Handle when some MediaItems require transcoding but others don't

- For single-asset, the behavior stays the same. Transcode if and only
  if it's necessary,
- For constrained multi-asset, always transcode, except if the setter to
  transmux is set. This is to avoid failing if a MediaItem that doesn't
  require transcoding is followed by a MediaItem that does require
  transcoding.

PiperOrigin-RevId: 508097798

library/transformer/src/main/java/com/google/android/exoplayer2/transformer/Transformer.java

@@ -83,6 +83,7 @@ public final class Transformer {
     private boolean removeAudio;
     private boolean removeVideo;
     private boolean flattenForSlowMotion;
+    private boolean transmux;
     private boolean generateSilentAudio;
     private ListenerSet<Transformer.Listener> listeners;
     private AssetLoader.@MonotonicNonNull Factory assetLoaderFactory;
@@ -205,6 +206,28 @@ public final class Transformer {
     }
 
     /**
+     * Sets whether to transmux the {@linkplain MediaItem media items} in the input {@link
+     * Composition}.
+     *
+     * <p>The default value is {@code false}.
+     *
+     * <p>If the input {@link Composition} contains one {@link MediaItem}, the value set is ignored.
+     * The {@link MediaItem} will only be transcoded if necessary.
+     *
+     * <p>If the input {@link Composition} contains multiple {@linkplain MediaItem media items},
+     * they are all transmuxed if {@code transmux} is {@code true} and exporting the first {@link
+     * MediaItem} doesn't require transcoding. Otherwise, they are all transcoded.
+     *
+     * @param transmux Whether to transmux.
+     * @return This builder.
+     */
+    @CanIgnoreReturnValue
+    public Builder setTransmux(boolean transmux) {
+      this.transmux = transmux;
+      return this;
+    }
+
+    /**
      * @deprecated Use {@link #addListener(Listener)}, {@link #removeListener(Listener)} or {@link
      *     #removeAllListeners()} instead.
      */
@@ -421,6 +444,7 @@ public final class Transformer {
           removeAudio,
           removeVideo,
           flattenForSlowMotion,
+          transmux,
           generateSilentAudio,
           listeners,
           assetLoaderFactory,
@@ -578,6 +602,7 @@ public final class Transformer {
   private final boolean removeAudio;
   private final boolean removeVideo;
   private final boolean flattenForSlowMotion;
+  private final boolean transmux;
   private final boolean generateSilentAudio;
   private final ListenerSet<Transformer.Listener> listeners;
   private final AssetLoader.Factory assetLoaderFactory;
@@ -598,6 +623,7 @@ public final class Transformer {
       boolean removeAudio,
       boolean removeVideo,
       boolean flattenForSlowMotion,
+      boolean transmux,
       boolean generateSilentAudio,
       ListenerSet<Listener> listeners,
       AssetLoader.Factory assetLoaderFactory,
@@ -615,6 +641,7 @@ public final class Transformer {
     this.removeAudio = removeAudio;
     this.removeVideo = removeVideo;
     this.flattenForSlowMotion = flattenForSlowMotion;
+    this.transmux = transmux;
     this.generateSilentAudio = generateSilentAudio;
     this.listeners = listeners;
     this.assetLoaderFactory = assetLoaderFactory;
@@ -692,7 +719,6 @@ public final class Transformer {
    *             flattening}).
    *         <li>have identical {@link EditedMediaItem#effects Effects} applied.
    *         <li>not represent an image.
-   *         <li>be such that either all or none requires transcoding.
    *       </ul>
    * </ul>
    *
@@ -735,6 +761,7 @@ public final class Transformer {
             composition,
             path,
             transformationRequest,
+            transmux,
             generateSilentAudio,
             assetLoaderFactory,
             encoderFactory,

library/transformer/src/main/java/com/google/android/exoplayer2/transformer/TransformerInternal.java

@@ -112,6 +112,7 @@ import org.checkerframework.checker.nullness.qual.MonotonicNonNull;
       Composition composition,
       String outputPath,
       TransformationRequest transformationRequest,
+      boolean transmux,
       boolean generateSilentAudio,
       AssetLoader.Factory assetLoaderFactory,
       Codec.EncoderFactory encoderFactory,
@@ -133,7 +134,8 @@ import org.checkerframework.checker.nullness.qual.MonotonicNonNull;
     internalHandlerThread.start();
     Looper internalLooper = internalHandlerThread.getLooper();
     EditedMediaItemSequence sequence = composition.sequences.get(0);
-    ComponentListener componentListener = new ComponentListener(sequence, fallbackListener);
+    ComponentListener componentListener =
+        new ComponentListener(sequence, transmux, fallbackListener);
     compositeAssetLoader =
         new CompositeAssetLoader(
             sequence, assetLoaderFactory, internalLooper, componentListener, clock);
@@ -314,6 +316,8 @@ import org.checkerframework.checker.nullness.qual.MonotonicNonNull;
 
     // The first EditedMediaItem in the sequence determines which SamplePipeline to use.
     private final EditedMediaItem firstEditedMediaItem;
+    private final int mediaItemCount;
+    private final boolean transmux;
     private final FallbackListener fallbackListener;
     private final AtomicInteger trackCount;
 
@@ -321,8 +325,11 @@ import org.checkerframework.checker.nullness.qual.MonotonicNonNull;
 
     private volatile long durationUs;
 
-    public ComponentListener(EditedMediaItemSequence sequence, FallbackListener fallbackListener) {
+    public ComponentListener(
+        EditedMediaItemSequence sequence, boolean transmux, FallbackListener fallbackListener) {
       firstEditedMediaItem = sequence.editedMediaItems.get(0);
+      mediaItemCount = sequence.editedMediaItems.size();
+      this.transmux = transmux;
       this.fallbackListener = fallbackListener;
       trackCount = new AtomicInteger();
       durationUs = C.TIME_UNSET;
@@ -457,10 +464,15 @@ import org.checkerframework.checker.nullness.qual.MonotonicNonNull;
         throws TransformationException {
       checkState(supportedOutputTypes != 0);
       boolean isAudio = MimeTypes.isAudio(firstInputFormat.sampleMimeType);
-      boolean shouldTranscode =
-          isAudio
-              ? shouldTranscodeAudio(firstInputFormat)
-              : shouldTranscodeVideo(firstInputFormat, streamStartPositionUs, streamOffsetUs);
+      boolean shouldTranscode;
+      if (mediaItemCount > 1 && !transmux) {
+        shouldTranscode = true;
+      } else {
+        shouldTranscode =
+            isAudio
+                ? shouldTranscodeAudio(firstInputFormat)
+                : shouldTranscodeVideo(firstInputFormat, streamStartPositionUs, streamOffsetUs);
+      }
       boolean assetLoaderNeverDecodes = (supportedOutputTypes & SUPPORTED_OUTPUT_TYPE_DECODED) == 0;
       checkState(!shouldTranscode || !assetLoaderNeverDecodes);
       boolean assetLoaderAlwaysDecodes =

library/transformer/src/test/java/com/google/android/exoplayer2/transformer/TransformerEndToEndTest.java

@@ -379,7 +379,8 @@ public final class TransformerEndToEndTest {
   @Test
   public void startTransformation_concatenateMediaItemsWithSameFormat_completesSuccessfully()
       throws Exception {
-    Transformer transformer = createTransformerBuilder(/* enableFallback= */ false).build();
+    Transformer transformer =
+        createTransformerBuilder(/* enableFallback= */ false).setTransmux(true).build();
     MediaItem mediaItem = MediaItem.fromUri(ASSET_URI_PREFIX + FILE_AUDIO_VIDEO);
     EditedMediaItem editedMediaItem =
         new EditedMediaItem.Builder(mediaItem).setEffects(Effects.EMPTY).build();
@@ -424,6 +425,51 @@ public final class TransformerEndToEndTest {
   }
 
   @Test
+  public void startTransformation_singleMediaItemAndTransmux_ignoresTransmux() throws Exception {
+    SonicAudioProcessor sonicAudioProcessor = new SonicAudioProcessor();
+    sonicAudioProcessor.setOutputSampleRateHz(48000);
+    Transformer transformer =
+        createTransformerBuilder(/* enableFallback= */ false).setTransmux(true).build();
+    MediaItem mediaItem = MediaItem.fromUri(ASSET_URI_PREFIX + FILE_AUDIO_VIDEO);
+    ImmutableList<AudioProcessor> audioProcessors = ImmutableList.of(sonicAudioProcessor);
+    Effects effects = new Effects(audioProcessors, /* videoEffects= */ ImmutableList.of());
+    EditedMediaItem editedMediaItem =
+        new EditedMediaItem.Builder(mediaItem).setEffects(effects).build();
+
+    transformer.start(editedMediaItem, outputPath);
+    TransformerTestRunner.runLooper(transformer);
+
+    DumpFileAsserts.assertOutput(
+        context, testMuxer, getDumpFileName(FILE_AUDIO_VIDEO + ".48000hz"));
+  }
+
+  @Test
+  public void startTransformation_multipleMediaItemsWithEffectsAndTransmux_ignoresTransmux()
+      throws Exception {
+    Transformer transformer =
+        createTransformerBuilder(/* enableFallback= */ false).setTransmux(true).build();
+    MediaItem mediaItem = MediaItem.fromUri(ASSET_URI_PREFIX + FILE_AUDIO_VIDEO);
+    AudioProcessor audioProcessor = new SilenceSkippingAudioProcessor();
+    Effects effects =
+        new Effects(ImmutableList.of(audioProcessor), /* videoEffects= */ ImmutableList.of());
+    EditedMediaItem editedMediaItem =
+        new EditedMediaItem.Builder(mediaItem).setEffects(effects).setRemoveVideo(true).build();
+    EditedMediaItemSequence editedMediaItemSequence =
+        new EditedMediaItemSequence(ImmutableList.of(editedMediaItem, editedMediaItem));
+    Composition composition =
+        new Composition(ImmutableList.of(editedMediaItemSequence), Effects.EMPTY);
+
+    transformer.start(composition, outputPath);
+    TransformerTestRunner.runLooper(transformer);
+
+    // The inputs should be transcoded even though transmuxing has been requested. This is because
+    // audio effects have been added to the first MediaItem in the sequence, so the transcoding
+    // audio sample pipeline should be picked to apply these effects.
+    DumpFileAsserts.assertOutput(
+        context, testMuxer, getDumpFileName(FILE_AUDIO_VIDEO + ".silence_skipped_concatenated"));
+  }
+
+  @Test
   public void startTransformation_withMultipleListeners_callsEachOnCompletion() throws Exception {
     Transformer.Listener mockListener1 = mock(Transformer.Listener.class);
     Transformer.Listener mockListener2 = mock(Transformer.Listener.class);