Opus: Add utility for handling header and initialization data

PiperOrigin-RevId: 325202386

extensions/opus/src/main/java/com/google/android/exoplayer2/ext/opus/LibopusAudioRenderer.java

@@ -24,6 +24,7 @@ import com.google.android.exoplayer2.audio.AudioRendererEventListener;
 import com.google.android.exoplayer2.audio.AudioSink;
 import com.google.android.exoplayer2.audio.AudioSink.SinkFormatSupport;
 import com.google.android.exoplayer2.audio.DecoderAudioRenderer;
+import com.google.android.exoplayer2.audio.OpusUtil;
 import com.google.android.exoplayer2.drm.ExoMediaCrypto;
 import com.google.android.exoplayer2.util.MimeTypes;
 import com.google.android.exoplayer2.util.TraceUtil;
@@ -125,6 +126,6 @@ public class LibopusAudioRenderer extends DecoderAudioRenderer<OpusDecoder> {
   protected Format getOutputFormat(OpusDecoder decoder) {
     @C.PcmEncoding
     int pcmEncoding = decoder.outputFloat ? C.ENCODING_PCM_FLOAT : C.ENCODING_PCM_16BIT;
-    return Util.getPcmFormat(pcmEncoding, decoder.channelCount, OpusDecoder.SAMPLE_RATE);
+    return Util.getPcmFormat(pcmEncoding, decoder.channelCount, OpusUtil.SAMPLE_RATE);
   }
 }

extensions/opus/src/main/java/com/google/android/exoplayer2/ext/opus/OpusDecoder.java

@@ -17,6 +17,7 @@ package com.google.android.exoplayer2.ext.opus;
 
 import androidx.annotation.Nullable;
 import com.google.android.exoplayer2.C;
+import com.google.android.exoplayer2.audio.OpusUtil;
 import com.google.android.exoplayer2.decoder.CryptoInfo;
 import com.google.android.exoplayer2.decoder.DecoderInputBuffer;
 import com.google.android.exoplayer2.decoder.SimpleDecoder;
@@ -26,18 +27,12 @@ import com.google.android.exoplayer2.drm.ExoMediaCrypto;
 import com.google.android.exoplayer2.util.Assertions;
 import com.google.android.exoplayer2.util.Util;
 import java.nio.ByteBuffer;
-import java.nio.ByteOrder;
 import java.util.List;
 
 /** Opus decoder. */
 /* package */ final class OpusDecoder
     extends SimpleDecoder<DecoderInputBuffer, SimpleOutputBuffer, OpusDecoderException> {
 
-  private static final int DEFAULT_SEEK_PRE_ROLL_SAMPLES = 3840;
-
-  /** Opus streams are always decoded at 48000 Hz. */
-  public static final int SAMPLE_RATE = 48_000;
-
   private static final int NO_ERROR = 0;
   private static final int DECODE_ERROR = -1;
   private static final int DRM_ERROR = -2;
@@ -46,9 +41,8 @@ import java.util.List;
   public final int channelCount;
 
   @Nullable private final ExoMediaCrypto exoMediaCrypto;
-
+  private final int preSkipSamples;
-  private final int headerSkipSamples;
+  private final int seekPreRollSamples;
-  private final int headerSeekPreRollSamples;
   private final long nativeDecoderContext;
 
   private int skipSamples;
@@ -77,21 +71,31 @@ import java.util.List;
       throws OpusDecoderException {
     super(new DecoderInputBuffer[numInputBuffers], new SimpleOutputBuffer[numOutputBuffers]);
     if (!OpusLibrary.isAvailable()) {
-      throw new OpusDecoderException("Failed to load decoder native libraries.");
+      throw new OpusDecoderException("Failed to load decoder native libraries");
     }
     this.exoMediaCrypto = exoMediaCrypto;
     if (exoMediaCrypto != null && !OpusLibrary.opusIsSecureDecodeSupported()) {
-      throw new OpusDecoderException("Opus decoder does not support secure decode.");
+      throw new OpusDecoderException("Opus decoder does not support secure decode");
     }
+    int initializationDataSize = initializationData.size();
+    if (initializationDataSize != 1 && initializationDataSize != 3) {
+      throw new OpusDecoderException("Invalid initialization data size");
+    }
+    if (initializationDataSize == 3
+        && (initializationData.get(1).length != 8 || initializationData.get(2).length != 8)) {
+      throw new OpusDecoderException("Invalid pre-skip or seek pre-roll");
+    }
+    preSkipSamples = OpusUtil.getPreSkipSamples(initializationData);
+    seekPreRollSamples = OpusUtil.getSeekPreRollSamples(initializationData);
+
     byte[] headerBytes = initializationData.get(0);
     if (headerBytes.length < 19) {
-      throw new OpusDecoderException("Header size is too small.");
+      throw new OpusDecoderException("Invalid header length");
     }
-    channelCount = headerBytes[9] & 0xFF;
+    channelCount = OpusUtil.getChannelCount(headerBytes);
     if (channelCount > 8) {
       throw new OpusDecoderException("Invalid channel count: " + channelCount);
     }
-    int preskip = readUnsignedLittleEndian16(headerBytes, 10);
     int gain = readSignedLittleEndian16(headerBytes, 16);
 
     byte[] streamMap = new byte[8];
@@ -100,7 +104,7 @@ import java.util.List;
     if (headerBytes[18] == 0) { // Channel mapping
       // If there is no channel mapping, use the defaults.
       if (channelCount > 2) { // Maximum channel count with default layout.
-        throw new OpusDecoderException("Invalid Header, missing stream map.");
+        throw new OpusDecoderException("Invalid header, missing stream map");
       }
       numStreams = 1;
       numCoupled = (channelCount == 2) ? 1 : 0;
@@ -108,29 +112,15 @@ import java.util.List;
       streamMap[1] = 1;
     } else {
       if (headerBytes.length < 21 + channelCount) {
-        throw new OpusDecoderException("Header size is too small.");
+        throw new OpusDecoderException("Invalid header length");
       }
       // Read the channel mapping.
       numStreams = headerBytes[19] & 0xFF;
       numCoupled = headerBytes[20] & 0xFF;
       System.arraycopy(headerBytes, 21, streamMap, 0, channelCount);
     }
-    if (initializationData.size() == 3) {
-      if (initializationData.get(1).length != 8 || initializationData.get(2).length != 8) {
-        throw new OpusDecoderException("Invalid Codec Delay or Seek Preroll");
-      }
-      long codecDelayNs =
-          ByteBuffer.wrap(initializationData.get(1)).order(ByteOrder.nativeOrder()).getLong();
-      long seekPreRollNs =
-          ByteBuffer.wrap(initializationData.get(2)).order(ByteOrder.nativeOrder()).getLong();
-      headerSkipSamples = nsToSamples(codecDelayNs);
-      headerSeekPreRollSamples = nsToSamples(seekPreRollNs);
-    } else {
-      headerSkipSamples = preskip;
-      headerSeekPreRollSamples = DEFAULT_SEEK_PRE_ROLL_SAMPLES;
-    }
     nativeDecoderContext =
-        opusInit(SAMPLE_RATE, channelCount, numStreams, numCoupled, gain, streamMap);
+        opusInit(OpusUtil.SAMPLE_RATE, channelCount, numStreams, numCoupled, gain, streamMap);
     if (nativeDecoderContext == 0) {
       throw new OpusDecoderException("Failed to initialize decoder");
     }
@@ -170,7 +160,7 @@ import java.util.List;
       opusReset(nativeDecoderContext);
       // When seeking to 0, skip number of samples as specified in opus header. When seeking to
       // any other time, skip number of samples as specified by seek preroll.
-      skipSamples = (inputBuffer.timeUs == 0) ? headerSkipSamples : headerSeekPreRollSamples;
+      skipSamples = (inputBuffer.timeUs == 0) ? preSkipSamples : seekPreRollSamples;
     }
     ByteBuffer inputData = Util.castNonNull(inputBuffer.data);
     CryptoInfo cryptoInfo = inputBuffer.cryptoInfo;
@@ -182,7 +172,7 @@ import java.util.List;
                 inputData,
                 inputData.limit(),
                 outputBuffer,
-                SAMPLE_RATE,
+                OpusUtil.SAMPLE_RATE,
                 exoMediaCrypto,
                 cryptoInfo.mode,
                 Assertions.checkNotNull(cryptoInfo.key),
@@ -231,18 +221,10 @@ import java.util.List;
     opusClose(nativeDecoderContext);
   }
 
-  private static int nsToSamples(long ns) {
+  private static int readSignedLittleEndian16(byte[] input, int offset) {
-    return (int) (ns * SAMPLE_RATE / 1000000000);
-  }
-
-  private static int readUnsignedLittleEndian16(byte[] input, int offset) {
     int value = input[offset] & 0xFF;
     value |= (input[offset + 1] & 0xFF) << 8;
-    return value;
+    return (short) value;
-  }
-
-  private static int readSignedLittleEndian16(byte[] input, int offset) {
-    return (short) readUnsignedLittleEndian16(input, offset);
   }
 
   private native long opusInit(

library/common/src/main/java/com/google/android/exoplayer2/audio/OpusUtil.java

@@ -0,0 +1,112 @@
+/*
+ * Copyright (C) 2020 The Android Open Source Project
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *      http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+package com.google.android.exoplayer2.audio;
+
+import com.google.android.exoplayer2.C;
+import java.nio.ByteBuffer;
+import java.nio.ByteOrder;
+import java.util.ArrayList;
+import java.util.List;
+
+/** Utility methods for handling Opus audio streams. */
+public class OpusUtil {
+
+  /** Opus streams are always 48000 Hz. */
+  public static final int SAMPLE_RATE = 48_000;
+
+  private static final int DEFAULT_SEEK_PRE_ROLL_SAMPLES = 3840;
+  private static final int FULL_CODEC_INITIALIZATION_DATA_BUFFER_COUNT = 3;
+
+  private OpusUtil() {} // Prevents instantiation.
+
+  /**
+   * Parses the channel count from an Opus Identification Header.
+   *
+   * @param header An Opus Identification Header, as defined by RFC 7845.
+   * @return The parsed channel count.
+   */
+  public static int getChannelCount(byte[] header) {
+    return header[9] & 0xFF;
+  }
+
+  /**
+   * Builds codec initialization data from an Opus Identification Header.
+   *
+   * @param header An Opus Identification Header, as defined by RFC 7845.
+   * @return Codec initialization data suitable for an Opus <a
+   *     href="https://developer.android.com/reference/android/media/MediaCodec#initialization">MediaCodec</a>.
+   */
+  public static List<byte[]> buildInitializationData(byte[] header) {
+    int preSkipSamples = getPreSkipSamples(header);
+    long preSkipNanos = sampleCountToNanoseconds(preSkipSamples);
+    long seekPreRollNanos = sampleCountToNanoseconds(DEFAULT_SEEK_PRE_ROLL_SAMPLES);
+
+    List<byte[]> initializationData = new ArrayList<>(FULL_CODEC_INITIALIZATION_DATA_BUFFER_COUNT);
+    initializationData.add(header);
+    initializationData.add(buildNativeOrderByteArray(preSkipNanos));
+    initializationData.add(buildNativeOrderByteArray(seekPreRollNanos));
+    return initializationData;
+  }
+
+  /**
+   * Returns the number of pre-skip samples specified by the given Opus codec initialization data.
+   *
+   * @param initializationData The codec initialization data.
+   * @return The number of pre-skip samples.
+   */
+  public static int getPreSkipSamples(List<byte[]> initializationData) {
+    if (initializationData.size() == FULL_CODEC_INITIALIZATION_DATA_BUFFER_COUNT) {
+      long codecDelayNs =
+          ByteBuffer.wrap(initializationData.get(1)).order(ByteOrder.nativeOrder()).getLong();
+      return (int) nanosecondsToSampleCount(codecDelayNs);
+    }
+    // Fall back to parsing directly from the Opus Identification header.
+    return getPreSkipSamples(initializationData.get(0));
+  }
+
+  /**
+   * Returns the number of seek per-roll samples specified by the given Opus codec initialization
+   * data.
+   *
+   * @param initializationData The codec initialization data.
+   * @return The number of seek pre-roll samples.
+   */
+  public static int getSeekPreRollSamples(List<byte[]> initializationData) {
+    if (initializationData.size() == FULL_CODEC_INITIALIZATION_DATA_BUFFER_COUNT) {
+      long seekPreRollNs =
+          ByteBuffer.wrap(initializationData.get(2)).order(ByteOrder.nativeOrder()).getLong();
+      return (int) nanosecondsToSampleCount(seekPreRollNs);
+    }
+    // Fall back to returning the default seek pre-roll.
+    return DEFAULT_SEEK_PRE_ROLL_SAMPLES;
+  }
+
+  private static int getPreSkipSamples(byte[] header) {
+    return ((header[11] & 0xFF) << 8) | (header[10] & 0xFF);
+  }
+
+  private static byte[] buildNativeOrderByteArray(long value) {
+    return ByteBuffer.allocate(8).order(ByteOrder.nativeOrder()).putLong(value).array();
+  }
+
+  private static long sampleCountToNanoseconds(long sampleCount) {
+    return (sampleCount * C.NANOS_PER_SECOND) / SAMPLE_RATE;
+  }
+
+  private static long nanosecondsToSampleCount(long nanoseconds) {
+    return (nanoseconds * SAMPLE_RATE) / C.NANOS_PER_SECOND;
+  }
+}

library/common/src/test/java/com/google/android/exoplayer2/audio/OpusUtilTest.java

@@ -0,0 +1,104 @@
+/*
+ * Copyright (C) 2020 The Android Open Source Project
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *      http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+package com.google.android.exoplayer2.audio;
+
+import static com.google.common.truth.Truth.assertThat;
+
+import androidx.test.ext.junit.runners.AndroidJUnit4;
+import com.google.android.exoplayer2.C;
+import com.google.common.collect.ImmutableList;
+import java.nio.ByteBuffer;
+import java.nio.ByteOrder;
+import java.util.List;
+import org.junit.Test;
+import org.junit.runner.RunWith;
+
+/** Unit tests for {@link OpusUtil}. */
+@RunWith(AndroidJUnit4.class)
+public final class OpusUtilTest {
+
+  private static final byte[] HEADER =
+      new byte[] {79, 112, 117, 115, 72, 101, 97, 100, 0, 2, 1, 56, 0, 0, -69, -128, 0, 0, 0};
+
+  private static final int HEADER_PRE_SKIP_SAMPLES = 14337;
+  private static final byte[] HEADER_PRE_SKIP_BYTES =
+      buildNativeOrderByteArray(sampleCountToNanoseconds(HEADER_PRE_SKIP_SAMPLES));
+
+  private static final int DEFAULT_SEEK_PRE_ROLL_SAMPLES = 3840;
+  private static final byte[] DEFAULT_SEEK_PRE_ROLL_BYTES =
+      buildNativeOrderByteArray(sampleCountToNanoseconds(DEFAULT_SEEK_PRE_ROLL_SAMPLES));
+
+  private static final ImmutableList<byte[]> HEADER_ONLY_INITIALIZATION_DATA =
+      ImmutableList.of(HEADER);
+
+  private static final long CUSTOM_PRE_SKIP_SAMPLES = 28674;
+  private static final byte[] CUSTOM_PRE_SKIP_BYTES =
+      buildNativeOrderByteArray(sampleCountToNanoseconds(CUSTOM_PRE_SKIP_SAMPLES));
+
+  private static final long CUSTOM_SEEK_PRE_ROLL_SAMPLES = 7680;
+  private static final byte[] CUSTOM_SEEK_PRE_ROLL_BYTES =
+      buildNativeOrderByteArray(sampleCountToNanoseconds(CUSTOM_SEEK_PRE_ROLL_SAMPLES));
+
+  private static final ImmutableList<byte[]> FULL_INITIALIZATION_DATA =
+      ImmutableList.of(HEADER, CUSTOM_PRE_SKIP_BYTES, CUSTOM_SEEK_PRE_ROLL_BYTES);
+
+  @Test
+  public void buildInitializationData() {
+    List<byte[]> initializationData = OpusUtil.buildInitializationData(HEADER);
+    assertThat(initializationData).hasSize(3);
+    assertThat(initializationData.get(0)).isEqualTo(HEADER);
+    assertThat(initializationData.get(1)).isEqualTo(HEADER_PRE_SKIP_BYTES);
+    assertThat(initializationData.get(2)).isEqualTo(DEFAULT_SEEK_PRE_ROLL_BYTES);
+  }
+
+  @Test
+  public void getChannelCount() {
+    int channelCount = OpusUtil.getChannelCount(HEADER);
+    assertThat(channelCount).isEqualTo(2);
+  }
+
+  @Test
+  public void getPreSkipSamples_fullInitializationData_returnsOverrideValue() {
+    int preSkipSamples = OpusUtil.getPreSkipSamples(FULL_INITIALIZATION_DATA);
+    assertThat(preSkipSamples).isEqualTo(CUSTOM_PRE_SKIP_SAMPLES);
+  }
+
+  @Test
+  public void getPreSkipSamples_headerOnlyInitializationData_returnsHeaderValue() {
+    int preSkipSamples = OpusUtil.getPreSkipSamples(HEADER_ONLY_INITIALIZATION_DATA);
+    assertThat(preSkipSamples).isEqualTo(HEADER_PRE_SKIP_SAMPLES);
+  }
+
+  @Test
+  public void getSeekPreRollSamples_fullInitializationData_returnsInitializationDataValue() {
+    int seekPreRollSamples = OpusUtil.getSeekPreRollSamples(FULL_INITIALIZATION_DATA);
+    assertThat(seekPreRollSamples).isEqualTo(CUSTOM_SEEK_PRE_ROLL_SAMPLES);
+  }
+
+  @Test
+  public void getSeekPreRollSamples_headerOnlyInitializationData_returnsDefaultValue() {
+    int seekPreRollSamples = OpusUtil.getSeekPreRollSamples(HEADER_ONLY_INITIALIZATION_DATA);
+    assertThat(seekPreRollSamples).isEqualTo(DEFAULT_SEEK_PRE_ROLL_SAMPLES);
+  }
+
+  private static long sampleCountToNanoseconds(long sampleCount) {
+    return (sampleCount * C.NANOS_PER_SECOND) / OpusUtil.SAMPLE_RATE;
+  }
+
+  private static byte[] buildNativeOrderByteArray(long value) {
+    return ByteBuffer.allocate(8).order(ByteOrder.nativeOrder()).putLong(value).array();
+  }
+}

library/extractor/src/main/java/com/google/android/exoplayer2/extractor/ogg/OpusReader.java

@@ -15,13 +15,10 @@
  */
 package com.google.android.exoplayer2.extractor.ogg;
 
-import com.google.android.exoplayer2.C;
 import com.google.android.exoplayer2.Format;
+import com.google.android.exoplayer2.audio.OpusUtil;
 import com.google.android.exoplayer2.util.MimeTypes;
 import com.google.android.exoplayer2.util.ParsableByteArray;
-import java.nio.ByteBuffer;
-import java.nio.ByteOrder;
-import java.util.ArrayList;
 import java.util.Arrays;
 import java.util.List;
 
@@ -30,11 +27,6 @@ import java.util.List;
  */
 /* package */ final class OpusReader extends StreamReader {
 
-  private static final int DEFAULT_SEEK_PRE_ROLL_SAMPLES = 3840;
-
-  /** Opus streams are always decoded at 48000 Hz. */
-  private static final int SAMPLE_RATE = 48_000;
-
   private static final int OPUS_CODE = 0x4f707573;
   private static final byte[] OPUS_SIGNATURE = {'O', 'p', 'u', 's', 'H', 'e', 'a', 'd'};
 
@@ -65,20 +57,14 @@ import java.util.List;
   @Override
   protected boolean readHeaders(ParsableByteArray packet, long position, SetupData setupData) {
     if (!headerRead) {
-      byte[] metadata = Arrays.copyOf(packet.getData(), packet.limit());
+      byte[] headerBytes = Arrays.copyOf(packet.getData(), packet.limit());
-      int channelCount = metadata[9] & 0xFF;
+      int channelCount = OpusUtil.getChannelCount(headerBytes);
-      int preskip = ((metadata[11] & 0xFF) << 8) | (metadata[10] & 0xFF);
+      List<byte[]> initializationData = OpusUtil.buildInitializationData(headerBytes);
-
-      List<byte[]> initializationData = new ArrayList<>(3);
-      initializationData.add(metadata);
-      putNativeOrderLong(initializationData, preskip);
-      putNativeOrderLong(initializationData, DEFAULT_SEEK_PRE_ROLL_SAMPLES);
-
       setupData.format =
           new Format.Builder()
               .setSampleMimeType(MimeTypes.AUDIO_OPUS)
               .setChannelCount(channelCount)
-              .setSampleRate(SAMPLE_RATE)
+              .setSampleRate(OpusUtil.SAMPLE_RATE)
               .setInitializationData(initializationData)
               .build();
       headerRead = true;
@@ -90,12 +76,6 @@ import java.util.List;
     return true;
   }
 
-  private void putNativeOrderLong(List<byte[]> initializationData, int samples) {
-    long ns = (samples * C.NANOS_PER_SECOND) / SAMPLE_RATE;
-    byte[] array = ByteBuffer.allocate(8).order(ByteOrder.nativeOrder()).putLong(ns).array();
-    initializationData.add(array);
-  }
-
   /**
    * Returns the duration of the given audio packet.
    *