4Muxer.writeSampleData(track2, track2Sample3.first, track2Sample3.second);
@@ -337,7 +336,7 @@ public class Mp4MuxerEndToEndTest {
         getFakeSampleAndSampleInfo(/* presentationTimeUs= */ 100L);
 
     try {
-      TrackToken track1 = mp4Muxer.addTrack(FAKE_VIDEO_FORMAT);
+      int track1 = mp4Muxer.addTrack(FAKE_VIDEO_FORMAT);
       mp4Muxer.writeSampleData(track1, track1Sample1.first, track1Sample1.second);
       mp4Muxer.writeSampleData(track1, track1Sample2.first, track1Sample2.second);
       // Add same track again but without any samples.
@@ -365,11 +364,11 @@ public class Mp4MuxerEndToEndTest {
           new Mp4TimestampData(
               /* creationTimestampSeconds= */ 1_000_000L,
               /* modificationTimestampSeconds= */ 5_000_000L));
-      TrackToken token = muxer.addTrack(FAKE_VIDEO_FORMAT);
+      int trackId = muxer.addTrack(FAKE_VIDEO_FORMAT);
       for (int i = 0; i < 50_000; i++) {
         Pair<ByteBuffer, BufferInfo> sampleAndSampleInfo =
             getFakeSampleAndSampleInfo(/* presentationTimeUs= */ i);
-        muxer.writeSampleData(token, sampleAndSampleInfo.first, sampleAndSampleInfo.second);
+        muxer.writeSampleData(trackId, sampleAndSampleInfo.first, sampleAndSampleInfo.second);
       }
     } finally {
       muxer.close();
@@ -397,11 +396,11 @@ public class Mp4MuxerEndToEndTest {
           new Mp4TimestampData(
               /* creationTimestampSeconds= */ 1_000_000L,
               /* modificationTimestampSeconds= */ 5_000_000L));
-      TrackToken token = muxer.addTrack(FAKE_VIDEO_FORMAT);
+      int trackId = muxer.addTrack(FAKE_VIDEO_FORMAT);
       for (int i = 0; i < 1_000; i++) {
         Pair<ByteBuffer, BufferInfo> sampleAndSampleInfo =
             getFakeSampleAndSampleInfo(/* presentationTimeUs= */ i);
-        muxer.writeSampleData(token, sampleAndSampleInfo.first, sampleAndSampleInfo.second);
+        muxer.writeSampleData(trackId, sampleAndSampleInfo.first, sampleAndSampleInfo.second);
       }
     } finally {
       muxer.close();
@@ -448,24 +447,24 @@ public class Mp4MuxerEndToEndTest {
           new Mp4TimestampData(
               /* creationTimestampSeconds= */ 1_000_000L,
               /* modificationTimestampSeconds= */ 5_000_000L));
-      TrackToken primaryVideoTrackToken = muxer.addTrack(FAKE_VIDEO_FORMAT);
+      int primaryVideoTrackId = muxer.addTrack(FAKE_VIDEO_FORMAT);
-      TrackToken sharpVideoTrackToken =
+      int sharpVideoTrackId =
           muxer.addTrack(
               FAKE_VIDEO_FORMAT
                   .buildUpon()
                   .setRoleFlags(C.ROLE_FLAG_AUXILIARY)
                   .setAuxiliaryTrackType(C.AUXILIARY_TRACK_TYPE_ORIGINAL)
                   .build());
-      TrackToken depthLinearVideoTrackToken =
+      int depthLinearVideoTrackId =
           muxer.addTrack(
               FAKE_VIDEO_FORMAT
                   .buildUpon()
                   .setRoleFlags(C.ROLE_FLAG_AUXILIARY)
                   .setAuxiliaryTrackType(C.AUXILIARY_TRACK_TYPE_DEPTH_LINEAR)
                   .build());
-      writeFakeSamples(muxer, primaryVideoTrackToken, /* sampleCount= */ 5);
+      writeFakeSamples(muxer, primaryVideoTrackId, /* sampleCount= */ 5);
-      writeFakeSamples(muxer, sharpVideoTrackToken, /* sampleCount= */ 5);
+      writeFakeSamples(muxer, sharpVideoTrackId, /* sampleCount= */ 5);
-      writeFakeSamples(muxer, depthLinearVideoTrackToken, /* sampleCount= */ 5);
+      writeFakeSamples(muxer, depthLinearVideoTrackId, /* sampleCount= */ 5);
     } finally {
       muxer.close();
     }
@@ -490,24 +489,24 @@ public class Mp4MuxerEndToEndTest {
           new Mp4TimestampData(
               /* creationTimestampSeconds= */ 1_000_000L,
               /* modificationTimestampSeconds= */ 5_000_000L));
-      TrackToken primaryVideoTrackToken = muxer.addTrack(FAKE_VIDEO_FORMAT);
+      int primaryVideoTrackId = muxer.addTrack(FAKE_VIDEO_FORMAT);
-      TrackToken sharpVideoTrackToken =
+      int sharpVideoTrackId =
           muxer.addTrack(
               FAKE_VIDEO_FORMAT
                   .buildUpon()
                   .setRoleFlags(C.ROLE_FLAG_AUXILIARY)
                   .setAuxiliaryTrackType(C.AUXILIARY_TRACK_TYPE_ORIGINAL)
                   .build());
-      TrackToken depthLinearVideoTrackToken =
+      int depthLinearVideoTrackId =
           muxer.addTrack(
               FAKE_VIDEO_FORMAT
                   .buildUpon()
                   .setRoleFlags(C.ROLE_FLAG_AUXILIARY)
                   .setAuxiliaryTrackType(C.AUXILIARY_TRACK_TYPE_DEPTH_LINEAR)
                   .build());
-      writeFakeSamples(muxer, primaryVideoTrackToken, /* sampleCount= */ 5);
+      writeFakeSamples(muxer, primaryVideoTrackId, /* sampleCount= */ 5);
-      writeFakeSamples(muxer, sharpVideoTrackToken, /* sampleCount= */ 5);
+      writeFakeSamples(muxer, sharpVideoTrackId, /* sampleCount= */ 5);
-      writeFakeSamples(muxer, depthLinearVideoTrackToken, /* sampleCount= */ 5);
+      writeFakeSamples(muxer, depthLinearVideoTrackId, /* sampleCount= */ 5);
     } finally {
       muxer.close();
     }
@@ -540,24 +539,24 @@ public class Mp4MuxerEndToEndTest {
           new Mp4TimestampData(
               /* creationTimestampSeconds= */ 1_000_000L,
               /* modificationTimestampSeconds= */ 5_000_000L));
-      TrackToken primaryVideoTrackToken = muxer.addTrack(FAKE_VIDEO_FORMAT);
+      int primaryVideoTrackId = muxer.addTrack(FAKE_VIDEO_FORMAT);
-      TrackToken sharpVideoTrackToken =
+      int sharpVideoTrackId =
           muxer.addTrack(
               FAKE_VIDEO_FORMAT
                   .buildUpon()
                   .setRoleFlags(C.ROLE_FLAG_AUXILIARY)
                   .setAuxiliaryTrackType(C.AUXILIARY_TRACK_TYPE_ORIGINAL)
                   .build());
-      TrackToken depthLinearVideoTrackToken =
+      int depthLinearVideoTrackId =
           muxer.addTrack(
               FAKE_VIDEO_FORMAT
                   .buildUpon()
                   .setRoleFlags(C.ROLE_FLAG_AUXILIARY)
                   .setAuxiliaryTrackType(C.AUXILIARY_TRACK_TYPE_DEPTH_LINEAR)
                   .build());
-      writeFakeSamples(muxer, primaryVideoTrackToken, /* sampleCount= */ 5);
+      writeFakeSamples(muxer, primaryVideoTrackId, /* sampleCount= */ 5);
-      writeFakeSamples(muxer, sharpVideoTrackToken, /* sampleCount= */ 5);
+      writeFakeSamples(muxer, sharpVideoTrackId, /* sampleCount= */ 5);
-      writeFakeSamples(muxer, depthLinearVideoTrackToken, /* sampleCount= */ 5);
+      writeFakeSamples(muxer, depthLinearVideoTrackId, /* sampleCount= */ 5);
     } finally {
       muxer.close();
     }
@@ -591,24 +590,24 @@ public class Mp4MuxerEndToEndTest {
           new Mp4TimestampData(
               /* creationTimestampSeconds= */ 1_000_000L,
               /* modificationTimestampSeconds= */ 5_000_000L));
-      TrackToken primaryVideoTrackToken = muxer.addTrack(FAKE_VIDEO_FORMAT);
+      int primaryVideoTrackId = muxer.addTrack(FAKE_VIDEO_FORMAT);
-      TrackToken sharpVideoTrackToken =
+      int sharpVideoTrackId =
           muxer.addTrack(
               FAKE_VIDEO_FORMAT
                   .buildUpon()
                   .setRoleFlags(C.ROLE_FLAG_AUXILIARY)
                   .setAuxiliaryTrackType(C.AUXILIARY_TRACK_TYPE_ORIGINAL)
                   .build());
-      TrackToken depthLinearVideoTrackToken =
+      int depthLinearVideoTrackId =
           muxer.addTrack(
               FAKE_VIDEO_FORMAT
                   .buildUpon()
                   .setRoleFlags(C.ROLE_FLAG_AUXILIARY)
                   .setAuxiliaryTrackType(C.AUXILIARY_TRACK_TYPE_DEPTH_LINEAR)
                   .build());
-      writeFakeSamples(muxer, primaryVideoTrackToken, /* sampleCount= */ 5);
+      writeFakeSamples(muxer, primaryVideoTrackId, /* sampleCount= */ 5);
-      writeFakeSamples(muxer, sharpVideoTrackToken, /* sampleCount= */ 5);
+      writeFakeSamples(muxer, sharpVideoTrackId, /* sampleCount= */ 5);
-      writeFakeSamples(muxer, depthLinearVideoTrackToken, /* sampleCount= */ 5);
+      writeFakeSamples(muxer, depthLinearVideoTrackId, /* sampleCount= */ 5);
     } finally {
       muxer.close();
     }
@@ -642,24 +641,24 @@ public class Mp4MuxerEndToEndTest {
           new Mp4TimestampData(
               /* creationTimestampSeconds= */ 1_000_000L,
               /* modificationTimestampSeconds= */ 5_000_000L));
-      TrackToken primaryVideoTrackToken = muxer.addTrack(FAKE_VIDEO_FORMAT);
+      int primaryVideoTrackId = muxer.addTrack(FAKE_VIDEO_FORMAT);
-      TrackToken sharpVideoTrackToken =
+      int sharpVideoTrackId =
           muxer.addTrack(
               FAKE_VIDEO_FORMAT
                   .buildUpon()
                   .setRoleFlags(C.ROLE_FLAG_AUXILIARY)
                   .setAuxiliaryTrackType(C.AUXILIARY_TRACK_TYPE_ORIGINAL)
                   .build());
-      TrackToken depthLinearVideoTrackToken =
+      int depthLinearVideoTrackId =
           muxer.addTrack(
               FAKE_VIDEO_FORMAT
                   .buildUpon()
                   .setRoleFlags(C.ROLE_FLAG_AUXILIARY)
                   .setAuxiliaryTrackType(C.AUXILIARY_TRACK_TYPE_DEPTH_LINEAR)
                   .build());
-      writeFakeSamples(muxer, primaryVideoTrackToken, /* sampleCount= */ 5);
+      writeFakeSamples(muxer, primaryVideoTrackId, /* sampleCount= */ 5);
-      writeFakeSamples(muxer, sharpVideoTrackToken, /* sampleCount= */ 5);
+      writeFakeSamples(muxer, sharpVideoTrackId, /* sampleCount= */ 5);
-      writeFakeSamples(muxer, depthLinearVideoTrackToken, /* sampleCount= */ 5);
+      writeFakeSamples(muxer, depthLinearVideoTrackId, /* sampleCount= */ 5);
     } finally {
       muxer.close();
     }
@@ -693,24 +692,24 @@ public class Mp4MuxerEndToEndTest {
           new Mp4TimestampData(
               /* creationTimestampSeconds= */ 1_000_000L,
               /* modificationTimestampSeconds= */ 5_000_000L));
-      TrackToken primaryVideoTrackToken = muxer.addTrack(FAKE_VIDEO_FORMAT);
+      int primaryVideoTrackId = muxer.addTrack(FAKE_VIDEO_FORMAT);
-      TrackToken sharpVideoTrackToken =
+      int sharpVideoTrackId =
           muxer.addTrack(
               FAKE_VIDEO_FORMAT
                   .buildUpon()
                   .setRoleFlags(C.ROLE_FLAG_AUXILIARY)
                   .setAuxiliaryTrackType(C.AUXILIARY_TRACK_TYPE_ORIGINAL)
                   .build());
-      TrackToken depthLinearVideoTrackToken =
+      int depthLinearVideoTrackId =
           muxer.addTrack(
               FAKE_VIDEO_FORMAT
                   .buildUpon()
                   .setRoleFlags(C.ROLE_FLAG_AUXILIARY)
                   .setAuxiliaryTrackType(C.AUXILIARY_TRACK_TYPE_DEPTH_LINEAR)
                   .build());
-      writeFakeSamples(muxer, primaryVideoTrackToken, /* sampleCount= */ 5);
+      writeFakeSamples(muxer, primaryVideoTrackId, /* sampleCount= */ 5);
-      writeFakeSamples(muxer, sharpVideoTrackToken, /* sampleCount= */ 5);
+      writeFakeSamples(muxer, sharpVideoTrackId, /* sampleCount= */ 5);
-      writeFakeSamples(muxer, depthLinearVideoTrackToken, /* sampleCount= */ 5);
+      writeFakeSamples(muxer, depthLinearVideoTrackId, /* sampleCount= */ 5);
     } finally {
       muxer.close();
     }
@@ -751,7 +750,7 @@ public class Mp4MuxerEndToEndTest {
 
     long expectedDurationUs = 1_000L;
     try {
-      TrackToken track = mp4Muxer.addTrack(FAKE_VIDEO_FORMAT);
+      int track = mp4Muxer.addTrack(FAKE_VIDEO_FORMAT);
       mp4Muxer.writeSampleData(track, sample1.first, sample1.second);
       mp4Muxer.writeSampleData(track, sample2.first, sample2.second);
       mp4Muxer.writeSampleData(track, sample3.first, sample3.second);
@@ -798,7 +797,7 @@ public class Mp4MuxerEndToEndTest {
         getFakeSampleAndSampleInfo(/* presentationTimeUs= */ 300L);
 
     try {
-      TrackToken track = mp4Muxer.addTrack(FAKE_VIDEO_FORMAT);
+      int track = mp4Muxer.addTrack(FAKE_VIDEO_FORMAT);
       mp4Muxer.writeSampleData(track, sample1.first, sample1.second);
       mp4Muxer.writeSampleData(track, sample2.first, sample2.second);
       mp4Muxer.writeSampleData(track, sample3.first, sample3.second);
@@ -814,12 +813,12 @@ public class Mp4MuxerEndToEndTest {
     assertThat(fakeExtractorOutput.seekMap.getDurationUs()).isEqualTo(400L);
   }
 
-  private static void writeFakeSamples(Mp4Muxer muxer, TrackToken trackToken, int sampleCount)
+  private static void writeFakeSamples(Mp4Muxer muxer, int trackId, int sampleCount)
       throws MuxerException {
     for (int i = 0; i < sampleCount; i++) {
       Pair<ByteBuffer, BufferInfo> sampleAndSampleInfo =
           getFakeSampleAndSampleInfo(/* presentationTimeUs= */ i);
-      muxer.writeSampleData(trackToken, sampleAndSampleInfo.first, sampleAndSampleInfo.second);
+      muxer.writeSampleData(trackId, sampleAndSampleInfo.first, sampleAndSampleInfo.second);
     }
   }
 }

libraries/muxer/src/test/java/androidx/media3/muxer/Mp4MuxerMetadataTest.java

@@ -33,7 +33,6 @@ import androidx.media3.container.Mp4TimestampData;
 import androidx.media3.container.XmpData;
 import androidx.media3.extractor.mp4.Mp4Extractor;
 import androidx.media3.extractor.text.DefaultSubtitleParserFactory;
-import androidx.media3.muxer.Muxer.TrackToken;
 import androidx.media3.test.utils.DumpFileAsserts;
 import androidx.media3.test.utils.DumpableMp4Box;
 import androidx.media3.test.utils.FakeExtractorOutput;
@@ -66,8 +65,8 @@ public class Mp4MuxerMetadataTest {
           new Mp4TimestampData(
               /* creationTimestampSeconds= */ 1_000_000L,
               /* modificationTimestampSeconds= */ 5_000_000L));
-      TrackToken token = muxer.addTrack(/* sortKey= */ 0, FAKE_VIDEO_FORMAT);
+      int trackId = muxer.addTrack(/* sortKey= */ 0, FAKE_VIDEO_FORMAT);
-      muxer.writeSampleData(token, sampleAndSampleInfo.first, sampleAndSampleInfo.second);
+      muxer.writeSampleData(trackId, sampleAndSampleInfo.first, sampleAndSampleInfo.second);
     } finally {
       muxer.close();
     }
@@ -92,8 +91,8 @@ public class Mp4MuxerMetadataTest {
           new Mp4TimestampData(
               /* creationTimestampSeconds= */ 1_000_000L,
               /* modificationTimestampSeconds= */ 5_000_000L));
-      TrackToken token = muxer.addTrack(/* sortKey= */ 0, FAKE_VIDEO_FORMAT);
+      int trackId = muxer.addTrack(/* sortKey= */ 0, FAKE_VIDEO_FORMAT);
-      muxer.writeSampleData(token, sampleAndSampleInfo.first, sampleAndSampleInfo.second);
+      muxer.writeSampleData(trackId, sampleAndSampleInfo.first, sampleAndSampleInfo.second);
 
       muxer.addMetadataEntry(new Mp4OrientationData(/* orientation= */ 90));
     } finally {
@@ -120,8 +119,8 @@ public class Mp4MuxerMetadataTest {
           new Mp4TimestampData(
               /* creationTimestampSeconds= */ 1_000_000L,
               /* modificationTimestampSeconds= */ 5_000_000L));
-      TrackToken token = muxer.addTrack(/* sortKey= */ 0, FAKE_VIDEO_FORMAT);
+      int trackId = muxer.addTrack(/* sortKey= */ 0, FAKE_VIDEO_FORMAT);
-      muxer.writeSampleData(token, sampleAndSampleInfo.first, sampleAndSampleInfo.second);
+      muxer.writeSampleData(trackId, sampleAndSampleInfo.first, sampleAndSampleInfo.second);
 
       muxer.addMetadataEntry(new Mp4OrientationData(/* orientation= */ 180));
     } finally {
@@ -148,8 +147,8 @@ public class Mp4MuxerMetadataTest {
           new Mp4TimestampData(
               /* creationTimestampSeconds= */ 1_000_000L,
               /* modificationTimestampSeconds= */ 5_000_000L));
-      TrackToken token = muxer.addTrack(/* sortKey= */ 0, FAKE_VIDEO_FORMAT);
+      int trackId = muxer.addTrack(/* sortKey= */ 0, FAKE_VIDEO_FORMAT);
-      muxer.writeSampleData(token, sampleAndSampleInfo.first, sampleAndSampleInfo.second);
+      muxer.writeSampleData(trackId, sampleAndSampleInfo.first, sampleAndSampleInfo.second);
 
       muxer.addMetadataEntry(new Mp4OrientationData(/* orientation= */ 270));
     } finally {
@@ -176,8 +175,8 @@ public class Mp4MuxerMetadataTest {
           new Mp4TimestampData(
               /* creationTimestampSeconds= */ 1_000_000L,
               /* modificationTimestampSeconds= */ 5_000_000L));
-      TrackToken token = muxer.addTrack(/* sortKey= */ 0, FAKE_VIDEO_FORMAT);
+      int trackId = muxer.addTrack(/* sortKey= */ 0, FAKE_VIDEO_FORMAT);
-      muxer.writeSampleData(token, sampleAndSampleInfo.first, sampleAndSampleInfo.second);
+      muxer.writeSampleData(trackId, sampleAndSampleInfo.first, sampleAndSampleInfo.second);
       muxer.addMetadataEntry(new Mp4LocationData(/* latitude= */ 33.0f, /* longitude= */ -120f));
     } finally {
       muxer.close();
@@ -203,8 +202,8 @@ public class Mp4MuxerMetadataTest {
           new Mp4TimestampData(
               /* creationTimestampSeconds= */ 1_000_000L,
               /* modificationTimestampSeconds= */ 5_000_000L));
-      TrackToken token = muxer.addTrack(/* sortKey= */ 0, FAKE_VIDEO_FORMAT);
+      int trackId = muxer.addTrack(/* sortKey= */ 0, FAKE_VIDEO_FORMAT);
-      muxer.writeSampleData(token, sampleAndSampleInfo.first, sampleAndSampleInfo.second);
+      muxer.writeSampleData(trackId, sampleAndSampleInfo.first, sampleAndSampleInfo.second);
     } finally {
       muxer.close();
     }
@@ -233,8 +232,8 @@ public class Mp4MuxerMetadataTest {
       muxer.addMetadataEntry(
           new MdtaMetadataEntry(
               KEY_ANDROID_CAPTURE_FPS, Util.toByteArray(captureFps), TYPE_INDICATOR_FLOAT32));
-      TrackToken token = muxer.addTrack(/* sortKey= */ 0, FAKE_VIDEO_FORMAT);
+      int trackId = muxer.addTrack(/* sortKey= */ 0, FAKE_VIDEO_FORMAT);
-      muxer.writeSampleData(token, sampleAndSampleInfo.first, sampleAndSampleInfo.second);
+      muxer.writeSampleData(trackId, sampleAndSampleInfo.first, sampleAndSampleInfo.second);
     } finally {
       muxer.close();
     }
@@ -262,8 +261,8 @@ public class Mp4MuxerMetadataTest {
       muxer.addMetadataEntry(
           new MdtaMetadataEntry(
               "SomeStringKey", Util.getUtf8Bytes("Some Random String"), TYPE_INDICATOR_STRING));
-      TrackToken token = muxer.addTrack(/* sortKey= */ 0, FAKE_VIDEO_FORMAT);
+      int trackId = muxer.addTrack(/* sortKey= */ 0, FAKE_VIDEO_FORMAT);
-      muxer.writeSampleData(token, sampleAndSampleInfo.first, sampleAndSampleInfo.second);
+      muxer.writeSampleData(trackId, sampleAndSampleInfo.first, sampleAndSampleInfo.second);
     } finally {
       muxer.close();
     }
@@ -289,10 +288,10 @@ public class Mp4MuxerMetadataTest {
       muxer.addMetadataEntry(
           new MdtaMetadataEntry(metadataKey, metadataValue, TYPE_INDICATOR_STRING));
     }
-    TrackToken token = muxer.addTrack(FAKE_VIDEO_FORMAT);
+    int trackId = muxer.addTrack(FAKE_VIDEO_FORMAT);
 
     try {
-      muxer.writeSampleData(token, sampleAndSampleInfo.first, sampleAndSampleInfo.second);
+      muxer.writeSampleData(trackId, sampleAndSampleInfo.first, sampleAndSampleInfo.second);
       assertThat(sampleAndSampleInfo.first.remaining()).isEqualTo(0);
     } finally {
       muxer.close();
@@ -313,8 +312,8 @@ public class Mp4MuxerMetadataTest {
       muxer.addMetadataEntry(
           new MdtaMetadataEntry(
               "SomeStringKey", Util.toByteArray(floatValue), TYPE_INDICATOR_FLOAT32));
-      TrackToken token = muxer.addTrack(/* sortKey= */ 0, FAKE_VIDEO_FORMAT);
+      int trackId = muxer.addTrack(/* sortKey= */ 0, FAKE_VIDEO_FORMAT);
-      muxer.writeSampleData(token, sampleAndSampleInfo.first, sampleAndSampleInfo.second);
+      muxer.writeSampleData(trackId, sampleAndSampleInfo.first, sampleAndSampleInfo.second);
     } finally {
       muxer.close();
     }
@@ -342,8 +341,8 @@ public class Mp4MuxerMetadataTest {
       Context context = ApplicationProvider.getApplicationContext();
       byte[] xmpBytes = TestUtil.getByteArray(context, XMP_SAMPLE_DATA);
       muxer.addMetadataEntry(new XmpData(xmpBytes));
-      TrackToken token = muxer.addTrack(0, FAKE_VIDEO_FORMAT);
+      int trackId = muxer.addTrack(0, FAKE_VIDEO_FORMAT);
-      muxer.writeSampleData(token, sampleAndSampleInfo.first, sampleAndSampleInfo.second);
+      muxer.writeSampleData(trackId, sampleAndSampleInfo.first, sampleAndSampleInfo.second);
     } finally {
       muxer.close();
     }

libraries/transformer/src/androidTest/java/androidx/media3/transformer/TransformerPauseResumeTest.java

@@ -24,7 +24,6 @@ import static org.junit.Assume.assumeFalse;
 
 import android.content.Context;
 import android.media.MediaCodec.BufferInfo;
-import androidx.annotation.Nullable;
 import androidx.media3.common.C;
 import androidx.media3.common.Effect;
 import androidx.media3.common.Format;
@@ -448,7 +447,7 @@ public class TransformerPauseResumeTest {
     private final FrameBlockingMuxer.Listener listener;
 
     private boolean notifiedListener;
-    @Nullable private TrackToken videoTrackToken;
+    private int videoTrackId;
 
     private FrameBlockingMuxer(Muxer wrappedMuxer, FrameBlockingMuxer.Listener listener) {
       this.wrappedMuxer = wrappedMuxer;
@@ -456,18 +455,18 @@ public class TransformerPauseResumeTest {
     }
 
     @Override
-    public TrackToken addTrack(Format format) throws MuxerException {
+    public int addTrack(Format format) throws MuxerException {
-      TrackToken trackToken = wrappedMuxer.addTrack(format);
+      int trackId = wrappedMuxer.addTrack(format);
       if (MimeTypes.isVideo(format.sampleMimeType)) {
-        videoTrackToken = trackToken;
+        videoTrackId = trackId;
       }
-      return trackToken;
+      return trackId;
     }
 
     @Override
-    public void writeSampleData(TrackToken trackToken, ByteBuffer data, BufferInfo bufferInfo)
+    public void writeSampleData(int trackId, ByteBuffer data, BufferInfo bufferInfo)
         throws MuxerException {
-      if (trackToken == videoTrackToken
+      if (trackId == videoTrackId
           && bufferInfo.presentationTimeUs >= DEFAULT_PRESENTATION_TIME_US_TO_BLOCK_FRAME) {
         if (!notifiedListener) {
           listener.onFrameBlocked();
@@ -475,7 +474,7 @@ public class TransformerPauseResumeTest {
         }
         return;
       }
-      wrappedMuxer.writeSampleData(trackToken, data, bufferInfo);
+      wrappedMuxer.writeSampleData(trackId, data, bufferInfo);
     }
 
     @Override

libraries/transformer/src/main/java/androidx/media3/transformer/DefaultMuxer.java

@@ -84,14 +84,14 @@ public final class DefaultMuxer implements Muxer {
   }
 
   @Override
-  public TrackToken addTrack(Format format) throws MuxerException {
+  public int addTrack(Format format) throws MuxerException {
     return muxer.addTrack(format);
   }
 
   @Override
-  public void writeSampleData(TrackToken trackToken, ByteBuffer byteBuffer, BufferInfo bufferInfo)
+  public void writeSampleData(int trackId, ByteBuffer byteBuffer, BufferInfo bufferInfo)
       throws MuxerException {
-    muxer.writeSampleData(trackToken, byteBuffer, bufferInfo);
+    muxer.writeSampleData(trackId, byteBuffer, bufferInfo);
   }
 
   @Override

libraries/transformer/src/main/java/androidx/media3/transformer/FrameworkMuxer.java

@@ -24,7 +24,7 @@ import android.annotation.SuppressLint;
 import android.media.MediaCodec.BufferInfo;
 import android.media.MediaFormat;
 import android.media.MediaMuxer;
-import androidx.annotation.Nullable;
+import android.util.SparseArray;
 import androidx.media3.common.C;
 import androidx.media3.common.Format;
 import androidx.media3.common.Metadata;
@@ -40,9 +40,7 @@ import com.google.errorprone.annotations.CanIgnoreReturnValue;
 import java.io.IOException;
 import java.lang.reflect.Field;
 import java.nio.ByteBuffer;
-import java.util.HashMap;
 import java.util.Locale;
-import java.util.Map;
 
 /** {@link Muxer} implementation that uses a {@link MediaMuxer}. */
 /* package */ final class FrameworkMuxer implements Muxer {
@@ -105,13 +103,14 @@ import java.util.Map;
   private static final ImmutableList<String> SUPPORTED_AUDIO_SAMPLE_MIME_TYPES =
       ImmutableList.of(MimeTypes.AUDIO_AAC, MimeTypes.AUDIO_AMR_NB, MimeTypes.AUDIO_AMR_WB);
   private static final String TAG = "FrameworkMuxer";
+  private static final int TRACK_ID_UNSET = -1;
 
   private final MediaMuxer mediaMuxer;
   private final long videoDurationUs;
-  private final Map<TrackToken, Long> trackTokenToLastPresentationTimeUs;
+  private final SparseArray<Long> trackIdToLastPresentationTimeUs;
-  private final Map<TrackToken, Long> trackTokenToPresentationTimeOffsetUs;
+  private final SparseArray<Long> trackIdToPresentationTimeOffsetUs;
 
-  @Nullable private TrackToken videoTrackToken;
+  private int videoTrackId;
 
   private boolean isStarted;
   private boolean isReleased;
@@ -119,12 +118,13 @@ import java.util.Map;
   private FrameworkMuxer(MediaMuxer mediaMuxer, long videoDurationUs) {
     this.mediaMuxer = mediaMuxer;
     this.videoDurationUs = videoDurationUs;
-    trackTokenToLastPresentationTimeUs = new HashMap<>();
+    trackIdToLastPresentationTimeUs = new SparseArray<>();
-    trackTokenToPresentationTimeOffsetUs = new HashMap<>();
+    trackIdToPresentationTimeOffsetUs = new SparseArray<>();
+    videoTrackId = TRACK_ID_UNSET;
   }
 
   @Override
-  public TrackToken addTrack(Format format) throws MuxerException {
+  public int addTrack(Format format) throws MuxerException {
     String sampleMimeType = checkNotNull(format.sampleMimeType);
     MediaFormat mediaFormat;
     boolean isVideo = MimeTypes.isVideo(sampleMimeType);
@@ -150,20 +150,19 @@ import java.util.Map;
       throw new MuxerException("Failed to add track with format=" + format, e);
     }
 
-    TrackToken trackToken = new TrackTokenImpl(trackIndex);
     if (isVideo) {
-      videoTrackToken = trackToken;
+      videoTrackId = trackIndex;
     }
 
-    return trackToken;
+    return trackIndex;
   }
 
   @Override
-  public void writeSampleData(TrackToken trackToken, ByteBuffer data, BufferInfo bufferInfo)
+  public void writeSampleData(int trackId, ByteBuffer data, BufferInfo bufferInfo)
       throws MuxerException {
     long presentationTimeUs = bufferInfo.presentationTimeUs;
     if (videoDurationUs != C.TIME_UNSET
-        && trackToken == videoTrackToken
+        && trackId == videoTrackId
         && presentationTimeUs > videoDurationUs) {
       Log.w(
           TAG,
@@ -176,20 +175,18 @@ import java.util.Map;
     }
     if (!isStarted) {
       if (Util.SDK_INT < 30 && presentationTimeUs < 0) {
-        trackTokenToPresentationTimeOffsetUs.put(trackToken, -presentationTimeUs);
+        trackIdToPresentationTimeOffsetUs.put(trackId, -presentationTimeUs);
       }
       startMuxer();
     }
 
     long presentationTimeOffsetUs =
-        trackTokenToPresentationTimeOffsetUs.containsKey(trackToken)
+        trackIdToPresentationTimeOffsetUs.get(trackId, /* valueIfKeyNotFound= */ 0L);
-            ? trackTokenToPresentationTimeOffsetUs.get(trackToken)
-            : 0;
     presentationTimeUs += presentationTimeOffsetUs;
 
     long lastSamplePresentationTimeUs =
-        trackTokenToLastPresentationTimeUs.containsKey(trackToken)
+        Util.contains(trackIdToLastPresentationTimeUs, trackId)
-            ? trackTokenToLastPresentationTimeUs.get(trackToken)
+            ? trackIdToLastPresentationTimeUs.get(trackId)
             : 0;
     // writeSampleData blocks on old API versions, so check here to avoid calling the method.
     checkState(
@@ -199,7 +196,7 @@ import java.util.Map;
             + " < "
             + lastSamplePresentationTimeUs
             + ") unsupported on this API version");
-    trackTokenToLastPresentationTimeUs.put(trackToken, presentationTimeUs);
+    trackIdToLastPresentationTimeUs.put(trackId, presentationTimeUs);
 
     checkState(
         presentationTimeOffsetUs == 0 || presentationTimeUs >= 0,
@@ -212,8 +209,8 @@ import java.util.Map;
     bufferInfo.set(bufferInfo.offset, bufferInfo.size, presentationTimeUs, bufferInfo.flags);
 
     try {
-      checkState(trackToken instanceof TrackTokenImpl);
+
-      mediaMuxer.writeSampleData(((TrackTokenImpl) trackToken).trackIndex, data, bufferInfo);
+      mediaMuxer.writeSampleData(trackId, data, bufferInfo);
     } catch (RuntimeException e) {
       throw new MuxerException(
           "Failed to write sample for presentationTimeUs="
@@ -244,14 +241,14 @@ import java.util.Map;
       startMuxer();
     }
 
-    if (videoDurationUs != C.TIME_UNSET && videoTrackToken != null) {
+    if (videoDurationUs != C.TIME_UNSET && videoTrackId != TRACK_ID_UNSET) {
       BufferInfo bufferInfo = new BufferInfo();
       bufferInfo.set(
           /* newOffset= */ 0,
           /* newSize= */ 0,
           videoDurationUs,
           TransformerUtil.getMediaCodecFlags(C.BUFFER_FLAG_END_OF_STREAM));
-      writeSampleData(checkNotNull(videoTrackToken), ByteBuffer.allocateDirect(0), bufferInfo);
+      writeSampleData(videoTrackId, ByteBuffer.allocateDirect(0), bufferInfo);
     }
 
     isStarted = false;
@@ -314,12 +311,4 @@ import java.util.Map;
     }
     return supportedMimeTypes.build();
   }
-
-  private static class TrackTokenImpl implements TrackToken {
-    public final int trackIndex;
-
-    public TrackTokenImpl(int trackIndex) {
-      this.trackIndex = trackIndex;
-    }
-  }
 }

libraries/transformer/src/main/java/androidx/media3/transformer/InAppMuxer.java

@@ -15,7 +15,6 @@
  */
 package androidx.media3.transformer;
 
-import static androidx.media3.common.util.Assertions.checkNotNull;
 import static androidx.media3.muxer.Mp4Muxer.LAST_SAMPLE_DURATION_BEHAVIOR_SET_FROM_END_OF_STREAM_BUFFER_OR_DUPLICATE_PREVIOUS;
 
 import android.media.MediaCodec;
@@ -207,13 +206,14 @@ public final class InAppMuxer implements Muxer {
   }
 
   private static final String TAG = "InAppMuxer";
+  private static final int TRACK_ID_UNSET = -1;
 
   private final Muxer muxer;
   @Nullable private final MetadataProvider metadataProvider;
   private final long videoDurationUs;
   private final Set<Metadata.Entry> metadataEntries;
 
-  @Nullable private TrackToken videoTrackToken;
+  private int videoTrackId;
 
   private InAppMuxer(
       Muxer muxer, @Nullable MetadataProvider metadataProvider, long videoDurationUs) {
@@ -221,23 +221,24 @@ public final class InAppMuxer implements Muxer {
     this.metadataProvider = metadataProvider;
     this.videoDurationUs = videoDurationUs;
     metadataEntries = new LinkedHashSet<>();
+    videoTrackId = TRACK_ID_UNSET;
   }
 
   @Override
-  public TrackToken addTrack(Format format) throws MuxerException {
+  public int addTrack(Format format) throws MuxerException {
-    TrackToken trackToken = muxer.addTrack(format);
+    int trackId = muxer.addTrack(format);
     if (MimeTypes.isVideo(format.sampleMimeType)) {
       muxer.addMetadataEntry(new Mp4OrientationData(format.rotationDegrees));
-      videoTrackToken = trackToken;
+      videoTrackId = trackId;
     }
-    return trackToken;
+    return trackId;
   }
 
   @Override
-  public void writeSampleData(TrackToken trackToken, ByteBuffer byteBuffer, BufferInfo bufferInfo)
+  public void writeSampleData(int trackId, ByteBuffer byteBuffer, BufferInfo bufferInfo)
       throws MuxerException {
     if (videoDurationUs != C.TIME_UNSET
-        && trackToken == videoTrackToken
+        && trackId == videoTrackId
         && bufferInfo.presentationTimeUs > videoDurationUs) {
       Log.w(
           TAG,
@@ -248,7 +249,7 @@ public final class InAppMuxer implements Muxer {
               videoDurationUs));
       return;
     }
-    muxer.writeSampleData(trackToken, byteBuffer, bufferInfo);
+    muxer.writeSampleData(trackId, byteBuffer, bufferInfo);
   }
 
   @Override
@@ -260,14 +261,14 @@ public final class InAppMuxer implements Muxer {
 
   @Override
   public void close() throws MuxerException {
-    if (videoDurationUs != C.TIME_UNSET && videoTrackToken != null) {
+    if (videoDurationUs != C.TIME_UNSET && videoTrackId != TRACK_ID_UNSET) {
       BufferInfo bufferInfo = new BufferInfo();
       bufferInfo.set(
           /* newOffset= */ 0,
           /* newSize= */ 0,
           videoDurationUs,
           MediaCodec.BUFFER_FLAG_END_OF_STREAM);
-      writeSampleData(checkNotNull(videoTrackToken), ByteBuffer.allocateDirect(0), bufferInfo);
+      writeSampleData(videoTrackId, ByteBuffer.allocateDirect(0), bufferInfo);
     }
     writeMetadata();
     muxer.close();

libraries/transformer/src/main/java/androidx/media3/transformer/MuxerWrapper.java

@@ -48,7 +48,6 @@ import androidx.media3.common.util.Util;
 import androidx.media3.container.NalUnitUtil;
 import androidx.media3.effect.DebugTraceUtil;
 import androidx.media3.muxer.Muxer;
-import androidx.media3.muxer.Muxer.TrackToken;
 import androidx.media3.muxer.MuxerException;
 import com.google.common.collect.ImmutableList;
 import java.io.File;
@@ -580,7 +579,7 @@ import org.checkerframework.checker.nullness.qual.MonotonicNonNull;
         data.remaining(),
         presentationTimeUs,
         TransformerUtil.getMediaCodecFlags(isKeyFrame ? C.BUFFER_FLAG_KEY_FRAME : 0));
-    muxer.writeSampleData(trackInfo.trackToken, data, bufferInfo);
+    muxer.writeSampleData(trackInfo.trackId, data, bufferInfo);
 
     DebugTraceUtil.logEvent(
         COMPONENT_MUXER,
@@ -749,16 +748,16 @@ import org.checkerframework.checker.nullness.qual.MonotonicNonNull;
 
   private static final class TrackInfo {
     public final Format format;
-    public final TrackToken trackToken;
+    public final int trackId;
 
     public long startTimeUs;
     public long bytesWritten;
     public int sampleCount;
     public long timeUs;
 
-    public TrackInfo(Format format, TrackToken trackToken) {
+    public TrackInfo(Format format, int trackId) {
       this.format = format;
-      this.trackToken = trackToken;
+      this.trackId = trackId;
     }
 
     /**

libraries/transformer/src/main/java/androidx/media3/transformer/NoWriteMuxer.java

@@ -63,13 +63,12 @@ import java.nio.ByteBuffer;
   }
 
   @Override
-  public TrackToken addTrack(Format format) {
+  public int addTrack(Format format) {
-    return new TrackToken() {};
+    return 0;
   }
 
   @Override
-  public void writeSampleData(
+  public void writeSampleData(int trackId, ByteBuffer data, MediaCodec.BufferInfo bufferInfo) {}
-      TrackToken trackToken, ByteBuffer data, MediaCodec.BufferInfo bufferInfo) {}
 
   @Override
   public void addMetadataEntry(Metadata.Entry metadataEntry) {}

libraries/transformer/src/test/java/androidx/media3/transformer/CapturingMuxer.java

@@ -38,8 +38,6 @@ import java.util.ArrayList;
 import java.util.Arrays;
 import java.util.Collections;
 import java.util.Comparator;
-import java.util.HashMap;
-import java.util.Map;
 
 /**
  * A {@link Dumpable} {@link Muxer} implementation that supports dumping information about all
@@ -88,7 +86,7 @@ public final class CapturingMuxer implements Muxer, Dumpable {
   private final boolean handleAudioAsPcm;
   private final SparseArray<DumpableFormat> dumpableFormatByTrackType;
   private final SparseArray<DumpableStream> dumpableStreamByTrackType;
-  private final Map<TrackToken, Integer> trackTokenToType;
+  private final SparseArray<Integer> trackIdToType;
   private final ArrayList<Metadata.Entry> metadataList;
   private boolean released;
 
@@ -98,18 +96,18 @@ public final class CapturingMuxer implements Muxer, Dumpable {
     this.handleAudioAsPcm = handleAudioAsPcm;
     dumpableFormatByTrackType = new SparseArray<>();
     dumpableStreamByTrackType = new SparseArray<>();
-    trackTokenToType = new HashMap<>();
+    trackIdToType = new SparseArray<>();
     metadataList = new ArrayList<>();
   }
 
   // Muxer implementation.
 
   @Override
-  public TrackToken addTrack(Format format) throws MuxerException {
+  public int addTrack(Format format) throws MuxerException {
-    TrackToken trackToken = wrappedMuxer.addTrack(format);
+    int trackId = wrappedMuxer.addTrack(format);
     @C.TrackType int trackType = getProcessedTrackType(format.sampleMimeType);
 
-    trackTokenToType.put(trackToken, trackType);
+    trackIdToType.put(trackId, trackType);
 
     dumpableFormatByTrackType.append(
         trackType, new DumpableFormat(format, /* tag= */ Util.getTrackTypeString(trackType)));
@@ -120,20 +118,20 @@ public final class CapturingMuxer implements Muxer, Dumpable {
             ? new DumpablePcmAudioStream(trackType)
             : new DumpableStream(trackType));
 
-    return trackToken;
+    return trackId;
   }
 
   @Override
-  public void writeSampleData(TrackToken trackToken, ByteBuffer data, BufferInfo bufferInfo)
+  public void writeSampleData(int trackId, ByteBuffer data, BufferInfo bufferInfo)
       throws MuxerException {
-    @C.TrackType int trackType = checkNotNull(trackTokenToType.get(trackToken));
+    @C.TrackType int trackType = checkNotNull(trackIdToType.get(trackId));
     dumpableStreamByTrackType
         .get(trackType)
         .addSample(
             data,
             (bufferInfo.flags & C.BUFFER_FLAG_KEY_FRAME) == C.BUFFER_FLAG_KEY_FRAME,
             bufferInfo.presentationTimeUs);
-    wrappedMuxer.writeSampleData(trackToken, data, bufferInfo);
+    wrappedMuxer.writeSampleData(trackId, data, bufferInfo);
   }
 
   @Override