Source: lib/hls/hls_parser.js

/**
 * @license
 * Copyright 2016 Google Inc.
 *
 * 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.
 */


goog.provide('shaka.hls.HlsParser');

goog.require('goog.Uri');
goog.require('goog.asserts');
goog.require('shaka.Deprecate');
goog.require('shaka.hls.ManifestTextParser');
goog.require('shaka.hls.Playlist');
goog.require('shaka.hls.PlaylistType');
goog.require('shaka.hls.Tag');
goog.require('shaka.hls.Utils');
goog.require('shaka.log');
goog.require('shaka.media.DrmEngine');
goog.require('shaka.media.InitSegmentReference');
goog.require('shaka.media.ManifestParser');
goog.require('shaka.media.PresentationTimeline');
goog.require('shaka.media.SegmentIndex');
goog.require('shaka.media.SegmentReference');
goog.require('shaka.net.DataUriPlugin');
goog.require('shaka.net.NetworkingEngine');
goog.require('shaka.text.TextEngine');
goog.require('shaka.util.ArrayUtils');
goog.require('shaka.util.DataViewReader');
goog.require('shaka.util.Error');
goog.require('shaka.util.Functional');
goog.require('shaka.util.LanguageUtils');
goog.require('shaka.util.ManifestParserUtils');
goog.require('shaka.util.MimeUtils');
goog.require('shaka.util.Mp4Parser');
goog.require('shaka.util.Networking');
goog.require('shaka.util.OperationManager');
goog.require('shaka.util.Timer');


/**
 * Creates a new HLS parser.
 *
 * @struct
 * @constructor
 * @implements {shaka.extern.ManifestParser}
 * @export
 */
shaka.hls.HlsParser = function() {
  /** @private {?shaka.extern.ManifestParser.PlayerInterface} */
  this.playerInterface_ = null;

  /** @private {?shaka.extern.ManifestConfiguration} */
  this.config_ = null;

  /** @private {number} */
  this.globalId_ = 1;

  /**
   * @private {!Map.<number, shaka.hls.HlsParser.StreamInfo>}
   */
  // TODO: This is now only used for text codec detection, try to remove.
  this.mediaTagsToStreamInfosMap_ = new Map();

  /**
   * The values are strings of the form "<VIDEO URI> - <AUDIO URI>",
   * where the URIs are the verbatim media playlist URIs as they appeared in the
   * master playlist.
   *
   * Used to avoid duplicates that vary only in their text stream.
   *
   * @private {!Set.<string>}
   */
  this.variantUriSet_ = new Set();

  /**
   * A map from (verbatim) media playlist URI to stream infos representing the
   * playlists.
   *
   * On update, used to iterate through and update from media playlists.
   *
   * On initial parse, used to iterate through and determine minimum timestamps,
   * offsets, and to handle TS rollover.
   *
   * During parsing, used to avoid duplicates in the async methods
   * createStreamInfoFromMediaTag_ and createStreamInfoFromVariantTag_.
   *
   * During parsing of updates, used by getStartTime_ to determine the start
   * time of the first segment from existing segment references.
   *
   * @private {!Map.<string, shaka.hls.HlsParser.StreamInfo>}
   */
  this.uriToStreamInfosMap_ = new Map();

  /** @private {?shaka.media.PresentationTimeline} */
  this.presentationTimeline_ = null;

  /**
   * The master playlist URI, after redirects.
   *
   * @private {string}
   */
  this.masterPlaylistUri_ = '';

  /** @private {shaka.hls.ManifestTextParser} */
  this.manifestTextParser_ = new shaka.hls.ManifestTextParser();

  /**
   * This is the number of seconds we want to wait between finishing a manifest
   * update and starting the next one. This will be set when we parse the
   * manifest.
   *
   * @private {number}
   */
  this.updatePlaylistDelay_ = 0;

  /**
   * This timer is used to trigger the start of a manifest update. A manifest
   * update is async. Once the update is finished, the timer will be restarted
   * to trigger the next update. The timer will only be started if the content
   * is live content.
   *
   * @private {shaka.util.Timer}
   */
  this.updatePlaylistTimer_ = new shaka.util.Timer(() => {
    this.onUpdate_();
  });

  /** @private {shaka.hls.HlsParser.PresentationType_} */
  this.presentationType_ = shaka.hls.HlsParser.PresentationType_.VOD;

  /** @private {?shaka.extern.Manifest} */
  this.manifest_ = null;

  /** @private {number} */
  this.maxTargetDuration_ = 0;

  /** @private {number} */
  this.minTargetDuration_ = Infinity;

  /** @private {shaka.util.OperationManager} */
  this.operationManager_ = new shaka.util.OperationManager();

  /** @private {!Array.<!Array.<!shaka.media.SegmentReference>>} */
  this.segmentsToNotifyByStream_ = [];

  /** A map from closed captions' group id, to a map of closed captions info.
   * {group id -> {closed captions channel id -> language}}
   * @private {Map.<string, Map.<string, string>>}
   */
  this.groupIdToClosedCaptionsMap_ = new Map();

  /** True if some of the variants in  the playlist is encrypted with AES-128.
   * @private {boolean} */
  this.aesEncrypted_ = false;
};


/**
 * @typedef {{
 *   stream: !shaka.extern.Stream,
 *   segmentIndex: !shaka.media.SegmentIndex,
 *   drmInfos: !Array.<shaka.extern.DrmInfo>,
 *   verbatimMediaPlaylistUri: string,
 *   absoluteMediaPlaylistUri: string,
 *   minTimestamp: number,
 *   maxTimestamp: number,
 *   duration: number
 * }}
 *
 * @description
 * Contains a stream and information about it.
 *
 * @property {!shaka.extern.Stream} stream
 *   The Stream itself.
 * @property {!shaka.media.SegmentIndex} segmentIndex
 *   SegmentIndex of the stream.
 * @property {!Array.<shaka.extern.DrmInfo>} drmInfos
 *   DrmInfos of the stream.  There may be multiple for multi-DRM content.
 * @property {string} verbatimMediaPlaylistUri
 *   The verbatim media playlist URI, as it appeared in the master playlist.
 *   This has not been canonicalized into an absolute URI.  This gives us a
 *   consistent key for this playlist, even if redirects cause us to update
 *   from different origins each time.
 * @property {string} absoluteMediaPlaylistUri
 *   The absolute media playlist URI, resolved relative to the master playlist
 *   and updated to reflect any redirects.
 * @property {number} minTimestamp
 *   The minimum timestamp found in the stream.
 * @property {number} maxTimestamp
 *   The maximum timestamp found in the stream.
 * @property {number} duration
 *   The duration of the playlist.  Used for VOD only.
 */
shaka.hls.HlsParser.StreamInfo;


/**
 * @override
 * @exportInterface
 */
shaka.hls.HlsParser.prototype.configure = function(config) {
  this.config_ = config;
};


/**
 * @override
 * @exportInterface
 */
shaka.hls.HlsParser.prototype.start = async function(uri, playerInterface) {
  goog.asserts.assert(this.config_, 'Must call configure() before start()!');
  this.playerInterface_ = playerInterface;

  const response = await this.requestManifest_(uri);

  // Record the master playlist URI after redirects.
  this.masterPlaylistUri_ = response.uri;

  goog.asserts.assert(response.data, 'Response data should be non-null!');
  await this.parseManifest_(response.data);

  // Start the update timer if we want updates.
  const delay = this.updatePlaylistDelay_;
  if (delay > 0) {
    this.updatePlaylistTimer_.tickAfter(/* seconds = */ delay);
  }

  goog.asserts.assert(this.manifest_, 'Manifest should be non-null');
  return this.manifest_;
};


/**
 * @override
 * @exportInterface
 */
shaka.hls.HlsParser.prototype.stop = function() {
  // Make sure we don't update the manifest again. Even if the timer is not
  // running, this is safe to call.
  if (this.updatePlaylistTimer_) {
    this.updatePlaylistTimer_.stop();
    this.updatePlaylistTimer_ = null;
  }

  /** @type {!Array.<!Promise>} */
  const pending = [];

  if (this.operationManager_) {
    pending.push(this.operationManager_.destroy());
    this.operationManager_ = null;
  }

  this.playerInterface_ = null;
  this.config_ = null;
  this.mediaTagsToStreamInfosMap_.clear();
  this.variantUriSet_.clear();
  this.uriToStreamInfosMap_.clear();
  this.manifest_ = null;

  return Promise.all(pending);
};


/**
 * @override
 * @exportInterface
 */
shaka.hls.HlsParser.prototype.update = function() {
  if (!this.isLive_()) {
    return;
  }

  /** @type {!Array.<!Promise>} */
  const updates = [];

  for (const streamInfo of this.uriToStreamInfosMap_.values()) {
    updates.push(this.updateStream_(streamInfo));
  }

  return Promise.all(updates);
};


/**
 * Updates a stream.
 *
 * @param {!shaka.hls.HlsParser.StreamInfo} streamInfo
 * @return {!Promise}
 * @throws shaka.util.Error
 * @private
 */
shaka.hls.HlsParser.prototype.updateStream_ = async function(streamInfo) {
  const Utils = shaka.hls.Utils;
  const PresentationType = shaka.hls.HlsParser.PresentationType_;

  const manifestUri = streamInfo.absoluteMediaPlaylistUri;
  const response = await this.requestManifest_(manifestUri);

  /** @type {shaka.hls.Playlist} */
  const playlist = this.manifestTextParser_.parsePlaylist(
      response.data, response.uri);

  if (playlist.type != shaka.hls.PlaylistType.MEDIA) {
    throw new shaka.util.Error(
        shaka.util.Error.Severity.CRITICAL,
        shaka.util.Error.Category.MANIFEST,
        shaka.util.Error.Code.HLS_INVALID_PLAYLIST_HIERARCHY);
  }

  const mediaSequenceTag = Utils.getFirstTagWithName(
      playlist.tags, 'EXT-X-MEDIA-SEQUENCE');

  const startPosition = mediaSequenceTag ? Number(mediaSequenceTag.value) : 0;
  const stream = streamInfo.stream;

  const segments = await this.createSegments_(
        streamInfo.verbatimMediaPlaylistUri,
        playlist,
        startPosition,
        stream.mimeType,
        stream.codecs);

  streamInfo.segmentIndex.replace(segments);

  const newestSegment = segments[segments.length - 1];
  goog.asserts.assert(newestSegment, 'Should have segments!');

  // Once the last segment has been added to the playlist,
  // #EXT-X-ENDLIST tag will be appended.
  // If that happened, treat the rest of the EVENT presentation as VOD.
  const endListTag = Utils.getFirstTagWithName(playlist.tags, 'EXT-X-ENDLIST');

  if (endListTag) {
    // Convert the presentation to VOD and set the duration to the last
    // segment's end time.
    this.setPresentationType_(PresentationType.VOD);
    this.presentationTimeline_.setDuration(newestSegment.endTime);
  }
};


/**
 * @override
 * @exportInterface
 */
shaka.hls.HlsParser.prototype.onExpirationUpdated = function(
    sessionId, expiration) {
  // No-op
};


/**
 * Parses the manifest.
 *
 * @param {!ArrayBuffer} data
 * @throws shaka.util.Error When there is a parsing error.
 * @return {!Promise}
 * @private
 */
shaka.hls.HlsParser.prototype.parseManifest_ = async function(data) {
  goog.asserts.assert(this.masterPlaylistUri_,
      'Master playlist URI must be set before calling parseManifest_!');

  const playlist = this.manifestTextParser_.parsePlaylist(
      data, this.masterPlaylistUri_);

  // We don't support directly providing a Media Playlist.
  // See the error code for details.
  if (playlist.type != shaka.hls.PlaylistType.MASTER) {
    throw new shaka.util.Error(
        shaka.util.Error.Severity.CRITICAL,
        shaka.util.Error.Category.MANIFEST,
        shaka.util.Error.Code.HLS_MASTER_PLAYLIST_NOT_PROVIDED);
  }

  const period = await this.createPeriod_(playlist);

  // Make sure that the parser has not been destroyed.
  if (!this.playerInterface_) {
    throw new shaka.util.Error(
        shaka.util.Error.Severity.CRITICAL,
        shaka.util.Error.Category.PLAYER,
        shaka.util.Error.Code.OPERATION_ABORTED);
  }

  if (this.aesEncrypted_ && period.variants.length == 0) {
    // We do not support AES-128 encryption with HLS yet. Variants is null
    // when the playlist is encrypted with AES-128.
    shaka.log.info('No stream is created, because we don\'t support AES-128',
        'encryption yet');
    throw new shaka.util.Error(
        shaka.util.Error.Severity.CRITICAL,
        shaka.util.Error.Category.MANIFEST,
        shaka.util.Error.Code.HLS_AES_128_ENCRYPTION_NOT_SUPPORTED);
  }

  // HLS has no notion of periods.  We're treating the whole presentation as
  // one period.
  this.playerInterface_.filterAllPeriods([period]);

  // Find the min and max timestamp of the earliest segment in all streams.
  // Find the minimum duration of all streams as well.
  let minFirstTimestamp = Infinity;
  let maxFirstTimestamp = 0;
  let maxLastTimestamp = 0;
  let minDuration = Infinity;

  for (const streamInfo of this.uriToStreamInfosMap_.values()) {
    minFirstTimestamp =
        Math.min(minFirstTimestamp, streamInfo.minTimestamp);
    maxFirstTimestamp =
        Math.max(maxFirstTimestamp, streamInfo.minTimestamp);
    maxLastTimestamp =
        Math.max(maxLastTimestamp, streamInfo.maxTimestamp);
    if (streamInfo.stream.type != 'text') {
      minDuration = Math.min(minDuration, streamInfo.duration);
    }
  }

  // This assert is our own sanity check.
  goog.asserts.assert(this.presentationTimeline_ == null,
                      'Presentation timeline created early!');
  this.createPresentationTimeline_(maxLastTimestamp);

  // This assert satisfies the compiler that it is not null for the rest of
  // the method.
  goog.asserts.assert(this.presentationTimeline_,
                      'Presentation timeline not created!');

  if (this.isLive_()) {
    // The HLS spec (RFC 8216) states in 6.3.4:
    // "the client MUST wait for at least the target duration before
    // attempting to reload the Playlist file again"
    this.updatePlaylistDelay_ = this.minTargetDuration_;

    // The spec says nothing much about seeking in live content, but Safari's
    // built-in HLS implementation does not allow it.  Therefore we will set
    // the availability window equal to the presentation delay.  The player
    // will be able to buffer ahead three segments, but the seek window will
    // be zero-sized.
    const PresentationType = shaka.hls.HlsParser.PresentationType_;

    if (this.presentationType_ == PresentationType.LIVE) {
      // This defaults to the presentation delay, which has the effect of
      // making the live stream unseekable.  This is consistent with Apple's
      // HLS implementation.
      let segmentAvailabilityDuration = this.presentationTimeline_.getDelay();

      // The app can override that with a longer duration, to allow seeking.
      if (!isNaN(this.config_.availabilityWindowOverride)) {
        segmentAvailabilityDuration = this.config_.availabilityWindowOverride;
      }

      this.presentationTimeline_.setSegmentAvailabilityDuration(
          segmentAvailabilityDuration);
    }

    let rolloverSeconds =
        shaka.hls.HlsParser.TS_ROLLOVER_ / shaka.hls.HlsParser.TS_TIMESCALE_;
    let offset = 0;
    while (maxFirstTimestamp >= rolloverSeconds) {
      offset += rolloverSeconds;
      maxFirstTimestamp -= rolloverSeconds;
    }
    if (offset) {
      shaka.log.debug('Offsetting live streams by', offset,
                      'to compensate for rollover');

      for (const streamInfo of this.uriToStreamInfosMap_.values()) {
        if (streamInfo.minTimestamp < rolloverSeconds) {
          shaka.log.v1('Offset applied to', streamInfo.stream.type);
          // This is the offset that StreamingEngine must apply to align the
          // actual segment times with the period.
          streamInfo.stream.presentationTimeOffset = -offset;
          // The segments were created with actual media times, rather than
          // period-aligned times, so offset them all to period time.
          streamInfo.segmentIndex.offset(offset);
        } else {
          shaka.log.v1('Offset NOT applied to', streamInfo.stream.type);
        }
      }
    }
  } else {
    // For VOD/EVENT content, offset everything back to 0.
    // Use the minimum timestamp as the offset for all streams.
    // Use the minimum duration as the presentation duration.
    this.presentationTimeline_.setDuration(minDuration);
    // Use a negative offset to adjust towards 0.
    this.presentationTimeline_.offset(-minFirstTimestamp);

    for (const streamInfo of this.uriToStreamInfosMap_.values()) {
      // This is the offset that StreamingEngine must apply to align the
      // actual segment times with the period.
      streamInfo.stream.presentationTimeOffset = minFirstTimestamp;
      // The segments were created with actual media times, rather than
      // period-aligned times, so offset them all now.
      streamInfo.segmentIndex.offset(-minFirstTimestamp);
      // Finally, fit the segments to the period duration.
      streamInfo.segmentIndex.fit(minDuration);
    }
  }

  this.manifest_ = {
    presentationTimeline: this.presentationTimeline_,
    periods: [period],
    offlineSessionIds: [],
    minBufferTime: 0,
  };
};


/**
 * Parses a playlist into a Period object.
 *
 * @param {!shaka.hls.Playlist} playlist
 * @return {!Promise.<!shaka.extern.Period>}
 * @private
 */
shaka.hls.HlsParser.prototype.createPeriod_ = async function(playlist) {
  const Utils = shaka.hls.Utils;
  const Functional = shaka.util.Functional;
  let tags = playlist.tags;

  let mediaTags = Utils.filterTagsByName(playlist.tags, 'EXT-X-MEDIA');
  let textStreamTags = mediaTags.filter(function(tag) {
    let type = shaka.hls.HlsParser.getRequiredAttributeValue_(tag, 'TYPE');
    return type == 'SUBTITLES';
  }.bind(this));

  let textStreamPromises = textStreamTags.map(async function(tag) {
    try {
      return await this.createTextStream_(tag, playlist);
    } catch (e) {
      if (this.config_.hls.ignoreTextStreamFailures) {
        return null;
      }
      throw e;
    }
  }.bind(this));

  const closedCaptionsTags = mediaTags.filter((tag) => {
    const type = shaka.hls.HlsParser.getRequiredAttributeValue_(tag, 'TYPE');
    return type == 'CLOSED-CAPTIONS';
  });

  this.parseClosedCaptions_(closedCaptionsTags);

  const textStreams = await Promise.all(textStreamPromises);
  // Create Variants for every 'EXT-X-STREAM-INF' tag.  Do this after text
  // streams have been created, so that we can push text codecs found on the
  // variant tag back into the created text streams.
  let variantTags = Utils.filterTagsByName(tags, 'EXT-X-STREAM-INF');
  let variantsPromises = variantTags.map(function(tag) {
    return this.createVariantsForTag_(tag, playlist);
  }.bind(this));

  const allVariants = await Promise.all(variantsPromises);
  let variants = allVariants.reduce(Functional.collapseArrays, []);
  // Filter out null variants.
  variants = variants.filter((variant) => variant != null);

  return {
    startTime: 0,
    variants: variants,
    textStreams: textStreams.filter((t) => t != null),
  };
};


/**
 * @param {!shaka.hls.Tag} tag
 * @param {!shaka.hls.Playlist} playlist
 * @return {!Promise.<!Array.<!shaka.extern.Variant>>}
 * @private
 */
shaka.hls.HlsParser.prototype.createVariantsForTag_ =
    async function(tag, playlist) {
  goog.asserts.assert(tag.name == 'EXT-X-STREAM-INF',
                      'Should only be called on variant tags!');
  const ContentType = shaka.util.ManifestParserUtils.ContentType;
  const Utils = shaka.hls.Utils;

  // These are the default codecs to assume if none are specified.
  //
  // The video codec is H.264, with baseline profile and level 3.0.
  // http://blog.pearce.org.nz/2013/11/what-does-h264avc1-codecs-parameters.html
  //
  // The audio codec is "low-complexity" AAC.
  const defaultCodecs = 'avc1.42E01E,mp4a.40.2';

  const codecsString = tag.getAttributeValue('CODECS', defaultCodecs);
  // Strip out internal whitespace while splitting on commas:
  /** @type {!Array.<string>} */
  let codecs =
      shaka.hls.HlsParser.filterDuplicateCodecs_(codecsString.split(/\s*,\s*/));
  let resolutionAttr = tag.getAttribute('RESOLUTION');
  let width = null;
  let height = null;
  let frameRate = tag.getAttributeValue('FRAME-RATE');
  let bandwidth =
      Number(shaka.hls.HlsParser.getRequiredAttributeValue_(tag, 'BANDWIDTH'));

  if (resolutionAttr) {
    let resBlocks = resolutionAttr.value.split('x');
    width = resBlocks[0];
    height = resBlocks[1];
  }

  // After filtering, this is a list of the media tags we will process to
  // combine with the variant tag (EXT-X-STREAM-INF) we are working on.
  let mediaTags = Utils.filterTagsByName(playlist.tags, 'EXT-X-MEDIA');

  // Do not create stream info from closed captions media tags, which are
  // embedded in video streams.
  mediaTags = mediaTags.filter((tag) => {
    const type = shaka.hls.HlsParser.getRequiredAttributeValue_(tag, 'TYPE');
    return type != 'CLOSED-CAPTIONS';
  });

  // AUDIO or VIDEO tags without a URI attribute are valid.
  // If there is no uri, it means that audio/video is embedded in the
  // stream described by the Variant tag.
  // Do not create stream from AUDIO/VIDEO EXT-X-MEDIA tags without URI
  mediaTags = mediaTags.filter((tag) => {
    const uri = tag.getAttributeValue('URI') || '';
    const type = tag.getAttributeValue('TYPE') || '';
    return type == 'SUBTITLES' || uri != '';
  });

  let audioGroupId = tag.getAttributeValue('AUDIO');
  let videoGroupId = tag.getAttributeValue('VIDEO');
  goog.asserts.assert(audioGroupId == null || videoGroupId == null,
      'Unexpected: both video and audio described by media tags!');

  // Find any associated audio or video groups and create streams for them.
  if (audioGroupId) {
    mediaTags = Utils.findMediaTags(mediaTags, 'AUDIO', audioGroupId);
  } else if (videoGroupId) {
    mediaTags = Utils.findMediaTags(mediaTags, 'VIDEO', videoGroupId);
  }

  // There may be a codec string for the text stream.  We should identify it,
  // add it to the appropriate stream, then strip it out of the variant to
  // avoid confusing our multiplex detection below.
  let textCodecs = this.guessCodecsSafe_(ContentType.TEXT, codecs);
  if (textCodecs) {
    // We found a text codec in the list, so look for an associated text stream.
    let subGroupId = tag.getAttributeValue('SUBTITLES');
    if (subGroupId) {
      let textTags = Utils.findMediaTags(mediaTags, 'SUBTITLES', subGroupId);
      goog.asserts.assert(textTags.length == 1,
                          'Exactly one text tag expected!');
      if (textTags.length) {
        // We found a text codec and text stream, so make sure the codec is
        // attached to the stream.
        const textStreamInfo =
            this.mediaTagsToStreamInfosMap_.get(textTags[0].id);
        if (textStreamInfo) {
          textStreamInfo.stream.codecs = textCodecs;
        }
      }
    }

    // Remove this entry from the list of codecs that belong to audio/video.
    shaka.util.ArrayUtils.remove(codecs, textCodecs);
  }

  let promises = mediaTags.map(function(tag) {
    return this.createStreamInfoFromMediaTag_(tag, codecs);
  }.bind(this));

  let audioStreamInfos = [];
  let videoStreamInfos = [];

  let streamInfo;
  let data = await Promise.all(promises);
  // Filter out null streamInfo.
  data = data.filter((info) => info != null);
  if (audioGroupId) {
    audioStreamInfos = data;
  } else if (videoGroupId) {
    videoStreamInfos = data;
  }

  // Make an educated guess about the stream type.
  shaka.log.debug('Guessing stream type for', tag.toString());
  let type;
  let ignoreStream = false;
  if (!audioStreamInfos.length && !videoStreamInfos.length) {
    // There are no associated streams.  This is either an audio-only stream,
    // a video-only stream, or a multiplexed stream.

    if (codecs.length == 1) {
      // There is only one codec, so it shouldn't be multiplexed.

      let videoCodecs = this.guessCodecsSafe_(ContentType.VIDEO, codecs);
      if (resolutionAttr || frameRate || videoCodecs) {
        // Assume video-only.
        shaka.log.debug('Guessing video-only.');
        type = ContentType.VIDEO;
      } else {
        // Assume audio-only.
        shaka.log.debug('Guessing audio-only.');
        type = ContentType.AUDIO;
      }
    } else {
      // There are multiple codecs, so assume multiplexed content.
      // Note that the default used when CODECS is missing assumes multiple
      // (and therefore multiplexed).
      // Recombine the codec strings into one so that MediaSource isn't
      // lied to later.  (That would trigger an error in Chrome.)
      shaka.log.debug('Guessing multiplexed audio+video.');
      type = ContentType.VIDEO;
      codecs = [codecs.join(',')];
    }
  } else if (audioStreamInfos.length) {
    let streamURI = shaka.hls.HlsParser.getRequiredAttributeValue_(tag, 'URI');
    let firstAudioStreamURI = audioStreamInfos[0].verbatimMediaPlaylistUri;
    if (streamURI == firstAudioStreamURI) {
      // The Microsoft HLS manifest generators will make audio-only variants
      // that link to their URI both directly and through an audio tag.
      // In that case, ignore the local URI and use the version in the
      // AUDIO tag, so you inherit its language.
      // As an example, see the manifest linked in issue #860.
      shaka.log.debug('Guessing audio-only.');
      type = ContentType.AUDIO;
      ignoreStream = true;
    } else {
      // There are associated audio streams.  Assume this is video.
      shaka.log.debug('Guessing video.');
      type = ContentType.VIDEO;
    }
  } else {
    // There are associated video streams.  Assume this is audio.
    goog.asserts.assert(videoStreamInfos.length,
        'No video streams!  This should have been handled already!');
    shaka.log.debug('Guessing audio.');
    type = ContentType.AUDIO;
  }

  goog.asserts.assert(type, 'Type should have been set by now!');
  if (!ignoreStream) {
    streamInfo =
        await this.createStreamInfoFromVariantTag_(tag, codecs, type);
  }

  if (streamInfo) {
    if (streamInfo.stream.type == ContentType.AUDIO) {
      audioStreamInfos = [streamInfo];
    } else {
      videoStreamInfos = [streamInfo];
    }
  } else if (streamInfo === null) {  // Triple-equals to distinguish undefined
    // We do not support AES-128 encryption with HLS yet. If the streamInfo is
    // null because of AES-128 encryption, do not create variants for that.
    shaka.log.debug('streamInfo is null');
    return [];
  }

  goog.asserts.assert(videoStreamInfos.length || audioStreamInfos.length,
      'We should have created a stream!');

  if (videoStreamInfos) {
    this.filterLegacyCodecs_(videoStreamInfos);
  }
  if (audioStreamInfos) {
    this.filterLegacyCodecs_(audioStreamInfos);
  }

  return this.createVariants_(
      audioStreamInfos,
      videoStreamInfos,
      bandwidth,
      width,
      height,
      frameRate);
};


/**
 * Filters out unsupported codec strings from an array of stream infos.
 * @param {!Array.<shaka.hls.HlsParser.StreamInfo>} streamInfos
 * @private
 */
shaka.hls.HlsParser.prototype.filterLegacyCodecs_ = function(streamInfos) {
  streamInfos.forEach(function(streamInfo) {
    let codecs = streamInfo.stream.codecs.split(',');
    codecs = codecs.filter(function(codec) {
      // mp4a.40.34 is a nonstandard codec string that is sometimes used in HLS
      // for legacy reasons.  It is not recognized by non-Apple MSE.
      // See https://bugs.chromium.org/p/chromium/issues/detail?id=489520
      // Therefore, ignore this codec string.
      return codec != 'mp4a.40.34';
    });
    streamInfo.stream.codecs = codecs.join(',');
  });
};


/**
 * @param {!Array.<!shaka.hls.HlsParser.StreamInfo>} audioInfos
 * @param {!Array.<!shaka.hls.HlsParser.StreamInfo>} videoInfos
 * @param {number} bandwidth
 * @param {?string} width
 * @param {?string} height
 * @param {?string} frameRate
 * @return {!Array.<!shaka.extern.Variant>}
 * @private
 */
shaka.hls.HlsParser.prototype.createVariants_ =
    function(audioInfos, videoInfos, bandwidth, width, height, frameRate) {
  const DrmEngine = shaka.media.DrmEngine;

  videoInfos.forEach(function(info) {
    this.addVideoAttributes_(info.stream, width, height, frameRate);
  }.bind(this));

    // In case of audio-only or video-only content or the audio is disabled by
    // the config, we create an array of one item containing a null.  This way,
    // the double-loop works for all kinds of content.
  // NOTE: we currently don't have support for audio-only content.
    const disableAudio = this.config_ ? this.config_.disableAudio : false;
    if (!audioInfos.length || disableAudio) {
    audioInfos = [null];
  }
  if (!videoInfos.length) {
    videoInfos = [null];
  }

  const variants = [];
  for (const audioInfo of audioInfos) {
    for (const videoInfo of videoInfos) {
      const audioStream = audioInfo ? audioInfo.stream : null;
      const videoStream = videoInfo ? videoInfo.stream : null;
      const audioDrmInfos = audioInfo ? audioInfo.drmInfos : null;
      const videoDrmInfos = videoInfo ? videoInfo.drmInfos : null;
      const videoStreamUri =
          videoInfo ? videoInfo.verbatimMediaPlaylistUri : '';
      const audioStreamUri =
          audioInfo ? audioInfo.verbatimMediaPlaylistUri : '';
      const variantUriKey = videoStreamUri + ' - ' + audioStreamUri;

      let drmInfos;
      if (audioStream && videoStream) {
        if (DrmEngine.areDrmCompatible(audioDrmInfos, videoDrmInfos)) {
          drmInfos = DrmEngine.getCommonDrmInfos(audioDrmInfos, videoDrmInfos);
        } else {
          shaka.log.warning('Incompatible DRM info in HLS variant.  Skipping.');
          continue;
        }
      } else if (audioStream) {
        drmInfos = audioDrmInfos;
      } else if (videoStream) {
        drmInfos = videoDrmInfos;
      }

      if (this.variantUriSet_.has(variantUriKey)) {
        // This happens when two variants only differ in their text streams.
        shaka.log.debug('Skipping variant which only differs in text streams.');
        continue;
      }

      const variant = this.createVariant_(
          audioStream, videoStream, bandwidth, drmInfos);
      variants.push(variant);
      this.variantUriSet_.add(variantUriKey);
    }
  }
  return variants;
};


/**
 * @param {shaka.extern.Stream} audio
 * @param {shaka.extern.Stream} video
 * @param {number} bandwidth
 * @param {!Array.<shaka.extern.DrmInfo>} drmInfos
 * @return {!shaka.extern.Variant}
 * @private
 */
shaka.hls.HlsParser.prototype.createVariant_ =
    function(audio, video, bandwidth, drmInfos) {
  const ContentType = shaka.util.ManifestParserUtils.ContentType;

  // Since both audio and video are of the same type, this assertion will catch
  // certain mistakes at runtime that the compiler would miss.
  goog.asserts.assert(!audio || audio.type == ContentType.AUDIO,
                      'Audio parameter mismatch!');
  goog.asserts.assert(!video || video.type == ContentType.VIDEO,
                      'Video parameter mismatch!');

  return {
    id: this.globalId_++,
    language: audio ? audio.language : 'und',
    primary: (!!audio && audio.primary) || (!!video && video.primary),
    audio: audio,
    video: video,
    bandwidth: bandwidth,
    drmInfos: drmInfos,
    allowedByApplication: true,
    allowedByKeySystem: true,
  };
};


/**
 * Parses an EXT-X-MEDIA tag with TYPE="SUBTITLES" into a text stream.
 *
 * @param {!shaka.hls.Tag} tag
 * @param {!shaka.hls.Playlist} playlist
 * @return {!Promise.<?shaka.extern.Stream>}
 * @private
 */
shaka.hls.HlsParser.prototype.createTextStream_ =
    async function(tag, playlist) {
  goog.asserts.assert(tag.name == 'EXT-X-MEDIA',
                      'Should only be called on media tags!');

  let type = shaka.hls.HlsParser.getRequiredAttributeValue_(tag, 'TYPE');
  goog.asserts.assert(type == 'SUBTITLES',
                      'Should only be called on tags with TYPE="SUBTITLES"!');

  const streamInfo = await this.createStreamInfoFromMediaTag_(tag, []);
  goog.asserts.assert(streamInfo, 'Should always have a streamInfo for text');
  return streamInfo.stream;
};


/**
 * Parses an EXT-X-MEDIA tag with TYPE="CLOSED-CAPTIONS", add store the values
 * into the map of group id to closed captions.
 *
 * @param {!Array.<shaka.hls.Tag>} tags
 * @private
 */
shaka.hls.HlsParser.prototype.parseClosedCaptions_ = function(tags) {
  for (const tag of tags) {
    goog.asserts.assert(tag.name == 'EXT-X-MEDIA',
        'Should only be called on media tags!');
    const type = shaka.hls.HlsParser.getRequiredAttributeValue_(tag, 'TYPE');
    goog.asserts.assert(type == 'CLOSED-CAPTIONS',
        'Should only be called on tags with TYPE="CLOSED-CAPTIONS"!');

    const LanguageUtils = shaka.util.LanguageUtils;
    const languageValue = tag.getAttributeValue('LANGUAGE') || 'und';
    const language = LanguageUtils.normalize(languageValue);

    // The GROUP-ID value is a quoted-string that specifies the group to which
    // the Rendition belongs.
    const groupId =
        shaka.hls.HlsParser.getRequiredAttributeValue_(tag, 'GROUP-ID');

    // The value of INSTREAM-ID is a quoted-string that specifies a Rendition
    // within the segments in the Media Playlist. This attribute is REQUIRED if
    // the TYPE attribute is CLOSED-CAPTIONS.
    const instreamId =
        shaka.hls.HlsParser.getRequiredAttributeValue_(tag, 'INSTREAM-ID');
    if (!this.groupIdToClosedCaptionsMap_.get(groupId)) {
      this.groupIdToClosedCaptionsMap_.set(groupId, new Map());
    }
    this.groupIdToClosedCaptionsMap_.get(groupId).set(instreamId, language);
  }
};


/**
 * Parse EXT-X-MEDIA media tag into a Stream object.
 *
 * @param {shaka.hls.Tag} tag
 * @param {!Array.<string>} allCodecs
 * @return {!Promise.<?shaka.hls.HlsParser.StreamInfo>}
 * @private
 */
shaka.hls.HlsParser.prototype.createStreamInfoFromMediaTag_ =
    async function(tag, allCodecs) {
  goog.asserts.assert(tag.name == 'EXT-X-MEDIA',
                      'Should only be called on media tags!');

  const HlsParser = shaka.hls.HlsParser;
  const verbatimMediaPlaylistUri = HlsParser.getRequiredAttributeValue_(
      tag, 'URI');

  // Check if the stream has already been created as part of another Variant
  // and return it if it has.
  if (this.uriToStreamInfosMap_.has(verbatimMediaPlaylistUri)) {
    return this.uriToStreamInfosMap_.get(verbatimMediaPlaylistUri);
  }

  let type = HlsParser.getRequiredAttributeValue_(tag, 'TYPE').toLowerCase();
  // Shaka recognizes the content types 'audio', 'video' and 'text'.
  // The HLS 'subtitles' type needs to be mapped to 'text'.
  const ContentType = shaka.util.ManifestParserUtils.ContentType;
  if (type == 'subtitles') type = ContentType.TEXT;

  const LanguageUtils = shaka.util.LanguageUtils;
  let language = LanguageUtils.normalize(/** @type {string} */(
      tag.getAttributeValue('LANGUAGE', 'und')));
  const name = tag.getAttributeValue('NAME');

  let defaultAttr = tag.getAttribute('DEFAULT');
  let autoselectAttr = tag.getAttribute('AUTOSELECT');
  // TODO: Should we take into account some of the currently ignored attributes:
  // FORCED, INSTREAM-ID, CHARACTERISTICS, CHANNELS?
  // Attribute descriptions: https://bit.ly/2lpjOhj
  let channelsAttribute = tag.getAttributeValue('CHANNELS');
  let channelsCount = type == 'audio' ?
      this.getChannelCount_(channelsAttribute) : null;
  let primary = !!defaultAttr || !!autoselectAttr;
  const streamInfo = await this.createStreamInfo_(
      verbatimMediaPlaylistUri, allCodecs, type, language, primary, name,
      channelsCount, /* closedCaptions */ null);
  if (streamInfo == null) return null;
  // TODO: This check is necessary because of the possibility of multiple
  // calls to createStreamInfoFromMediaTag_ before either has resolved.
  if (this.uriToStreamInfosMap_.has(verbatimMediaPlaylistUri)) {
    return this.uriToStreamInfosMap_.get(verbatimMediaPlaylistUri);
  }

  this.mediaTagsToStreamInfosMap_.set(tag.id, streamInfo);
  this.uriToStreamInfosMap_.set(verbatimMediaPlaylistUri, streamInfo);
  return streamInfo;
};


/**
 * Get the channel count information for an HLS audio track.
 *
 * @param {?string} channels A string that specifies an ordered, "/" separated
 *   list of parameters.  If the type is audio, the first parameter will be a
 *   decimal integer specifying the number of independent, simultaneous audio
 *   channels.
 *   No other channels parameters are currently defined.
 * @return {?number} channelcount
 * @private
 */
shaka.hls.HlsParser.prototype.getChannelCount_ = function(channels) {
  if (!channels) return null;
  let channelcountstring = channels.split('/')[0];
  let count = parseInt(channelcountstring, 10);
  return count;
};


/**
 * Parse an EXT-X-STREAM-INF media tag into a Stream object.
 *
 * @param {!shaka.hls.Tag} tag
 * @param {!Array.<string>} allCodecs
 * @param {string} type
 * @return {!Promise.<?shaka.hls.HlsParser.StreamInfo>}
 * @private
 */
shaka.hls.HlsParser.prototype.createStreamInfoFromVariantTag_ =
    async function(tag, allCodecs, type) {
  goog.asserts.assert(tag.name == 'EXT-X-STREAM-INF',
                      'Should only be called on media tags!');
  const ContentType = shaka.util.ManifestParserUtils.ContentType;

  const HlsParser = shaka.hls.HlsParser;
  const verbatimMediaPlaylistUri = HlsParser.getRequiredAttributeValue_(
      tag, 'URI');

  if (this.uriToStreamInfosMap_.has(verbatimMediaPlaylistUri)) {
    return this.uriToStreamInfosMap_.get(verbatimMediaPlaylistUri);
  }
  // The attribute of closed captions is optional, and the value may be 'NONE'.
  const closedCaptionsAttr = tag.getAttributeValue('CLOSED-CAPTIONS');

  // EXT-X-STREAM-INF tags may have CLOSED-CAPTIONS attributes.
  // The value can be either a quoted-string or an enumerated-string with the
  // value NONE. If the value is a quoted-string, it MUST match the value of
  // the GROUP-ID attribute of an EXT-X-MEDIA tag elsewhere in the Playlist
  // whose TYPE attribute is CLOSED-CAPTIONS.
  let closedCaptions = null;
  if (type == ContentType.VIDEO && closedCaptionsAttr &&
      closedCaptionsAttr != 'NONE') {
    closedCaptions = this.groupIdToClosedCaptionsMap_.get(closedCaptionsAttr);
  }

  const streamInfo = await this.createStreamInfo_(verbatimMediaPlaylistUri,
       allCodecs, type, /* language */ 'und', /* primary */ false,
       /* name */ null, /* channelcount */ null, closedCaptions);
  if (streamInfo == null) return null;
  // TODO: This check is necessary because of the possibility of multiple
  // calls to createStreamInfoFromVariantTag_ before either has resolved.
  if (this.uriToStreamInfosMap_.has(verbatimMediaPlaylistUri)) {
    return this.uriToStreamInfosMap_.get(verbatimMediaPlaylistUri);
  }

  this.uriToStreamInfosMap_.set(verbatimMediaPlaylistUri, streamInfo);
  return streamInfo;
};


/**
 * @param {string} verbatimMediaPlaylistUri
 * @param {!Array.<string>} allCodecs
 * @param {string} type
 * @param {string} language
 * @param {boolean} primary
 * @param {?string} name
 * @param {?number} channelsCount
 * @param {Map.<string, string>} closedCaptions
 * @return {!Promise.<?shaka.hls.HlsParser.StreamInfo>}
 * @throws shaka.util.Error
 * @private
 */
shaka.hls.HlsParser.prototype.createStreamInfo_ = async function(
    verbatimMediaPlaylistUri, allCodecs, type, language, primary, name,
    channelsCount, closedCaptions) {
  // TODO: Refactor, too many parameters
  const Utils = shaka.hls.Utils;

  let absoluteMediaPlaylistUri = Utils.constructAbsoluteUri(
      this.masterPlaylistUri_, verbatimMediaPlaylistUri);

  /** @type {!shaka.hls.Playlist} */
  let playlist;
  /** @type {string} */
  let codecs = '';
  /** @type {string} */
  let mimeType;

  const response = await this.requestManifest_(absoluteMediaPlaylistUri);
  // Record the final URI after redirects.
  absoluteMediaPlaylistUri = response.uri;

  // Record the redirected, final URI of this media playlist when we parse it.
  playlist = this.manifestTextParser_.parsePlaylist(
      response.data, absoluteMediaPlaylistUri);

  if (playlist.type != shaka.hls.PlaylistType.MEDIA) {
    // EXT-X-MEDIA tags should point to media playlists.
    throw new shaka.util.Error(
        shaka.util.Error.Severity.CRITICAL,
        shaka.util.Error.Category.MANIFEST,
        shaka.util.Error.Code.HLS_INVALID_PLAYLIST_HIERARCHY);
  }

  /** @type {!Array.<!shaka.hls.Tag>} */
  let drmTags = [];
  playlist.segments.forEach(function(segment) {
    const segmentKeyTags = Utils.filterTagsByName(segment.tags,
                                                'EXT-X-KEY');
    drmTags.push.apply(drmTags, segmentKeyTags);
  });

  let encrypted = false;
  /** @type {!Array.<shaka.extern.DrmInfo>}*/
  let drmInfos = [];
  let keyId = null;

  // TODO: May still need changes to support key rotation.
  for (const drmTag of drmTags) {
    let method =
        shaka.hls.HlsParser.getRequiredAttributeValue_(drmTag, 'METHOD');
    if (method != 'NONE') {
      encrypted = true;

      // We do not support AES-128 encryption with HLS yet. So, do not create
      // StreamInfo for the playlist encrypted with AES-128.
      // TODO: Remove the error message once we add support for AES-128.
      if (method == 'AES-128') {
        shaka.log.warning('Unsupported HLS Encryption', method);
        this.aesEncrypted_ = true;
        return null;
      }

      let keyFormat =
          shaka.hls.HlsParser.getRequiredAttributeValue_(drmTag, 'KEYFORMAT');
      let drmParser =
          shaka.hls.HlsParser.KEYFORMATS_TO_DRM_PARSERS_[keyFormat];

      let drmInfo = drmParser ? drmParser(drmTag) : null;
      if (drmInfo) {
        if (drmInfo.keyIds.length) {
          keyId = drmInfo.keyIds[0];
        }
        drmInfos.push(drmInfo);
      } else {
        shaka.log.warning('Unsupported HLS KEYFORMAT', keyFormat);
      }
    }
  }

  if (encrypted && !drmInfos.length) {
    throw new shaka.util.Error(
        shaka.util.Error.Severity.CRITICAL,
        shaka.util.Error.Category.MANIFEST,
        shaka.util.Error.Code.HLS_KEYFORMATS_NOT_SUPPORTED);
  }


  goog.asserts.assert(playlist.segments != null,
                      'Media playlist should have segments!');

  this.determinePresentationType_(playlist);

  codecs = this.guessCodecs_(type, allCodecs);
  const mimeTypeArg = await this.guessMimeType_(type, codecs, playlist);

  mimeType = mimeTypeArg;

  let mediaSequenceTag = Utils.getFirstTagWithName(playlist.tags,
                                                   'EXT-X-MEDIA-SEQUENCE');

  let startPosition = mediaSequenceTag ? Number(mediaSequenceTag.value) : 0;

  const segments = await this.createSegments_(
      verbatimMediaPlaylistUri, playlist, startPosition, mimeType, codecs);

  let minTimestamp = segments[0].startTime;
  let lastEndTime = segments[segments.length - 1].endTime;
  let duration = lastEndTime - minTimestamp;
  let segmentIndex = new shaka.media.SegmentIndex(segments);

  const initSegmentReference = this.createInitSegmentReference_(playlist);

  let kind = undefined;
  if (type == shaka.util.ManifestParserUtils.ContentType.TEXT) {
    kind = shaka.util.ManifestParserUtils.TextStreamKind.SUBTITLE;
  }


  /** @type {shaka.extern.Stream} */
  let stream = {
    id: this.globalId_++,
    originalId: name,
    createSegmentIndex: Promise.resolve.bind(Promise),
    findSegmentPosition: segmentIndex.find.bind(segmentIndex),
    getSegmentReference: segmentIndex.get.bind(segmentIndex),
    initSegmentReference: initSegmentReference,
    presentationTimeOffset: 0,
    mimeType: mimeType,
    codecs: codecs,
    kind: kind,
    encrypted: encrypted,
    keyId: keyId,
    language: language,
    label: name,  // For historical reasons, since before "originalId".
    type: type,
    primary: primary,
    // TODO: trick mode
    trickModeVideo: null,
    emsgSchemeIdUris: null,
    frameRate: undefined,
    width: undefined,
    height: undefined,
    bandwidth: undefined,
    roles: [],
    channelsCount: channelsCount,
    closedCaptions: closedCaptions,
  };

  return {
    stream: stream,
    segmentIndex: segmentIndex,
    drmInfos: drmInfos,
    verbatimMediaPlaylistUri: verbatimMediaPlaylistUri,
    absoluteMediaPlaylistUri: absoluteMediaPlaylistUri,
    minTimestamp: minTimestamp,
    maxTimestamp: lastEndTime,
    duration: duration,
  };
};


/**
 * @param {!shaka.hls.Playlist} playlist
 * @private
 */
shaka.hls.HlsParser.prototype.determinePresentationType_ = function(playlist) {
  const Utils = shaka.hls.Utils;
  const PresentationType = shaka.hls.HlsParser.PresentationType_;
  let presentationTypeTag = Utils.getFirstTagWithName(playlist.tags,
                                                      'EXT-X-PLAYLIST-TYPE');
  let endListTag = Utils.getFirstTagWithName(playlist.tags, 'EXT-X-ENDLIST');

  let isVod = (presentationTypeTag && presentationTypeTag.value == 'VOD') ||
      endListTag;
  let isEvent = presentationTypeTag && presentationTypeTag.value == 'EVENT' &&
      !isVod;
  let isLive = !isVod && !isEvent;

  if (isVod) {
    this.setPresentationType_(PresentationType.VOD);
  } else {
    // If it's not VOD, it must be presentation type LIVE or an ongoing EVENT.
    if (isLive) {
      this.setPresentationType_(PresentationType.LIVE);
    } else {
      this.setPresentationType_(PresentationType.EVENT);
    }

    let targetDurationTag = this.getRequiredTag_(playlist.tags,
                                                 'EXT-X-TARGETDURATION');
    let targetDuration = Number(targetDurationTag.value);

    // According to the HLS spec, updates should not happen more often than
    // once in targetDuration.  It also requires us to only update the active
    // variant.  We might implement that later, but for now every variant
    // will be updated.  To get the update period, choose the smallest
    // targetDuration value across all playlists.

    // Update the longest target duration if need be to use as a presentation
    // delay later.
    this.maxTargetDuration_ = Math.max(targetDuration, this.maxTargetDuration_);
    // Update the shortest one to use as update period and segment availability
    // time (for LIVE).
    this.minTargetDuration_ = Math.min(targetDuration, this.minTargetDuration_);
  }
};


/**
 * @param {number} lastTimestamp
 * @throws shaka.util.Error
 * @private
 */
shaka.hls.HlsParser.prototype.createPresentationTimeline_ =
    function(lastTimestamp) {
  if (this.isLive_()) {
    // The live edge will be calculated from segments, so we don't need to set
    // a presentation start time.  We will assert later that this is working as
    // expected.

    // The HLS spec (RFC 8216) states in 6.3.3:
    //
    // "The client SHALL choose which Media Segment to play first ... the
    // client SHOULD NOT choose a segment that starts less than three target
    // durations from the end of the Playlist file.  Doing so can trigger
    // playback stalls."
    //
    // We accomplish this in our DASH-y model by setting a presentation delay
    // of 3 segments.  This will be the "live edge" of the presentation.
    this.presentationTimeline_ = new shaka.media.PresentationTimeline(
        /* presentationStartTime */ 0, /* delay */ this.maxTargetDuration_ * 3);
    this.presentationTimeline_.setStatic(false);
  } else {
    this.presentationTimeline_ = new shaka.media.PresentationTimeline(
        /* presentationStartTime */ null, /* delay */ 0);
    this.presentationTimeline_.setStatic(true);
  }

  this.notifySegments_();

  // This asserts that the live edge is being calculated from segment times.
  // For VOD and event streams, this check should still pass.
  goog.asserts.assert(
      !this.presentationTimeline_.usingPresentationStartTime(),
      'We should not be using the presentation start time in HLS!');
};


/**
 * @param {!shaka.hls.Playlist} playlist
 * @return {shaka.media.InitSegmentReference}
 * @private
 * @throws {shaka.util.Error}
 */
shaka.hls.HlsParser.prototype.createInitSegmentReference_ = function(playlist) {
  const Utils = shaka.hls.Utils;
  let mapTags = Utils.filterTagsByName(playlist.tags, 'EXT-X-MAP');
  // TODO: Support multiple map tags?
  // For now, we don't support multiple map tags and will throw an error.
  if (!mapTags.length) {
    return null;
  } else if (mapTags.length > 1) {
    throw new shaka.util.Error(
        shaka.util.Error.Severity.CRITICAL,
        shaka.util.Error.Category.MANIFEST,
        shaka.util.Error.Code.HLS_MULTIPLE_MEDIA_INIT_SECTIONS_FOUND);
  }

  // Map tag example: #EXT-X-MAP:URI="main.mp4",BYTERANGE="720@0"
  let mapTag = mapTags[0];
  const verbatimInitSegmentUri =
      shaka.hls.HlsParser.getRequiredAttributeValue_(mapTag, 'URI');
  const absoluteInitSegmentUri =
      Utils.constructAbsoluteUri(playlist.absoluteUri, verbatimInitSegmentUri);

  let startByte = 0;
  let endByte = null;
  let byterange = mapTag.getAttributeValue('BYTERANGE');
  // If a BYTERANGE attribute is not specified, the segment consists
  // of the entire resource.
  if (byterange) {
    let blocks = byterange.split('@');
    let byteLength = Number(blocks[0]);
    startByte = Number(blocks[1]);
    endByte = startByte + byteLength - 1;
  }

  return new shaka.media.InitSegmentReference(
      () => [absoluteInitSegmentUri],
      startByte,
      endByte);
};


/**
 * Parses one shaka.hls.Segment object into a shaka.media.SegmentReference.
 *
 * @param {!shaka.hls.Playlist} playlist
 * @param {shaka.media.SegmentReference} previousReference
 * @param {!shaka.hls.Segment} hlsSegment
 * @param {number} position
 * @param {number} startTime
 * @return {!shaka.media.SegmentReference}
 * @private
 */
shaka.hls.HlsParser.prototype.createSegmentReference_ =
    function(playlist, previousReference, hlsSegment, position, startTime) {
  const Utils = shaka.hls.Utils;
  const tags = hlsSegment.tags;
  const absoluteSegmentUri = hlsSegment.absoluteUri;

  let extinfTag = this.getRequiredTag_(tags, 'EXTINF');
  // The EXTINF tag format is '#EXTINF:<duration>,[<title>]'.
  // We're interested in the duration part.
  let extinfValues = extinfTag.value.split(',');
  let duration = Number(extinfValues[0]);
  let endTime = startTime + duration;

  let startByte = 0;
  let endByte = null;
  let byterange = Utils.getFirstTagWithName(tags, 'EXT-X-BYTERANGE');

  // If BYTERANGE is not specified, the segment consists of the entire resource.
  if (byterange) {
    let blocks = byterange.value.split('@');
    let byteLength = Number(blocks[0]);
    if (blocks[1]) {
      startByte = Number(blocks[1]);
    } else {
      goog.asserts.assert(previousReference,
                          'Cannot refer back to previous HLS segment!');
      startByte = previousReference.endByte + 1;
    }
    endByte = startByte + byteLength - 1;
  }

  return new shaka.media.SegmentReference(
      position,
      startTime,
      endTime,
      () => [absoluteSegmentUri],
      startByte,
      endByte);
};


/** @private */
shaka.hls.HlsParser.prototype.notifySegments_ = function() {
  // The presentation timeline may or may not be set yet.
  // If it does not yet exist, hold onto the segments until it does.
  if (!this.presentationTimeline_) {
    return;
  }
  this.segmentsToNotifyByStream_.forEach((segments) => {
    // HLS doesn't have separate periods.
    this.presentationTimeline_.notifySegments(segments, /* periodStart */ 0);
  });
  this.segmentsToNotifyByStream_ = [];
};


/**
 * Parses shaka.hls.Segment objects into shaka.media.SegmentReferences.
 *
 * @param {string} verbatimMediaPlaylistUri
 * @param {!shaka.hls.Playlist} playlist
 * @param {number} startPosition
 * @param {string} mimeType
 * @param {string} codecs
 * @return {!Promise<!Array.<!shaka.media.SegmentReference>>}
 * @private
 */
shaka.hls.HlsParser.prototype.createSegments_ = async function(
    verbatimMediaPlaylistUri, playlist, startPosition, mimeType, codecs) {
  /** @type {Array.<!shaka.hls.Segment>} */
  const hlsSegments = playlist.segments;
  /** @type {!Array.<!shaka.media.SegmentReference>} */
  const references = [];

  goog.asserts.assert(hlsSegments.length, 'Playlist should have segments!');
  // We may need to look at the media itself to determine a segment start time.
  const firstSegmentUri = hlsSegments[0].absoluteUri;
  const firstSegmentRef =
      this.createSegmentReference_(
          playlist,
          null /* previousReference */,
          hlsSegments[0],
          startPosition,
          0 /* startTime, irrelevant */);

  const initSegmentRef = this.createInitSegmentReference_(playlist);

  const firstStartTime = await this.getStartTime_(verbatimMediaPlaylistUri,
                            initSegmentRef, firstSegmentRef, mimeType, codecs);
  shaka.log.debug('First segment', firstSegmentUri.split('/').pop(),
                  'starts at', firstStartTime);
  for (let i = 0; i < hlsSegments.length; ++i) {
    let hlsSegment = hlsSegments[i];
    let previousReference = references[references.length - 1];
    let startTime = (i == 0) ? firstStartTime : previousReference.endTime;
    let position = startPosition + i;

    let reference = this.createSegmentReference_(
        playlist,
        previousReference,
        hlsSegment,
        position,
        startTime);
    references.push(reference);
  }

  this.segmentsToNotifyByStream_.push(references);
  this.notifySegments_();

  return references;
};


/**
 * Try to fetch a partial segment, and fall back to a full segment if we have
 * to.
 *
 * @param {!shaka.media.AnySegmentReference} reference
 * @return {!Promise.<shaka.extern.Response>}
 * @throws {shaka.util.Error}
 * @private
 */
shaka.hls.HlsParser.prototype.fetchPartialSegment_ = async function(reference) {
  const requestType = shaka.net.NetworkingEngine.RequestType.SEGMENT;

  // Create two requests:
  //  1. A partial request meant to fetch the smallest part of the segment
  //     required to get the time stamp.
  //  2. A full request meant as a fallback for when the server does not support
  //     partial requests.

  const partialRequest = shaka.util.Networking.createSegmentRequest(
      reference.getUris(),
      reference.startByte,
      reference.startByte + shaka.hls.HlsParser.PARTIAL_SEGMENT_SIZE_ - 1,
      this.config_.retryParameters);

  const fullRequest = shaka.util.Networking.createSegmentRequest(
      reference.getUris(),
      reference.startByte,
      reference.endByte,
      this.config_.retryParameters);

  // TODO(vaage): The need to do fall back requests is not likely to be unique
  //    to here. It would be nice if the fallback(s) could be included into the
  //    same abortable operation as the original request.
  //
  //    What would need to change with networking engine to support requests
  //    with fallback(s)?

  try {
    const response = await this.makeNetworkRequest_(
          partialRequest, requestType);

    return response;
  } catch (e) {
    // If the networking operation was aborted, we don't want to treat it as
    // a request failure. We surface the error so that the OPERATION_ABORTED
    // error will be handled correctly.
    if (e.code == shaka.util.Error.Code.OPERATION_ABORTED) {
      throw e;
    }

    // The partial request may fail for a number of reasons.
    // Some servers do not support Range requests, and others do not support
    // the OPTIONS request which must be made before any cross-origin Range
    // request.  Since this fallback is expensive, warn the app developer.
    shaka.log.alwaysWarn('Unable to fetch a partial HLS segment! ' +
                         'Falling back to a full segment request, ' +
                         'which is expensive!  Your server should ' +
                         'support Range requests and CORS preflights.',
                         partialRequest.uris[0]);

      const response = await this.makeNetworkRequest_(fullRequest, requestType);

    return response;
  }
};


/**
 * Gets the start time of a segment from the existing manifest (if possible) or
 * by downloading it and parsing it otherwise.
 *
 * @param {string} verbatimMediaPlaylistUri
 * @param {shaka.media.InitSegmentReference} initSegmentRef
 * @param {!shaka.media.SegmentReference} segmentRef
 * @param {string} mimeType
 * @param {string} codecs
 * @return {!Promise.<number>}
 * @throws {shaka.util.Error}
 * @private
 */
shaka.hls.HlsParser.prototype.getStartTime_ = async function(
    verbatimMediaPlaylistUri, initSegmentRef, segmentRef, mimeType, codecs) {
  // If we are updating the manifest, we can usually skip fetching the segment
  // by examining the references we already have.  This won't be possible if
  // there was some kind of lag or delay updating the manifest on the server,
  // in which extreme case we would fall back to fetching a segment.  This
  // allows us to both avoid fetching segments when possible, and recover from
  // certain server-side issues gracefully.
  if (this.manifest_) {
    const streamInfo = this.uriToStreamInfosMap_.get(verbatimMediaPlaylistUri);
    const segmentIndex = streamInfo.segmentIndex;
    const reference = segmentIndex.get(segmentRef.position);
    if (reference) {
      // We found it!  Avoid fetching and parsing the segment.
      shaka.log.v1('Found segment start time in previous manifest');
      return reference.startTime;
    }

    shaka.log.debug('Unable to find segment start time in previous manifest!');
  }

  // TODO: Introduce a new tag to extend HLS and provide the first segment's
  // start time.  This will avoid the need for these fetches in content packaged
  // with Shaka Packager.  This web-friendly extension to HLS can then be
  // proposed to Apple for inclusion in a future version of HLS.
  // See https://github.com/google/shaka-packager/issues/294

  shaka.log.v1('Fetching segment to find start time');

  if (mimeType == 'audio/mpeg') {
    // There is no standard way to embed timestamps in mp3 files, so the
    // start time is presumably 0.
    return 0;
  }

  if (mimeType == 'video/mp4' || mimeType == 'audio/mp4') {
    // We also need the init segment to get the correct timescale. But if the
    // stream is self-initializing, use the same response for both.
    const fetches = [this.fetchPartialSegment_(segmentRef)];

    if (initSegmentRef) {
      fetches.push(this.fetchPartialSegment_(initSegmentRef));
    }

    const responses = await Promise.all(fetches);

    // If the stream is self-initializing, use the main segment in-place of the
    // init segment.
    const segmentResponse = responses[0];
    const initSegmentResponse = responses[1] || responses[0];

    return this.getStartTimeFromMp4Segment_(
        segmentResponse.data, initSegmentResponse.data);
  }

  if (mimeType == 'video/mp2t') {
    const response = await this.fetchPartialSegment_(segmentRef);
    goog.asserts.assert(response.data, 'Should have a response body!');
    return this.getStartTimeFromTsSegment_(response.data);
  }

  if (mimeType == 'application/mp4' || mimeType.startsWith('text/')) {
    const response = await this.fetchPartialSegment_(segmentRef);
    goog.asserts.assert(response.data, 'Should have a response body!');
    return this.getStartTimeFromTextSegment_(mimeType, codecs, response.data);
  }

    if (mimeType == 'video/webm') {
      shaka.log.warning(
          'Hls+WebM combination is not supported at the moment. Skipping.');
      return null;
    }


  // TODO(vaage): Add support for additional formats.
  //
  //   Formats:
  //    - WebM
  //    - AAC
  //
  //    Since we want to add more formats, how would a more general registry
  //    system work to allow additional formats to be "plugged-into" the
  //    parser.

  throw new shaka.util.Error(
      shaka.util.Error.Severity.CRITICAL,
      shaka.util.Error.Category.MANIFEST,
      shaka.util.Error.Code.HLS_COULD_NOT_PARSE_SEGMENT_START_TIME);
};


/**
 * Parses an mp4 segment to get its start time.
 *
 * @param {!ArrayBuffer} mediaData
 * @param {!ArrayBuffer} initData
 * @return {number}
 * @throws {shaka.util.Error}
 * @private
 */
shaka.hls.HlsParser.prototype.getStartTimeFromMp4Segment_ =
    function(mediaData, initData) {
  const Mp4Parser = shaka.util.Mp4Parser;

  let timescale = 0;
  new Mp4Parser()
      .box('moov', Mp4Parser.children)
      .box('trak', Mp4Parser.children)
      .box('mdia', Mp4Parser.children)
      .fullBox('mdhd', function(box) {
        goog.asserts.assert(
            box.version == 0 || box.version == 1,
            'MDHD version can only be 0 or 1');

        // Skip "creation_time" and "modification_time".
        // They are 4 bytes each if the mdhd box is version 0, 8 bytes each if
        // it is version 1.
        box.reader.skip(box.version == 0 ? 8 : 16);

        timescale = box.reader.readUint32();
        box.parser.stop();
      }).parse(initData, true /* partialOkay */);

  if (!timescale) {
    shaka.log.error('Unable to find timescale in init segment!');
    throw new shaka.util.Error(
        shaka.util.Error.Severity.CRITICAL,
        shaka.util.Error.Category.MANIFEST,
        shaka.util.Error.Code.HLS_COULD_NOT_PARSE_SEGMENT_START_TIME);
  }

  let startTime = 0;
  let parsedMedia = false;
  new Mp4Parser()
      .box('moof', Mp4Parser.children)
      .box('traf', Mp4Parser.children)
      .fullBox('tfdt', function(box) {
        goog.asserts.assert(
            box.version == 0 || box.version == 1,
            'TFDT version can only be 0 or 1');
        let baseTime = (box.version == 0) ?
            box.reader.readUint32() :
            box.reader.readUint64();
        startTime = baseTime / timescale;
        parsedMedia = true;
        box.parser.stop();
      }).parse(mediaData, true /* partialOkay */);

  if (!parsedMedia) {
    throw new shaka.util.Error(
        shaka.util.Error.Severity.CRITICAL,
        shaka.util.Error.Category.MANIFEST,
        shaka.util.Error.Code.HLS_COULD_NOT_PARSE_SEGMENT_START_TIME);
  }
  return startTime;
};


/**
 * Parses a TS segment to get its start time.
 *
 * @param {!ArrayBuffer} data
 * @return {number}
 * @throws {shaka.util.Error}
 * @private
 */
shaka.hls.HlsParser.prototype.getStartTimeFromTsSegment_ = function(data) {
  let reader = new shaka.util.DataViewReader(
      new DataView(data), shaka.util.DataViewReader.Endianness.BIG_ENDIAN);

  const fail = function() {
    throw new shaka.util.Error(
        shaka.util.Error.Severity.CRITICAL,
        shaka.util.Error.Category.MANIFEST,
        shaka.util.Error.Code.HLS_COULD_NOT_PARSE_SEGMENT_START_TIME);
  };

  let packetStart = 0;
  let syncByte = 0;

  const skipPacket = function() {
    // 188-byte packets are standard, so assume that.
    reader.seek(packetStart + 188);
    syncByte = reader.readUint8();
    if (syncByte != 0x47) {
      // We haven't found the sync byte, so try it as a 192-byte packet.
      reader.seek(packetStart + 192);
      syncByte = reader.readUint8();
    }
    if (syncByte != 0x47) {
      // We still haven't found the sync byte, so try as a 204-byte packet.
      reader.seek(packetStart + 204);
      syncByte = reader.readUint8();
    }
    if (syncByte != 0x47) {
      // We still haven't found the sync byte, so the packet was of a
      // non-standard size.
      fail();
    }
    // Put the sync byte back so we can read it in the next loop.
    reader.rewind(1);
  };

  // eslint-disable-next-line no-constant-condition
  while (true) {
    // Format reference: https://bit.ly/TsPacket
    packetStart = reader.getPosition();

    syncByte = reader.readUint8();
    if (syncByte != 0x47) fail();

    let flagsAndPacketId = reader.readUint16();
    let hasPesPacket = flagsAndPacketId & 0x4000;
    if (!hasPesPacket) fail();

    let flags = reader.readUint8();
    let adaptationFieldControl = (flags & 0x30) >> 4;
    if (adaptationFieldControl == 0 /* reserved */ ||
        adaptationFieldControl == 2 /* adaptation field, no payload */) {
      fail();
    }

    if (adaptationFieldControl == 3) {
      // Skip over adaptation field.
      let length = reader.readUint8();
      reader.skip(length);
    }

    // Now we come to the PES header (hopefully).
    // Format reference: https://bit.ly/TsPES
    let startCode = reader.readUint32();
    let startCodePrefix = startCode >> 8;
    if (startCodePrefix != 1) {
      // Not a PES packet yet.  Skip this TS packet and try again.
      skipPacket();
      continue;
    }

    // Skip the 16-bit PES length and the first 8 bits of the optional header.
    reader.skip(3);
    // The next 8 bits contain flags about DTS & PTS.
    let ptsDtsIndicator = reader.readUint8() >> 6;
    if (ptsDtsIndicator == 0 /* no timestamp */ ||
        ptsDtsIndicator == 1 /* forbidden */) {
      fail();
    }

    let pesHeaderLengthRemaining = reader.readUint8();
    if (pesHeaderLengthRemaining == 0) {
      fail();
    }

    if (ptsDtsIndicator == 2 /* PTS only */) {
      goog.asserts.assert(pesHeaderLengthRemaining == 5, 'Bad PES header?');
    } else if (ptsDtsIndicator == 3 /* PTS and DTS */) {
      goog.asserts.assert(pesHeaderLengthRemaining == 10, 'Bad PES header?');
    }

    let pts0 = reader.readUint8();
    let pts1 = reader.readUint16();
    let pts2 = reader.readUint16();
    // Reconstruct 33-bit PTS from the 5-byte, padded structure.
    let ptsHigh3 = (pts0 & 0x0e) >> 1;
    let ptsLow30 = ((pts1 & 0xfffe) << 14) | ((pts2 & 0xfffe) >> 1);
    // Reconstruct the PTS as a float.  Avoid bitwise operations to combine
    // because bitwise ops treat the values as 32-bit ints.
    let pts = ptsHigh3 * (1 << 30) + ptsLow30;
    return pts / shaka.hls.HlsParser.TS_TIMESCALE_;
  }
};


/**
 * Parses a text segment to get its start time.
 *
 * @param {string} mimeType
 * @param {string} codecs
 * @param {!ArrayBuffer} data
 * @return {number}
 * @throws {shaka.util.Error}
 * @private
 */
shaka.hls.HlsParser.prototype.getStartTimeFromTextSegment_ =
    function(mimeType, codecs, data) {
  let fullMimeType = shaka.util.MimeUtils.getFullType(mimeType, codecs);
  if (!shaka.text.TextEngine.isTypeSupported(fullMimeType)) {
    // We won't be able to parse this, but it will be filtered out anyway.
    // So we don't have to care about the start time.
    return 0;
  }

  let textEngine = new shaka.text.TextEngine(/* displayer */ null);
  textEngine.initParser(fullMimeType);
  return textEngine.getStartTime(data);
};


/**
 * Filters out duplicate codecs from the codec list.
 * @param {!Array.<string>} codecs
 * @return {!Array.<string>}
 * @private
 */
shaka.hls.HlsParser.filterDuplicateCodecs_ = function(codecs) {
  const seen = new Set();
  const ret = [];
  for (const codec of codecs) {
    // HLS says the CODECS field needs to include all codecs that appear in the
    // content.  This means that if the content changes profiles, it should
    // include both.  Since all known browsers support changing profiles without
    // any other work, just ignore them  See also:
    // https://github.com/google/shaka-player/issues/1817
    const shortCodec = shaka.util.MimeUtils.getCodecBase(codec);
    if (!seen.has(shortCodec)) {
      ret.push(codec);
      seen.add(shortCodec);
    } else {
      shaka.log.debug('Ignoring duplicate codec');
    }
  }
  return ret;
};


/**
 * Attempts to guess which codecs from the codecs list belong to a given content
 * type.  Does not assume a single codec is anything special, and does not throw
 * if it fails to match.
 *
 * @param {string} contentType
 * @param {!Array.<string>} codecs
 * @return {?string} or null if no match is found
 * @private
 */
shaka.hls.HlsParser.prototype.guessCodecsSafe_ = function(contentType, codecs) {
  const ContentType = shaka.util.ManifestParserUtils.ContentType;
  const HlsParser = shaka.hls.HlsParser;
  let formats = HlsParser.CODEC_REGEXPS_BY_CONTENT_TYPE_[contentType];

  for (let i = 0; i < formats.length; i++) {
    for (let j = 0; j < codecs.length; j++) {
      if (formats[i].test(codecs[j].trim())) {
        return codecs[j].trim();
      }
    }
  }

  // Text does not require a codec string.
  if (contentType == ContentType.TEXT) {
    return '';
  }

  return null;
};


/**
 * Attempts to guess which codecs from the codecs list belong to a given content
 * type.  Assumes that at least one codec is correct, and throws if none are.
 *
 * @param {string} contentType
 * @param {!Array.<string>} codecs
 * @return {string}
 * @private
 * @throws {shaka.util.Error}
 */
shaka.hls.HlsParser.prototype.guessCodecs_ = function(contentType, codecs) {
  if (codecs.length == 1) {
    return codecs[0];
  }

  let match = this.guessCodecsSafe_(contentType, codecs);
  // A failure is specifically denoted by null; an empty string represents a
  // valid match of no codec.
  if (match != null) {
    return match;
  }

  // Unable to guess codecs.
  throw new shaka.util.Error(
      shaka.util.Error.Severity.CRITICAL,
      shaka.util.Error.Category.MANIFEST,
      shaka.util.Error.Code.HLS_COULD_NOT_GUESS_CODECS,
      codecs);
};


/**
 * Attempts to guess stream's mime type based on content type and URI.
 *
 * @param {string} contentType
 * @param {string} codecs
 * @param {!shaka.hls.Playlist} playlist
 * @return {!Promise.<string>}
 * @private
 * @throws {shaka.util.Error}
 */
shaka.hls.HlsParser.prototype.guessMimeType_ =
    async function(contentType, codecs, playlist) {
  const ContentType = shaka.util.ManifestParserUtils.ContentType;
  const HlsParser = shaka.hls.HlsParser;
  const requestType = shaka.net.NetworkingEngine.RequestType.SEGMENT;

  goog.asserts.assert(playlist.segments.length,
                      'Playlist should have segments!');
  const firstSegmentUri = playlist.segments[0].absoluteUri;

  let parsedUri = new goog.Uri(firstSegmentUri);
  let extension = parsedUri.getPath().split('.').pop();
  let map = HlsParser.EXTENSION_MAP_BY_CONTENT_TYPE_[contentType];

  let mimeType = map[extension];
  if (mimeType) {
    return mimeType;
  }

  if (contentType == ContentType.TEXT) {
    // The extension map didn't work.
    if (!codecs || codecs == 'vtt') {
      // If codecs is 'vtt', it's WebVTT.
      // If there was no codecs string, assume HLS text streams are WebVTT.
      return 'text/vtt';
    } else {
      // Otherwise, assume MP4-embedded text, since text-based formats tend not
      // to have a codecs string at all.
      return 'application/mp4';
    }
  }

  // If unable to guess mime type, request a segment and try getting it
  // from the response.
  let headRequest = shaka.net.NetworkingEngine.makeRequest(
      [firstSegmentUri], this.config_.retryParameters);
  headRequest.method = 'HEAD';

  const response = await this.makeNetworkRequest_(
        headRequest, requestType);

  const contentMimeType = response.headers['content-type'];

  if (!contentMimeType) {
    throw new shaka.util.Error(
        shaka.util.Error.Severity.CRITICAL,
        shaka.util.Error.Category.MANIFEST,
        shaka.util.Error.Code.HLS_COULD_NOT_GUESS_MIME_TYPE,
        extension);
  }

  // Split the MIME type in case the server sent additional parameters.
  return contentMimeType.split(';')[0];
};


/**
 * Find the attribute and returns its value.
 * Throws an error if attribute was not found.
 *
 * @param {shaka.hls.Tag} tag
 * @param {string} attributeName
 * @return {string}
 * @private
 * @throws {shaka.util.Error}
 */
shaka.hls.HlsParser.getRequiredAttributeValue_ = function(tag, attributeName) {
  let attribute = tag.getAttribute(attributeName);
  if (!attribute) {
    throw new shaka.util.Error(
        shaka.util.Error.Severity.CRITICAL,
        shaka.util.Error.Category.MANIFEST,
        shaka.util.Error.Code.HLS_REQUIRED_ATTRIBUTE_MISSING,
        attributeName);
  }

  return attribute.value;
};


/**
 * Returns a tag with a given name.
 * Throws an error if tag was not found.
 *
 * @param {!Array.<shaka.hls.Tag>} tags
 * @param {string} tagName
 * @return {!shaka.hls.Tag}
 * @private
 * @throws {shaka.util.Error}
 */
shaka.hls.HlsParser.prototype.getRequiredTag_ = function(tags, tagName) {
  const Utils = shaka.hls.Utils;
  let tag = Utils.getFirstTagWithName(tags, tagName);
  if (!tag) {
    throw new shaka.util.Error(
        shaka.util.Error.Severity.CRITICAL,
        shaka.util.Error.Category.MANIFEST,
        shaka.util.Error.Code.HLS_REQUIRED_TAG_MISSING, tagName);
  }

  return tag;
};


/**
 * @param {shaka.extern.Stream} stream
 * @param {?string} width
 * @param {?string} height
 * @param {?string} frameRate
 * @private
 */
shaka.hls.HlsParser.prototype.addVideoAttributes_ =
    function(stream, width, height, frameRate) {
  if (stream) {
    stream.width = Number(width) || undefined;
    stream.height = Number(height) || undefined;
    stream.frameRate = Number(frameRate) || undefined;
  }
};


/**
 * Makes a network request for the manifest and returns a Promise
 * with the resulting data.
 *
 * @param {string} absoluteUri
 * @return {!Promise.<!shaka.extern.Response>}
 * @private
 */
shaka.hls.HlsParser.prototype.requestManifest_ = function(absoluteUri) {
  const requestType = shaka.net.NetworkingEngine.RequestType.MANIFEST;

  const request = shaka.net.NetworkingEngine.makeRequest(
      [absoluteUri], this.config_.retryParameters);

  return this.makeNetworkRequest_(request, requestType);
};


/**
 * A list of regexps to detect well-known video codecs.
 *
 * @const {!Array.<!RegExp>}
 * @private
 */
shaka.hls.HlsParser.VIDEO_CODEC_REGEXPS_ = [
  /^avc/,
  /^hev/,
  /^hvc/,
  /^vp0?[89]/,
  /^av1$/,
];


/**
 * A list of regexps to detect well-known audio codecs.
 *
 * @const {!Array.<!RegExp>}
 * @private
 */
shaka.hls.HlsParser.AUDIO_CODEC_REGEXPS_ = [
  /^vorbis$/,
  /^opus$/,
  /^flac$/,
  /^mp4a/,
  /^[ae]c-3$/,
];


/**
 * A list of regexps to detect well-known text codecs.
 *
 * @const {!Array.<!RegExp>}
 * @private
 */
shaka.hls.HlsParser.TEXT_CODEC_REGEXPS_ = [
  /^vtt$/,
  /^wvtt/,
  /^stpp/,
];


/**
 * @const {!Object.<string, !Array.<!RegExp>>}
 * @private
 */
shaka.hls.HlsParser.CODEC_REGEXPS_BY_CONTENT_TYPE_ = {
  'audio': shaka.hls.HlsParser.AUDIO_CODEC_REGEXPS_,
  'video': shaka.hls.HlsParser.VIDEO_CODEC_REGEXPS_,
  'text': shaka.hls.HlsParser.TEXT_CODEC_REGEXPS_,
};


/**
 * @const {!Object.<string, string>}
 * @private
 */
shaka.hls.HlsParser.AUDIO_EXTENSIONS_TO_MIME_TYPES_ = {
  'mp4': 'audio/mp4',
  'm4s': 'audio/mp4',
  'm4i': 'audio/mp4',
  'm4a': 'audio/mp4',
  // MPEG2-TS also uses video/ for audio: https://bit.ly/TsMse
  'ts': 'video/mp2t',
};


/**
 * @const {!Object.<string, string>}
 * @private
 */
shaka.hls.HlsParser.VIDEO_EXTENSIONS_TO_MIME_TYPES_ = {
  'mp4': 'video/mp4',
  'm4s': 'video/mp4',
  'm4i': 'video/mp4',
  'm4v': 'video/mp4',
  'ts': 'video/mp2t',
};


/**
 * @const {!Object.<string, string>}
 * @private
 */
shaka.hls.HlsParser.TEXT_EXTENSIONS_TO_MIME_TYPES_ = {
  'mp4': 'application/mp4',
  'm4s': 'application/mp4',
  'm4i': 'application/mp4',
  'vtt': 'text/vtt',
  'ttml': 'application/ttml+xml',
};


/**
 * @const {!Object.<string, !Object.<string, string>>}
 * @private
 */
shaka.hls.HlsParser.EXTENSION_MAP_BY_CONTENT_TYPE_ = {
  'audio': shaka.hls.HlsParser.AUDIO_EXTENSIONS_TO_MIME_TYPES_,
  'video': shaka.hls.HlsParser.VIDEO_EXTENSIONS_TO_MIME_TYPES_,
  'text': shaka.hls.HlsParser.TEXT_EXTENSIONS_TO_MIME_TYPES_,
};


/**
 * @typedef {function(!shaka.hls.Tag):?shaka.extern.DrmInfo}
 * @private
 */
shaka.hls.HlsParser.DrmParser_;


/**
 * @param {!shaka.hls.Tag} drmTag
 * @return {?shaka.extern.DrmInfo}
 * @private
 */
shaka.hls.HlsParser.widevineDrmParser_ = function(drmTag) {
  const HlsParser = shaka.hls.HlsParser;
  let method = HlsParser.getRequiredAttributeValue_(drmTag, 'METHOD');
  shaka.Deprecate.deprecateFeature(
      2, 6,
      'HLS SAMPLE-AES-CENC',
      'SAMPLE-AES-CENC will no longer be supported, see Issue #1227');
  const VALID_METHODS = ['SAMPLE-AES', 'SAMPLE-AES-CTR', 'SAMPLE-AES-CENC'];
  if (!VALID_METHODS.includes(method)) {
    shaka.log.error('Widevine in HLS is only supported with [',
                    VALID_METHODS.join(', '), '], not', method);
    return null;
  }

  let uri = HlsParser.getRequiredAttributeValue_(drmTag, 'URI');
  let parsedData = shaka.net.DataUriPlugin.parse(uri);

  // The data encoded in the URI is a PSSH box to be used as init data.
  let pssh = new Uint8Array(parsedData.data);
  let drmInfo = shaka.util.ManifestParserUtils.createDrmInfo(
      'com.widevine.alpha', [
        {initDataType: 'cenc', initData: pssh},
      ]);

  let keyId = drmTag.getAttributeValue('KEYID');
  if (keyId) {
    // This value should begin with '0x':
    goog.asserts.assert(keyId.startsWith('0x'), 'Incorrect KEYID format!');
    // But the output should not contain the '0x':
    drmInfo.keyIds = [keyId.substr(2).toLowerCase()];
  }
  return drmInfo;
};


/**
 * Called when the update timer ticks. Because parsing a manifest is async,
 * this method is async. To work with this, this method will schedule the next
 * update when it finished instead of using a repeating-start.
 *
 * @return {!Promise}
 * @private
 */
shaka.hls.HlsParser.prototype.onUpdate_ = async function() {
  shaka.log.info('Updating manifest...');

  goog.asserts.assert(
      this.updatePlaylistDelay_ > 0,
      'We should only call |onUpdate_| when we are suppose to be updating.');

  // Detect a call to stop()
  if (!this.playerInterface_) {
    return;
  }

  try {
    await this.update();

    const delay = this.updatePlaylistDelay_;
    this.updatePlaylistTimer_.tickAfter(/* seconds= */ delay);
  } catch (error) {
    goog.asserts.assert(error instanceof shaka.util.Error,
                        'Should only receive a Shaka error');

    // We will retry updating, so override the severity of the error.
    error.severity = shaka.util.Error.Severity.RECOVERABLE;
    this.playerInterface_.onError(error);

    // Try again very soon.
    this.updatePlaylistTimer_.tickAfter(/* seconds= */ 0.1);
  }
};


/**
 * @return {boolean}
 * @private
 */
shaka.hls.HlsParser.prototype.isLive_ = function() {
  const PresentationType = shaka.hls.HlsParser.PresentationType_;
  return this.presentationType_ != PresentationType.VOD;
};


/**
 * @param {shaka.hls.HlsParser.PresentationType_} type
 * @private
 */
shaka.hls.HlsParser.prototype.setPresentationType_ = function(type) {
  this.presentationType_ = type;

  if (this.presentationTimeline_) {
    this.presentationTimeline_.setStatic(!this.isLive_());
  }

  // If this manifest is not for live content, then we have no reason to
  // update it.
  if (!this.isLive_()) {
    this.updatePlaylistTimer_.stop();
  }
};


/**
 * Create a networking request. This will manage the request using the parser's
 * operation manager. If the parser has already been stopped, the request will
 * not be made.
 *
 * @param {shaka.extern.Request} request
 * @param {shaka.net.NetworkingEngine.RequestType} type
 * @return {!Promise.<shaka.extern.Response>}
 * @private
 */
shaka.hls.HlsParser.prototype.makeNetworkRequest_ = function(request, type) {
  if (!this.operationManager_) {
    throw new shaka.util.Error(
        shaka.util.Error.Severity.CRITICAL,
        shaka.util.Error.Category.PLAYER,
        shaka.util.Error.Code.OPERATION_ABORTED);
  }

  const op = this.playerInterface_.networkingEngine.request(type, request);
  this.operationManager_.manage(op);

  return op.promise;
};


/**
 * @const {!Object.<string, shaka.hls.HlsParser.DrmParser_>}
 * @private
 */
shaka.hls.HlsParser.KEYFORMATS_TO_DRM_PARSERS_ = {
  /* TODO: https://github.com/google/shaka-player/issues/382
  'com.apple.streamingkeydelivery':
      shaka.hls.HlsParser.fairplayDrmParser_,
  */
  'urn:uuid:edef8ba9-79d6-4ace-a3c8-27dcd51d21ed':
      shaka.hls.HlsParser.widevineDrmParser_,
};


/**
 * @enum {string}
 * @private
 */
shaka.hls.HlsParser.PresentationType_ = {
  VOD: 'VOD',
  EVENT: 'EVENT',
  LIVE: 'LIVE',
};


/**
 * @const {number}
 * @private
 */
shaka.hls.HlsParser.TS_TIMESCALE_ = 90000;


/**
 * At this value, timestamps roll over in TS content.
 * @const {number}
 * @private
 */
shaka.hls.HlsParser.TS_ROLLOVER_ = 0x200000000;


/**
 * The amount of data from the start of a segment we will try to fetch when we
 * need to know the segment start time.  This allows us to avoid fetching the
 * entire segment in many cases.
 *
 * @const {number}
 * @private
 */
shaka.hls.HlsParser.PARTIAL_SEGMENT_SIZE_ = 2048;


shaka.media.ManifestParser.registerParserByExtension(
    'm3u8', shaka.hls.HlsParser);
shaka.media.ManifestParser.registerParserByMime(
    'application/x-mpegurl', shaka.hls.HlsParser);
shaka.media.ManifestParser.registerParserByMime(
    'application/vnd.apple.mpegurl', shaka.hls.HlsParser);