Add "Webvtt embedded in MP4" support

Issue: #689
-------------
Created by MOE: https://github.com/google/moe
MOE_MIGRATED_REVID=110003312

library/src/main/java/com/google/android/exoplayer/extractor/mp4/Atom.java

@@ -110,6 +110,7 @@ import java.util.List;
   public static final int TYPE_stco = Util.getIntegerCodeForString("stco");
   public static final int TYPE_co64 = Util.getIntegerCodeForString("co64");
   public static final int TYPE_tx3g = Util.getIntegerCodeForString("tx3g");
+  public static final int TYPE_wvtt = Util.getIntegerCodeForString("wvtt");
   public static final int TYPE_stpp = Util.getIntegerCodeForString("stpp");
   public static final int TYPE_samr = Util.getIntegerCodeForString("samr");
   public static final int TYPE_sawb = Util.getIntegerCodeForString("sawb");

library/src/main/java/com/google/android/exoplayer/extractor/mp4/AtomParsers.java

@@ -462,6 +462,9 @@ import java.util.List;
       } else if (childAtomType == Atom.TYPE_tx3g) {
         out.mediaFormat = MediaFormat.createTextFormat(Integer.toString(trackId),
             MimeTypes.APPLICATION_TX3G, MediaFormat.NO_VALUE, durationUs, language);
+      } else if (childAtomType == Atom.TYPE_wvtt) {
+        out.mediaFormat = MediaFormat.createTextFormat(Integer.toString(trackId),
+            MimeTypes.APPLICATION_MP4VTT, MediaFormat.NO_VALUE, durationUs, language);
       } else if (childAtomType == Atom.TYPE_stpp) {
         out.mediaFormat = MediaFormat.createTextFormat(Integer.toString(trackId),
             MimeTypes.APPLICATION_TTML, MediaFormat.NO_VALUE, durationUs, language,

library/src/main/java/com/google/android/exoplayer/text/TextTrackRenderer.java

@@ -87,6 +87,13 @@ public final class TextTrackRenderer extends SampleSourceTrackRenderer implement
     } catch (ClassNotFoundException e) {
       // Parser not found.
     }
+    try {
+      DEFAULT_PARSER_CLASSES.add(
+          Class.forName("com.google.android.exoplayer.text.mp4webvtt.Mp4WebvttParser")
+              .asSubclass(SubtitleParser.class));
+    } catch (ClassNotFoundException e) {
+      // Parser not found.
+    }
     try {
       DEFAULT_PARSER_CLASSES.add(
           Class.forName("com.google.android.exoplayer.text.subrip.SubripParser")

library/src/main/java/com/google/android/exoplayer/text/mp4webvtt/Mp4WebvttParser.java

@@ -0,0 +1,100 @@
+/*
+ * Copyright (C) 2014 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.exoplayer.text.mp4webvtt;
+
+import com.google.android.exoplayer.ParserException;
+import com.google.android.exoplayer.text.Cue;
+import com.google.android.exoplayer.text.Subtitle;
+import com.google.android.exoplayer.text.SubtitleParser;
+import com.google.android.exoplayer.util.MimeTypes;
+import com.google.android.exoplayer.util.ParsableByteArray;
+import com.google.android.exoplayer.util.Util;
+
+import java.io.IOException;
+import java.io.InputStream;
+import java.util.ArrayList;
+import java.util.List;
+
+/**
+ * A {@link SubtitleParser} for Webvtt embedded in a Mp4 container file.
+ */
+public final class Mp4WebvttParser implements SubtitleParser {
+
+  private static final int BOX_HEADER_SIZE = 8;
+
+  private static final int TYPE_vttc = Util.getIntegerCodeForString("vttc");
+  private static final int TYPE_payl = Util.getIntegerCodeForString("payl");
+
+  private final ParsableByteArray sampleData;
+  private byte[] inputBytesBuffer;
+
+  public Mp4WebvttParser() {
+    sampleData = new ParsableByteArray();
+  }
+
+  @Override
+  public boolean canParse(String mimeType) {
+    return MimeTypes.APPLICATION_MP4VTT.equals(mimeType);
+  }
+
+  @Override
+  public Subtitle parse(InputStream inputStream) throws IOException {
+    // Webvtt in Mp4 samples have boxes inside of them, so we have to do a traditional box parsing:
+    // first 4 bytes size and then 4 bytes type.
+    int inputStreamByteCount = inputStream.available();
+    if (inputBytesBuffer == null || inputBytesBuffer.length < inputStreamByteCount) {
+      inputBytesBuffer = new byte[inputStreamByteCount];
+    }
+    inputStream.read(inputBytesBuffer, 0, inputStreamByteCount);
+    sampleData.reset(inputBytesBuffer, inputStreamByteCount);
+    List<Cue> resultingCueList = new ArrayList<>();
+    while (sampleData.bytesLeft() > 0) {
+      if (sampleData.bytesLeft() < BOX_HEADER_SIZE) {
+        throw new ParserException("Incomplete Mp4Webvtt Top Level box header found.");
+      }
+      int boxSize = sampleData.readInt();
+      int boxType = sampleData.readInt();
+      if (boxType == TYPE_vttc) {
+        resultingCueList.add(parseVttCueBox(sampleData));
+      } else {
+        // Peers of the VTTCueBox are still not supported and are skipped.
+        sampleData.skipBytes(boxSize - BOX_HEADER_SIZE);
+      }
+    }
+    return new Mp4WebvttSubtitle(resultingCueList);
+  }
+
+  private static Cue parseVttCueBox(ParsableByteArray sampleData) throws IOException {
+    while (sampleData.bytesLeft() > 0) {
+      if (sampleData.bytesLeft() < BOX_HEADER_SIZE) {
+        throw new ParserException("Incomplete vtt cue box header found.");
+      }
+      int boxSize = sampleData.readInt();
+      int boxType = sampleData.readInt();
+      if (boxType == TYPE_payl) {
+        int payloadLength = boxSize - BOX_HEADER_SIZE;
+        String cueText = new String(sampleData.data, sampleData.getPosition(), payloadLength);
+        sampleData.skipBytes(payloadLength);
+        return new Cue(cueText.trim());
+      } else {
+        // Other VTTCueBox children are still not supported and are skipped.
+        sampleData.skipBytes(boxSize - BOX_HEADER_SIZE);
+      }
+    }
+    throw new ParserException("VTTCueBox does not contain mandatory payload box.");
+  }
+
+}

library/src/main/java/com/google/android/exoplayer/text/mp4webvtt/Mp4WebvttSubtitle.java

@@ -0,0 +1,61 @@
+/*
+ * Copyright (C) 2014 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.exoplayer.text.mp4webvtt;
+
+import com.google.android.exoplayer.text.Cue;
+import com.google.android.exoplayer.text.Subtitle;
+import com.google.android.exoplayer.util.Assertions;
+
+import java.util.Collections;
+import java.util.List;
+
+/**
+ * Representation of a Webvtt subtitle embedded in a MP4 container file.
+ */
+/* package */ final class Mp4WebvttSubtitle implements Subtitle {
+
+  private final List<Cue> cues;
+
+  public Mp4WebvttSubtitle(List<Cue> cueList) {
+    cues = Collections.unmodifiableList(cueList);
+  }
+
+  @Override
+  public int getNextEventTimeIndex(long timeUs) {
+    return timeUs < 0 ? 0 : -1;
+  }
+
+  @Override
+  public int getEventTimeCount() {
+    return 1;
+  }
+
+  @Override
+  public long getEventTime(int index) {
+    Assertions.checkArgument(index == 0);
+    return 0;
+  }
+
+  @Override
+  public long getLastEventTime() {
+    return 0;
+  }
+
+  @Override
+  public List<Cue> getCues(long timeUs) {
+    return timeUs >= 0 ? cues : Collections.<Cue>emptyList();
+  }
+}

library/src/main/java/com/google/android/exoplayer/util/MimeTypes.java

@@ -65,6 +65,7 @@ public final class MimeTypes {
   public static final String APPLICATION_TTML = BASE_TYPE_APPLICATION + "/ttml+xml";
   public static final String APPLICATION_M3U8 = BASE_TYPE_APPLICATION + "/x-mpegURL";
   public static final String APPLICATION_TX3G = BASE_TYPE_APPLICATION + "/x-quicktime-tx3g";
+  public static final String APPLICATION_MP4VTT = BASE_TYPE_APPLICATION + "/x-mp4vtt";
 
   private MimeTypes() {}