Add WebVTT parser.

library/src/main/java/com/google/android/exoplayer/text/webvtt/WebvttParser.java

+/*
+ * 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.webvtt;
+
+import com.google.android.exoplayer.C;
+import com.google.android.exoplayer.ParserException;
+import com.google.android.exoplayer.text.SubtitleParser;
+import com.google.android.exoplayer.util.MimeTypes;
+
+import java.io.BufferedReader;
+import java.io.IOException;
+import java.io.InputStream;
+import java.io.InputStreamReader;
+import java.util.ArrayList;
+import java.util.regex.Matcher;
+import java.util.regex.Pattern;
+
+/**
+ * A simple WebVTT parser.
+ * <p>
+ * @see <a href="http://dev.w3.org/html5/webvtt">WebVTT specification</a>
+ * <p>
+ */
+public class WebvttParser implements SubtitleParser {
+
+  /**
+   * This parser allows a custom header to be prepended to the WebVTT data, in the form of a text
+   * line starting with this string.
+   *
+   * @hide
+   */
+  public static final String EXO_HEADER = "EXO-HEADER";
+  /**
+   * A {@code OFFSET + value} element can be added to the custom header to specify an offset time
+   * (in microseconds) that should be subtracted from the embedded MPEGTS value.
+   *
+   * @hide
+   */
+  public static final String OFFSET = "OFFSET:";
+
+  private static final long SAMPLING_RATE = 90;
+
+  private static final String WEBVTT_TIMESTAMP_STRING = "(\\d+:)?[0-5]\\d:[0-5]\\d\\.\\d{3}";
+  private static final Pattern WEBVTT_TIMESTAMP = Pattern.compile(WEBVTT_TIMESTAMP_STRING);
+  private static final Pattern MEDIA_TIMESTAMP_OFFSET = Pattern.compile(OFFSET + "\\d+");
+  private static final Pattern MEDIA_TIMESTAMP = Pattern.compile("MPEGTS:\\d+");
+
+  @Override
+  public WebvttSubtitle parse(InputStream inputStream, String inputEncoding, long startTimeUs)
+      throws IOException {
+    ArrayList<WebvttCue> subtitles = new ArrayList<WebvttCue>();
+    long mediaTimestampUs = startTimeUs;
+    long mediaTimestampOffsetUs = 0;
+
+    BufferedReader webvttData = new BufferedReader(new InputStreamReader(inputStream, C.UTF8_NAME));
+    String line;
+
+    // file should start with "WEBVTT" on the first line or "EXO-HEADER"
+    line = webvttData.readLine();
+    if (line == null) {
+      throw new ParserException("Expected WEBVTT or EXO-HEADER. Got null");
+    }
+    if (line.startsWith(EXO_HEADER)) {
+      // parse the timestamp offset, if present
+      Matcher matcher = MEDIA_TIMESTAMP_OFFSET.matcher(line);
+      if (matcher.find()) {
+        mediaTimestampOffsetUs = Long.parseLong(matcher.group().substring(7));
+      }
+
+      // read the next line, which should now be WEBVTT
+      line = webvttData.readLine();
+      if (line == null) {
+        throw new ParserException("Expected WEBVTT. Got null");
+      }
+    }
+    if (!line.equals("WEBVTT")) {
+      throw new ParserException("Expected WEBVTT. Got " + line);
+    }
+
+    // after "WEBVTT" there should be either an empty line or an "X-TIMESTAMP-MAP" line and then
+    // and empty line
+    line = webvttData.readLine();
+    if (!line.isEmpty()) {
+      if (!line.startsWith("X-TIMESTAMP-MAP")) {
+        throw new ParserException("Expected an empty line or X-TIMESTAMP-MAP. Got " + line);
+      }
+
+      // parse the media timestamp
+      Matcher matcher = MEDIA_TIMESTAMP.matcher(line);
+      if (!matcher.find()) {
+        throw new ParserException("X-TIMESTAMP-MAP doesn't contain media timestmap: " + line);
+      } else {
+        mediaTimestampUs = (Long.parseLong(matcher.group().substring(7)) * 1000) / SAMPLING_RATE
+            - mediaTimestampOffsetUs;
+      }
+      mediaTimestampUs = getAdjustedStartTime(mediaTimestampUs);
+
+      // read in the next line (which should be an empty line)
+      line = webvttData.readLine();
+    }
+    if (!line.isEmpty()) {
+      throw new ParserException("Expected an empty line after WEBVTT or X-TIMESTAMP-MAP. Got "
+          + line);
+    }
+
+    // process the cues and text
+    while ((line = webvttData.readLine()) != null) {
+      // parse the cue timestamps
+      Matcher matcher = WEBVTT_TIMESTAMP.matcher(line);
+      long startTime;
+      long endTime;
+      String text = "";
+
+      // parse start timestamp
+      if (!matcher.find()) {
+        throw new ParserException("Expected cue start time: " + line);
+      } else {
+        startTime = parseTimestampUs(matcher.group()) + mediaTimestampUs;
+      }
+
+      // parse end timestamp
+      if (!matcher.find()) {
+        throw new ParserException("Expected cue end time: " + line);
+      } else {
+        endTime = parseTimestampUs(matcher.group()) + mediaTimestampUs;
+      }
+
+      // parse text
+      while (((line = webvttData.readLine()) != null) && (!line.isEmpty())) {
+        text += line.trim() + "\n";
+      }
+
+      WebvttCue cue = new WebvttCue(startTime, endTime, text);
+      subtitles.add(cue);
+    }
+
+    webvttData.close();
+    inputStream.close();
+
+    // copy WebvttCue data into arrays for WebvttSubtitle constructor
+    String[] cueText = new String[subtitles.size()];
+    long[] cueTimesUs = new long[2 * subtitles.size()];
+    for (int subtitleIndex = 0; subtitleIndex < subtitles.size(); subtitleIndex++) {
+      int arrayIndex = subtitleIndex * 2;
+      WebvttCue cue = subtitles.get(subtitleIndex);
+      cueTimesUs[arrayIndex] = cue.startTime;
+      cueTimesUs[arrayIndex + 1] = cue.endTime;
+      cueText[subtitleIndex] = cue.text;
+    }
+
+    WebvttSubtitle subtitle = new WebvttSubtitle(cueText, mediaTimestampUs, cueTimesUs);
+    return subtitle;
+  }
+
+  @Override
+  public boolean canParse(String mimeType) {
+    return MimeTypes.TEXT_VTT.equals(mimeType);
+  }
+
+  protected long getAdjustedStartTime(long startTimeUs) {
+    return startTimeUs;
+  }
+
+  private static long parseTimestampUs(String s) throws NumberFormatException {
+    if (!s.matches(WEBVTT_TIMESTAMP_STRING)) {
+      throw new NumberFormatException("has invalid format");
+    }
+
+    String[] parts = s.split("\\.", 2);
+    long value = 0;
+    for (String group : parts[0].split(":")) {
+      value = value * 60 + Long.parseLong(group);
+    }
+    return (value * 1000 + Long.parseLong(parts[1])) * 1000;
+  }
+
+  private static class WebvttCue {
+    public final long startTime;
+    public final long endTime;
+    public final String text;
+
+    public WebvttCue(long startTime, long endTime, String text) {
+      this.startTime = startTime;
+      this.endTime = endTime;
+      this.text = text;
+    }
+  }
+
+}

library/src/main/java/com/google/android/exoplayer/text/webvtt/WebvttSubtitle.java

+/*
+ * 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.webvtt;
+
+import com.google.android.exoplayer.text.Subtitle;
+import com.google.android.exoplayer.util.Assertions;
+import com.google.android.exoplayer.util.Util;
+
+import java.util.Arrays;
+
+/**
+ * A representation of a WebVTT subtitle.
+ */
+public class WebvttSubtitle implements Subtitle {
+
+  private final String[] cueText;
+  private final long startTimeUs;
+  private final long[] cueTimesUs;
+  private final long[] sortedCueTimesUs;
+
+  /**
+   * @param cueText Text to be displayed during each cue.
+   * @param startTimeUs The start time of the subtitle.
+   * @param cueTimesUs Cue event times, where cueTimesUs[2 * i] and cueTimesUs[(2 * i) + 1] are
+   *     the start and end times, respectively, corresponding to cueText[i].
+   */
+  public WebvttSubtitle(String[] cueText, long startTimeUs, long[] cueTimesUs) {
+    this.cueText = cueText;
+    this.startTimeUs = startTimeUs;
+    this.cueTimesUs = cueTimesUs;
+    this.sortedCueTimesUs = Arrays.copyOf(cueTimesUs, cueTimesUs.length);
+    Arrays.sort(sortedCueTimesUs);
+  }
+
+  @Override
+  public long getStartTime() {
+    return startTimeUs;
+  }
+
+  @Override
+  public int getNextEventTimeIndex(long timeUs) {
+    Assertions.checkArgument(timeUs >= 0);
+    int index = Util.binarySearchCeil(sortedCueTimesUs, timeUs, false, false);
+    return index < sortedCueTimesUs.length ? index : -1;
+  }
+
+  @Override
+  public int getEventTimeCount() {
+    return sortedCueTimesUs.length;
+  }
+
+  @Override
+  public long getEventTime(int index) {
+    Assertions.checkArgument(index >= 0);
+    Assertions.checkArgument(index < sortedCueTimesUs.length);
+    return sortedCueTimesUs[index];
+  }
+
+  @Override
+  public long getLastEventTime() {
+    if (getEventTimeCount() == 0) {
+      return -1;
+    }
+    return sortedCueTimesUs[sortedCueTimesUs.length - 1];
+  }
+
+  @Override
+  public String getText(long timeUs) {
+    StringBuilder subtitleStringBuilder = new StringBuilder();
+
+    for (int i = 0; i < cueTimesUs.length; i += 2) {
+      if ((cueTimesUs[i] <= timeUs) && (timeUs < cueTimesUs[i + 1])) {
+        subtitleStringBuilder.append(cueText[i / 2]);
+      }
+    }
+
+    return (subtitleStringBuilder.length() > 0) ? subtitleStringBuilder.toString() : null;
+  }
+
+}