Allow output audio MIME type to be set in TranscodingTransformer.

This introduces a new option `setAudioMimeType` in `TranscodingTransformer.Builder` and a corresponding check whether the selected type is supported. This check is done using `supportsSampleMimeType` which is now part of the `Muxer.Factory` and `MuxerWrapper` rather than `Muxer`.
A new field `audioMimeType` is added to `Transformation` and the `TransformerAudioRenderer` uses this instead of the input MIME type if requested.

PiperOrigin-RevId: 405367817

Author: ojw28

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

@@ -42,7 +42,7 @@ public static final class Factory implements Muxer.Factory {
     @Override
     public FrameworkMuxer create(String path, String outputMimeType) throws IOException {
       MediaMuxer mediaMuxer = new MediaMuxer(path, mimeTypeToMuxerOutputFormat(outputMimeType));
-      return new FrameworkMuxer(mediaMuxer, outputMimeType);
+      return new FrameworkMuxer(mediaMuxer);
     }
 
     @RequiresApi(26)
@@ -53,7 +53,7 @@ public FrameworkMuxer create(ParcelFileDescriptor parcelFileDescriptor, String o
           new MediaMuxer(
               parcelFileDescriptor.getFileDescriptor(),
               mimeTypeToMuxerOutputFormat(outputMimeType));
-      return new FrameworkMuxer(mediaMuxer, outputMimeType);
+      return new FrameworkMuxer(mediaMuxer);
     }
 
     @Override
@@ -65,47 +65,46 @@ public boolean supportsOutputMimeType(String mimeType) {
       }
       return true;
     }
+
+    @Override
+    public boolean supportsSampleMimeType(
+        @Nullable String sampleMimeType, String containerMimeType) {
+      // MediaMuxer supported sample formats are documented in MediaMuxer.addTrack(MediaFormat).
+      boolean isAudio = MimeTypes.isAudio(sampleMimeType);
+      boolean isVideo = MimeTypes.isVideo(sampleMimeType);
+      if (containerMimeType.equals(MimeTypes.VIDEO_MP4)) {
+        if (isVideo) {
+          return MimeTypes.VIDEO_H263.equals(sampleMimeType)
+              || MimeTypes.VIDEO_H264.equals(sampleMimeType)
+              || MimeTypes.VIDEO_MP4V.equals(sampleMimeType)
+              || (Util.SDK_INT >= 24 && MimeTypes.VIDEO_H265.equals(sampleMimeType));
+        } else if (isAudio) {
+          return MimeTypes.AUDIO_AAC.equals(sampleMimeType)
+              || MimeTypes.AUDIO_AMR_NB.equals(sampleMimeType)
+              || MimeTypes.AUDIO_AMR_WB.equals(sampleMimeType);
+        }
+      } else if (containerMimeType.equals(MimeTypes.VIDEO_WEBM) && SDK_INT >= 21) {
+        if (isVideo) {
+          return MimeTypes.VIDEO_VP8.equals(sampleMimeType)
+              || (Util.SDK_INT >= 24 && MimeTypes.VIDEO_VP9.equals(sampleMimeType));
+        } else if (isAudio) {
+          return MimeTypes.AUDIO_VORBIS.equals(sampleMimeType);
+        }
+      }
+      return false;
+    }
   }
 
   private final MediaMuxer mediaMuxer;
-  private final String outputMimeType;
   private final MediaCodec.BufferInfo bufferInfo;
 
   private boolean isStarted;
 
-  private FrameworkMuxer(MediaMuxer mediaMuxer, String outputMimeType) {
+  private FrameworkMuxer(MediaMuxer mediaMuxer) {
     this.mediaMuxer = mediaMuxer;
-    this.outputMimeType = outputMimeType;
     bufferInfo = new MediaCodec.BufferInfo();
   }
 
-  @Override
-  public boolean supportsSampleMimeType(@Nullable String mimeType) {
-    // MediaMuxer supported sample formats are documented in MediaMuxer.addTrack(MediaFormat).
-    boolean isAudio = MimeTypes.isAudio(mimeType);
-    boolean isVideo = MimeTypes.isVideo(mimeType);
-    if (outputMimeType.equals(MimeTypes.VIDEO_MP4)) {
-      if (isVideo) {
-        return MimeTypes.VIDEO_H263.equals(mimeType)
-            || MimeTypes.VIDEO_H264.equals(mimeType)
-            || MimeTypes.VIDEO_MP4V.equals(mimeType)
-            || (Util.SDK_INT >= 24 && MimeTypes.VIDEO_H265.equals(mimeType));
-      } else if (isAudio) {
-        return MimeTypes.AUDIO_AAC.equals(mimeType)
-            || MimeTypes.AUDIO_AMR_NB.equals(mimeType)
-            || MimeTypes.AUDIO_AMR_WB.equals(mimeType);
-      }
-    } else if (outputMimeType.equals(MimeTypes.VIDEO_WEBM) && SDK_INT >= 21) {
-      if (isVideo) {
-        return MimeTypes.VIDEO_VP8.equals(mimeType)
-            || (Util.SDK_INT >= 24 && MimeTypes.VIDEO_VP9.equals(mimeType));
-      } else if (isAudio) {
-        return MimeTypes.AUDIO_VORBIS.equals(mimeType);
-      }
-    }
-    return false;
-  }
-
   @Override
   public int addTrack(Format format) {
     String sampleMimeType = checkNotNull(format.sampleMimeType);

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

@@ -25,11 +25,12 @@
 /**
  * Abstracts media muxing operations.
  *
- * <p>Query whether {@link #supportsSampleMimeType(String) sample MIME types are supported} and
- * {@link #addTrack(Format) add all tracks}, then {@link #writeSampleData(int, ByteBuffer, boolean,
- * long) write sample data} to mux samples. Once any sample data has been written, it is not
- * possible to add tracks. After writing all sample data, {@link #release(boolean) release} the
- * instance to finish writing to the output and return any resources to the system.
+ * <p>Query whether {@link Factory#supportsOutputMimeType(String) container MIME type} and {@link
+ * Factory#supportsSampleMimeType(String, String) sample MIME types} are supported and {@link
+ * #addTrack(Format) add all tracks}, then {@link #writeSampleData(int, ByteBuffer, boolean, long)
+ * write sample data} to mux samples. Once any sample data has been written, it is not possible to
+ * add tracks. After writing all sample data, {@link #release(boolean) release} the instance to
+ * finish writing to the output and return any resources to the system.
  */
 /* package */ interface Muxer {
 
@@ -62,10 +63,13 @@ Muxer create(ParcelFileDescriptor parcelFileDescriptor, String outputMimeType)
 
     /** Returns whether the {@link MimeTypes MIME type} provided is a supported output format. */
     boolean supportsOutputMimeType(String mimeType);
-  }
 
-  /** Returns whether the sample {@link MimeTypes MIME type} is supported. */
-  boolean supportsSampleMimeType(@Nullable String mimeType);
+    /**
+     * Returns whether the sample {@link MimeTypes MIME type} is supported with the given container
+     * {@link MimeTypes MIME type}.
+     */
+    boolean supportsSampleMimeType(@Nullable String sampleMimeType, String containerMimeType);
+  }
 
   /**
    * Adds a track with the specified format, and returns its index (to be passed in subsequent calls

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

@@ -45,17 +45,21 @@
   private static final long MAX_TRACK_WRITE_AHEAD_US = C.msToUs(500);
 
   private final Muxer muxer;
+  private final Muxer.Factory muxerFactory;
   private final SparseIntArray trackTypeToIndex;
   private final SparseLongArray trackTypeToTimeUs;
+  private final String containerMimeType;
 
   private int trackCount;
   private int trackFormatCount;
   private boolean isReady;
   private @C.TrackType int previousTrackType;
   private long minTrackTimeUs;
 
-  public MuxerWrapper(Muxer muxer) {
+  public MuxerWrapper(Muxer muxer, Muxer.Factory muxerFactory, String containerMimeType) {
     this.muxer = muxer;
+    this.muxerFactory = muxerFactory;
+    this.containerMimeType = containerMimeType;
     trackTypeToIndex = new SparseIntArray();
     trackTypeToTimeUs = new SparseLongArray();
     previousTrackType = C.TRACK_TYPE_NONE;
@@ -78,7 +82,7 @@ public void registerTrack() {
 
   /** Returns whether the sample {@link MimeTypes MIME type} is supported. */
   public boolean supportsSampleMimeType(@Nullable String mimeType) {
-    return muxer.supportsSampleMimeType(mimeType);
+    return muxerFactory.supportsSampleMimeType(mimeType, containerMimeType);
   }
 
   /**

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

@@ -100,6 +100,7 @@ public static final class Builder {
     private boolean removeVideo;
     private boolean flattenForSlowMotion;
     private String outputMimeType;
+    @Nullable private String audioMimeType;
     private TranscodingTransformer.Listener listener;
     private Looper looper;
     private Clock clock;
@@ -122,6 +123,7 @@ private Builder(TranscodingTransformer transcodingTransformer) {
       this.removeVideo = transcodingTransformer.transformation.removeVideo;
       this.flattenForSlowMotion = transcodingTransformer.transformation.flattenForSlowMotion;
       this.outputMimeType = transcodingTransformer.transformation.outputMimeType;
+      this.audioMimeType = transcodingTransformer.transformation.audioMimeType;
       this.listener = transcodingTransformer.listener;
       this.looper = transcodingTransformer.looper;
       this.clock = transcodingTransformer.clock;
@@ -212,10 +214,8 @@ public Builder setFlattenForSlowMotion(boolean flattenForSlowMotion) {
     }
 
     /**
-     * Sets the MIME type of the output. The default value is {@link MimeTypes#VIDEO_MP4}. The
-     * output MIME type should be supported by the {@link
-     * Muxer.Factory#supportsOutputMimeType(String) muxer}. Values supported by the default {@link
-     * FrameworkMuxer} are:
+     * Sets the MIME type of the output. The default value is {@link MimeTypes#VIDEO_MP4}. Supported
+     * values are:
      *
      * <ul>
      *   <li>{@link MimeTypes#VIDEO_MP4}
@@ -230,6 +230,31 @@ public Builder setOutputMimeType(String outputMimeType) {
       return this;
     }
 
+    /**
+     * Sets the audio MIME type of the output. The default value is to use the same MIME type as the
+     * input. Supported values are:
+     *
+     * <ul>
+     *   <li>when the container MIME type is {@link MimeTypes#VIDEO_MP4}:
+     *       <ul>
+     *         <li>{@link MimeTypes#AUDIO_AAC}
+     *         <li>{@link MimeTypes#AUDIO_AMR_NB}
+     *         <li>{@link MimeTypes#AUDIO_AMR_WB}
+     *       </ul>
+     *   <li>when the container MIME type is {@link MimeTypes#VIDEO_WEBM}:
+     *       <ul>
+     *         <li>{@link MimeTypes#AUDIO_VORBIS}
+     *       </ul>
+     * </ul>
+     *
+     * @param audioMimeType The MIME type of the audio samples in the output.
+     * @return This builder.
+     */
+    public Builder setAudioMimeType(String audioMimeType) {
+      this.audioMimeType = audioMimeType;
+      return this;
+    }
+
     /**
      * Sets the {@link TranscodingTransformer.Listener} to listen to the transformation events.
      *
@@ -290,6 +315,7 @@ public Builder setLooper(Looper looper) {
      * @throws IllegalStateException If both audio and video have been removed (otherwise the output
      *     would not contain any samples).
      * @throws IllegalStateException If the muxer doesn't support the requested output MIME type.
+     * @throws IllegalStateException If the muxer doesn't support the requested audio MIME type.
      */
     public TranscodingTransformer build() {
       checkStateNotNull(context);
@@ -303,8 +329,17 @@ public TranscodingTransformer build() {
       checkState(
           muxerFactory.supportsOutputMimeType(outputMimeType),
           "Unsupported output MIME type: " + outputMimeType);
+      if (audioMimeType != null) {
+        checkState(
+            muxerFactory.supportsSampleMimeType(audioMimeType, outputMimeType),
+            "Unsupported sample MIME type "
+                + audioMimeType
+                + " for container MIME type "
+                + outputMimeType);
+      }
       Transformation transformation =
-          new Transformation(removeAudio, removeVideo, flattenForSlowMotion, outputMimeType);
+          new Transformation(
+              removeAudio, removeVideo, flattenForSlowMotion, outputMimeType, audioMimeType);
       return new TranscodingTransformer(
           context, mediaSourceFactory, muxerFactory, transformation, listener, looper, clock);
     }
@@ -469,7 +504,8 @@ private void startTransformation(MediaItem mediaItem, Muxer muxer) {
       throw new IllegalStateException("There is already a transformation in progress.");
     }
 
-    MuxerWrapper muxerWrapper = new MuxerWrapper(muxer);
+    MuxerWrapper muxerWrapper =
+        new MuxerWrapper(muxer, muxerFactory, transformation.outputMimeType);
     this.muxerWrapper = muxerWrapper;
     DefaultTrackSelector trackSelector = new DefaultTrackSelector(context);
     trackSelector.setParameters(

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

@@ -16,22 +16,27 @@
 
 package com.google.android.exoplayer2.transformer;
 
+import androidx.annotation.Nullable;
+
 /** A media transformation configuration. */
 /* package */ final class Transformation {
 
   public final boolean removeAudio;
   public final boolean removeVideo;
   public final boolean flattenForSlowMotion;
   public final String outputMimeType;
+  @Nullable public final String audioMimeType;
 
   public Transformation(
       boolean removeAudio,
       boolean removeVideo,
       boolean flattenForSlowMotion,
-      String outputMimeType) {
+      String outputMimeType,
+      @Nullable String audioMimeType) {
     this.removeAudio = removeAudio;
     this.removeVideo = removeVideo;
     this.flattenForSlowMotion = flattenForSlowMotion;
     this.outputMimeType = outputMimeType;
+    this.audioMimeType = audioMimeType;
   }
 }

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

@@ -209,10 +209,8 @@ public Builder setFlattenForSlowMotion(boolean flattenForSlowMotion) {
     }
 
     /**
-     * Sets the MIME type of the output. The default value is {@link MimeTypes#VIDEO_MP4}. The
-     * output MIME type should be supported by the {@link
-     * Muxer.Factory#supportsOutputMimeType(String) muxer}. Values supported by the default {@link
-     * FrameworkMuxer} are:
+     * Sets the MIME type of the output. The default value is {@link MimeTypes#VIDEO_MP4}. Supported
+     * values are:
      *
      * <ul>
      *   <li>{@link MimeTypes#VIDEO_MP4}
@@ -301,7 +299,12 @@ public Transformer build() {
           muxerFactory.supportsOutputMimeType(outputMimeType),
           "Unsupported output MIME type: " + outputMimeType);
       Transformation transformation =
-          new Transformation(removeAudio, removeVideo, flattenForSlowMotion, outputMimeType);
+          new Transformation(
+              removeAudio,
+              removeVideo,
+              flattenForSlowMotion,
+              outputMimeType,
+              /* audioMimeType= */ null);
       return new Transformer(
           context, mediaSourceFactory, muxerFactory, transformation, listener, looper, clock);
     }
@@ -464,7 +467,8 @@ private void startTransformation(MediaItem mediaItem, Muxer muxer) {
       throw new IllegalStateException("There is already a transformation in progress.");
     }
 
-    MuxerWrapper muxerWrapper = new MuxerWrapper(muxer);
+    MuxerWrapper muxerWrapper =
+        new MuxerWrapper(muxer, muxerFactory, transformation.outputMimeType);
     this.muxerWrapper = muxerWrapper;
     DefaultTrackSelector trackSelector = new DefaultTrackSelector(context);
     trackSelector.setParameters(

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

@@ -350,11 +350,15 @@ private boolean ensureEncoderAndAudioProcessingConfigured() throws ExoPlaybackEx
         throw createRendererException(e, PlaybackException.ERROR_CODE_UNSPECIFIED);
       }
     }
+    String audioMimeType =
+        transformation.audioMimeType == null
+            ? checkNotNull(inputFormat).sampleMimeType
+            : transformation.audioMimeType;
     try {
       encoder =
           MediaCodecAdapterWrapper.createForAudioEncoding(
               new Format.Builder()
-                  .setSampleMimeType(checkNotNull(inputFormat).sampleMimeType)
+                  .setSampleMimeType(audioMimeType)
                   .setSampleRate(outputAudioFormat.sampleRate)
                   .setChannelCount(outputAudioFormat.channelCount)
                   .setAverageBitrate(DEFAULT_ENCODER_BITRATE)

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

@@ -52,7 +52,13 @@ public final int supportsFormat(Format format) {
     @Nullable String sampleMimeType = format.sampleMimeType;
     if (MimeTypes.getTrackType(sampleMimeType) != getTrackType()) {
       return RendererCapabilities.create(C.FORMAT_UNSUPPORTED_TYPE);
-    } else if (muxerWrapper.supportsSampleMimeType(sampleMimeType)) {
+    } else if ((MimeTypes.isAudio(sampleMimeType)
+            && muxerWrapper.supportsSampleMimeType(
+                transformation.audioMimeType == null
+                    ? sampleMimeType
+                    : transformation.audioMimeType))
+        || (MimeTypes.isVideo(sampleMimeType)
+            && muxerWrapper.supportsSampleMimeType(sampleMimeType))) {
       return RendererCapabilities.create(C.FORMAT_HANDLED);
     } else {
       return RendererCapabilities.create(C.FORMAT_UNSUPPORTED_SUBTYPE);