diff --git a/libraries/transformer/src/main/java/androidx/media3/transformer/Muxer.java b/libraries/transformer/src/main/java/androidx/media3/transformer/Muxer.java
index be0b0de1ef..cebf94d7eb 100644
--- a/libraries/transformer/src/main/java/androidx/media3/transformer/Muxer.java
+++ b/libraries/transformer/src/main/java/androidx/media3/transformer/Muxer.java
@@ -80,10 +80,10 @@ public interface Muxer {
   }
 
   /**
-   * Adds a track with the specified format, and returns its index (to be passed in subsequent calls
-   * to {@link #writeSampleData(int, ByteBuffer, boolean, long)}).
+   * Adds a track with the specified format.
    *
    * @param format The {@link Format} of the track.
+   * @return The index for this track, which should be passed to {@link #writeSampleData}.
    * @throws MuxerException If the muxer encounters a problem while adding the track.
    */
   int addTrack(Format format) throws MuxerException;
diff --git a/libraries/transformer/src/main/java/androidx/media3/transformer/MuxerWrapper.java b/libraries/transformer/src/main/java/androidx/media3/transformer/MuxerWrapper.java
index 98b09dfc69..0e3e03412d 100644
--- a/libraries/transformer/src/main/java/androidx/media3/transformer/MuxerWrapper.java
+++ b/libraries/transformer/src/main/java/androidx/media3/transformer/MuxerWrapper.java
@@ -16,15 +16,15 @@
 
 package androidx.media3.transformer;
 
+import static androidx.media3.common.util.Assertions.checkArgument;
 import static androidx.media3.common.util.Assertions.checkNotNull;
 import static androidx.media3.common.util.Assertions.checkState;
-import static androidx.media3.common.util.Util.maxValue;
-import static androidx.media3.common.util.Util.minValue;
+import static java.lang.Math.max;
+import static java.lang.Math.min;
 import static java.util.concurrent.TimeUnit.MILLISECONDS;
 
 import android.os.ParcelFileDescriptor;
-import android.util.SparseIntArray;
-import android.util.SparseLongArray;
+import android.util.SparseArray;
 import androidx.annotation.IntRange;
 import androidx.annotation.Nullable;
 import androidx.media3.common.C;
@@ -49,7 +49,8 @@ import org.checkerframework.checker.nullness.qual.RequiresNonNull;
 /* package */ final class MuxerWrapper {
 
   public interface Listener {
-    void onTrackEnded(@C.TrackType int trackType, int averageBitrate, int sampleCount);
+    void onTrackEnded(
+        @C.TrackType int trackType, Format format, int averageBitrate, int sampleCount);
 
     void onEnded(long durationMs, long fileSizeBytes);
 
@@ -68,18 +69,15 @@ import org.checkerframework.checker.nullness.qual.RequiresNonNull;
   @Nullable private final ParcelFileDescriptor outputParcelFileDescriptor;
   private final Muxer.Factory muxerFactory;
   private final Listener listener;
-  private final SparseIntArray trackTypeToIndex;
-  private final SparseIntArray trackTypeToSampleCount;
-  private final SparseLongArray trackTypeToTimeUs;
-  private final SparseLongArray trackTypeToBytesWritten;
+  private final SparseArray<TrackInfo> trackTypeToInfo;
   private final ScheduledExecutorService abortScheduledExecutorService;
 
   private int trackCount;
-  private int trackFormatCount;
   private boolean isReady;
   private boolean isEnded;
   private @C.TrackType int previousTrackType;
   private long minTrackTimeUs;
+  private long maxEndedTrackTimeUs;
   private @MonotonicNonNull ScheduledFuture<?> abortScheduledFuture;
   private boolean isAborted;
   private @MonotonicNonNull Muxer muxer;
@@ -98,10 +96,7 @@ import org.checkerframework.checker.nullness.qual.RequiresNonNull;
     this.muxerFactory = muxerFactory;
     this.listener = listener;
 
-    trackTypeToIndex = new SparseIntArray();
-    trackTypeToSampleCount = new SparseIntArray();
-    trackTypeToTimeUs = new SparseLongArray();
-    trackTypeToBytesWritten = new SparseLongArray();
+    trackTypeToInfo = new SparseArray<>();
     previousTrackType = C.TRACK_TYPE_NONE;
     abortScheduledExecutorService = Executors.newSingleThreadScheduledExecutor();
   }
@@ -117,7 +112,7 @@ import org.checkerframework.checker.nullness.qual.RequiresNonNull;
    */
   public void setTrackCount(@IntRange(from = 1) int trackCount) {
     checkState(
-        trackFormatCount == 0,
+        trackTypeToInfo.size() == 0,
         "The track count cannot be set after track formats have been added.");
     this.trackCount = trackCount;
   }
@@ -151,25 +146,21 @@ import org.checkerframework.checker.nullness.qual.RequiresNonNull;
    */
   public void addTrackFormat(Format format) throws Muxer.MuxerException {
     checkState(trackCount > 0, "The track count should be set before the formats are added.");
-    checkState(trackFormatCount < trackCount, "All track formats have already been added.");
+    checkState(trackTypeToInfo.size() < trackCount, "All track formats have already been added.");
     @Nullable String sampleMimeType = format.sampleMimeType;
     boolean isAudio = MimeTypes.isAudio(sampleMimeType);
     boolean isVideo = MimeTypes.isVideo(sampleMimeType);
     checkState(isAudio || isVideo, "Unsupported track format: " + sampleMimeType);
     @C.TrackType int trackType = MimeTypes.getTrackType(sampleMimeType);
+    // SparseArray.get() returns null by default if the value is not found.
     checkState(
-        trackTypeToIndex.get(trackType, /* valueIfKeyNotFound= */ C.INDEX_UNSET) == C.INDEX_UNSET,
-        "There is already a track of type " + trackType);
+        trackTypeToInfo.get(trackType) == null, "There is already a track of type " + trackType);
 
     ensureMuxerInitialized();
 
-    int trackIndex = muxer.addTrack(format);
-    trackTypeToIndex.put(trackType, trackIndex);
-    trackTypeToSampleCount.put(trackType, 0);
-    trackTypeToTimeUs.put(trackType, 0L);
-    trackTypeToBytesWritten.put(trackType, 0L);
-    trackFormatCount++;
-    if (trackFormatCount == trackCount) {
+    TrackInfo trackInfo = new TrackInfo(format, muxer.addTrack(format));
+    trackTypeToInfo.put(trackType, trackInfo);
+    if (trackTypeToInfo.size() == trackCount) {
       isReady = true;
       resetAbortTimer();
     }
@@ -193,25 +184,22 @@ import org.checkerframework.checker.nullness.qual.RequiresNonNull;
   public boolean writeSample(
       @C.TrackType int trackType, ByteBuffer data, boolean isKeyFrame, long presentationTimeUs)
       throws Muxer.MuxerException {
-    int trackIndex = trackTypeToIndex.get(trackType, /* valueIfKeyNotFound= */ C.INDEX_UNSET);
-    checkState(
-        trackIndex != C.INDEX_UNSET,
-        "Could not write sample because there is no track of type " + trackType);
+    @Nullable TrackInfo trackInfo = trackTypeToInfo.get(trackType);
+    // SparseArray.get() returns null by default if the value is not found.
+    checkArgument(
+        trackInfo != null, "Could not write sample because there is no track of type " + trackType);
 
     if (!canWriteSampleOfType(trackType)) {
       return false;
     }
 
-    trackTypeToSampleCount.put(trackType, trackTypeToSampleCount.get(trackType) + 1);
-    trackTypeToBytesWritten.put(
-        trackType, trackTypeToBytesWritten.get(trackType) + data.remaining());
-    if (trackTypeToTimeUs.get(trackType) < presentationTimeUs) {
-      trackTypeToTimeUs.put(trackType, presentationTimeUs);
-    }
+    trackInfo.sampleCount++;
+    trackInfo.bytesWritten += data.remaining();
+    trackInfo.timeUs = max(trackInfo.timeUs, presentationTimeUs);
 
     checkNotNull(muxer);
     resetAbortTimer();
-    muxer.writeSampleData(trackIndex, data, isKeyFrame, presentationTimeUs);
+    muxer.writeSampleData(trackInfo.index, data, isKeyFrame, presentationTimeUs);
     previousTrackType = trackType;
     return true;
   }
@@ -223,17 +211,22 @@ import org.checkerframework.checker.nullness.qual.RequiresNonNull;
    * @param trackType The {@link C.TrackType track type}.
    */
   public void endTrack(@C.TrackType int trackType) {
-    listener.onTrackEnded(
-        trackType,
-        getTrackAverageBitrate(trackType),
-        trackTypeToSampleCount.get(trackType, /* valueIfKeyNotFound= */ 0));
+    @Nullable TrackInfo trackInfo = trackTypeToInfo.get(trackType);
+    if (trackInfo == null) {
+      // SparseArray.get() returns null by default if the value is not found.
+      return;
+    }
 
-    trackTypeToIndex.delete(trackType);
-    if (trackTypeToIndex.size() == 0) {
+    maxEndedTrackTimeUs = max(maxEndedTrackTimeUs, trackInfo.timeUs);
+    listener.onTrackEnded(
+        trackType, trackInfo.format, trackInfo.getAverageBitrate(), trackInfo.sampleCount);
+
+    trackTypeToInfo.delete(trackType);
+    if (trackTypeToInfo.size() == 0) {
       abortScheduledExecutorService.shutdownNow();
       if (!isEnded) {
         isEnded = true;
-        listener.onEnded(getDurationMs(), getCurrentOutputSizeBytes());
+        listener.onEnded(Util.usToMs(maxEndedTrackTimeUs), getCurrentOutputSizeBytes());
       }
     }
   }
@@ -273,18 +266,20 @@ import org.checkerframework.checker.nullness.qual.RequiresNonNull;
    *     track of the given track type.
    */
   private boolean canWriteSampleOfType(int trackType) {
-    long trackTimeUs = trackTypeToTimeUs.get(trackType, /* valueIfKeyNotFound= */ C.TIME_UNSET);
-    checkState(trackTimeUs != C.TIME_UNSET);
+    @Nullable TrackInfo trackInfo = trackTypeToInfo.get(trackType);
+    // SparseArray.get() returns null by default if the value is not found.
+    checkArgument(trackInfo != null, "There is no track of type " + trackType);
+
     if (!isReady) {
       return false;
     }
-    if (trackTypeToIndex.size() == 1) {
+    if (trackTypeToInfo.size() == 1) {
       return true;
     }
     if (trackType != previousTrackType) {
-      minTrackTimeUs = minValue(trackTypeToTimeUs);
+      minTrackTimeUs = getMinTrackTimeUs(trackTypeToInfo);
     }
-    return trackTimeUs - minTrackTimeUs <= MAX_TRACK_WRITE_AHEAD_US;
+    return trackInfo.timeUs - minTrackTimeUs <= MAX_TRACK_WRITE_AHEAD_US;
   }
 
   @RequiresNonNull("muxer")
@@ -327,17 +322,6 @@ import org.checkerframework.checker.nullness.qual.RequiresNonNull;
     }
   }
 
-  /**
-   * Returns the duration of the longest track in milliseconds, or {@link C#TIME_UNSET} if there is
-   * no track.
-   */
-  private long getDurationMs() {
-    if (trackTypeToTimeUs.size() == 0) {
-      return C.TIME_UNSET;
-    }
-    return Util.usToMs(maxValue(trackTypeToTimeUs));
-  }
-
   /** Returns the current size in bytes of the output, or {@link C#LENGTH_UNSET} if unavailable. */
   private long getCurrentOutputSizeBytes() {
     long fileSize = C.LENGTH_UNSET;
@@ -351,22 +335,47 @@ import org.checkerframework.checker.nullness.qual.RequiresNonNull;
     return fileSize > 0 ? fileSize : C.LENGTH_UNSET;
   }
 
-  /**
-   * 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.
-   */
-  private int getTrackAverageBitrate(@C.TrackType int trackType) {
-    long trackDurationUs = trackTypeToTimeUs.get(trackType, /* valueIfKeyNotFound= */ -1);
-    long trackBytes = trackTypeToBytesWritten.get(trackType, /* valueIfKeyNotFound= */ -1);
-    if (trackDurationUs <= 0 || trackBytes <= 0) {
-      return C.RATE_UNSET_INT;
+  private static long getMinTrackTimeUs(SparseArray<TrackInfo> trackTypeToInfo) {
+    if (trackTypeToInfo.size() == 0) {
+      return C.TIME_UNSET;
+    }
+
+    long minTrackTimeUs = Long.MAX_VALUE;
+    for (int i = 0; i < trackTypeToInfo.size(); i++) {
+      minTrackTimeUs = min(minTrackTimeUs, trackTypeToInfo.valueAt(i).timeUs);
+    }
+    return minTrackTimeUs;
+  }
+
+  private static final class TrackInfo {
+    public final Format format;
+    public final int index;
+
+    public long bytesWritten;
+    public int sampleCount;
+    public long timeUs;
+
+    public TrackInfo(Format format, int index) {
+      this.format = format;
+      this.index = index;
+    }
+
+    /**
+     * Returns the average bitrate of data written to the track, or {@link C#RATE_UNSET_INT} if
+     * there is no track data.
+     */
+    public int getAverageBitrate() {
+      if (timeUs <= 0 || bytesWritten <= 0) {
+        return C.RATE_UNSET_INT;
+      }
+
+      // The number of bytes written is not a timestamp, however this utility method provides
+      // overflow-safe multiplication & division.
+      return (int)
+          Util.scaleLargeTimestamp(
+              /* timestamp= */ bytesWritten,
+              /* multiplier= */ C.BITS_PER_BYTE * C.MICROS_PER_SECOND,
+              /* divisor= */ timeUs);
     }
-    // The number of bytes written is not a timestamp, however this utility method provides
-    // overflow-safe multiplication & division.
-    return (int)
-        Util.scaleLargeTimestamp(
-            /* timestamp= */ trackBytes,
-            /* multiplier= */ C.BITS_PER_BYTE * C.MICROS_PER_SECOND,
-            /* divisor= */ trackDurationUs);
   }
 }
diff --git a/libraries/transformer/src/main/java/androidx/media3/transformer/TransformerInternal.java b/libraries/transformer/src/main/java/androidx/media3/transformer/TransformerInternal.java
index 10e8b5ea5f..2bd8705140 100644
--- a/libraries/transformer/src/main/java/androidx/media3/transformer/TransformerInternal.java
+++ b/libraries/transformer/src/main/java/androidx/media3/transformer/TransformerInternal.java
@@ -465,7 +465,8 @@ import org.checkerframework.checker.nullness.qual.MonotonicNonNull;
     // MuxerWrapper.Listener implementation.
 
     @Override
-    public void onTrackEnded(@C.TrackType int trackType, int averageBitrate, int sampleCount) {
+    public void onTrackEnded(
+        @C.TrackType int trackType, Format format, int averageBitrate, int sampleCount) {
       if (trackType == C.TRACK_TYPE_AUDIO) {
         transformationResultBuilder.setAverageAudioBitrate(averageBitrate);
       } else if (trackType == C.TRACK_TYPE_VIDEO) {