Support FLAC files with ID3 headers.

Support parsing ID3 tags at the beginning of FLAC files, even though FLAC spec
does not require this.

GitHub: #4055.

-------------
Created by MOE: https://github.com/google/moe
MOE_MIGRATED_REVID=192127929

RELEASENOTES.md

@@ -30,6 +30,8 @@
   * Allow setting tags for all media sources in their factories. The tag of the
     current window can be retrieved with `ExoPlayer.getCurrentTag`.
 * Audio:
+  * FLAC: Sniff FLAC files correctly if they have ID3 headers
+    ([#4055](https://github.com/google/ExoPlayer/issues/4055)).
   * Factor out `AudioTrack` position tracking from `DefaultAudioSink`.
   * Fix an issue where the playback position would pause just after playback
     begins, and poll the audio timestamp less frequently once it starts

extensions/flac/build.gradle

@@ -31,6 +31,7 @@ android {
 }
 
 dependencies {
+    implementation 'com.android.support:support-annotations:' + supportLibraryVersion
     implementation project(modulePrefix + 'library-core')
     androidTestImplementation project(modulePrefix + 'testutils')
 }

extensions/flac/src/androidTest/assets/bear_with_id3.flac.0.dump

@@ -0,0 +1,162 @@
+seekMap:
+  isSeekable = true
+  duration = 2741000
+  getPosition(0) = [[timeUs=0, position=55284]]
+numberOfTracks = 1
+track 0:
+  format:
+    bitrate = 768000
+    id = null
+    containerMimeType = null
+    sampleMimeType = audio/raw
+    maxInputSize = 16384
+    width = -1
+    height = -1
+    frameRate = -1.0
+    rotationDegrees = 0
+    pixelWidthHeightRatio = 1.0
+    channelCount = 2
+    sampleRate = 48000
+    pcmEncoding = 2
+    encoderDelay = 0
+    encoderPadding = 0
+    subsampleOffsetUs = 9223372036854775807
+    selectionFlags = 0
+    language = null
+    drmInitData = -
+    initializationData:
+  total output bytes = 526272
+  sample count = 33
+  sample 0:
+    time = 0
+    flags = 1
+    data = length 16384, hash 61D2C5C2
+  sample 1:
+    time = 85333
+    flags = 1
+    data = length 16384, hash E6D7F214
+  sample 2:
+    time = 170666
+    flags = 1
+    data = length 16384, hash 59BF0D5D
+  sample 3:
+    time = 256000
+    flags = 1
+    data = length 16384, hash 3625F468
+  sample 4:
+    time = 341333
+    flags = 1
+    data = length 16384, hash F66A323
+  sample 5:
+    time = 426666
+    flags = 1
+    data = length 16384, hash CDBAE629
+  sample 6:
+    time = 512000
+    flags = 1
+    data = length 16384, hash 536F3A91
+  sample 7:
+    time = 597333
+    flags = 1
+    data = length 16384, hash D4F35C9C
+  sample 8:
+    time = 682666
+    flags = 1
+    data = length 16384, hash EE04CEBF
+  sample 9:
+    time = 768000
+    flags = 1
+    data = length 16384, hash 647E2A67
+  sample 10:
+    time = 853333
+    flags = 1
+    data = length 16384, hash 31583F2C
+  sample 11:
+    time = 938666
+    flags = 1
+    data = length 16384, hash E433A93D
+  sample 12:
+    time = 1024000
+    flags = 1
+    data = length 16384, hash 5E1C7051
+  sample 13:
+    time = 1109333
+    flags = 1
+    data = length 16384, hash 43E6E358
+  sample 14:
+    time = 1194666
+    flags = 1
+    data = length 16384, hash 5DC1B256
+  sample 15:
+    time = 1280000
+    flags = 1
+    data = length 16384, hash 3D9D95CF
+  sample 16:
+    time = 1365333
+    flags = 1
+    data = length 16384, hash 2A5BD2C0
+  sample 17:
+    time = 1450666
+    flags = 1
+    data = length 16384, hash 93E25061
+  sample 18:
+    time = 1536000
+    flags = 1
+    data = length 16384, hash B81793D8
+  sample 19:
+    time = 1621333
+    flags = 1
+    data = length 16384, hash 1A3BD49F
+  sample 20:
+    time = 1706666
+    flags = 1
+    data = length 16384, hash FB672FF1
+  sample 21:
+    time = 1792000
+    flags = 1
+    data = length 16384, hash 48AB8B45
+  sample 22:
+    time = 1877333
+    flags = 1
+    data = length 16384, hash 13C9640A
+  sample 23:
+    time = 1962666
+    flags = 1
+    data = length 16384, hash 499E4A0B
+  sample 24:
+    time = 2048000
+    flags = 1
+    data = length 16384, hash F9A783E6
+  sample 25:
+    time = 2133333
+    flags = 1
+    data = length 16384, hash D2B77598
+  sample 26:
+    time = 2218666
+    flags = 1
+    data = length 16384, hash CE5B826C
+  sample 27:
+    time = 2304000
+    flags = 1
+    data = length 16384, hash E99EE956
+  sample 28:
+    time = 2389333
+    flags = 1
+    data = length 16384, hash F2DB1486
+  sample 29:
+    time = 2474666
+    flags = 1
+    data = length 16384, hash 1636EAB
+  sample 30:
+    time = 2560000
+    flags = 1
+    data = length 16384, hash 23457C08
+  sample 31:
+    time = 2645333
+    flags = 1
+    data = length 16384, hash 30EB8381
+  sample 32:
+    time = 2730666
+    flags = 1
+    data = length 1984, hash 59CFDE1B
+tracksEnded = true

extensions/flac/src/androidTest/assets/bear_with_id3.flac.1.dump

@@ -0,0 +1,122 @@
+seekMap:
+  isSeekable = true
+  duration = 2741000
+  getPosition(0) = [[timeUs=0, position=55284]]
+numberOfTracks = 1
+track 0:
+  format:
+    bitrate = 768000
+    id = null
+    containerMimeType = null
+    sampleMimeType = audio/raw
+    maxInputSize = 16384
+    width = -1
+    height = -1
+    frameRate = -1.0
+    rotationDegrees = 0
+    pixelWidthHeightRatio = 1.0
+    channelCount = 2
+    sampleRate = 48000
+    pcmEncoding = 2
+    encoderDelay = 0
+    encoderPadding = 0
+    subsampleOffsetUs = 9223372036854775807
+    selectionFlags = 0
+    language = null
+    drmInitData = -
+    initializationData:
+  total output bytes = 362432
+  sample count = 23
+  sample 0:
+    time = 853333
+    flags = 1
+    data = length 16384, hash 31583F2C
+  sample 1:
+    time = 938666
+    flags = 1
+    data = length 16384, hash E433A93D
+  sample 2:
+    time = 1024000
+    flags = 1
+    data = length 16384, hash 5E1C7051
+  sample 3:
+    time = 1109333
+    flags = 1
+    data = length 16384, hash 43E6E358
+  sample 4:
+    time = 1194666
+    flags = 1
+    data = length 16384, hash 5DC1B256
+  sample 5:
+    time = 1280000
+    flags = 1
+    data = length 16384, hash 3D9D95CF
+  sample 6:
+    time = 1365333
+    flags = 1
+    data = length 16384, hash 2A5BD2C0
+  sample 7:
+    time = 1450666
+    flags = 1
+    data = length 16384, hash 93E25061
+  sample 8:
+    time = 1536000
+    flags = 1
+    data = length 16384, hash B81793D8
+  sample 9:
+    time = 1621333
+    flags = 1
+    data = length 16384, hash 1A3BD49F
+  sample 10:
+    time = 1706666
+    flags = 1
+    data = length 16384, hash FB672FF1
+  sample 11:
+    time = 1792000
+    flags = 1
+    data = length 16384, hash 48AB8B45
+  sample 12:
+    time = 1877333
+    flags = 1
+    data = length 16384, hash 13C9640A
+  sample 13:
+    time = 1962666
+    flags = 1
+    data = length 16384, hash 499E4A0B
+  sample 14:
+    time = 2048000
+    flags = 1
+    data = length 16384, hash F9A783E6
+  sample 15:
+    time = 2133333
+    flags = 1
+    data = length 16384, hash D2B77598
+  sample 16:
+    time = 2218666
+    flags = 1
+    data = length 16384, hash CE5B826C
+  sample 17:
+    time = 2304000
+    flags = 1
+    data = length 16384, hash E99EE956
+  sample 18:
+    time = 2389333
+    flags = 1
+    data = length 16384, hash F2DB1486
+  sample 19:
+    time = 2474666
+    flags = 1
+    data = length 16384, hash 1636EAB
+  sample 20:
+    time = 2560000
+    flags = 1
+    data = length 16384, hash 23457C08
+  sample 21:
+    time = 2645333
+    flags = 1
+    data = length 16384, hash 30EB8381
+  sample 22:
+    time = 2730666
+    flags = 1
+    data = length 1984, hash 59CFDE1B
+tracksEnded = true

extensions/flac/src/androidTest/assets/bear_with_id3.flac.2.dump

@@ -0,0 +1,78 @@
+seekMap:
+  isSeekable = true
+  duration = 2741000
+  getPosition(0) = [[timeUs=0, position=55284]]
+numberOfTracks = 1
+track 0:
+  format:
+    bitrate = 768000
+    id = null
+    containerMimeType = null
+    sampleMimeType = audio/raw
+    maxInputSize = 16384
+    width = -1
+    height = -1
+    frameRate = -1.0
+    rotationDegrees = 0
+    pixelWidthHeightRatio = 1.0
+    channelCount = 2
+    sampleRate = 48000
+    pcmEncoding = 2
+    encoderDelay = 0
+    encoderPadding = 0
+    subsampleOffsetUs = 9223372036854775807
+    selectionFlags = 0
+    language = null
+    drmInitData = -
+    initializationData:
+  total output bytes = 182208
+  sample count = 12
+  sample 0:
+    time = 1792000
+    flags = 1
+    data = length 16384, hash 48AB8B45
+  sample 1:
+    time = 1877333
+    flags = 1
+    data = length 16384, hash 13C9640A
+  sample 2:
+    time = 1962666
+    flags = 1
+    data = length 16384, hash 499E4A0B
+  sample 3:
+    time = 2048000
+    flags = 1
+    data = length 16384, hash F9A783E6
+  sample 4:
+    time = 2133333
+    flags = 1
+    data = length 16384, hash D2B77598
+  sample 5:
+    time = 2218666
+    flags = 1
+    data = length 16384, hash CE5B826C
+  sample 6:
+    time = 2304000
+    flags = 1
+    data = length 16384, hash E99EE956
+  sample 7:
+    time = 2389333
+    flags = 1
+    data = length 16384, hash F2DB1486
+  sample 8:
+    time = 2474666
+    flags = 1
+    data = length 16384, hash 1636EAB
+  sample 9:
+    time = 2560000
+    flags = 1
+    data = length 16384, hash 23457C08
+  sample 10:
+    time = 2645333
+    flags = 1
+    data = length 16384, hash 30EB8381
+  sample 11:
+    time = 2730666
+    flags = 1
+    data = length 1984, hash 59CFDE1B
+tracksEnded = true

extensions/flac/src/androidTest/assets/bear_with_id3.flac.3.dump

@@ -0,0 +1,38 @@
+seekMap:
+  isSeekable = true
+  duration = 2741000
+  getPosition(0) = [[timeUs=0, position=55284]]
+numberOfTracks = 1
+track 0:
+  format:
+    bitrate = 768000
+    id = null
+    containerMimeType = null
+    sampleMimeType = audio/raw
+    maxInputSize = 16384
+    width = -1
+    height = -1
+    frameRate = -1.0
+    rotationDegrees = 0
+    pixelWidthHeightRatio = 1.0
+    channelCount = 2
+    sampleRate = 48000
+    pcmEncoding = 2
+    encoderDelay = 0
+    encoderPadding = 0
+    subsampleOffsetUs = 9223372036854775807
+    selectionFlags = 0
+    language = null
+    drmInitData = -
+    initializationData:
+  total output bytes = 18368
+  sample count = 2
+  sample 0:
+    time = 2645333
+    flags = 1
+    data = length 16384, hash 30EB8381
+  sample 1:
+    time = 2730666
+    flags = 1
+    data = length 1984, hash 59CFDE1B
+tracksEnded = true

extensions/flac/src/androidTest/java/com/google/android/exoplayer2/ext/flac/FlacExtractorTest.java

@@ -33,7 +33,7 @@ public class FlacExtractorTest extends InstrumentationTestCase {
     }
   }
 
-  public void testSample() throws Exception {
+  public void testExtractFlacSample() throws Exception {
     ExtractorAsserts.assertBehavior(
         new ExtractorFactory() {
           @Override
@@ -44,4 +44,16 @@ public class FlacExtractorTest extends InstrumentationTestCase {
         "bear.flac",
         getInstrumentation().getContext());
   }
+
+  public void testExtractFlacSampleWithId3Header() throws Exception {
+    ExtractorAsserts.assertBehavior(
+        new ExtractorFactory() {
+          @Override
+          public Extractor create() {
+            return new FlacExtractor();
+          }
+        },
+        "bear_with_id3.flac",
+        getInstrumentation().getContext());
+  }
 }

extensions/flac/src/main/java/com/google/android/exoplayer2/ext/flac/FlacExtractor.java

@@ -17,20 +17,27 @@ package com.google.android.exoplayer2.ext.flac;
 
 import static com.google.android.exoplayer2.util.Util.getPcmEncoding;
 
+import android.support.annotation.IntDef;
+import android.support.annotation.Nullable;
 import com.google.android.exoplayer2.C;
 import com.google.android.exoplayer2.Format;
 import com.google.android.exoplayer2.extractor.Extractor;
 import com.google.android.exoplayer2.extractor.ExtractorInput;
 import com.google.android.exoplayer2.extractor.ExtractorOutput;
 import com.google.android.exoplayer2.extractor.ExtractorsFactory;
+import com.google.android.exoplayer2.extractor.Id3Peeker;
 import com.google.android.exoplayer2.extractor.PositionHolder;
 import com.google.android.exoplayer2.extractor.SeekMap;
 import com.google.android.exoplayer2.extractor.SeekPoint;
 import com.google.android.exoplayer2.extractor.TrackOutput;
+import com.google.android.exoplayer2.metadata.Metadata;
+import com.google.android.exoplayer2.metadata.id3.Id3Decoder;
 import com.google.android.exoplayer2.util.FlacStreamInfo;
 import com.google.android.exoplayer2.util.MimeTypes;
 import com.google.android.exoplayer2.util.ParsableByteArray;
 import java.io.IOException;
+import java.lang.annotation.Retention;
+import java.lang.annotation.RetentionPolicy;
 import java.nio.ByteBuffer;
 import java.util.Arrays;
 
@@ -51,22 +58,57 @@ public final class FlacExtractor implements Extractor {
 
   };
 
+  /** Flags controlling the behavior of the extractor. */
+  @Retention(RetentionPolicy.SOURCE)
+  @IntDef(
+    flag = true,
+    value = {FLAG_DISABLE_ID3_METADATA}
+  )
+  public @interface Flags {}
+
+  /**
+   * Flag to disable parsing of ID3 metadata. Can be set to save memory if ID3 metadata is not
+   * required.
+   */
+  public static final int FLAG_DISABLE_ID3_METADATA = 1;
+
   /**
    * FLAC signature: first 4 is the signature word, second 4 is the sizeof STREAMINFO. 0x22 is the
    * mandatory STREAMINFO.
    */
   private static final byte[] FLAC_SIGNATURE = {'f', 'L', 'a', 'C', 0, 0, 0, 0x22};
 
-  private ExtractorOutput extractorOutput;
+  private final Id3Peeker id3Peeker;
-  private TrackOutput trackOutput;
+  private final @Flags int flags;
 
   private FlacDecoderJni decoderJni;
 
-  private boolean metadataParsed;
+  private ExtractorOutput extractorOutput;
+  private TrackOutput trackOutput;
 
   private ParsableByteArray outputBuffer;
   private ByteBuffer outputByteBuffer;
 
+  private Metadata id3Metadata;
+  private long id3SectionSize;
+
+  private boolean metadataParsed;
+
+  /** Constructs an instance with flags = 0. */
+  public FlacExtractor() {
+    this(0);
+  }
+
+  /**
+   * Constructs an instance.
+   *
+   * @param flags Flags that control the extractor's behavior.
+   */
+  public FlacExtractor(int flags) {
+    this.flags = flags;
+    id3Peeker = new Id3Peeker();
+  }
+
   @Override
   public void init(ExtractorOutput output) {
     extractorOutput = output;
@@ -81,14 +123,27 @@ public final class FlacExtractor implements Extractor {
 
   @Override
   public boolean sniff(ExtractorInput input) throws IOException, InterruptedException {
-    byte[] header = new byte[FLAC_SIGNATURE.length];
+    if (input.getPosition() == 0) {
-    input.peekFully(header, 0, FLAC_SIGNATURE.length);
+      id3Metadata = peekId3Data(input);
-    return Arrays.equals(header, FLAC_SIGNATURE);
+      id3SectionSize = input.getPeekPosition();
+    }
+    boolean isFlacFormat = peekFlacSignature(input);
+    if (isFlacFormat) {
+      // If this is FLAC format, we should skip the whole ID3 section.
+      skipFullyId3Section(input);
+    }
+    return isFlacFormat;
   }
 
   @Override
   public int read(final ExtractorInput input, PositionHolder seekPosition)
       throws IOException, InterruptedException {
+    if (input.getPosition() == 0) {
+      id3Metadata = peekId3Data(input);
+      id3SectionSize = input.getPeekPosition();
+    }
+    skipFullyId3Section(input);
+
     decoderJni.setData(input);
 
     if (!metadataParsed) {
@@ -100,7 +155,7 @@ public final class FlacExtractor implements Extractor {
         }
       } catch (IOException e) {
         decoderJni.reset(0);
-        input.setRetryPosition(0, e);
+        input.setRetryPosition(id3SectionSize, e);
         throw e; // never executes
       }
       metadataParsed = true;
@@ -108,22 +163,25 @@ public final class FlacExtractor implements Extractor {
       boolean isSeekable = decoderJni.getSeekPosition(0) != -1;
       extractorOutput.seekMap(
           isSeekable
-              ? new FlacSeekMap(streamInfo.durationUs(), decoderJni)
+              ? new FlacSeekMap(streamInfo.durationUs(), decoderJni, id3SectionSize)
               : new SeekMap.Unseekable(streamInfo.durationUs(), 0));
       Format mediaFormat =
           Format.createAudioSampleFormat(
-              null,
+              /* id= */ null,
               MimeTypes.AUDIO_RAW,
-              null,
+              /* codecs= */ null,
               streamInfo.bitRate(),
               streamInfo.maxDecodedFrameSize(),
               streamInfo.channels,
               streamInfo.sampleRate,
               getPcmEncoding(streamInfo.bitsPerSample),
-              null,
+              /* encoderDelay= */ 0,
-              null,
+              /* encoderPadding= */ 0,
-              0,
+              /* initializationData= */ null,
-              null);
+              /* drmInitData= */ null,
+              /* selectionFlags= */ 0,
+              /* language= */ null,
+              (flags & FLAG_DISABLE_ID3_METADATA) != 0 ? null : id3Metadata);
       trackOutput.format(mediaFormat);
 
       outputBuffer = new ParsableByteArray(streamInfo.maxDecodedFrameSize());
@@ -138,7 +196,7 @@ public final class FlacExtractor implements Extractor {
     } catch (IOException e) {
       if (lastDecodePosition >= 0) {
         decoderJni.reset(lastDecodePosition);
-        input.setRetryPosition(lastDecodePosition, e);
+        input.setRetryPosition(id3SectionSize + lastDecodePosition, e);
       }
       throw e;
     }
@@ -154,11 +212,12 @@ public final class FlacExtractor implements Extractor {
 
   @Override
   public void seek(long position, long timeUs) {
-    if (position == 0) {
+    if (position <= id3SectionSize) {
       metadataParsed = false;
     }
+    long flacStreamPosition = Math.max(0, position - id3SectionSize);
     if (decoderJni != null) {
-      decoderJni.reset(position);
+      decoderJni.reset(flacStreamPosition);
     }
   }
 
@@ -170,14 +229,48 @@ public final class FlacExtractor implements Extractor {
     }
   }
 
+  /**
+   * Peeks ID3 tag data (if present) at the beginning of the input.
+   *
+   * @return The first ID3 tag decoded into a {@link Metadata} object. May be null if ID3 tag is not
+   *     present in the input.
+   */
+  @Nullable
+  private Metadata peekId3Data(ExtractorInput input) throws IOException, InterruptedException {
+    input.resetPeekPosition();
+    boolean disableId3Frames = (flags & FLAG_DISABLE_ID3_METADATA) != 0;
+    Id3Decoder.FramePredicate id3FramePredicate =
+        disableId3Frames ? Id3Decoder.NO_FRAMES_PREDICATE : null;
+    return id3Peeker.peekId3Data(input, id3FramePredicate);
+  }
+
+  /**
+   * Peeks from the beginning of the input to see if {@link #FLAC_SIGNATURE} is present.
+   *
+   * @return Whether the input begins with {@link #FLAC_SIGNATURE}.
+   */
+  private boolean peekFlacSignature(ExtractorInput input) throws IOException, InterruptedException {
+    byte[] header = new byte[FLAC_SIGNATURE.length];
+    input.peekFully(header, 0, FLAC_SIGNATURE.length);
+    return Arrays.equals(header, FLAC_SIGNATURE);
+  }
+
+  /** Skips input until we have passed the whole Id3 section. */
+  private void skipFullyId3Section(ExtractorInput input) throws IOException, InterruptedException {
+    int bytesToSkip = Math.max(0, (int) (id3SectionSize - input.getPosition()));
+    input.skipFully(bytesToSkip);
+  }
+
   private static final class FlacSeekMap implements SeekMap {
 
     private final long durationUs;
     private final FlacDecoderJni decoderJni;
+    private final long id3SectionSize;
 
-    public FlacSeekMap(long durationUs, FlacDecoderJni decoderJni) {
+    public FlacSeekMap(long durationUs, FlacDecoderJni decoderJni, long id3SectionSize) {
       this.durationUs = durationUs;
       this.decoderJni = decoderJni;
+      this.id3SectionSize = id3SectionSize;
     }
 
     @Override
@@ -188,7 +281,8 @@ public final class FlacExtractor implements Extractor {
     @Override
     public SeekPoints getSeekPoints(long timeUs) {
       // TODO: Access the seek table via JNI to return two seek points when appropriate.
-      return new SeekPoints(new SeekPoint(timeUs, decoderJni.getSeekPosition(timeUs)));
+      return new SeekPoints(
+          new SeekPoint(timeUs, id3SectionSize + decoderJni.getSeekPosition(timeUs)));
     }
 
     @Override

library/core/src/main/java/com/google/android/exoplayer2/extractor/Id3Peeker.java

@@ -0,0 +1,87 @@
+/*
+ * Copyright (C) 2018 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.extractor;
+
+import android.support.annotation.Nullable;
+import com.google.android.exoplayer2.metadata.Metadata;
+import com.google.android.exoplayer2.metadata.id3.Id3Decoder;
+import com.google.android.exoplayer2.util.ParsableByteArray;
+import java.io.EOFException;
+import java.io.IOException;
+
+/**
+ * Peeks data from the beginning of an {@link ExtractorInput} to determine if there is any ID3 tag.
+ */
+public final class Id3Peeker {
+
+  private final ParsableByteArray scratch;
+
+  public Id3Peeker() {
+    scratch = new ParsableByteArray(Id3Decoder.ID3_HEADER_LENGTH);
+  }
+
+  /**
+   * Peeks ID3 data from the input and parses the first ID3 tag.
+   *
+   * @param input The {@link ExtractorInput} from which data should be peeked.
+   * @param id3FramePredicate Determines which ID3 frames are decoded. May be null to decode all
+   *     frames.
+   * @return The first ID3 tag decoded into a {@link Metadata} object. May be null if ID3 tag is not
+   *     present in the input.
+   * @throws IOException If an error occurred peeking from the input.
+   * @throws InterruptedException If the thread was interrupted.
+   */
+  @Nullable
+  public Metadata peekId3Data(
+      ExtractorInput input, @Nullable Id3Decoder.FramePredicate id3FramePredicate)
+      throws IOException, InterruptedException {
+    int peekedId3Bytes = 0;
+    Metadata metadata = null;
+    while (true) {
+      try {
+        input.peekFully(scratch.data, 0, Id3Decoder.ID3_HEADER_LENGTH);
+      } catch (EOFException e) {
+        // If input has less than ID3_HEADER_LENGTH, ignore the rest.
+        break;
+      }
+      scratch.setPosition(0);
+      if (scratch.readUnsignedInt24() != Id3Decoder.ID3_TAG) {
+        // Not an ID3 tag.
+        break;
+      }
+      scratch.skipBytes(3); // Skip major version, minor version and flags.
+      int framesLength = scratch.readSynchSafeInt();
+      int tagLength = Id3Decoder.ID3_HEADER_LENGTH + framesLength;
+
+      if (metadata == null) {
+        byte[] id3Data = new byte[tagLength];
+        System.arraycopy(scratch.data, 0, id3Data, 0, Id3Decoder.ID3_HEADER_LENGTH);
+        input.peekFully(id3Data, Id3Decoder.ID3_HEADER_LENGTH, framesLength);
+
+        metadata = new Id3Decoder(id3FramePredicate).decode(id3Data, tagLength);
+      } else {
+        input.advancePeekPosition(framesLength);
+      }
+
+      peekedId3Bytes += tagLength;
+    }
+
+    input.resetPeekPosition();
+    input.advancePeekPosition(peekedId3Bytes);
+    return metadata;
+  }
+}

library/core/src/main/java/com/google/android/exoplayer2/extractor/mp3/Mp3Extractor.java

@@ -24,6 +24,7 @@ import com.google.android.exoplayer2.extractor.ExtractorInput;
 import com.google.android.exoplayer2.extractor.ExtractorOutput;
 import com.google.android.exoplayer2.extractor.ExtractorsFactory;
 import com.google.android.exoplayer2.extractor.GaplessInfoHolder;
+import com.google.android.exoplayer2.extractor.Id3Peeker;
 import com.google.android.exoplayer2.extractor.MpegAudioHeader;
 import com.google.android.exoplayer2.extractor.PositionHolder;
 import com.google.android.exoplayer2.extractor.SeekMap;
@@ -99,6 +100,7 @@ public final class Mp3Extractor implements Extractor {
   private final ParsableByteArray scratch;
   private final MpegAudioHeader synchronizedHeader;
   private final GaplessInfoHolder gaplessInfoHolder;
+  private final Id3Peeker id3Peeker;
 
   // Extractor outputs.
   private ExtractorOutput extractorOutput;
@@ -135,6 +137,7 @@ public final class Mp3Extractor implements Extractor {
     synchronizedHeader = new MpegAudioHeader();
     gaplessInfoHolder = new GaplessInfoHolder();
     basisTimeUs = C.TIME_UNSET;
+    id3Peeker = new Id3Peeker();
   }
 
   // Extractor implementation.
@@ -181,10 +184,22 @@ public final class Mp3Extractor implements Extractor {
         seeker = getConstantBitrateSeeker(input);
       }
       extractorOutput.seekMap(seeker);
-      trackOutput.format(Format.createAudioSampleFormat(null, synchronizedHeader.mimeType, null,
+      trackOutput.format(
-          Format.NO_VALUE, MpegAudioHeader.MAX_FRAME_SIZE_BYTES, synchronizedHeader.channels,
+          Format.createAudioSampleFormat(
-          synchronizedHeader.sampleRate, Format.NO_VALUE, gaplessInfoHolder.encoderDelay,
+              /* id= */ null,
-          gaplessInfoHolder.encoderPadding, null, null, 0, null,
+              synchronizedHeader.mimeType,
+              /* codecs= */ null,
+              /* bitrate= */ Format.NO_VALUE,
+              MpegAudioHeader.MAX_FRAME_SIZE_BYTES,
+              synchronizedHeader.channels,
+              synchronizedHeader.sampleRate,
+              /* pcmEncoding= */ Format.NO_VALUE,
+              gaplessInfoHolder.encoderDelay,
+              gaplessInfoHolder.encoderPadding,
+              /* initializationData= */ null,
+              /* drmInitData= */ null,
+              /* selectionFlags= */ 0,
+              /* language= */ null,
               (flags & FLAG_DISABLE_ID3_METADATA) != 0 ? null : metadata));
     }
     return readSample(input);
@@ -242,7 +257,15 @@ public final class Mp3Extractor implements Extractor {
     int searchLimitBytes = sniffing ? MAX_SNIFF_BYTES : MAX_SYNC_BYTES;
     input.resetPeekPosition();
     if (input.getPosition() == 0) {
-      peekId3Data(input);
+      // We need to parse enough ID3 metadata to retrieve any gapless playback information even
+      // if ID3 metadata parsing is disabled.
+      boolean onlyDecodeGaplessInfoFrames = (flags & FLAG_DISABLE_ID3_METADATA) != 0;
+      Id3Decoder.FramePredicate id3FramePredicate =
+          onlyDecodeGaplessInfoFrames ? GaplessInfoHolder.GAPLESS_INFO_ID3_FRAME_PREDICATE : null;
+      metadata = id3Peeker.peekId3Data(input, id3FramePredicate);
+      if (metadata != null) {
+        gaplessInfoHolder.setFromMetadata(metadata);
+      }
       peekedId3Bytes = (int) input.getPeekPosition();
       if (!sniffing) {
         input.skipFully(peekedId3Bytes);
@@ -296,49 +319,6 @@ public final class Mp3Extractor implements Extractor {
     return true;
   }
 
-  /**
-   * Peeks ID3 data from the input, including gapless playback information.
-   *
-   * @param input The {@link ExtractorInput} from which data should be peeked.
-   * @throws IOException If an error occurred peeking from the input.
-   * @throws InterruptedException If the thread was interrupted.
-   */
-  private void peekId3Data(ExtractorInput input) throws IOException, InterruptedException {
-    int peekedId3Bytes = 0;
-    while (true) {
-      input.peekFully(scratch.data, 0, Id3Decoder.ID3_HEADER_LENGTH);
-      scratch.setPosition(0);
-      if (scratch.readUnsignedInt24() != Id3Decoder.ID3_TAG) {
-        // Not an ID3 tag.
-        break;
-      }
-      scratch.skipBytes(3); // Skip major version, minor version and flags.
-      int framesLength = scratch.readSynchSafeInt();
-      int tagLength = Id3Decoder.ID3_HEADER_LENGTH + framesLength;
-
-      if (metadata == null) {
-        byte[] id3Data = new byte[tagLength];
-        System.arraycopy(scratch.data, 0, id3Data, 0, Id3Decoder.ID3_HEADER_LENGTH);
-        input.peekFully(id3Data, Id3Decoder.ID3_HEADER_LENGTH, framesLength);
-        // We need to parse enough ID3 metadata to retrieve any gapless playback information even
-        // if ID3 metadata parsing is disabled.
-        Id3Decoder.FramePredicate id3FramePredicate = (flags & FLAG_DISABLE_ID3_METADATA) != 0
-            ? GaplessInfoHolder.GAPLESS_INFO_ID3_FRAME_PREDICATE : null;
-        metadata = new Id3Decoder(id3FramePredicate).decode(id3Data, tagLength);
-        if (metadata != null) {
-          gaplessInfoHolder.setFromMetadata(metadata);
-        }
-      } else {
-        input.advancePeekPosition(framesLength);
-      }
-
-      peekedId3Bytes += tagLength;
-    }
-
-    input.resetPeekPosition();
-    input.advancePeekPosition(peekedId3Bytes);
-  }
-
   /**
    * Consumes the next frame from the {@code input} if it contains VBRI or Xing seeking metadata,
    * returning a {@link Seeker} if the metadata was present and valid, or {@code null} otherwise.

library/core/src/main/java/com/google/android/exoplayer2/metadata/id3/Id3Decoder.java

@@ -53,6 +53,16 @@ public final class Id3Decoder implements MetadataDecoder {
 
   }
 
+  /** A predicate that indicates no frames should be decoded. */
+  public static final FramePredicate NO_FRAMES_PREDICATE =
+      new FramePredicate() {
+
+        @Override
+        public boolean evaluate(int majorVersion, int id0, int id1, int id2, int id3) {
+          return false;
+        }
+      };
+
   private static final String TAG = "Id3Decoder";
 
   /**

library/core/src/test/java/com/google/android/exoplayer2/extractor/Id3PeekerTest.java

@@ -0,0 +1,111 @@
+/*
+ * Copyright (C) 2018 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.extractor;
+
+import static com.google.common.truth.Truth.assertThat;
+
+import com.google.android.exoplayer2.metadata.Metadata;
+import com.google.android.exoplayer2.metadata.id3.ApicFrame;
+import com.google.android.exoplayer2.metadata.id3.CommentFrame;
+import com.google.android.exoplayer2.metadata.id3.Id3Decoder;
+import com.google.android.exoplayer2.metadata.id3.Id3DecoderTest;
+import com.google.android.exoplayer2.testutil.FakeExtractorInput;
+import java.io.IOException;
+import org.junit.Test;
+import org.junit.runner.RunWith;
+import org.robolectric.RobolectricTestRunner;
+
+/** Unit test for {@link Id3Peeker}. */
+@RunWith(RobolectricTestRunner.class)
+public final class Id3PeekerTest {
+
+  @Test
+  public void testPeekId3Data_returnNull_ifId3TagNotPresentAtBeginningOfInput()
+      throws IOException, InterruptedException {
+    Id3Peeker id3Peeker = new Id3Peeker();
+    FakeExtractorInput input =
+        new FakeExtractorInput.Builder()
+            .setData(new byte[] {1, 'I', 'D', '3', 2, 3, 4, 5, 6, 7, 8, 9, 10})
+            .build();
+
+    Metadata metadata = id3Peeker.peekId3Data(input, /* id3FramePredicate= */ null);
+    assertThat(metadata).isNull();
+  }
+
+  @Test
+  public void testPeekId3Data_returnId3Tag_ifId3TagPresent()
+      throws IOException, InterruptedException {
+    Id3Peeker id3Peeker = new Id3Peeker();
+
+    byte[] rawId3 =
+        Id3DecoderTest.buildSingleFrameTag(
+            "APIC",
+            new byte[] {
+              3, 105, 109, 97, 103, 101, 47, 106, 112, 101, 103, 0, 16, 72, 101, 108, 108, 111, 32,
+              87, 111, 114, 108, 100, 0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 0
+            });
+    FakeExtractorInput input = new FakeExtractorInput.Builder().setData(rawId3).build();
+
+    Metadata metadata = id3Peeker.peekId3Data(input, /* id3FramePredicate= */ null);
+    assertThat(metadata.length()).isEqualTo(1);
+
+    ApicFrame apicFrame = (ApicFrame) metadata.get(0);
+    assertThat(apicFrame.mimeType).isEqualTo("image/jpeg");
+    assertThat(apicFrame.pictureType).isEqualTo(16);
+    assertThat(apicFrame.description).isEqualTo("Hello World");
+    assertThat(apicFrame.pictureData).hasLength(10);
+    assertThat(apicFrame.pictureData).isEqualTo(new byte[] {1, 2, 3, 4, 5, 6, 7, 8, 9, 0});
+  }
+
+  @Test
+  public void testPeekId3Data_returnId3TagAccordingToGivenPredicate_ifId3TagPresent()
+      throws IOException, InterruptedException {
+    Id3Peeker id3Peeker = new Id3Peeker();
+
+    byte[] rawId3 =
+        Id3DecoderTest.buildMultiFramesTag(
+            new Id3DecoderTest.FrameSpec(
+                "COMM",
+                new byte[] {
+                  3, 101, 110, 103, 100, 101, 115, 99, 114, 105, 112, 116, 105, 111, 110, 0, 116,
+                  101, 120, 116, 0
+                }),
+            new Id3DecoderTest.FrameSpec(
+                "APIC",
+                new byte[] {
+                  3, 105, 109, 97, 103, 101, 47, 106, 112, 101, 103, 0, 16, 72, 101, 108, 108, 111,
+                  32, 87, 111, 114, 108, 100, 0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 0
+                }));
+    FakeExtractorInput input = new FakeExtractorInput.Builder().setData(rawId3).build();
+
+    Metadata metadata =
+        id3Peeker.peekId3Data(
+            input,
+            new Id3Decoder.FramePredicate() {
+              @Override
+              public boolean evaluate(int majorVersion, int id0, int id1, int id2, int id3) {
+                return id0 == 'C' && id1 == 'O' && id2 == 'M' && id3 == 'M';
+              }
+            });
+    assertThat(metadata.length()).isEqualTo(1);
+
+    CommentFrame commentFrame = (CommentFrame) metadata.get(0);
+    assertThat(commentFrame.language).isEqualTo("eng");
+    assertThat(commentFrame.description).isEqualTo("description");
+    assertThat(commentFrame.text).isEqualTo("text");
+  }
+}

library/core/src/test/java/com/google/android/exoplayer2/metadata/id3/Id3DecoderTest.java

@@ -22,6 +22,7 @@ import com.google.android.exoplayer2.metadata.Metadata;
 import com.google.android.exoplayer2.metadata.MetadataDecoderException;
 import com.google.android.exoplayer2.util.Assertions;
 import java.nio.charset.Charset;
+import java.util.Arrays;
 import org.junit.Test;
 import org.junit.runner.RunWith;
 import org.robolectric.RobolectricTestRunner;
@@ -32,7 +33,7 @@ import org.robolectric.RobolectricTestRunner;
 @RunWith(RobolectricTestRunner.class)
 public final class Id3DecoderTest {
 
-  private static final byte[] TAG_HEADER = new byte[] {73, 68, 51, 4, 0, 0, 0, 0, 0, 0};
+  private static final byte[] TAG_HEADER = new byte[] {'I', 'D', '3', 4, 0, 0, 0, 0, 0, 0};
   private static final int FRAME_HEADER_LENGTH = 10;
   private static final int ID3_TEXT_ENCODING_UTF_8 = 3;
 
@@ -202,19 +203,64 @@ public final class Id3DecoderTest {
     assertThat(commentFrame.text).isEmpty();
   }
 
-  private static byte[] buildSingleFrameTag(String frameId, byte[] frameData) {
+  @Test
-    byte[] frameIdBytes = frameId.getBytes(Charset.forName(C.UTF8_NAME));
+  public void testDecodeMultiFrames() throws MetadataDecoderException {
-    Assertions.checkState(frameIdBytes.length == 4);
+    byte[] rawId3 =
+        buildMultiFramesTag(
+            new FrameSpec(
+                "COMM",
+                new byte[] {
+                  3, 101, 110, 103, 100, 101, 115, 99, 114, 105, 112, 116, 105, 111, 110, 0, 116,
+                  101, 120, 116, 0
+                }),
+            new FrameSpec(
+                "APIC",
+                new byte[] {
+                  3, 105, 109, 97, 103, 101, 47, 106, 112, 101, 103, 0, 16, 72, 101, 108, 108, 111,
+                  32, 87, 111, 114, 108, 100, 0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 0
+                }));
+    Id3Decoder decoder = new Id3Decoder();
+    Metadata metadata = decoder.decode(rawId3, rawId3.length);
+    assertThat(metadata.length()).isEqualTo(2);
+    CommentFrame commentFrame = (CommentFrame) metadata.get(0);
+    ApicFrame apicFrame = (ApicFrame) metadata.get(1);
 
-    byte[] tagData = new byte[TAG_HEADER.length + FRAME_HEADER_LENGTH + frameData.length];
+    assertThat(commentFrame.language).isEqualTo("eng");
-    System.arraycopy(TAG_HEADER, 0, tagData, 0, TAG_HEADER.length);
+    assertThat(commentFrame.description).isEqualTo("description");
+    assertThat(commentFrame.text).isEqualTo("text");
+
+    assertThat(apicFrame.mimeType).isEqualTo("image/jpeg");
+    assertThat(apicFrame.pictureType).isEqualTo(16);
+    assertThat(apicFrame.description).isEqualTo("Hello World");
+    assertThat(apicFrame.pictureData).hasLength(10);
+    assertThat(apicFrame.pictureData).isEqualTo(new byte[] {1, 2, 3, 4, 5, 6, 7, 8, 9, 0});
+  }
+
+  public static byte[] buildSingleFrameTag(String frameId, byte[] frameData) {
+    return buildMultiFramesTag(new FrameSpec(frameId, frameData));
+  }
+
+  public static byte[] buildMultiFramesTag(FrameSpec... frames) {
+    int totalLength = TAG_HEADER.length;
+    for (FrameSpec frame : frames) {
+      byte[] frameData = frame.frameData;
+      totalLength += FRAME_HEADER_LENGTH + frameData.length;
+    }
+    byte[] tagData = Arrays.copyOf(TAG_HEADER, totalLength);
     // Fill in the size part of the tag header.
     int offset = TAG_HEADER.length - 4;
-    int tagSize = frameData.length + FRAME_HEADER_LENGTH;
+    int tagSize = totalLength - TAG_HEADER.length;
     tagData[offset++] = (byte) ((tagSize >> 21) & 0x7F);
     tagData[offset++] = (byte) ((tagSize >> 14) & 0x7F);
     tagData[offset++] = (byte) ((tagSize >> 7) & 0x7F);
     tagData[offset++] = (byte) (tagSize & 0x7F);
+
+    for (FrameSpec frame : frames) {
+      byte[] frameData = frame.frameData;
+      String frameId = frame.frameId;
+      byte[] frameIdBytes = frameId.getBytes(Charset.forName(C.UTF8_NAME));
+      Assertions.checkState(frameIdBytes.length == 4);
+
       // Fill in the frame header.
       tagData[offset++] = frameIdBytes[0];
       tagData[offset++] = frameIdBytes[1];
@@ -225,10 +271,22 @@ public final class Id3DecoderTest {
       tagData[offset++] = (byte) ((frameData.length >> 8) & 0xFF);
       tagData[offset++] = (byte) (frameData.length & 0xFF);
       offset += 2; // Frame flags set to 0
+
       // Fill in the frame data.
       System.arraycopy(frameData, 0, tagData, offset, frameData.length);
-
+      offset += frameData.length;
+    }
     return tagData;
   }
 
+  /** Specify an ID3 frame. */
+  public static final class FrameSpec {
+    public final String frameId;
+    public final byte[] frameData;
+
+    public FrameSpec(String frameId, byte[] frameData) {
+      this.frameId = frameId;
+      this.frameData = frameData;
+    }
+  }
 }