Make the base values of SilenceSkippingAudioProcessor configurable.

Issue:#6705
PiperOrigin-RevId: 310907118

RELEASENOTES.md

@@ -84,6 +84,8 @@
         ([#7247](https://github.com/google/ExoPlayer/pull/7247)).
     *   Replace `CacheDataSinkFactory` and `CacheDataSourceFactory` with
         `CacheDataSink.Factory` and `CacheDataSource.Factory` respectively.
+    *   Enable the configuration of `SilenceSkippingAudioProcessor`
+        ([#6705](https://github.com/google/ExoPlayer/issues/6705)).
 *   Video: Pass frame rate hint to `Surface.setFrameRate` on Android R devices.
 *   Text:
     *   Parse `<ruby>` and `<rt>` tags in WebVTT subtitles (rendering is coming

library/core/src/main/java/com/google/android/exoplayer2/audio/DefaultAudioSink.java

@@ -131,9 +131,20 @@ public final class DefaultAudioSink implements AudioSink {
 
     /**
      * Creates a new default chain of audio processors, with the user-defined {@code
-     * audioProcessors} applied before silence skipping and playback parameters.
+     * audioProcessors} applied before silence skipping and speed adjustment processors.
      */
     public DefaultAudioProcessorChain(AudioProcessor... audioProcessors) {
+      this(audioProcessors, new SilenceSkippingAudioProcessor(), new SonicAudioProcessor());
+    }
+
+    /**
+     * Creates a new default chain of audio processors, with the user-defined {@code
+     * audioProcessors} applied before silence skipping and speed adjustment processors.
+     */
+    public DefaultAudioProcessorChain(
+        AudioProcessor[] audioProcessors,
+        SilenceSkippingAudioProcessor silenceSkippingAudioProcessor,
+        SonicAudioProcessor sonicAudioProcessor) {
       // The passed-in type may be more specialized than AudioProcessor[], so allocate a new array
       // rather than using Arrays.copyOf.
       this.audioProcessors = new AudioProcessor[audioProcessors.length + 2];
@@ -143,8 +154,8 @@ public final class DefaultAudioSink implements AudioSink {
           /* dest= */ this.audioProcessors,
           /* destPos= */ 0,
           /* length= */ audioProcessors.length);
-      silenceSkippingAudioProcessor = new SilenceSkippingAudioProcessor();
-      sonicAudioProcessor = new SonicAudioProcessor();
+      this.silenceSkippingAudioProcessor = silenceSkippingAudioProcessor;
+      this.sonicAudioProcessor = sonicAudioProcessor;
       this.audioProcessors[audioProcessors.length] = silenceSkippingAudioProcessor;
       this.audioProcessors[audioProcessors.length + 1] = sonicAudioProcessor;
     }

library/core/src/main/java/com/google/android/exoplayer2/audio/SilenceSkippingAudioProcessor.java

@@ -17,6 +17,7 @@ package com.google.android.exoplayer2.audio;
 
 import androidx.annotation.IntDef;
 import com.google.android.exoplayer2.C;
+import com.google.android.exoplayer2.util.Assertions;
 import com.google.android.exoplayer2.util.Util;
 import java.lang.annotation.Documented;
 import java.lang.annotation.Retention;
@@ -30,17 +31,20 @@ import java.nio.ByteBuffer;
 public final class SilenceSkippingAudioProcessor extends BaseAudioProcessor {
 
   /**
-   * The minimum duration of audio that must be below {@link #SILENCE_THRESHOLD_LEVEL} to classify
-   * that part of audio as silent, in microseconds.
+   * The default value for {@link #SilenceSkippingAudioProcessor(long, long, short)
+   * minimumSilenceDurationUs}.
    */
-  private static final long MINIMUM_SILENCE_DURATION_US = 150_000;
+  public static final long DEFAULT_MINIMUM_SILENCE_DURATION_US = 150_000;
   /**
-   * The duration of silence by which to extend non-silent sections, in microseconds. The value must
-   * not exceed {@link #MINIMUM_SILENCE_DURATION_US}.
+   * The default value for {@link #SilenceSkippingAudioProcessor(long, long, short)
+   * paddingSilenceUs}.
    */
-  private static final long PADDING_SILENCE_US = 20_000;
-  /** The absolute level below which an individual PCM sample is classified as silent. */
-  private static final short SILENCE_THRESHOLD_LEVEL = 1024;
+  public static final long DEFAULT_PADDING_SILENCE_US = 20_000;
+  /**
+   * The default value for {@link #SilenceSkippingAudioProcessor(long, long, short)
+   * silenceThresholdLevel}.
+   */
+  public static final short DEFAULT_SILENCE_THRESHOLD_LEVEL = 1024;
 
   /** Trimming states. */
   @Documented
@@ -58,8 +62,10 @@ public final class SilenceSkippingAudioProcessor extends BaseAudioProcessor {
   /** State when the input is silent. */
   private static final int STATE_SILENT = 2;
 
+  private final long minimumSilenceDurationUs;
+  private final long paddingSilenceUs;
+  private final short silenceThresholdLevel;
   private int bytesPerFrame;
-
   private boolean enabled;
 
   /**
@@ -81,8 +87,31 @@ public final class SilenceSkippingAudioProcessor extends BaseAudioProcessor {
   private boolean hasOutputNoise;
   private long skippedFrames;
 
-  /** Creates a new silence trimming audio processor. */
+  /** Creates a new silence skipping audio processor. */
   public SilenceSkippingAudioProcessor() {
+    this(
+        DEFAULT_MINIMUM_SILENCE_DURATION_US,
+        DEFAULT_PADDING_SILENCE_US,
+        DEFAULT_SILENCE_THRESHOLD_LEVEL);
+  }
+
+  /**
+   * Creates a new silence skipping audio processor.
+   *
+   * @param minimumSilenceDurationUs The minimum duration of audio that must be below {@code
+   *     silenceThresholdLevel} to classify that part of audio as silent, in microseconds.
+   * @param paddingSilenceUs The duration of silence by which to extend non-silent sections, in
+   *     microseconds. The value must not exceed {@code minimumSilenceDurationUs}.
+   * @param silenceThresholdLevel The absolute level below which an individual PCM sample is
+   *     classified as silent.
+   */
+  public SilenceSkippingAudioProcessor(
+      long minimumSilenceDurationUs, long paddingSilenceUs, short silenceThresholdLevel) {
+    Assertions.checkArgument(paddingSilenceUs <= minimumSilenceDurationUs);
+    this.minimumSilenceDurationUs = minimumSilenceDurationUs;
+    this.paddingSilenceUs = paddingSilenceUs;
+    this.silenceThresholdLevel = silenceThresholdLevel;
+
     maybeSilenceBuffer = Util.EMPTY_BYTE_ARRAY;
     paddingBuffer = Util.EMPTY_BYTE_ARRAY;
   }
@@ -156,11 +185,11 @@ public final class SilenceSkippingAudioProcessor extends BaseAudioProcessor {
   protected void onFlush() {
     if (enabled) {
       bytesPerFrame = inputAudioFormat.bytesPerFrame;
-      int maybeSilenceBufferSize = durationUsToFrames(MINIMUM_SILENCE_DURATION_US) * bytesPerFrame;
+      int maybeSilenceBufferSize = durationUsToFrames(minimumSilenceDurationUs) * bytesPerFrame;
       if (maybeSilenceBuffer.length != maybeSilenceBufferSize) {
         maybeSilenceBuffer = new byte[maybeSilenceBufferSize];
       }
-      paddingSize = durationUsToFrames(PADDING_SILENCE_US) * bytesPerFrame;
+      paddingSize = durationUsToFrames(paddingSilenceUs) * bytesPerFrame;
       if (paddingBuffer.length != paddingSize) {
         paddingBuffer = new byte[paddingSize];
       }
@@ -317,7 +346,7 @@ public final class SilenceSkippingAudioProcessor extends BaseAudioProcessor {
   private int findNoisePosition(ByteBuffer buffer) {
     // The input is in ByteOrder.nativeOrder(), which is little endian on Android.
     for (int i = buffer.position(); i < buffer.limit(); i += 2) {
-      if (Math.abs(buffer.getShort(i)) > SILENCE_THRESHOLD_LEVEL) {
+      if (Math.abs(buffer.getShort(i)) > silenceThresholdLevel) {
         // Round to the start of the frame.
         return bytesPerFrame * (i / bytesPerFrame);
       }
@@ -332,7 +361,7 @@ public final class SilenceSkippingAudioProcessor extends BaseAudioProcessor {
   private int findNoiseLimit(ByteBuffer buffer) {
     // The input is in ByteOrder.nativeOrder(), which is little endian on Android.
     for (int i = buffer.limit() - 2; i >= buffer.position(); i -= 2) {
-      if (Math.abs(buffer.getShort(i)) > SILENCE_THRESHOLD_LEVEL) {
+      if (Math.abs(buffer.getShort(i)) > silenceThresholdLevel) {
         // Return the start of the next frame.
         return bytesPerFrame * (i / bytesPerFrame) + bytesPerFrame;
       }

library/core/src/test/java/com/google/android/exoplayer2/audio/SilenceSkippingAudioProcessorTest.java

@@ -202,6 +202,33 @@ public final class SilenceSkippingAudioProcessorTest {
     assertThat(silenceSkippingAudioProcessor.getSkippedFrames()).isEqualTo(42020);
   }
 
+  @Test
+  public void customPaddingValue_hasCorrectOutputAndSkippedFrameCounts() throws Exception {
+    // Given a signal that alternates between silence and noise.
+    InputBufferProvider inputBufferProvider =
+        getInputBufferProviderForAlternatingSilenceAndNoise(
+            TEST_SIGNAL_SILENCE_DURATION_MS,
+            TEST_SIGNAL_NOISE_DURATION_MS,
+            TEST_SIGNAL_FRAME_COUNT);
+
+    // When processing the entire signal with a larger than normal padding silence.
+    SilenceSkippingAudioProcessor silenceSkippingAudioProcessor =
+        new SilenceSkippingAudioProcessor(
+            SilenceSkippingAudioProcessor.DEFAULT_MINIMUM_SILENCE_DURATION_US,
+            /* paddingSilenceUs= */ 21_000,
+            SilenceSkippingAudioProcessor.DEFAULT_SILENCE_THRESHOLD_LEVEL);
+    silenceSkippingAudioProcessor.setEnabled(true);
+    silenceSkippingAudioProcessor.configure(AUDIO_FORMAT);
+    silenceSkippingAudioProcessor.flush();
+    assertThat(silenceSkippingAudioProcessor.isActive()).isTrue();
+    long totalOutputFrames =
+        process(silenceSkippingAudioProcessor, inputBufferProvider, /* inputBufferSize= */ 120);
+
+    // The right number of frames are skipped/output.
+    assertThat(totalOutputFrames).isEqualTo(58379);
+    assertThat(silenceSkippingAudioProcessor.getSkippedFrames()).isEqualTo(41621);
+  }
+
   @Test
   public void skipThenFlush_resetsSkippedFrameCount() throws Exception {
     // Given a signal that alternates between silence and noise.