Ensure audio components check incoming data is valid.

Default PCM encoding is only set for decoders outputting raw.

Tests migrated to abide by tighter restrictions.

PiperOrigin-RevId: 558129452

libraries/test_data/src/test/assets/transformerdumps/mkv/sample_with_srt.mkv.dump.noaudio

@@ -9,12 +9,6 @@ format 0:
   initializationData:
     data = length 30, hash F6F3D010
     data = length 10, hash 7A0D0F2B
-format 1:
-  averageBitrate = 131072
-  sampleMimeType = audio/mp4a-latm
-  channelCount = 1
-  sampleRate = 44100
-  pcmEncoding = 2
 sample:
   trackIndex = 0
   dataHashCode = -252482306
@@ -195,178 +189,4 @@ sample:
   size = 486
   isKeyFrame = false
   presentationTimeUs = 933000
-sample:
-  trackIndex = 1
-  dataHashCode = 555688582
-  size = 416
-  isKeyFrame = true
-  presentationTimeUs = 0
-sample:
-  trackIndex = 1
-  dataHashCode = 2000837254
-  size = 418
-  isKeyFrame = true
-  presentationTimeUs = 4716
-sample:
-  trackIndex = 1
-  dataHashCode = -1593942879
-  size = 418
-  isKeyFrame = true
-  presentationTimeUs = 9455
-sample:
-  trackIndex = 1
-  dataHashCode = 587837542
-  size = 418
-  isKeyFrame = true
-  presentationTimeUs = 14195
-sample:
-  trackIndex = 1
-  dataHashCode = -1836423877
-  size = 418
-  isKeyFrame = true
-  presentationTimeUs = 18934
-sample:
-  trackIndex = 1
-  dataHashCode = 874705099
-  size = 418
-  isKeyFrame = true
-  presentationTimeUs = 23673
-sample:
-  trackIndex = 1
-  dataHashCode = -269206181
-  size = 418
-  isKeyFrame = true
-  presentationTimeUs = 28412
-sample:
-  trackIndex = 1
-  dataHashCode = -58682425
-  size = 418
-  isKeyFrame = true
-  presentationTimeUs = 33151
-sample:
-  trackIndex = 1
-  dataHashCode = -859796970
-  size = 418
-  isKeyFrame = true
-  presentationTimeUs = 37891
-sample:
-  trackIndex = 1
-  dataHashCode = 711911523
-  size = 418
-  isKeyFrame = true
-  presentationTimeUs = 42630
-sample:
-  trackIndex = 1
-  dataHashCode = -694513071
-  size = 418
-  isKeyFrame = true
-  presentationTimeUs = 47369
-sample:
-  trackIndex = 1
-  dataHashCode = -1124371059
-  size = 418
-  isKeyFrame = true
-  presentationTimeUs = 52108
-sample:
-  trackIndex = 1
-  dataHashCode = 297166745
-  size = 418
-  isKeyFrame = true
-  presentationTimeUs = 56848
-sample:
-  trackIndex = 1
-  dataHashCode = -937110638
-  size = 418
-  isKeyFrame = true
-  presentationTimeUs = 61587
-sample:
-  trackIndex = 1
-  dataHashCode = -1050158990
-  size = 418
-  isKeyFrame = true
-  presentationTimeUs = 66326
-sample:
-  trackIndex = 1
-  dataHashCode = 1109510229
-  size = 418
-  isKeyFrame = true
-  presentationTimeUs = 71065
-sample:
-  trackIndex = 1
-  dataHashCode = 1297086772
-  size = 418
-  isKeyFrame = true
-  presentationTimeUs = 75804
-sample:
-  trackIndex = 1
-  dataHashCode = -1739939803
-  size = 418
-  isKeyFrame = true
-  presentationTimeUs = 80544
-sample:
-  trackIndex = 1
-  dataHashCode = -1149727930
-  size = 418
-  isKeyFrame = true
-  presentationTimeUs = 85283
-sample:
-  trackIndex = 1
-  dataHashCode = -1627652713
-  size = 418
-  isKeyFrame = true
-  presentationTimeUs = 90022
-sample:
-  trackIndex = 1
-  dataHashCode = -551926260
-  size = 418
-  isKeyFrame = true
-  presentationTimeUs = 94761
-sample:
-  trackIndex = 1
-  dataHashCode = 45987178
-  size = 418
-  isKeyFrame = true
-  presentationTimeUs = 99501
-sample:
-  trackIndex = 1
-  dataHashCode = -903675808
-  size = 418
-  isKeyFrame = true
-  presentationTimeUs = 104240
-sample:
-  trackIndex = 1
-  dataHashCode = -755916991
-  size = 418
-  isKeyFrame = true
-  presentationTimeUs = 108979
-sample:
-  trackIndex = 1
-  dataHashCode = -1355207303
-  size = 418
-  isKeyFrame = true
-  presentationTimeUs = 113718
-sample:
-  trackIndex = 1
-  dataHashCode = -975703389
-  size = 418
-  isKeyFrame = true
-  presentationTimeUs = 118458
-sample:
-  trackIndex = 1
-  dataHashCode = 1933194670
-  size = 418
-  isKeyFrame = true
-  presentationTimeUs = 123197
-sample:
-  trackIndex = 1
-  dataHashCode = -565778989
-  size = 418
-  isKeyFrame = true
-  presentationTimeUs = 127936
-sample:
-  trackIndex = 1
-  dataHashCode = 1454083383
-  size = 418
-  isKeyFrame = true
-  presentationTimeUs = 132675
 released = true

libraries/test_data/src/test/assets/transformerdumps/mp4/sample_sef_slow_motion.mp4.dump.noaudio

@@ -11,14 +11,6 @@ format 0:
     data = length 33, hash D3FB879D
     data = length 10, hash 7A0D0F2B
 container metadata = entries=[mdta: key=com.android.version, value=10, mdta: key=com.android.video.temporal_layers_count, value=4, mdta: key=com.android.capture.fps, value=240.0, SlowMotion: segments=[Segment: startTimeMs=88, endTimeMs=879, speedDivisor=2, Segment: startTimeMs=1255, endTimeMs=1970, speedDivisor=8], smta: captureFrameRate=240.0, svcTemporalLayerCount=4, Mp4Timestamp: creation time=3686904890, modification time=3686904890, timescale=1000]
-format 1:
-  averageBitrate = 131072
-  sampleMimeType = audio/mp4a-latm
-  channelCount = 2
-  sampleRate = 12000
-  pcmEncoding = 2
-  metadata = entries=[mdta: key=com.android.version, value=10, mdta: key=com.android.video.temporal_layers_count, value=4, SlowMotion: segments=[Segment: startTimeMs=88, endTimeMs=879, speedDivisor=2, Segment: startTimeMs=1255, endTimeMs=1970, speedDivisor=8], smta: captureFrameRate=240.0, svcTemporalLayerCount=4, Mp4Timestamp: creation time=3686904890, modification time=3686904890, timescale=1000]
-container metadata = entries=[mdta: key=com.android.version, value=10, mdta: key=com.android.video.temporal_layers_count, value=4, SlowMotion: segments=[Segment: startTimeMs=88, endTimeMs=879, speedDivisor=2, Segment: startTimeMs=1255, endTimeMs=1970, speedDivisor=8], smta: captureFrameRate=240.0, svcTemporalLayerCount=4, Mp4Timestamp: creation time=3686904890, modification time=3686904890, timescale=1000]
 sample:
   trackIndex = 0
   dataHashCode = 1949079733
@@ -193,160 +185,4 @@ sample:
   size = 138
   isKeyFrame = false
   presentationTimeUs = 834083
-sample:
-  trackIndex = 1
-  dataHashCode = -212376212
-  size = 20
-  isKeyFrame = true
-  presentationTimeUs = 0
-sample:
-  trackIndex = 1
-  dataHashCode = -1948569090
-  size = 72
-  isKeyFrame = true
-  presentationTimeUs = 416
-sample:
-  trackIndex = 1
-  dataHashCode = -1316750072
-  size = 84
-  isKeyFrame = true
-  presentationTimeUs = 1916
-sample:
-  trackIndex = 1
-  dataHashCode = 1016428949
-  size = 88
-  isKeyFrame = true
-  presentationTimeUs = 3666
-sample:
-  trackIndex = 1
-  dataHashCode = -1127325245
-  size = 96
-  isKeyFrame = true
-  presentationTimeUs = 5500
-sample:
-  trackIndex = 1
-  dataHashCode = 1148147726
-  size = 92
-  isKeyFrame = true
-  presentationTimeUs = 7500
-sample:
-  trackIndex = 1
-  dataHashCode = -2125685540
-  size = 76
-  isKeyFrame = true
-  presentationTimeUs = 9416
-sample:
-  trackIndex = 1
-  dataHashCode = 473329679
-  size = 24
-  isKeyFrame = true
-  presentationTimeUs = 11000
-sample:
-  trackIndex = 1
-  dataHashCode = 240990900
-  size = 176
-  isKeyFrame = true
-  presentationTimeUs = 11500
-sample:
-  trackIndex = 1
-  dataHashCode = 777637182
-  size = 196
-  isKeyFrame = true
-  presentationTimeUs = 15166
-sample:
-  trackIndex = 1
-  dataHashCode = 1872106264
-  size = 180
-  isKeyFrame = true
-  presentationTimeUs = 19250
-sample:
-  trackIndex = 1
-  dataHashCode = -1520711499
-  size = 140
-  isKeyFrame = true
-  presentationTimeUs = 23000
-sample:
-  trackIndex = 1
-  dataHashCode = 1580199067
-  size = 232
-  isKeyFrame = true
-  presentationTimeUs = 25916
-sample:
-  trackIndex = 1
-  dataHashCode = 475464086
-  size = 184
-  isKeyFrame = true
-  presentationTimeUs = 30750
-sample:
-  trackIndex = 1
-  dataHashCode = -211754132
-  size = 172
-  isKeyFrame = true
-  presentationTimeUs = 34583
-sample:
-  trackIndex = 1
-  dataHashCode = 1236547164
-  size = 172
-  isKeyFrame = true
-  presentationTimeUs = 38166
-sample:
-  trackIndex = 1
-  dataHashCode = -2064216186
-  size = 188
-  isKeyFrame = true
-  presentationTimeUs = 41750
-sample:
-  trackIndex = 1
-  dataHashCode = -682950885
-  size = 260
-  isKeyFrame = true
-  presentationTimeUs = 45666
-sample:
-  trackIndex = 1
-  dataHashCode = 1301206627
-  size = 236
-  isKeyFrame = true
-  presentationTimeUs = 51083
-sample:
-  trackIndex = 1
-  dataHashCode = 256580525
-  size = 236
-  isKeyFrame = true
-  presentationTimeUs = 56000
-sample:
-  trackIndex = 1
-  dataHashCode = -1086601304
-  size = 236
-  isKeyFrame = true
-  presentationTimeUs = 60916
-sample:
-  trackIndex = 1
-  dataHashCode = -2046131588
-  size = 224
-  isKeyFrame = true
-  presentationTimeUs = 65833
-sample:
-  trackIndex = 1
-  dataHashCode = 1550955865
-  size = 224
-  isKeyFrame = true
-  presentationTimeUs = 70500
-sample:
-  trackIndex = 1
-  dataHashCode = -274800552
-  size = 220
-  isKeyFrame = true
-  presentationTimeUs = 75166
-sample:
-  trackIndex = 1
-  dataHashCode = 382420909
-  size = 224
-  isKeyFrame = true
-  presentationTimeUs = 79750
-sample:
-  trackIndex = 1
-  dataHashCode = -1431575865
-  size = 232
-  isKeyFrame = true
-  presentationTimeUs = 84416
 released = true

libraries/test_data/src/test/assets/transformerdumps/wav/sample.wav.48000hz.dump

@@ -0,0 +1,73 @@
+format 0:
+  averageBitrate = 131072
+  sampleMimeType = audio/mp4a-latm
+  channelCount = 1
+  sampleRate = 48000
+  pcmEncoding = 2
+sample:
+  trackIndex = 0
+  dataHashCode = -206878443
+  size = 9598
+  isKeyFrame = true
+  presentationTimeUs = 0
+sample:
+  trackIndex = 0
+  dataHashCode = 1925380271
+  size = 9600
+  isKeyFrame = true
+  presentationTimeUs = 99979
+sample:
+  trackIndex = 0
+  dataHashCode = -1463691457
+  size = 9600
+  isKeyFrame = true
+  presentationTimeUs = 199979
+sample:
+  trackIndex = 0
+  dataHashCode = -1949646832
+  size = 9600
+  isKeyFrame = true
+  presentationTimeUs = 299979
+sample:
+  trackIndex = 0
+  dataHashCode = 448289446
+  size = 9600
+  isKeyFrame = true
+  presentationTimeUs = 399979
+sample:
+  trackIndex = 0
+  dataHashCode = 774
+  size = 2
+  isKeyFrame = true
+  presentationTimeUs = 499979
+sample:
+  trackIndex = 0
+  dataHashCode = 389300669
+  size = 19198
+  isKeyFrame = true
+  presentationTimeUs = 500000
+sample:
+  trackIndex = 0
+  dataHashCode = 1861606067
+  size = 9600
+  isKeyFrame = true
+  presentationTimeUs = 699979
+sample:
+  trackIndex = 0
+  dataHashCode = -1038569478
+  size = 9600
+  isKeyFrame = true
+  presentationTimeUs = 799979
+sample:
+  trackIndex = 0
+  dataHashCode = 646441790
+  size = 9600
+  isKeyFrame = true
+  presentationTimeUs = 899979
+sample:
+  trackIndex = 0
+  dataHashCode = 340
+  size = 2
+  isKeyFrame = true
+  presentationTimeUs = 999979
+released = true

libraries/transformer/src/androidTest/java/androidx/media3/transformer/mh/ExportTest.java

@@ -27,6 +27,7 @@ import static androidx.media3.transformer.AndroidTestUtil.MP4_ASSET_WITH_INCREAS
 import static androidx.media3.transformer.AndroidTestUtil.MP4_REMOTE_8K24_FORMAT;
 import static androidx.media3.transformer.AndroidTestUtil.MP4_REMOTE_8K24_URI_STRING;
 import static androidx.media3.transformer.AndroidTestUtil.recordTestSkipped;
+import static com.google.common.truth.Truth.assertThat;
 
 import android.content.Context;
 import android.net.Uri;
@@ -39,6 +40,7 @@ import androidx.media3.transformer.AndroidTestUtil.ForceEncodeEncoderFactory;
 import androidx.media3.transformer.DefaultEncoderFactory;
 import androidx.media3.transformer.EditedMediaItem;
 import androidx.media3.transformer.Effects;
+import androidx.media3.transformer.ExportTestResult;
 import androidx.media3.transformer.Transformer;
 import androidx.media3.transformer.TransformerAndroidTestRunner;
 import androidx.media3.transformer.VideoEncoderSettings;
@@ -237,9 +239,13 @@ public class ExportTest {
         new EditedMediaItem.Builder(MediaItem.fromUri(Uri.parse(MP4_ASSET_SEF_URI_STRING)))
             .setFlattenForSlowMotion(true)
             .build();
+    ExportTestResult result =
         new TransformerAndroidTestRunner.Builder(context, transformer)
             .build()
             .run(testId, editedMediaItem);
+
+    assertThat(result.exportResult.durationMs).isGreaterThan(800);
+    assertThat(result.exportResult.durationMs).isLessThan(950);
   }
 
   @Test

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

@@ -68,7 +68,9 @@ import java.util.concurrent.atomic.AtomicReference;
 
   public AudioGraphInput(EditedMediaItem item, Format inputFormat)
       throws UnhandledAudioFormatException {
-    checkArgument(inputFormat.pcmEncoding != Format.NO_VALUE);
+    AudioFormat inputAudioFormat = new AudioFormat(inputFormat);
+    checkArgument(isInputAudioFormatValid(inputAudioFormat), /* errorMessage= */ inputAudioFormat);
+
     availableInputBuffers = new ConcurrentLinkedDeque<>();
     ByteBuffer emptyBuffer = ByteBuffer.allocateDirect(0).order(ByteOrder.nativeOrder());
     for (int i = 0; i < MAX_INPUT_BUFFER_COUNT; i++) {
@@ -78,7 +80,6 @@ import java.util.concurrent.atomic.AtomicReference;
     }
     pendingInputBuffers = new ConcurrentLinkedDeque<>();
     pendingMediaItemChange = new AtomicReference<>();
-    AudioFormat inputAudioFormat = new AudioFormat(inputFormat);
     silentAudioGenerator = new SilentAudioGenerator(inputAudioFormat);
     audioProcessingPipeline =
         configureProcessing(
@@ -127,7 +128,8 @@ import java.util.concurrent.atomic.AtomicReference;
           "Could not generate silent audio because duration is unknown.");
     } else {
       checkState(MimeTypes.isAudio(trackFormat.sampleMimeType));
-      checkState(trackFormat.pcmEncoding != Format.NO_VALUE);
+      AudioFormat trackAudioFormat = new AudioFormat(trackFormat);
+      checkState(isInputAudioFormatValid(trackAudioFormat), /* errorMessage= */ trackAudioFormat);
     }
     pendingMediaItemChange.set(
         new MediaItemChange(editedMediaItem, durationUs, trackFormat, isLast));
@@ -365,6 +367,22 @@ import java.util.concurrent.atomic.AtomicReference;
     return audioProcessingPipeline;
   }
 
+  private static boolean isInputAudioFormatValid(AudioFormat format) {
+    if (format.encoding == Format.NO_VALUE) {
+      return false;
+    }
+    if (format.sampleRate == Format.NO_VALUE) {
+      return false;
+    }
+    if (format.channelCount == Format.NO_VALUE) {
+      return false;
+    }
+    if (format.bytesPerFrame == Format.NO_VALUE) {
+      return false;
+    }
+    return true;
+  }
+
   private static final class MediaItemChange {
     public final EditedMediaItem editedMediaItem;
     public final long durationUs;

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

@@ -45,6 +45,7 @@ import androidx.media3.decoder.DecoderInputBuffer;
 import androidx.media3.effect.DebugTraceUtil;
 import java.io.IOException;
 import java.nio.ByteBuffer;
+import java.util.Objects;
 import org.checkerframework.checker.initialization.qual.UnknownInitialization;
 import org.checkerframework.checker.nullness.qual.EnsuresNonNullIf;
 import org.checkerframework.checker.nullness.qual.MonotonicNonNull;
@@ -72,7 +73,6 @@ public final class DefaultCodec implements Codec {
 
   private @MonotonicNonNull Format outputFormat;
   @Nullable private ByteBuffer outputBuffer;
-
   private int inputBufferIndex;
   private int outputBufferIndex;
   private boolean inputStreamEnded;
@@ -413,16 +413,12 @@ public final class DefaultCodec implements Codec {
 
   private static Format convertToFormat(
       MediaFormat mediaFormat, boolean isDecoder, @Nullable Metadata metadata) {
-    Format.Builder formatBuilder =
+    Format format = MediaFormatUtil.createFormatFromMediaFormat(mediaFormat);
-        MediaFormatUtil.createFormatFromMediaFormat(mediaFormat).buildUpon().setMetadata(metadata);
+    Format.Builder formatBuilder = format.buildUpon().setMetadata(metadata);
-    if (isDecoder) {
-      // TODO(b/178685617): Restrict this to only set the PCM encoding for audio/raw once we have
-      // a way to simulate more realistic codec input/output formats in tests.
 
-      // With Robolectric, codecs do not actually encode/decode. The format of buffers is passed
+    if (isDecoder
-      // through. However downstream components need to know the PCM encoding of the data being
+        && format.pcmEncoding == Format.NO_VALUE
-      // output, so if a decoder is not outputting raw audio, we need to set the PCM
+        && Objects.equals(format.sampleMimeType, MimeTypes.AUDIO_RAW)) {
-      // encoding to the default.
       formatBuilder.setPcmEncoding(DEFAULT_PCM_ENCODING);
     }
     return formatBuilder.build();

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

@@ -20,7 +20,6 @@ import static androidx.media3.test.utils.robolectric.RobolectricUtil.runLooperUn
 import static androidx.media3.transformer.AssetLoader.SUPPORTED_OUTPUT_TYPE_DECODED;
 import static androidx.media3.transformer.AssetLoader.SUPPORTED_OUTPUT_TYPE_ENCODED;
 import static androidx.media3.transformer.TestUtil.ASSET_URI_PREFIX;
-import static androidx.media3.transformer.TestUtil.FILE_AUDIO_AC3_UNSUPPORTED_BY_MUXER;
 import static androidx.media3.transformer.TestUtil.FILE_AUDIO_AMR_NB;
 import static androidx.media3.transformer.TestUtil.FILE_AUDIO_AMR_WB;
 import static androidx.media3.transformer.TestUtil.FILE_AUDIO_RAW;
@@ -123,8 +122,8 @@ public final class MediaItemExportTest {
     muxerFactory = new CapturingMuxer.Factory();
     progressHolder = new ProgressHolder();
     compositionArgumentCaptor = ArgumentCaptor.forClass(Composition.class);
-    addAudioDecoders(MimeTypes.AUDIO_RAW, MimeTypes.AUDIO_AAC, MimeTypes.AUDIO_AC3);
+    addAudioDecoders(MimeTypes.AUDIO_RAW);
-    addAudioEncoders(MimeTypes.AUDIO_AAC, MimeTypes.AUDIO_AC3);
+    addAudioEncoders(MimeTypes.AUDIO_AAC);
   }
 
   @After
@@ -176,7 +175,7 @@ public final class MediaItemExportTest {
   }
 
   @Test
-  public void start_audioAndVideo_completesSuccessfully() throws Exception {
+  public void start_audioAndVideoPassthrough_completesSuccessfully() throws Exception {
     Transformer transformer =
         createTransformerBuilder(muxerFactory, /* enableFallback= */ false).build();
     MediaItem mediaItem = MediaItem.fromUri(ASSET_URI_PREFIX + FILE_AUDIO_VIDEO);
@@ -189,7 +188,7 @@ public final class MediaItemExportTest {
   }
 
   @Test
-  public void start_audioAndVideo_withClippingStartAtKeyFrame_completesSuccessfully()
+  public void start_audioAndVideoPassthrough_withClippingStartAtKeyFrame_completesSuccessfully()
       throws Exception {
     Transformer transformer =
         createTransformerBuilder(muxerFactory, /* enableFallback= */ false).build();
@@ -214,18 +213,21 @@ public final class MediaItemExportTest {
   }
 
   @Test
-  public void start_withSubtitles_completesSuccessfully() throws Exception {
+  public void start_withSubtitlesVideoOnly_completesSuccessfully() throws Exception {
     Transformer transformer =
         createTransformerBuilder(muxerFactory, /* enableFallback= */ false)
             .setAudioMimeType(MimeTypes.AUDIO_AAC)
             .build();
-    MediaItem mediaItem = MediaItem.fromUri(ASSET_URI_PREFIX + FILE_WITH_SUBTITLES);
+    EditedMediaItem editedMediaItem =
+        new EditedMediaItem.Builder(MediaItem.fromUri(ASSET_URI_PREFIX + FILE_WITH_SUBTITLES))
+            .setRemoveAudio(true)
+            .build();
 
-    transformer.start(mediaItem, outputPath);
+    transformer.start(editedMediaItem, outputPath);
     TransformerTestRunner.runLooper(transformer);
 
     DumpFileAsserts.assertOutput(
-        context, muxerFactory.getCreatedMuxer(), getDumpFileName(FILE_WITH_SUBTITLES));
+        context, muxerFactory.getCreatedMuxer(), getDumpFileName(FILE_WITH_SUBTITLES) + ".noaudio");
   }
 
   @Test
@@ -429,7 +431,7 @@ public final class MediaItemExportTest {
     sonicAudioProcessor.setOutputSampleRateHz(48000);
     Transformer transformer =
         createTransformerBuilder(muxerFactory, /* enableFallback= */ false).build();
-    MediaItem mediaItem = MediaItem.fromUri(ASSET_URI_PREFIX + FILE_AUDIO_VIDEO);
+    MediaItem mediaItem = MediaItem.fromUri(ASSET_URI_PREFIX + FILE_AUDIO_RAW);
 
     EditedMediaItem editedMediaItem =
         new EditedMediaItem.Builder(mediaItem)
@@ -440,7 +442,7 @@ public final class MediaItemExportTest {
     TransformerTestRunner.runLooper(transformer);
 
     DumpFileAsserts.assertOutput(
-        context, muxerFactory.getCreatedMuxer(), getDumpFileName(FILE_AUDIO_VIDEO + ".48000hz"));
+        context, muxerFactory.getCreatedMuxer(), getDumpFileName(FILE_AUDIO_RAW + ".48000hz"));
   }
 
   @Test
@@ -449,7 +451,7 @@ public final class MediaItemExportTest {
     sonicAudioProcessor.setOutputSampleRateHz(48000);
     Transformer transformer =
         createTransformerBuilder(muxerFactory, /* enableFallback= */ false).build();
-    MediaItem mediaItem = MediaItem.fromUri(ASSET_URI_PREFIX + FILE_AUDIO_VIDEO);
+    MediaItem mediaItem = MediaItem.fromUri(ASSET_URI_PREFIX + FILE_AUDIO_RAW);
     EditedMediaItem editedMediaItem =
         new EditedMediaItem.Builder(mediaItem)
             .setEffects(createAudioEffects(sonicAudioProcessor))
@@ -463,9 +465,8 @@ public final class MediaItemExportTest {
 
     transformer.start(composition, outputPath);
     TransformerTestRunner.runLooper(transformer);
-
     DumpFileAsserts.assertOutput(
-        context, muxerFactory.getCreatedMuxer(), getDumpFileName(FILE_AUDIO_VIDEO + ".48000hz"));
+        context, muxerFactory.getCreatedMuxer(), getDumpFileName(FILE_AUDIO_RAW + ".48000hz"));
   }
 
   @Test
@@ -530,9 +531,9 @@ public final class MediaItemExportTest {
             .addListener(mockListener2)
             .addListener(mockListener3)
             .build();
-    MediaItem mediaItem = MediaItem.fromUri(ASSET_URI_PREFIX + FILE_AUDIO_AC3_UNSUPPORTED_BY_MUXER);
 
-    transformer.start(mediaItem, outputPath);
+    // No RAW encoder/muxer support, so fallback.
+    transformer.start(MediaItem.fromUri(ASSET_URI_PREFIX + FILE_AUDIO_RAW), outputPath);
     TransformerTestRunner.runLooper(transformer);
 
     verify(mockListener1)
@@ -643,9 +644,9 @@ public final class MediaItemExportTest {
                   }
                 })
             .build();
-    MediaItem mediaItem = MediaItem.fromUri(ASSET_URI_PREFIX + FILE_AUDIO_AC3_UNSUPPORTED_BY_MUXER);
 
-    transformer.start(mediaItem, outputPath);
+    // No RAW encoder/muxer support, so fallback.
+    transformer.start(MediaItem.fromUri(ASSET_URI_PREFIX + FILE_AUDIO_RAW), outputPath);
     TransformerTestRunner.runLooper(transformer);
 
     assertThat(deprecatedFallbackCalled.get()).isTrue();
@@ -675,19 +676,22 @@ public final class MediaItemExportTest {
   }
 
   @Test
-  public void start_flattenForSlowMotion_completesSuccessfully() throws Exception {
+  public void start_flattenForSlowMotionVideoOnly_completesSuccessfully() throws Exception {
     Transformer transformer =
         createTransformerBuilder(muxerFactory, /* enableFallback= */ false).build();
     EditedMediaItem editedMediaItem =
         new EditedMediaItem.Builder(MediaItem.fromUri(ASSET_URI_PREFIX + FILE_WITH_SEF_SLOW_MOTION))
             .setFlattenForSlowMotion(true)
+            .setRemoveAudio(true)
             .build();
 
     transformer.start(editedMediaItem, outputPath);
     TransformerTestRunner.runLooper(transformer);
 
     DumpFileAsserts.assertOutput(
-        context, muxerFactory.getCreatedMuxer(), getDumpFileName(FILE_WITH_SEF_SLOW_MOTION));
+        context,
+        muxerFactory.getCreatedMuxer(),
+        getDumpFileName(FILE_WITH_SEF_SLOW_MOTION) + ".noaudio");
   }
 
   @Test
@@ -762,25 +766,29 @@ public final class MediaItemExportTest {
   public void
       start_withAudioFormatUnsupportedByMuxer_ignoresDisabledFallbackAndCompletesSuccessfully()
           throws Exception {
-    // Test succeeds because MIME type fallback is mandatory.
+    removeEncodersAndDecoders();
+    addAudioDecoders(MimeTypes.AUDIO_RAW);
+    // RAW supported by encoder, unsupported by muxer.
+    // AAC supported by encoder and muxer.
+    addAudioEncoders(MimeTypes.AUDIO_RAW, MimeTypes.AUDIO_AAC);
+
     Transformer.Listener mockListener = mock(Transformer.Listener.class);
     TransformationRequest originalTransformationRequest =
         new TransformationRequest.Builder().build();
     TransformationRequest fallbackTransformationRequest =
         new TransformationRequest.Builder().setAudioMimeType(MimeTypes.AUDIO_AAC).build();
+    // MIME type fallback is mandatory.
     Transformer transformer =
         createTransformerBuilder(muxerFactory, /* enableFallback= */ false)
             .addListener(mockListener)
             .build();
-    MediaItem mediaItem = MediaItem.fromUri(ASSET_URI_PREFIX + FILE_AUDIO_AC3_UNSUPPORTED_BY_MUXER);
+    MediaItem mediaItem = MediaItem.fromUri(ASSET_URI_PREFIX + FILE_AUDIO_RAW);
 
     transformer.start(mediaItem, outputPath);
     TransformerTestRunner.runLooper(transformer);
 
     DumpFileAsserts.assertOutput(
-        context,
+        context, muxerFactory.getCreatedMuxer(), getDumpFileName(FILE_AUDIO_RAW + ".aac"));
-        muxerFactory.getCreatedMuxer(),
-        getDumpFileName(FILE_AUDIO_AC3_UNSUPPORTED_BY_MUXER + ".fallback"));
     verify(mockListener)
         .onFallbackApplied(
             any(Composition.class),
@@ -791,6 +799,12 @@ public final class MediaItemExportTest {
   @Test
   public void start_withAudioFormatUnsupportedByMuxer_fallsBackAndCompletesSuccessfully()
       throws Exception {
+    removeEncodersAndDecoders();
+    addAudioDecoders(MimeTypes.AUDIO_RAW);
+    // RAW supported by encoder, unsupported by muxer.
+    // AAC supported by encoder and muxer.
+    addAudioEncoders(MimeTypes.AUDIO_RAW, MimeTypes.AUDIO_AAC);
+
     Transformer.Listener mockListener = mock(Transformer.Listener.class);
     TransformationRequest originalTransformationRequest =
         new TransformationRequest.Builder().build();
@@ -800,15 +814,13 @@ public final class MediaItemExportTest {
         createTransformerBuilder(muxerFactory, /* enableFallback= */ true)
             .addListener(mockListener)
             .build();
-    MediaItem mediaItem = MediaItem.fromUri(ASSET_URI_PREFIX + FILE_AUDIO_AC3_UNSUPPORTED_BY_MUXER);
+    MediaItem mediaItem = MediaItem.fromUri(ASSET_URI_PREFIX + FILE_AUDIO_RAW);
 
     transformer.start(mediaItem, outputPath);
     TransformerTestRunner.runLooper(transformer);
 
     DumpFileAsserts.assertOutput(
-        context,
+        context, muxerFactory.getCreatedMuxer(), getDumpFileName(FILE_AUDIO_RAW + ".aac"));
-        muxerFactory.getCreatedMuxer(),
-        getDumpFileName(FILE_AUDIO_AC3_UNSUPPORTED_BY_MUXER + ".fallback"));
     verify(mockListener)
         .onFallbackApplied(
             any(Composition.class),