/**
* @license
* Copyright 2015 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.dash.mpd');
goog.require('goog.Uri');
goog.require('shaka.log');
goog.require('shaka.util.DataViewReader');
goog.require('shaka.util.LanguageUtils');
goog.require('shaka.util.Pssh');
goog.require('shaka.util.Uint8ArrayUtils');
/**
* Creates an Mpd. The MPD XML text is parsed into a tree structure.
*
* If a tag that should only exist once exists more than once, then all
* instances of that tag are ignored; for example, if a "Representation" tag
* contains more than one "SegmentBase" tag, then every "SegmentBase" tag
* contained in that "Representation" tag is ignored.
*
* Numbers, times, and byte ranges are set to null if they cannot be parsed.
*
* @param {string} source The MPD XML text.
* @param {!Array.<!goog.Uri>} origUrl MPD URL for original download location.
* @param {!Array.<!goog.Uri>} baseUrl MPD URL for relative BaseURL resolution.
* @return {shaka.dash.mpd.Mpd}
*
* @see ISO/IEC 23009-1
*/
shaka.dash.mpd.parseMpd = function(source, origUrl, baseUrl) {
var parser = new DOMParser();
var xml = parser.parseFromString(source, 'text/xml');
if (!xml) {
shaka.log.error('Failed to parse MPD XML.');
return null;
}
// Construct a virtual parent for the MPD to use in resolving relative URLs.
var parent = { origUrl: origUrl, baseUrl: baseUrl };
return shaka.dash.mpd.parseChild_(parent, xml, shaka.dash.mpd.Mpd);
};
/**
* @private {number}
* @const
*/
shaka.dash.mpd.DEFAULT_MIN_BUFFER_TIME_ = 5.0;
/**
* @private {number}
* @const
*/
shaka.dash.mpd.DEFAULT_SUGGESTED_PRESENTATION_DELAY_ = 1.0;
/**
* @constructor
* @struct
*/
shaka.dash.mpd.Mpd = function() {
/**
* The MPD's URL.
* @type {Array.<!goog.Uri>}
*/
this.url = null;
/** @type {?string} */
this.id = null;
/** @type {string} */
this.type = 'static';
/** @type {Array.<!goog.Uri>} */
this.origUrl = null;
/** @type {Array.<!goog.Uri>} */
this.baseUrl = null;
/** @type {Array.<!goog.Uri>} */
this.updateLocation = null;
/**
* The entire stream's duration, in seconds.
* @type {?number}
*/
this.mediaPresentationDuration = null;
/**
* The amount of content to buffer, in seconds, before playback begins to
* ensure uninterrupted playback.
* @type {?number}
*/
this.minBufferTime = shaka.dash.mpd.DEFAULT_MIN_BUFFER_TIME_;
/**
* The interval, in seconds, to poll the media server for an updated
* MPD, or null if updates are not required.
* @type {?number}
*/
this.minUpdatePeriod = null;
/**
* The wall-clock time, in seconds, that the media content specified within
* the MPD started/will start to stream.
* @type {?number}
*/
this.availabilityStartTime = null;
/**
* The duration, in seconds, that the media server retains live media
* content, excluding the current segment and the previous segment, which are
* always available. For example, if this value is 60 then only media content
* up to 60 seconds from the beginning of the previous segment may be
* requested from the media server.
* @type {?number}
*/
this.timeShiftBufferDepth = null;
/**
* The duration, in seconds, that the media server takes to make live media
* content available. For example, if this value is 30 then only media
* content at least 30 seconds in the past may be requested from the media
* server.
* @type {?number}
*/
this.suggestedPresentationDelay =
shaka.dash.mpd.DEFAULT_SUGGESTED_PRESENTATION_DELAY_;
/** @type {!Array.<!shaka.dash.mpd.Period>} */
this.periods = [];
};
/**
* @constructor
* @struct
*/
shaka.dash.mpd.Period = function() {
/** @type {?string} */
this.id = null;
/**
* The start time of the Period, in seconds, with respect to the media
* presentation timeline. Note that the Period becomes/became available at
* Mpd.availabilityStartTime + Period.start.
* @type {?number}
*/
this.start = null;
/**
* The duration in seconds.
* @type {?number}
*/
this.duration = null;
/** @type {Array.<!goog.Uri>} */
this.baseUrl = null;
/** @type {shaka.dash.mpd.SegmentBase} */
this.segmentBase = null;
/** @type {shaka.dash.mpd.SegmentList} */
this.segmentList = null;
/** @type {shaka.dash.mpd.SegmentTemplate} */
this.segmentTemplate = null;
/** @type {!Array.<!shaka.dash.mpd.AdaptationSet>} */
this.adaptationSets = [];
};
/**
* @constructor
* @struct
*/
shaka.dash.mpd.AdaptationSet = function() {
/** @type {?string} */
this.id = null;
/**
* This value is never null after parsing.
* @type {?number}
*/
this.group = null;
/**
* The language.
* @type {?string}
* @see IETF RFC 5646
* @see ISO 639
*/
this.lang = null;
/**
* Should be 'video' or 'audio', not a MIME type.
* If not specified, will be inferred from the MIME type.
* @type {?string}
*/
this.contentType = null;
/** @type {?number} */
this.width = null;
/** @type {?number} */
this.height = null;
/**
* If not specified, will be inferred from the first representation.
* @type {?string}
*/
this.mimeType = null;
/** @type {?string} */
this.codecs = null;
/** @type {boolean} */
this.main = false;
/** @type {Array.<!goog.Uri>} */
this.baseUrl = null;
/** @type {shaka.dash.mpd.SegmentBase} */
this.segmentBase = null;
/** @type {shaka.dash.mpd.SegmentList} */
this.segmentList = null;
/** @type {shaka.dash.mpd.SegmentTemplate} */
this.segmentTemplate = null;
/** @type {!Array.<!shaka.dash.mpd.ContentProtection>} */
this.contentProtections = [];
/** @type {!Array.<!shaka.dash.mpd.Representation>} */
this.representations = [];
};
/**
* @constructor
* @struct
*/
shaka.dash.mpd.Role = function() {
/** @type {?string} */
this.value = null;
};
/**
* @constructor
* @struct
*/
shaka.dash.mpd.ContentComponent = function() {
/** @type {?string} */
this.id = null;
/**
* The language.
* @type {?string}
* @see IETF RFC 5646
* @see ISO 639
*/
this.lang = null;
/**
* Should be 'video' or 'audio', not a MIME type.
* @type {?string}
*/
this.contentType = null;
};
/**
* @constructor
* @struct
*/
shaka.dash.mpd.Representation = function() {
/** @type {?string} */
this.id = null;
/**
* Never seen on the Representation itself, but inherited from AdapationSet
* for convenience.
* @see AdaptationSet.lang
* @type {?string}
*/
this.lang = null;
/**
* Bandwidth required, in bits per second, to assure uninterrupted playback,
* assuming that |minBufferTime| seconds of video are in buffer before
* playback begins.
* @type {?number}
*/
this.bandwidth = null;
/** @type {?number} */
this.width = null;
/** @type {?number} */
this.height = null;
/** @type {?string} */
this.mimeType = null;
/** @type {?string} */
this.codecs = null;
/** @type {Array.<!goog.Uri>} */
this.baseUrl = null;
/** @type {shaka.dash.mpd.SegmentBase} */
this.segmentBase = null;
/** @type {shaka.dash.mpd.SegmentList} */
this.segmentList = null;
/** @type {shaka.dash.mpd.SegmentTemplate} */
this.segmentTemplate = null;
/** @type {!Array.<!shaka.dash.mpd.ContentProtection>} */
this.contentProtections = [];
};
/**
* @constructor
* @struct
*/
shaka.dash.mpd.ContentProtection = function() {
/**
* The entire ContentProtection XML element.
* @type {Node}
*/
this.element = null;
/**
* @type {?string}
*/
this.schemeIdUri = null;
/**
* @type {shaka.dash.mpd.CencPssh}
*/
this.pssh = null;
/**
* A key ID, as a hex string, that identifies a decryption key for any
* content specified at the same level and all levels below this
* ContentProtection element.
* @type {?string}
*/
this.defaultKeyId = null;
};
/**
* @constructor
* @struct
*/
shaka.dash.mpd.CencPssh = function() {
/**
* @type {Uint8Array}
* @expose
*/
this.psshBox = null;
/**
* @type {shaka.util.Pssh}
* @expose
*/
this.parsedPssh = null;
};
/**
* @constructor
* @struct
*/
shaka.dash.mpd.BaseUrl = function() {
/** @type {?string} */
this.url = null;
};
/**
* @constructor
* @struct
*/
shaka.dash.mpd.Location = function() {
/** @type {?string} */
this.url = null;
};
/**
* @constructor
* @struct
*/
shaka.dash.mpd.SegmentBase = function() {
/**
* This not an actual XML attribute of SegmentBase. It is inherited from the
* SegmentBase's parent Representation.
* @type {Array.<!goog.Uri>}
*/
this.baseUrl = null;
/** @type {?number} */
this.timescale = 1;
/** @type {?number} */
this.presentationTimeOffset = null;
/** @type {shaka.dash.mpd.Range} */
this.indexRange = null;
/** @type {shaka.dash.mpd.RepresentationIndex} */
this.representationIndex = null;
/** @type {shaka.dash.mpd.Initialization} */
this.initialization = null;
};
/**
* Creates a deep copy of this SegmentBase.
* @return {!shaka.dash.mpd.SegmentBase}
*/
shaka.dash.mpd.SegmentBase.prototype.clone = function() {
var mpd = shaka.dash.mpd;
var clone = new shaka.dash.mpd.SegmentBase();
clone.baseUrl = mpd.cloneA_(this.baseUrl);
clone.timescale = this.timescale;
clone.presentationTimeOffset = this.presentationTimeOffset;
clone.indexRange = mpd.clone_(this.indexRange);
clone.representationIndex = mpd.clone_(this.representationIndex);
clone.initialization = mpd.clone_(this.initialization);
return clone;
};
/**
* @constructor
* @struct
*/
shaka.dash.mpd.RepresentationIndex = function() {
/** @type {Array.<!goog.Uri>} */
this.url = null;
/**
* Inherits the value of SegmentBase.indexRange if not specified.
* @type {shaka.dash.mpd.Range}
*/
this.range = null;
};
/**
* Creates a deep copy of this RepresentationIndex.
* @return {!shaka.dash.mpd.RepresentationIndex}
*/
shaka.dash.mpd.RepresentationIndex.prototype.clone = function() {
var mpd = shaka.dash.mpd;
var clone = new shaka.dash.mpd.RepresentationIndex();
clone.url = mpd.cloneA_(this.url);
clone.range = mpd.clone_(this.range);
return clone;
};
/**
* @constructor
* @struct
*/
shaka.dash.mpd.Initialization = function() {
/** @type {Array.<!goog.Uri>} */
this.url = null;
/** @type {shaka.dash.mpd.Range} */
this.range = null;
};
/**
* Creates a deep copy of this Initialization.
* @return {!shaka.dash.mpd.Initialization}
*/
shaka.dash.mpd.Initialization.prototype.clone = function() {
var mpd = shaka.dash.mpd;
var clone = new shaka.dash.mpd.Initialization();
clone.url = mpd.cloneA_(this.url);
clone.range = mpd.clone_(this.range);
return clone;
};
/**
* @constructor
* @struct
*/
shaka.dash.mpd.SegmentList = function() {
/**
* This not an actual XML attribute of SegmentList. It is inherited from the
* SegmentList's parent Representation.
* @type {Array.<!goog.Uri>}
*/
this.baseUrl = null;
/** @type {?number} */
this.timescale = 1;
/** @type {?number} */
this.presentationTimeOffset = null;
/**
* Each segment's duration. This value is never zero.
* @type {?number}
*/
this.segmentDuration = null;
/**
* The segment number (one-based) of the first segment specified in the
* SegmentList's corresponding Representation, relative to the start of the
* Representation's Period.
*
* @type {number}
*/
this.startNumber = 1;
/** @type {shaka.dash.mpd.Initialization} */
this.initialization = null;
/** @type {!Array.<!shaka.dash.mpd.SegmentUrl>} */
this.segmentUrls = [];
/** @type {shaka.dash.mpd.SegmentTimeline} */
this.timeline = null;
};
/**
* Creates a deep copy of this SegmentList.
* @return {!shaka.dash.mpd.SegmentList}
*/
shaka.dash.mpd.SegmentList.prototype.clone = function() {
var mpd = shaka.dash.mpd;
var clone = new shaka.dash.mpd.SegmentList();
clone.baseUrl = mpd.cloneA_(this.baseUrl);
clone.timescale = this.timescale;
clone.presentationTimeOffset = this.presentationTimeOffset;
clone.segmentDuration = this.segmentDuration;
clone.startNumber = this.startNumber;
clone.initialization = mpd.clone_(this.initialization);
clone.segmentUrls = mpd.cloneA_(this.segmentUrls) || [];
clone.timeline = mpd.clone_(this.timeline);
return clone;
};
/**
* @constructor
* @struct
*/
shaka.dash.mpd.SegmentUrl = function() {
/** @type {Array.<!goog.Uri>} */
this.mediaUrl = null;
/** @type {shaka.dash.mpd.Range} */
this.mediaRange = null;
};
/**
* Creates a deep copy of this SegmentUrl.
* @return {!shaka.dash.mpd.SegmentUrl}
*/
shaka.dash.mpd.SegmentUrl.prototype.clone = function() {
var mpd = shaka.dash.mpd;
var clone = new shaka.dash.mpd.SegmentUrl();
clone.mediaUrl = mpd.cloneA_(this.mediaUrl);
clone.mediaRange = mpd.clone_(this.mediaRange);
return clone;
};
/**
* @constructor
* @struct
*/
shaka.dash.mpd.SegmentTemplate = function() {
/** @type {?number} */
this.timescale = 1;
/** @type {?number} */
this.presentationTimeOffset = null;
/**
* Each segment's duration. This value is never zero.
* @type {?number}
*/
this.segmentDuration = null;
/**
* The segment number (one-based) of the first segment specified in the
* SegmentTemplates's corresponding Representation, relative to the start of
* the Representation's Period.
* @type {number}
*/
this.startNumber = 1;
/** @type {?string} */
this.mediaUrlTemplate = null;
/** @type {?string} */
this.indexUrlTemplate = null;
/** @type {?string} */
this.initializationUrlTemplate = null;
/** @type {shaka.dash.mpd.SegmentTimeline} */
this.timeline = null;
};
/**
* Creates a deep copy of this SegmentTemplate.
* @return {!shaka.dash.mpd.SegmentTemplate}
*/
shaka.dash.mpd.SegmentTemplate.prototype.clone = function() {
var mpd = shaka.dash.mpd;
var clone = new shaka.dash.mpd.SegmentTemplate();
clone.timescale = this.timescale;
clone.presentationTimeOffset = this.presentationTimeOffset;
clone.segmentDuration = this.segmentDuration;
clone.startNumber = this.startNumber;
clone.mediaUrlTemplate = this.mediaUrlTemplate;
clone.indexUrlTemplate = this.indexUrlTemplate;
clone.initializationUrlTemplate = this.initializationUrlTemplate;
clone.timeline = mpd.clone_(this.timeline);
return clone;
};
/**
* @constructor
* @struct
*/
shaka.dash.mpd.SegmentTimeline = function() {
/** @type {!Array.<!shaka.dash.mpd.SegmentTimePoint>} */
this.timePoints = [];
};
/**
* Creates a deep copy of this SegmentTimeline.
* @return {!shaka.dash.mpd.SegmentTimeline}
*/
shaka.dash.mpd.SegmentTimeline.prototype.clone = function() {
var clone = new shaka.dash.mpd.SegmentTimeline();
clone.timePoints = shaka.dash.mpd.cloneA_(this.timePoints) || [];
return clone;
};
/**
* @constructor
* @struct
*/
shaka.dash.mpd.SegmentTimePoint = function() {
/**
* The start time of the media segment, in seconds, relative to the beginning
* of the Period.
* @type {?number}
*/
this.startTime = null;
/** @type {?number} */
this.duration = null;
/** @type {?number} */
this.repeat = null;
};
/**
* Creates a deep copy of this SegmentTimePoint.
* @return {!shaka.dash.mpd.SegmentTimePoint}
*/
shaka.dash.mpd.SegmentTimePoint.prototype.clone = function() {
var clone = new shaka.dash.mpd.SegmentTimePoint();
clone.startTime = this.startTime;
clone.duration = this.duration;
clone.repeat = this.repeat;
return clone;
};
/**
* Creates a Range.
* @param {number} begin The beginning of the range.
* @param {number} end The end of the range.
* @constructor
* @struct
*/
shaka.dash.mpd.Range = function(begin, end) {
/** @const {number} */
this.begin = begin;
/** @const {number} */
this.end = end;
};
/**
* Creates a deep copy of this Range.
* @return {!shaka.dash.mpd.Range}
*/
shaka.dash.mpd.Range.prototype.clone = function() {
return new shaka.dash.mpd.Range(this.begin, this.end);
};
// MPD tag names --------------------------------------------------------------
/**
* @const {string}
* @expose all TAG_NAME properties so that they do not get stripped during
* advanced compilation.
*/
shaka.dash.mpd.Mpd.TAG_NAME = 'MPD';
/** @const {string} */
shaka.dash.mpd.Period.TAG_NAME = 'Period';
/** @const {string} */
shaka.dash.mpd.AdaptationSet.TAG_NAME = 'AdaptationSet';
/** @const {string} */
shaka.dash.mpd.Role.TAG_NAME = 'Role';
/** @const {string} */
shaka.dash.mpd.ContentComponent.TAG_NAME = 'ContentComponent';
/** @const {string} */
shaka.dash.mpd.Representation.TAG_NAME = 'Representation';
/** @const {string} */
shaka.dash.mpd.ContentProtection.TAG_NAME = 'ContentProtection';
/** @const {string} */
shaka.dash.mpd.CencPssh.TAG_NAME = 'cenc:pssh';
/** @const {string} */
shaka.dash.mpd.BaseUrl.TAG_NAME = 'BaseURL';
/** @const {string} */
shaka.dash.mpd.Location.TAG_NAME = 'Location';
/** @const {string} */
shaka.dash.mpd.SegmentBase.TAG_NAME = 'SegmentBase';
/** @const {string} */
shaka.dash.mpd.RepresentationIndex.TAG_NAME = 'RepresentationIndex';
/** @const {string} */
shaka.dash.mpd.Initialization.TAG_NAME = 'Initialization';
/** @const {string} */
shaka.dash.mpd.SegmentList.TAG_NAME = 'SegmentList';
/** @const {string} */
shaka.dash.mpd.SegmentUrl.TAG_NAME = 'SegmentURL';
/** @const {string} */
shaka.dash.mpd.SegmentTemplate.TAG_NAME = 'SegmentTemplate';
/** @const {string} */
shaka.dash.mpd.SegmentTimeline.TAG_NAME = 'SegmentTimeline';
/** @const {string} */
shaka.dash.mpd.SegmentTimePoint.TAG_NAME = 'S';
// MPD parsing functions ------------------------------------------------------
/**
* Parses an "MPD" tag.
* @param {{baseUrl: !Array.<!goog.Uri>}} parent A virtual parent tag
* containing a BaseURL which refers to the MPD resource itself.
* @param {!Node} elem The MPD XML element.
*/
shaka.dash.mpd.Mpd.prototype.parse = function(parent, elem) {
var mpd = shaka.dash.mpd;
// Parse attributes.
this.url = parent.origUrl;
this.id = mpd.parseAttr_(elem, 'id', mpd.parseString_);
this.type = mpd.parseAttr_(elem, 'type', mpd.parseString_) || 'static';
this.mediaPresentationDuration = mpd.parseAttr_(
elem, 'mediaPresentationDuration', mpd.parseDuration_);
this.minBufferTime =
mpd.parseAttr_(elem,
'minBufferTime',
mpd.parseDuration_,
this.minBufferTime);
this.minUpdatePeriod =
mpd.parseAttr_(elem,
'minimumUpdatePeriod',
mpd.parseDuration_,
this.minUpdatePeriod);
this.availabilityStartTime =
mpd.parseAttr_(elem,
'availabilityStartTime',
mpd.parseDate_,
this.availabilityStartTime);
this.timeShiftBufferDepth =
mpd.parseAttr_(elem,
'timeShiftBufferDepth',
mpd.parseDuration_,
this.timeShiftBufferDepth);
this.suggestedPresentationDelay =
mpd.parseAttr_(elem,
'suggestedPresentationDelay',
mpd.parseDuration_,
this.suggestedPresentationDelay);
var base = parent.baseUrl;
// Parse simple child elements.
var baseUrl = mpd.parseChildren_(this, elem, mpd.BaseUrl);
this.baseUrl = mpd.resolveUrlArray_(base, baseUrl);
var updateLocation = mpd.parseChild_(this, elem, mpd.Location);
if (updateLocation) {
this.updateLocation = mpd.resolveUrl_(base, updateLocation.url);
}
// Parse hierarchical children.
this.periods = mpd.parseChildren_(this, elem, mpd.Period);
};
/**
* Adds a text set for the given external captions. This only effects the
* first period; has no effect if there are no periods.
*
* @param {string} url
* @param {string=} opt_lang Optional language of the text, defaults to 'en'.
* @param {string=} opt_mime Optional MIME type, defaults to 'text/vtt'.
*/
shaka.dash.mpd.Mpd.prototype.addExternalCaptions =
function(url, opt_lang, opt_mime) {
if (this.periods.length === 0) {
return;
}
var as = new shaka.dash.mpd.AdaptationSet();
as.contentType = 'text';
as.lang = opt_lang || 'en';
as.main = true;
var repr = new shaka.dash.mpd.Representation();
repr.bandwidth = 0;
repr.mimeType = opt_mime || 'text/vtt';
repr.baseUrl = [new goog.Uri(url)];
as.representations.push(repr);
this.periods[0].adaptationSets.push(as);
this.periods[0].assignGroups_();
};
/**
* Parses a "Period" tag.
* @param {!shaka.dash.mpd.Mpd} parent The parent Mpd.
* @param {!Node} elem The Period XML element.
*/
shaka.dash.mpd.Period.prototype.parse = function(parent, elem) {
var mpd = shaka.dash.mpd;
// Parse attributes.
this.id = mpd.parseAttr_(elem, 'id', mpd.parseString_);
this.start = mpd.parseAttr_(elem, 'start', mpd.parseDuration_);
this.duration = mpd.parseAttr_(elem, 'duration', mpd.parseDuration_);
// Parse simple child elements.
var baseUrl = mpd.parseChildren_(this, elem, mpd.BaseUrl);
this.baseUrl = mpd.resolveUrlArray_(parent.baseUrl, baseUrl);
// Parse hierarchical children.
this.segmentBase = mpd.parseChild_(this, elem, mpd.SegmentBase);
this.segmentList = mpd.parseChild_(this, elem, mpd.SegmentList);
this.segmentTemplate = mpd.parseChild_(this, elem, mpd.SegmentTemplate);
this.adaptationSets = mpd.parseChildren_(this, elem, mpd.AdaptationSet);
this.assignGroups_();
};
/**
* Assigns a unique non-zero group to each AdaptationSet without an explicitly
* set group.
*
* @private
* @see ISO/IEC 23009-1 5.3.3.1
*/
shaka.dash.mpd.Period.prototype.assignGroups_ = function() {
/** @type {!Array.<boolean|undefined>} */
var groups = [];
for (var i = 0; i < this.adaptationSets.length; ++i) {
var adaptationSet = this.adaptationSets[i];
if (adaptationSet.group != null) {
groups[adaptationSet.group] = true;
}
}
for (var i = 0; i < this.adaptationSets.length; ++i) {
var adaptationSet = this.adaptationSets[i];
if (adaptationSet.group == null) {
var group = 1;
while (groups[group] == true) ++group;
groups[group] = true;
adaptationSet.group = group;
}
}
};
/**
* Parses an "AdaptationSet" tag.
* @param {!shaka.dash.mpd.Period} parent The parent Period.
* @param {!Node} elem The AdaptationSet XML element.
*/
shaka.dash.mpd.AdaptationSet.prototype.parse = function(parent, elem) {
var mpd = shaka.dash.mpd;
// Parse children which provide properties of the AdaptationSet.
var contentComponent = mpd.parseChild_(this, elem, mpd.ContentComponent) ||
{};
var role = mpd.parseChild_(this, elem, mpd.Role);
// Parse attributes.
this.id = mpd.parseAttr_(elem, 'id', mpd.parseString_);
this.group = mpd.parseAttr_(elem, 'group', mpd.parseNonNegativeInt_);
this.lang = mpd.parseAttr_(
elem, 'lang', mpd.parseString_, contentComponent.lang);
this.contentType = mpd.parseAttr_(
elem, 'contentType', mpd.parseString_, contentComponent.contentType);
this.width = mpd.parseAttr_(elem, 'width', mpd.parsePositiveInt_);
this.height = mpd.parseAttr_(elem, 'height', mpd.parsePositiveInt_);
this.mimeType = mpd.parseAttr_(elem, 'mimeType', mpd.parseString_);
this.codecs = mpd.parseAttr_(elem, 'codecs', mpd.parseString_);
this.main = role && role.value == 'main';
// Normalize the language tag.
if (this.lang) this.lang = shaka.util.LanguageUtils.normalize(this.lang);
// Parse simple child elements.
var baseUrl = mpd.parseChildren_(this, elem, mpd.BaseUrl);
this.baseUrl = mpd.resolveUrlArray_(parent.baseUrl, baseUrl);
// TODO: Any initData values or default key IDs in generic MP4
// ContentProtection elements (i.e, urn:mpeg:dash:mp4protection:2011') should
// be inherited by other ContentProtection elements.
this.contentProtections =
mpd.parseChildren_(this, elem, mpd.ContentProtection);
if (!this.contentType && this.mimeType) {
// Infer contentType from mimeType. This must be done before parsing any
// child Representations, as Representation inherits contentType.
this.contentType = this.mimeType.split('/')[0];
}
// Parse hierarchical children.
this.segmentBase = parent.segmentBase ?
mpd.mergeChild_(this, elem, parent.segmentBase) :
mpd.parseChild_(this, elem, mpd.SegmentBase);
this.segmentList = parent.segmentList ?
mpd.mergeChild_(this, elem, parent.segmentList) :
mpd.parseChild_(this, elem, mpd.SegmentList);
this.segmentTemplate = parent.segmentTemplate ?
mpd.mergeChild_(this, elem, parent.segmentTemplate) :
mpd.parseChild_(this, elem, mpd.SegmentTemplate);
this.representations = mpd.parseChildren_(this, elem, mpd.Representation);
if (!this.mimeType && this.representations.length) {
// Infer mimeType from children. MpdProcessor will deal with the case
// where Representations have inconsistent mimeTypes.
this.mimeType = this.representations[0].mimeType;
if (!this.contentType && this.mimeType) {
this.contentType = this.mimeType.split('/')[0];
}
}
};
/**
* Parses a "Role" tag.
* @param {!shaka.dash.mpd.AdaptationSet} parent The parent AdaptationSet.
* @param {!Node} elem The Role XML element.
*/
shaka.dash.mpd.Role.prototype.parse = function(parent, elem) {
var mpd = shaka.dash.mpd;
// Parse attributes.
this.value = mpd.parseAttr_(elem, 'value', mpd.parseString_);
};
/**
* Parses a "ContentComponent" tag.
* @param {!shaka.dash.mpd.AdaptationSet} parent The parent AdaptationSet.
* @param {!Node} elem The ContentComponent XML element.
*/
shaka.dash.mpd.ContentComponent.prototype.parse = function(parent, elem) {
var mpd = shaka.dash.mpd;
// Parse attributes.
this.id = mpd.parseAttr_(elem, 'id', mpd.parseString_);
this.lang = mpd.parseAttr_(elem, 'lang', mpd.parseString_);
this.contentType = mpd.parseAttr_(elem, 'contentType', mpd.parseString_);
// Normalize the language tag.
if (this.lang) this.lang = shaka.util.LanguageUtils.normalize(this.lang);
};
/**
* Parses a "Representation" tag.
* @param {!shaka.dash.mpd.AdaptationSet} parent The parent AdaptationSet.
* @param {!Node} elem The Representation XML element.
*/
shaka.dash.mpd.Representation.prototype.parse = function(parent, elem) {
var mpd = shaka.dash.mpd;
// Parse attributes.
this.id = mpd.parseAttr_(elem, 'id', mpd.parseString_);
this.bandwidth = mpd.parseAttr_(elem, 'bandwidth', mpd.parsePositiveInt_);
this.width = mpd.parseAttr_(
elem, 'width', mpd.parsePositiveInt_, parent.width);
this.height = mpd.parseAttr_(
elem, 'height', mpd.parsePositiveInt_, parent.height);
this.mimeType = mpd.parseAttr_(
elem, 'mimeType', mpd.parseString_, parent.mimeType);
this.codecs = mpd.parseAttr_(elem, 'codecs', mpd.parseString_, parent.codecs);
// Never seen on this element itself, but inherited for convenience.
this.lang = parent.lang;
// Parse simple child elements.
var baseUrl = mpd.parseChildren_(this, elem, mpd.BaseUrl);
this.baseUrl = mpd.resolveUrlArray_(parent.baseUrl, baseUrl);
this.contentProtections =
mpd.parseChildren_(this, elem, mpd.ContentProtection);
// Parse hierarchical children.
this.segmentBase = parent.segmentBase ?
mpd.mergeChild_(this, elem, parent.segmentBase) :
mpd.parseChild_(this, elem, mpd.SegmentBase);
this.segmentList = parent.segmentList ?
mpd.mergeChild_(this, elem, parent.segmentList) :
mpd.parseChild_(this, elem, mpd.SegmentList);
this.segmentTemplate = parent.segmentTemplate ?
mpd.mergeChild_(this, elem, parent.segmentTemplate) :
mpd.parseChild_(this, elem, mpd.SegmentTemplate);
this.contentProtections =
this.contentProtections.concat(parent.contentProtections);
};
/**
* Parses a "ContentProtection" tag.
* @param {*} parent The parent object.
* @param {!Node} elem The ContentProtection XML element.
*/
shaka.dash.mpd.ContentProtection.prototype.parse = function(parent, elem) {
var mpd = shaka.dash.mpd;
this.element = elem;
// Parse attributes.
this.schemeIdUri = mpd.parseAttr_(elem, 'schemeIdUri', mpd.parseString_);
// The 'default_KID' is specified as a GUID, so remove the dashes.
var defaultKeyIdGuid =
mpd.parseAttr_(elem, 'cenc:default_KID', mpd.parseString_);
if (defaultKeyIdGuid) {
this.defaultKeyId = defaultKeyIdGuid.replace(/[-]/g, '');
}
// Parse simple child elements.
this.pssh = mpd.parseChild_(this, elem, mpd.CencPssh);
};
/**
* Parse a "cenc:pssh" tag.
* @param {*} parent The parent object.
* @param {!Node} elem The CencPssh XML element.
*/
shaka.dash.mpd.CencPssh.prototype.parse = function(parent, elem) {
var mpd = shaka.dash.mpd;
var Uint8ArrayUtils = shaka.util.Uint8ArrayUtils;
var contents = mpd.getContents_(elem);
if (!contents) {
return;
}
this.psshBox = Uint8ArrayUtils.fromBase64(contents);
try {
this.parsedPssh = new shaka.util.Pssh(this.psshBox);
} catch (exception) {
if (!(exception instanceof RangeError)) {
throw exception;
}
}
};
/**
* Parses a "BaseURL" tag.
* @param {*} parent The parent object.
* @param {!Node} elem The BaseURL XML element.
*/
shaka.dash.mpd.BaseUrl.prototype.parse = function(parent, elem) {
this.url = shaka.dash.mpd.getContents_(elem);
};
/**
* Parses a "Location" tag.
* @param {*} parent The parent object.
* @param {!Node} elem The Location XML element.
*/
shaka.dash.mpd.Location.prototype.parse = function(parent, elem) {
this.url = shaka.dash.mpd.getContents_(elem);
};
/**
* Parses a "SegmentBase" tag.
* @param {*} parent The parent object.
* @param {!Node} elem The SegmentBase XML element.
*/
shaka.dash.mpd.SegmentBase.prototype.parse = function(parent, elem) {
var mpd = shaka.dash.mpd;
this.baseUrl = parent.baseUrl || this.baseUrl;
// When parsing attributes and child elements fallback to |this| to provide
// default values. If |this| is a new SegmentBase then |this| will have
// default values from its constructor, and if |this| was cloned from a
// higher level SegmentBase then |this| will have values from that
// SegmentBase.
this.timescale = mpd.parseAttr_(
elem, 'timescale', mpd.parsePositiveInt_, this.timescale);
this.presentationTimeOffset =
mpd.parseAttr_(elem,
'presentationTimeOffset',
mpd.parseNonNegativeInt_,
this.presentationTimeOffset);
// Parse attributes.
this.indexRange = mpd.parseAttr_(
elem, 'indexRange', mpd.parseRange_, this.indexRange);
// Parse simple child elements.
this.representationIndex =
mpd.parseChild_(this, elem, mpd.RepresentationIndex) ||
this.representationIndex;
this.initialization =
mpd.parseChild_(this, elem, mpd.Initialization) ||
this.initialization;
};
/**
* Parses a "RepresentationIndex" tag.
* @param {!shaka.dash.mpd.SegmentBase} parent The parent SegmentBase.
* @param {!Node} elem The RepresentationIndex XML element.
*/
shaka.dash.mpd.RepresentationIndex.prototype.parse =
function(parent, elem) {
var mpd = shaka.dash.mpd;
// Parse attributes.
var url = mpd.parseAttr_(elem, 'sourceURL', mpd.parseString_);
this.url = mpd.resolveUrl_(parent.baseUrl, url);
this.range = mpd.parseAttr_(
elem, 'range', mpd.parseRange_, mpd.clone_(parent.indexRange));
};
/**
* Parses an "Initialization" tag.
* @param {!shaka.dash.mpd.SegmentBase|!shaka.dash.mpd.SegmentList} parent
* The parent SegmentBase or parent SegmentList.
* @param {!Node} elem The Initialization XML element.
*/
shaka.dash.mpd.Initialization.prototype.parse = function(parent, elem) {
var mpd = shaka.dash.mpd;
// Parse attributes.
var url = mpd.parseAttr_(elem, 'sourceURL', mpd.parseString_);
this.url = mpd.resolveUrl_(parent.baseUrl, url);
this.range = mpd.parseAttr_(elem, 'range', mpd.parseRange_);
};
/**
* Parses a "SegmentList" tag.
* @param {*} parent The parent object.
* @param {!Node} elem The SegmentList XML element.
*/
shaka.dash.mpd.SegmentList.prototype.parse = function(parent, elem) {
var mpd = shaka.dash.mpd;
this.baseUrl = parent.baseUrl || this.baseUrl;
// Parse attributes.
this.timescale = mpd.parseAttr_(
elem, 'timescale', mpd.parsePositiveInt_, this.timescale);
this.presentationTimeOffset =
mpd.parseAttr_(elem,
'presentationTimeOffset',
mpd.parseNonNegativeInt_,
this.presentationTimeOffset);
this.segmentDuration = mpd.parseAttr_(
elem, 'duration', mpd.parsePositiveInt_, this.segmentDuration);
// May not be zero, because that would lead to a negative start time.
var startNumber = mpd.parseAttr_(
elem, 'startNumber', mpd.parsePositiveInt_);
if (startNumber != null) {
this.startNumber = startNumber;
}
// Parse simple children
this.initialization =
mpd.parseChild_(this, elem, mpd.Initialization) ||
this.initialization;
var temp = mpd.parseChildren_(this, elem, mpd.SegmentUrl);
this.segmentUrls = temp && temp.length > 0 ? temp : this.segmentUrls;
// Parse hierarchical children.
this.timeline =
mpd.parseChild_(this, elem, mpd.SegmentTimeline) ||
this.timeline;
};
/**
* Parses a "SegmentUrl" tag.
* @param {!shaka.dash.mpd.SegmentList} parent The parent SegmentList.
* @param {!Node} elem The SegmentUrl XML element.
*/
shaka.dash.mpd.SegmentUrl.prototype.parse = function(parent, elem) {
var mpd = shaka.dash.mpd;
// Parse attributes.
var url = mpd.parseAttr_(elem, 'media', mpd.parseString_);
this.mediaUrl = mpd.resolveUrl_(parent.baseUrl, url);
this.mediaRange = mpd.parseAttr_(elem, 'mediaRange', mpd.parseRange_);
};
/**
* Parses a "SegmentTemplate" tag.
* @param {*} parent The parent object.
* @param {!Node} elem The SegmentTemplate XML element.
*/
shaka.dash.mpd.SegmentTemplate.prototype.parse = function(parent, elem) {
var mpd = shaka.dash.mpd;
// Parse attributes.
this.timescale = mpd.parseAttr_(
elem, 'timescale', mpd.parsePositiveInt_, this.timescale);
this.presentationTimeOffset =
mpd.parseAttr_(elem,
'presentationTimeOffset',
mpd.parseNonNegativeInt_,
this.presentationTimeOffset);
this.segmentDuration = mpd.parseAttr_(
elem, 'duration', mpd.parsePositiveInt_, this.segmentDuration);
// May be zero. It's questionable, but it does happen.
var startNumber = mpd.parseAttr_(
elem, 'startNumber', mpd.parseNonNegativeInt_);
if (startNumber != null) {
this.startNumber = startNumber;
}
this.mediaUrlTemplate = mpd.parseAttr_(
elem, 'media', mpd.parseString_, this.mediaUrlTemplate);
this.indexUrlTemplate = mpd.parseAttr_(
elem, 'index', mpd.parseString_, this.indexUrlTemplate);
this.initializationUrlTemplate = mpd.parseAttr_(
elem, 'initialization', mpd.parseString_, this.initializationUrlTemplate);
// Parse hierarchical children.
this.timeline =
mpd.parseChild_(this, elem, mpd.SegmentTimeline) ||
this.timeline;
};
/**
* Parses a "SegmentTimeline" tag.
* @param {!shaka.dash.mpd.SegmentTemplate} parent The parent SegmentTemplate.
* @param {!Node} elem The SegmentTimeline XML element.
*/
shaka.dash.mpd.SegmentTimeline.prototype.parse = function(parent, elem) {
var mpd = shaka.dash.mpd;
this.timePoints = mpd.parseChildren_(this, elem, mpd.SegmentTimePoint);
};
/**
* Parses an "S" tag.
* @param {!shaka.dash.mpd.SegmentTimeline} parent The parent SegmentTimeline.
* @param {!Node} elem The SegmentTimePoint XML element.
*/
shaka.dash.mpd.SegmentTimePoint.prototype.parse = function(parent, elem) {
var mpd = shaka.dash.mpd;
// Parse attributes.
this.startTime = mpd.parseAttr_(elem, 't', mpd.parseNonNegativeInt_);
this.duration = mpd.parseAttr_(elem, 'd', mpd.parseNonNegativeInt_);
this.repeat = mpd.parseAttr_(elem, 'r', mpd.parseInt_);
};
// MPD parsing utility functions ----------------------------------------------
/**
* Resolves each URL of |url| relative to the first URL of |parentUrl|.
*
* @param {Array.<!goog.Uri>} parentUrl
* @param {Array.<!shaka.dash.mpd.BaseUrl>} url
* @return {Array.<!goog.Uri>}
* @private
*/
shaka.dash.mpd.resolveUrlArray_ = function(parentUrl, url) {
if (!url || url.length === 0) {
return parentUrl;
}
/** @type {!Array.<!goog.Uri>} */
var ret = [];
for (var i = 0; i < url.length; i++) {
var current = url[i].url;
if (parentUrl == null || parentUrl.length === 0) {
ret.push(new goog.Uri(current));
} else {
var temp = shaka.dash.mpd.resolveUrl_(parentUrl.slice(0, 1), current);
ret.push(temp[0]);
}
}
return ret;
};
/**
* Resolves |urlString| relative to |baseUrl|.
* @param {Array.<!goog.Uri>} parentUrl
* @param {?string} urlString
* @return {Array.<!goog.Uri>}
* @private
*/
shaka.dash.mpd.resolveUrl_ = function(parentUrl, urlString) {
if (!urlString) {
return parentUrl;
}
var url = new goog.Uri(urlString);
if (parentUrl) {
return parentUrl.map(function(a) { return a.resolve(url); });
} else {
return [url];
}
};
/**
* Parses a child XML element and merges it into an existing MPD node object.
* @param {*} parent The parent MPD node object.
* @param {!Node} elem The parent XML element.
* @param {!T} original The existing MPD node object.
* @return {!T} The merged MPD node object. If a child XML element cannot be
* parsed (see parseChild_) then the merged MPD node object is identical
* to |original|, although it is not the same object.
* @template T
* @private
*/
shaka.dash.mpd.mergeChild_ = function(parent, elem, original) {
var mpd = shaka.dash.mpd;
var merged = mpd.clone_(original);
shaka.asserts.assert(merged);
var childElement = mpd.findChild_(elem, original.constructor.TAG_NAME);
if (childElement) {
merged.parse(parent, childElement);
}
return merged;
};
/**
* Parses a child XML element.
* @param {*} parent The parent MPD node object.
* @param {!Node} elem The parent XML element.
* @param {function(new:T)} constructor The constructor of the parsed
* child XML element. The constructor must define the attribute "TAG_NAME".
* @return {T} The parsed child XML element on success, or null if a child
* XML element does not exist with the given tag name OR if there exists
* more than one child XML element with the given tag name OR if the child
* XML element could not be parsed.
* @template T
* @private
*/
shaka.dash.mpd.parseChild_ = function(parent, elem, constructor) {
var mpd = shaka.dash.mpd;
var parsedChild = null;
var childElement = mpd.findChild_(elem, constructor.TAG_NAME);
if (childElement) {
parsedChild = new constructor();
parsedChild.parse(parent, childElement);
}
return parsedChild;
};
/**
* Finds a child XML element.
* @param {!Node} elem The parent XML element.
* @param {string} name The child XML element's tag name.
* @return {Node} The child XML element, or null if a child XML element does
* not exist with the given tag name OR if there exists more than one
* child XML element with the given tag name.
* @private
*/
shaka.dash.mpd.findChild_ = function(elem, name) {
var childElement = null;
for (var i = 0; i < elem.childNodes.length; i++) {
if (elem.childNodes[i].tagName != name) {
continue;
}
if (childElement) {
return null;
}
childElement = elem.childNodes[i];
}
return childElement;
};
/**
* Parses an array of child XML elements.
* @param {*} parent The parsed parent object.
* @param {!Node} elem The parent XML element.
* @param {function(new:T)} constructor The constructor of each parsed child
* XML element. The constructor must define the attribute "TAG_NAME".
* @return {!Array.<!T>} The parsed child XML elements.
* @template T
* @private
*/
shaka.dash.mpd.parseChildren_ = function(parent, elem, constructor) {
var parsedChildren = [];
for (var i = 0; i < elem.childNodes.length; i++) {
if (elem.childNodes[i].tagName != constructor.TAG_NAME) {
continue;
}
var parsedChild = new constructor();
parsedChild.parse.call(parsedChild, parent, elem.childNodes[i]);
parsedChildren.push(parsedChild);
}
return parsedChildren;
};
/**
* Gets the text contents of a node.
* @param {!Node} elem The XML element.
* @return {?string} The text contents, or null if there are none.
* @private
*/
shaka.dash.mpd.getContents_ = function(elem) {
var contents = elem.firstChild;
if (contents.nodeType != Node.TEXT_NODE) {
return null;
}
return contents.nodeValue;
};
/**
* @param {Array.<T>} obj
* @return {Array.<T>} A clone of |obj| if |obj| is non-null; otherwise,
* return null.
* @private
* @template T
*/
shaka.dash.mpd.cloneA_ = function(obj) {
return obj ? obj.map(function(o) { return o.clone(); }) : null;
};
/**
* @param {T} obj
* @return {T} A clone of |obj| if |obj| is non-null; otherwise, return null.
* @private
* @template T
*/
shaka.dash.mpd.clone_ = function(obj) {
return obj ? obj.clone() : null;
};
/**
* Parses an attribute by its name.
* @param {!Node} elem The XML element.
* @param {string} name The attribute name.
* @param {function(string): (T|null)} parseFunction A function that parses
* the attribute.
* @param {(T|null)=} opt_defaultValue The attribute's default value, if not
* specified, the attibute's default value is null.
* @return {(T|null)} The parsed attribute on success, or the attribute's
* default value if the attribute does not exist or could not be parsed.
* @template T
* @private
*/
shaka.dash.mpd.parseAttr_ = function(
elem, name, parseFunction, opt_defaultValue) {
var parsedValue = parseFunction(elem.getAttribute(name));
if (parsedValue != null) {
return parsedValue;
} else {
return opt_defaultValue !== undefined ? opt_defaultValue : null;
}
};
/**
* Parses an XML date string.
* @param {string} dateString
* @return {?number}
* @private
*/
shaka.dash.mpd.parseDate_ = function(dateString) {
if (!dateString) {
return null;
}
var result = Date.parse(dateString);
return (!isNaN(result) ? Math.floor(result / 1000.0) : null);
};
/**
* Parses an XML duration string.
* Negative values are not supported. Years and months are treated as exactly
* 365 and 30 days respectively.
* @param {string} durationString The duration string, e.g., "PT1H3M43.2S",
* which means 1 hour, 3 minutes, and 43.2 seconds.
* @return {?number} The parsed duration in seconds, or null if the duration
* string could not be parsed.
* @see http://www.datypic.com/sc/xsd/t-xsd_duration.html
* @private
*/
shaka.dash.mpd.parseDuration_ = function(durationString) {
if (!durationString) {
return null;
}
var regexpString = '^P(?:([0-9]*)Y)?(?:([0-9]*)M)?(?:([0-9]*)D)?' +
'(?:T(?:([0-9]*)H)?(?:([0-9]*)M)?(?:([0-9.]*)S)?)?$';
var matches = new RegExp(regexpString).exec(durationString);
if (!matches) {
shaka.log.warning('Invalid duration string:', durationString);
return null;
}
var duration = 0;
// Assume a year always has 365 days.
var years = shaka.dash.mpd.parseNonNegativeInt_(matches[1]);
if (years) {
duration += (60 * 60 * 24 * 365) * years;
}
// Assume a month is 30 days.
var months = shaka.dash.mpd.parseNonNegativeInt_(matches[2]);
if (months) {
duration += (60 * 60 * 24 * 30) * months;
}
var days = shaka.dash.mpd.parseNonNegativeInt_(matches[3]);
if (days) {
duration += (60 * 60 * 24) * days;
}
var hours = shaka.dash.mpd.parseNonNegativeInt_(matches[4]);
if (hours) {
duration += (60 * 60) * hours;
}
var minutes = shaka.dash.mpd.parseNonNegativeInt_(matches[5]);
if (minutes) {
duration += 60 * minutes;
}
var seconds = shaka.dash.mpd.parseFloat_(matches[6]);
if (seconds) {
duration += seconds;
}
return duration;
};
/**
* Parses a range string.
* @param {string} rangeString The range string, e.g., "101-9213"
* @return {shaka.dash.mpd.Range} The parsed range, or null if the range string
* could not be parsed.
* @private
*/
shaka.dash.mpd.parseRange_ = function(rangeString) {
var matches = /([0-9]+)-([0-9]+)/.exec(rangeString);
if (!matches) {
return null;
}
var begin = shaka.dash.mpd.parseNonNegativeInt_(matches[1]);
if (begin == null) {
return null;
}
var end = shaka.dash.mpd.parseNonNegativeInt_(matches[2]);
if (end == null) {
return null;
}
return new shaka.dash.mpd.Range(begin, end);
};
/**
* Parses an integer.
* @param {string} intString The integer string.
* @return {?number} The parsed integer on success; otherwise, return null.
* @private
*/
shaka.dash.mpd.parseInt_ = function(intString) {
var result = window.parseInt(intString, 10);
return (!isNaN(result) ? result : null);
};
/**
* Parses a positive integer.
* @param {string} intString The integer string.
* @return {?number} The parsed positive integer on success; otherwise,
* return null.
* @private
*/
shaka.dash.mpd.parsePositiveInt_ = function(intString) {
var result = window.parseInt(intString, 10);
return (result > 0 ? result : null);
};
/**
* Parses a non-negative integer.
* @param {string} intString The integer string.
* @return {?number} The parsed non-negative integer on success; otherwise,
* return null.
* @private
*/
shaka.dash.mpd.parseNonNegativeInt_ = function(intString) {
var result = window.parseInt(intString, 10);
return (result >= 0 ? result : null);
};
/**
* Parses a floating point number.
* @param {string} floatString The floating point number string.
* @return {?number} The parsed floating point number, or null if the floating
* point number string could not be parsed.
* @private
*/
shaka.dash.mpd.parseFloat_ = function(floatString) {
var result = window.parseFloat(floatString);
return (!isNaN(result) ? result : null);
};
/**
* A misnomer. Does no parsing, just returns the input string as-is.
* @param {string} inputString The inputString.
* @return {?string} The "parsed" string. The type is specified as nullable
* only to fit into the parseAttr_() template, but null will never be
* returned.
* @private
*/
shaka.dash.mpd.parseString_ = function(inputString) {
return inputString;
};