Add CompositionPlayer API to use a custom AudioMixer.Factory

PiperOrigin-RevId: 786264876

Author: ychaparov

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

@@ -123,6 +123,7 @@ public static final class Builder {
 
     private @MonotonicNonNull Looper looper;
     private @MonotonicNonNull AudioSink audioSink;
+    private AudioMixer.Factory audioMixerFactory;
     private MediaSource.Factory mediaSourceFactory;
     private ImageDecoder.Factory imageDecoderFactory;
     private boolean videoPrewarmingEnabled;
@@ -140,6 +141,7 @@ public static final class Builder {
      */
     public Builder(Context context) {
       this.context = context.getApplicationContext();
+      audioMixerFactory = new DefaultAudioMixer.Factory();
       mediaSourceFactory = new DefaultMediaSourceFactory(context);
       imageDecoderFactory =
           new BitmapFactoryImageDecoder.Factory(context)
@@ -177,6 +179,21 @@ public Builder setAudioSink(AudioSink audioSink) {
       return this;
     }
 
+    /**
+     * Sets the {@link AudioMixer.Factory} to be used when {@linkplain AudioMixer audio mixing} is
+     * needed.
+     *
+     * <p>The default value is a {@link DefaultAudioMixer.Factory} with default values.
+     *
+     * @param audioMixerFactory A {@link AudioMixer.Factory}.
+     * @return This builder.
+     */
+    @CanIgnoreReturnValue
+    public Builder setAudioMixerFactory(AudioMixer.Factory audioMixerFactory) {
+      this.audioMixerFactory = audioMixerFactory;
+      return this;
+    }
+
     /**
      * Sets the {@link MediaSource.Factory} that *creates* the {@link MediaSource} for {@link
      * EditedMediaItem#mediaItem MediaItems} in a {@link Composition}.
@@ -359,6 +376,7 @@ public CompositionPlayer build() {
   private final HandlerWrapper applicationHandler;
   private final List<SequencePlayerHolder> playerHolders;
   private final AudioSink finalAudioSink;
+  private final AudioMixer.Factory audioMixerFactory;
   private final MediaSource.Factory mediaSourceFactory;
   private final ImageDecoder.Factory imageDecoderFactory;
   private final VideoGraph.Factory videoGraphFactory;
@@ -406,6 +424,7 @@ private CompositionPlayer(Builder builder) {
     clock = builder.clock;
     applicationHandler = clock.createHandler(builder.looper, /* callback= */ null);
     finalAudioSink = checkNotNull(builder.audioSink);
+    audioMixerFactory = builder.audioMixerFactory;
     mediaSourceFactory = builder.mediaSourceFactory;
     imageDecoderFactory = new GapHandlingDecoderFactory(builder.imageDecoderFactory);
     videoGraphFactory = checkNotNull(builder.videoGraphFactory);
@@ -816,8 +835,7 @@ private void prepareCompositionPlayerInternal() {
     // must done on the playback thread only, to ensure related components are accessed from one
     // thread only.
     playbackAudioGraphWrapper =
-        new PlaybackAudioGraphWrapper(
-            new DefaultAudioMixer.Factory(), checkNotNull(finalAudioSink));
+        new PlaybackAudioGraphWrapper(audioMixerFactory, checkNotNull(finalAudioSink));
     VideoFrameReleaseControl videoFrameReleaseControl =
         new VideoFrameReleaseControl(
             context, new CompositionFrameTimingEvaluator(), /* allowedJoiningTimeMs= */ 0);

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

@@ -28,6 +28,7 @@
 import android.content.Context;
 import androidx.media3.common.MediaItem;
 import androidx.media3.common.Player;
+import androidx.media3.common.audio.AudioProcessor;
 import androidx.media3.exoplayer.audio.AudioSink;
 import androidx.media3.test.utils.CapturingAudioSink;
 import androidx.media3.test.utils.DumpFileAsserts;
@@ -36,7 +37,9 @@
 import androidx.test.core.app.ApplicationProvider;
 import androidx.test.ext.junit.runners.AndroidJUnit4;
 import java.io.IOException;
+import java.nio.ByteBuffer;
 import java.util.concurrent.TimeoutException;
+import java.util.concurrent.atomic.AtomicLong;
 import org.junit.Before;
 import org.junit.Test;
 import org.junit.runner.RunWith;
@@ -720,6 +723,108 @@ public void playSingleSequence_replayAfterEnd_outputCorrectSamples() throws Exce
         PREVIEW_DUMP_FILE_EXTENSION + FILE_AUDIO_RAW + "_playedTwice.dump");
   }
 
+  @Test
+  public void playSingleSequence_withCustomAudioMixer_mixesTheCorrectNumberOfBytes()
+      throws Exception {
+    AtomicLong bytesMixed = new AtomicLong();
+    AudioMixer.Factory forwardingAudioMixerFactory =
+        () ->
+            new ForwardingAudioMixer(new DefaultAudioMixer.Factory().create()) {
+              @Override
+              public void queueInput(int sourceId, ByteBuffer sourceBuffer) {
+                bytesMixed.addAndGet(sourceBuffer.remaining());
+                super.queueInput(sourceId, sourceBuffer);
+              }
+            };
+    CompositionPlayer player =
+        new CompositionPlayer.Builder(context)
+            .setClock(new FakeClock(/* isAutoAdvancing= */ true))
+            .setAudioMixerFactory(forwardingAudioMixerFactory)
+            .build();
+    EditedMediaItem editedMediaItem =
+        new EditedMediaItem.Builder(MediaItem.fromUri(ASSET_URI_PREFIX + FILE_AUDIO_RAW))
+            .setDurationUs(1_000_000L)
+            .build();
+    EditedMediaItemSequence sequence = new EditedMediaItemSequence.Builder(editedMediaItem).build();
+    Composition composition = new Composition.Builder(sequence).build();
+
+    player.setComposition(composition);
+    player.prepare();
+    player.play();
+    TestPlayerRunHelper.advance(player).untilState(Player.STATE_ENDED);
+    player.release();
+
+    // Expect 1 second of single-channel, 44_100Hz, 2 bytes per sample.
+    assertThat(bytesMixed.get()).isEqualTo(88_200);
+  }
+
+  private static class ForwardingAudioMixer implements AudioMixer {
+
+    private final AudioMixer wrappedAudioMixer;
+
+    public ForwardingAudioMixer(AudioMixer audioMixer) {
+      wrappedAudioMixer = audioMixer;
+    }
+
+    @Override
+    public void configure(
+        AudioProcessor.AudioFormat outputAudioFormat, int bufferSizeMs, long startTimeUs)
+        throws AudioProcessor.UnhandledAudioFormatException {
+      wrappedAudioMixer.configure(outputAudioFormat, bufferSizeMs, startTimeUs);
+    }
+
+    @Override
+    public void setEndTimeUs(long endTimeUs) {
+      wrappedAudioMixer.setEndTimeUs(endTimeUs);
+    }
+
+    @Override
+    public boolean supportsSourceAudioFormat(AudioProcessor.AudioFormat sourceFormat) {
+      return wrappedAudioMixer.supportsSourceAudioFormat(sourceFormat);
+    }
+
+    @Override
+    public int addSource(AudioProcessor.AudioFormat sourceFormat, long startTimeUs)
+        throws AudioProcessor.UnhandledAudioFormatException {
+      return wrappedAudioMixer.addSource(sourceFormat, startTimeUs);
+    }
+
+    @Override
+    public boolean hasSource(int sourceId) {
+      return wrappedAudioMixer.hasSource(sourceId);
+    }
+
+    @Override
+    public void setSourceVolume(int sourceId, float volume) {
+      wrappedAudioMixer.setSourceVolume(sourceId, volume);
+    }
+
+    @Override
+    public void removeSource(int sourceId) {
+      wrappedAudioMixer.removeSource(sourceId);
+    }
+
+    @Override
+    public void queueInput(int sourceId, ByteBuffer sourceBuffer) {
+      wrappedAudioMixer.queueInput(sourceId, sourceBuffer);
+    }
+
+    @Override
+    public ByteBuffer getOutput() {
+      return wrappedAudioMixer.getOutput();
+    }
+
+    @Override
+    public boolean isEnded() {
+      return wrappedAudioMixer.isEnded();
+    }
+
+    @Override
+    public void reset() {
+      wrappedAudioMixer.reset();
+    }
+  }
+
   private static CompositionPlayer createCompositionPlayer(Context context, AudioSink audioSink) {
     return new CompositionPlayer.Builder(context)
         .setClock(new FakeClock(/* isAutoAdvancing= */ true))