Generate silent audio if no audio track is available.

To always generate silent audio, `removeAudio(true)` can be used in conjunction.

PiperOrigin-RevId: 502814315

demos/transformer/src/main/java/com/google/android/exoplayer2/transformerdemo/ConfigurationActivity.java

@@ -61,7 +61,7 @@ public final class ConfigurationActivity extends AppCompatActivity {
   public static final String SHOULD_REMOVE_AUDIO = "should_remove_audio";
   public static final String SHOULD_REMOVE_VIDEO = "should_remove_video";
   public static final String SHOULD_FLATTEN_FOR_SLOW_MOTION = "should_flatten_for_slow_motion";
-  public static final String FORCE_SILENT_AUDIO = "force_silent_audio";
+  public static final String GENERATE_SILENT_AUDIO = "generate_silent_audio";
   public static final String AUDIO_MIME_TYPE = "audio_mime_type";
   public static final String VIDEO_MIME_TYPE = "video_mime_type";
   public static final String RESOLUTION_HEIGHT = "resolution_height";
@@ -210,7 +210,7 @@ public final class ConfigurationActivity extends AppCompatActivity {
   private @MonotonicNonNull CheckBox removeAudioCheckbox;
   private @MonotonicNonNull CheckBox removeVideoCheckbox;
   private @MonotonicNonNull CheckBox flattenForSlowMotionCheckbox;
-  private @MonotonicNonNull CheckBox forceSilentAudioCheckbox;
+  private @MonotonicNonNull CheckBox generateSilentAudioCheckbox;
   private @MonotonicNonNull Spinner audioMimeSpinner;
   private @MonotonicNonNull Spinner videoMimeSpinner;
   private @MonotonicNonNull Spinner resolutionHeightSpinner;
@@ -271,7 +271,7 @@ protected void onCreate(@Nullable Bundle savedInstanceState) {
 
     flattenForSlowMotionCheckbox = findViewById(R.id.flatten_for_slow_motion_checkbox);
 
-    forceSilentAudioCheckbox = findViewById(R.id.force_silent_audio_checkbox);
+    generateSilentAudioCheckbox = findViewById(R.id.generate_silent_audio_checkbox);
 
     ArrayAdapter<String> audioMimeAdapter =
         new ArrayAdapter<>(/* context= */ this, R.layout.spinner_item);
@@ -382,7 +382,7 @@ protected void onNewIntent(Intent intent) {
     "removeAudioCheckbox",
     "removeVideoCheckbox",
     "flattenForSlowMotionCheckbox",
-    "forceSilentAudioCheckbox",
+    "generateSilentAudioCheckbox",
     "audioMimeSpinner",
     "videoMimeSpinner",
     "resolutionHeightSpinner",
@@ -402,7 +402,7 @@ private void startTransformation(View view) {
     bundle.putBoolean(SHOULD_REMOVE_AUDIO, removeAudioCheckbox.isChecked());
     bundle.putBoolean(SHOULD_REMOVE_VIDEO, removeVideoCheckbox.isChecked());
     bundle.putBoolean(SHOULD_FLATTEN_FOR_SLOW_MOTION, flattenForSlowMotionCheckbox.isChecked());
-    bundle.putBoolean(FORCE_SILENT_AUDIO, forceSilentAudioCheckbox.isChecked());
+    bundle.putBoolean(GENERATE_SILENT_AUDIO, generateSilentAudioCheckbox.isChecked());
     String selectedAudioMimeType = String.valueOf(audioMimeSpinner.getSelectedItem());
     if (!SAME_AS_INPUT_OPTION.equals(selectedAudioMimeType)) {
       bundle.putString(AUDIO_MIME_TYPE, selectedAudioMimeType);
@@ -738,7 +738,7 @@ private void controlTextOverlaySettings() {
 
   @RequiresNonNull({
     "removeVideoCheckbox",
-    "forceSilentAudioCheckbox",
+    "generateSilentAudioCheckbox",
     "audioMimeSpinner",
     "videoMimeSpinner",
     "resolutionHeightSpinner",
@@ -760,7 +760,7 @@ private void onRemoveAudio(View view) {
 
   @RequiresNonNull({
     "removeAudioCheckbox",
-    "forceSilentAudioCheckbox",
+    "generateSilentAudioCheckbox",
     "audioMimeSpinner",
     "videoMimeSpinner",
     "resolutionHeightSpinner",
@@ -781,7 +781,7 @@ private void onRemoveVideo(View view) {
   }
 
   @RequiresNonNull({
-    "forceSilentAudioCheckbox",
+    "generateSilentAudioCheckbox",
     "audioMimeSpinner",
     "videoMimeSpinner",
     "resolutionHeightSpinner",
@@ -793,7 +793,7 @@ private void onRemoveVideo(View view) {
     "selectVideoEffectsButton"
   })
   private void enableTrackSpecificOptions(boolean isAudioEnabled, boolean isVideoEnabled) {
-    forceSilentAudioCheckbox.setEnabled(isVideoEnabled);
+    generateSilentAudioCheckbox.setEnabled(isVideoEnabled);
     audioMimeSpinner.setEnabled(isAudioEnabled);
     videoMimeSpinner.setEnabled(isVideoEnabled);
     resolutionHeightSpinner.setEnabled(isVideoEnabled);

demos/transformer/src/main/java/com/google/android/exoplayer2/transformerdemo/TransformerActivity.java

@@ -309,6 +309,8 @@ private Transformer createTransformer(@Nullable Bundle bundle, String filePath)
       transformerBuilder
           .setRemoveAudio(bundle.getBoolean(ConfigurationActivity.SHOULD_REMOVE_AUDIO))
           .setRemoveVideo(bundle.getBoolean(ConfigurationActivity.SHOULD_REMOVE_VIDEO))
+          .experimentalSetGenerateSilentAudio(
+              bundle.getBoolean(ConfigurationActivity.GENERATE_SILENT_AUDIO))
           .setEncoderFactory(
               new DefaultEncoderFactory.Builder(this.getApplicationContext())
                   .setEnableFallback(bundle.getBoolean(ConfigurationActivity.ENABLE_FALLBACK))
@@ -322,9 +324,6 @@ private Transformer createTransformer(@Nullable Bundle bundle, String filePath)
       if (bundle.getBoolean(ConfigurationActivity.ENABLE_DEBUG_PREVIEW)) {
         transformerBuilder.setDebugViewProvider(new DemoDebugViewProvider());
       }
-
-      transformerBuilder.experimentalSetForceSilentAudio(
-          bundle.getBoolean(ConfigurationActivity.FORCE_SILENT_AUDIO));
     }
 
     return transformerBuilder

demos/transformer/src/main/res/layout/configuration_activity.xml

@@ -116,9 +116,9 @@
         android:layout_weight="1">
         <TextView
           android:layout_gravity="center_vertical"
-          android:text="@string/force_silent_audio" />
+          android:text="@string/generate_silent_audio" />
         <CheckBox
-          android:id="@+id/force_silent_audio_checkbox"
+          android:id="@+id/generate_silent_audio_checkbox"
           android:layout_gravity="end" />
       </TableRow>
       <TableRow

demos/transformer/src/main/res/values/strings.xml

@@ -66,7 +66,7 @@
   <string name="permission_denied">Permission Denied</string>
   <string name="hide_input_video">Hide input video</string>
   <string name="show_input_video">Show input video</string>
-  <string name="force_silent_audio">Force silent audio</string>
+  <string name="generate_silent_audio">Generate silent audio</string>
   <string name="overlay_alpha">Alpha</string>
   <string name="overlay_uri">Uri</string>
   <string name="bitmap_overlay_settings">Specify bitmap overlay settings</string>

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

@@ -64,15 +64,15 @@ public AudioSamplePipeline(
       long streamOffsetUs,
       TransformationRequest transformationRequest,
       ImmutableList<AudioProcessor> audioProcessors,
-      long forceSilentAudioDurationUs,
+      long generateSilentAudioDurationUs,
       Codec.EncoderFactory encoderFactory,
       MuxerWrapper muxerWrapper,
       FallbackListener fallbackListener)
       throws TransformationException {
     super(inputFormat, streamStartPositionUs, muxerWrapper);
 
-    if (forceSilentAudioDurationUs != C.TIME_UNSET) {
-      silentAudioGenerator = new SilentAudioGenerator(inputFormat, forceSilentAudioDurationUs);
+    if (generateSilentAudioDurationUs != C.TIME_UNSET) {
+      silentAudioGenerator = new SilentAudioGenerator(inputFormat, generateSilentAudioDurationUs);
     } else {
       silentAudioGenerator = null;
     }

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

@@ -86,7 +86,7 @@ public static final class Builder {
     private ImmutableList<Effect> videoEffects;
     private boolean removeAudio;
     private boolean removeVideo;
-    private boolean forceSilentAudio;
+    private boolean generateSilentAudio;
     private ListenerSet<Transformer.Listener> listeners;
     @Nullable private AssetLoader.Factory assetLoaderFactory;
     private FrameProcessor.Factory frameProcessorFactory;
@@ -123,7 +123,7 @@ private Builder(Transformer transformer) {
       this.videoEffects = transformer.videoEffects;
       this.removeAudio = transformer.removeAudio;
       this.removeVideo = transformer.removeVideo;
-      this.forceSilentAudio = transformer.forceSilentAudio;
+      this.generateSilentAudio = transformer.generateSilentAudio;
       this.listeners = transformer.listeners;
       this.assetLoaderFactory = transformer.assetLoaderFactory;
       this.frameProcessorFactory = transformer.frameProcessorFactory;
@@ -398,29 +398,32 @@ public Builder setDebugViewProvider(DebugViewProvider debugViewProvider) {
     }
 
     /**
-     * Sets whether to force silent audio for the output file, ignoring any existing audio.
+     * Sets whether to generate silent audio for the output file, if there is no audio available.
      *
      * <p>This method is experimental and may be removed or changed without warning.
      *
+     * <p>To replace existing audio with silence, call {@link #setRemoveAudio(boolean)} as well.
+     *
      * <p>Audio properties/format:
      *
      * <ul>
      *   <li>Duration will match duration of the input media.
      *   <li>Sample mime type will match {@link TransformationRequest#audioMimeType}, or {@link
      *       MimeTypes#AUDIO_AAC} if {@code null}.
-     *   <li>Sample rate will be 44100hz. This can be modified by passing a {@link
+     *   <li>Sample rate will be {@code 44100} hz. This can be modified by passing a {@link
      *       SonicAudioProcessor} to {@link #setAudioProcessors(List)}, using {@link
      *       SonicAudioProcessor#setOutputSampleRateHz(int)}.
-     *   <li>Channel count will be 2. This can be modified by implementing a custom {@link
+     *   <li>Channel count will be {@code 2}. This can be modified by implementing a custom {@link
      *       AudioProcessor} and passing it to {@link #setAudioProcessors(List)}.
      * </ul>
      *
-     * @param forceSilentAudio Whether to output silent audio for the output file.
+     * @param generateSilentAudio Whether to generate silent audio for the output file if there is
+     *     no audio track.
      * @return This builder.
      */
     @CanIgnoreReturnValue
-    public Builder experimentalSetForceSilentAudio(boolean forceSilentAudio) {
-      this.forceSilentAudio = forceSilentAudio;
+    public Builder experimentalSetGenerateSilentAudio(boolean generateSilentAudio) {
+      this.generateSilentAudio = generateSilentAudio;
       return this;
     }
 
@@ -457,7 +460,7 @@ public Transformer build() {
           videoEffects,
           removeAudio,
           removeVideo,
-          forceSilentAudio,
+          generateSilentAudio,
           listeners,
           assetLoaderFactory,
           frameProcessorFactory,
@@ -577,7 +580,7 @@ default void onFallbackApplied(
   private final ImmutableList<Effect> videoEffects;
   private final boolean removeAudio;
   private final boolean removeVideo;
-  private final boolean forceSilentAudio;
+  private final boolean generateSilentAudio;
   private final ListenerSet<Transformer.Listener> listeners;
   private final AssetLoader.Factory assetLoaderFactory;
   private final FrameProcessor.Factory frameProcessorFactory;
@@ -596,7 +599,7 @@ private Transformer(
       ImmutableList<Effect> videoEffects,
       boolean removeAudio,
       boolean removeVideo,
-      boolean forceSilentAudio,
+      boolean generateSilentAudio,
       ListenerSet<Listener> listeners,
       AssetLoader.Factory assetLoaderFactory,
       FrameProcessor.Factory frameProcessorFactory,
@@ -605,18 +608,14 @@ private Transformer(
       Looper looper,
       DebugViewProvider debugViewProvider,
       Clock clock) {
-    if (forceSilentAudio) {
-      removeAudio = true;
-    }
-    checkState(!removeVideo || !forceSilentAudio, "Silent only audio track needs a video track.");
     checkState(!removeAudio || !removeVideo, "Audio and video cannot both be removed.");
     this.context = context;
     this.transformationRequest = transformationRequest;
     this.audioProcessors = audioProcessors;
     this.videoEffects = videoEffects;
     this.removeAudio = removeAudio;
     this.removeVideo = removeVideo;
-    this.forceSilentAudio = forceSilentAudio;
+    this.generateSilentAudio = generateSilentAudio;
     this.listeners = listeners;
     this.assetLoaderFactory = assetLoaderFactory;
     this.frameProcessorFactory = frameProcessorFactory;
@@ -759,7 +758,7 @@ private void startTransformationInternal(
             videoEffects,
             removeAudio,
             removeVideo,
-            forceSilentAudio,
+            generateSilentAudio,
             assetLoaderFactory,
             frameProcessorFactory,
             encoderFactory,

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

@@ -93,7 +93,6 @@ public interface Listener {
   private final TransformationRequest transformationRequest;
   private final ImmutableList<AudioProcessor> audioProcessors;
   private final ImmutableList<Effect> videoEffects;
-  private final boolean forceSilentAudio;
   private final FrameProcessor.Factory frameProcessorFactory;
   private final CapturingEncoderFactory encoderFactory;
   private final Listener listener;
@@ -108,6 +107,7 @@ public interface Listener {
   private final ConditionVariable transformerConditionVariable;
   private final TransformationResult.Builder transformationResultBuilder;
 
+  private boolean generateSilentAudio;
   private boolean isDrainingPipelines;
   private @Transformer.ProgressState int progressState;
   private @MonotonicNonNull RuntimeException cancelException;
@@ -124,7 +124,7 @@ public TransformerInternal(
       ImmutableList<Effect> videoEffects,
       boolean removeAudio,
       boolean removeVideo,
-      boolean forceSilentAudio,
+      boolean generateSilentAudio,
       AssetLoader.Factory assetLoaderFactory,
       FrameProcessor.Factory frameProcessorFactory,
       Codec.EncoderFactory encoderFactory,
@@ -138,7 +138,7 @@ public TransformerInternal(
     this.transformationRequest = transformationRequest;
     this.audioProcessors = audioProcessors;
     this.videoEffects = videoEffects;
-    this.forceSilentAudio = forceSilentAudio;
+    this.generateSilentAudio = generateSilentAudio;
     this.frameProcessorFactory = frameProcessorFactory;
     this.encoderFactory = new CapturingEncoderFactory(encoderFactory);
     this.listener = listener;
@@ -373,9 +373,6 @@ public void onTrackCount(int trackCount) {
         return;
       }
       this.trackCount.set(trackCount);
-      if (forceSilentAudio) {
-        this.trackCount.incrementAndGet();
-      }
     }
 
     @Override
@@ -386,6 +383,14 @@ public SampleConsumer onTrackAdded(
         long streamOffsetUs)
         throws TransformationException {
       if (!trackAdded) {
+        if (generateSilentAudio) {
+          if (this.trackCount.get() == 1 && MimeTypes.isVideo(format.sampleMimeType)) {
+            this.trackCount.incrementAndGet();
+          } else {
+            generateSilentAudio = false;
+          }
+        }
+
         // Call setTrackCount() methods here so that they are called from the same thread as the
         // MuxerWrapper and FallbackListener methods called when building the sample pipelines.
         muxerWrapper.setTrackCount(trackCount.get());
@@ -397,7 +402,7 @@ public SampleConsumer onTrackAdded(
           getSamplePipeline(format, supportedOutputTypes, streamStartPositionUs, streamOffsetUs);
       internalHandler.obtainMessage(MSG_REGISTER_SAMPLE_PIPELINE, samplePipeline).sendToTarget();
 
-      if (forceSilentAudio) {
+      if (generateSilentAudio) {
         Format silentAudioFormat =
             new Format.Builder()
                 .setSampleMimeType(MimeTypes.AUDIO_AAC)
@@ -482,7 +487,7 @@ private SamplePipeline getSamplePipeline(
             streamOffsetUs,
             transformationRequest,
             audioProcessors,
-            forceSilentAudio ? durationUs : C.TIME_UNSET,
+            generateSilentAudio ? durationUs : C.TIME_UNSET,
             encoderFactory,
             muxerWrapper,
             fallbackListener);
@@ -528,7 +533,7 @@ private boolean shouldTranscodeAudio(Format inputFormat) {
       if (!audioProcessors.isEmpty()) {
         return true;
       }
-      if (forceSilentAudio) {
+      if (generateSilentAudio) {
         return true;
       }