shaka-player
Version:
DASH/EME video player library
601 lines (536 loc) • 21.5 kB
JavaScript
/*! @license
* Shaka Player
* Copyright 2016 Google LLC
* SPDX-License-Identifier: Apache-2.0
*/
goog.provide('shaka.dash.MpdUtils');
goog.require('goog.asserts');
goog.require('shaka.log');
goog.require('shaka.net.NetworkingEngine');
goog.require('shaka.util.AbortableOperation');
goog.require('shaka.util.Error');
goog.require('shaka.util.Functional');
goog.require('shaka.util.ManifestParserUtils');
goog.require('shaka.util.TXml');
goog.requireType('shaka.dash.DashParser');
goog.requireType('shaka.media.PresentationTimeline');
/**
* @summary MPD processing utility functions.
*/
shaka.dash.MpdUtils = class {
/**
* Fills a SegmentTemplate URI template. This function does not validate the
* resulting URI.
*
* @param {string} uriTemplate
* @param {?string} representationId
* @param {?number} number
* @param {?number} subNumber
* @param {?number} bandwidth
* @param {?(number|bigint)} time
* @return {string} A URI string.
* @see ISO/IEC 23009-1:2014 section 5.3.9.4.4
*/
static fillUriTemplate(
uriTemplate, representationId, number, subNumber, bandwidth, time) {
/** @type {!Map<string, ?number | ?string>} */
const valueTable = new Map()
.set('RepresentationID', representationId)
.set('Number', number)
.set('SubNumber', subNumber)
.set('Bandwidth', bandwidth)
.set('Time', time);
// cspell: disable-next-line
const re = /\$(RepresentationID|Number|SubNumber|Bandwidth|Time)?(?:%0([0-9]+)([diouxX]))?\$/g; // eslint-disable-line @stylistic/max-len
const uri = uriTemplate.replace(re, (match, name, widthStr, format) => {
if (match == '$$') {
return '$';
}
let value = valueTable.get(name);
goog.asserts.assert(value !== undefined, 'Unrecognized identifier');
// Note that |value| may be 0 or ''.
if (value == null) {
shaka.log.warning(
'URL template does not have an available substitution for ',
'identifier "' + name + '":',
uriTemplate);
return match;
}
if (name == 'RepresentationID' && widthStr) {
shaka.log.warning(
'URL template should not contain a width specifier for identifier',
'"RepresentationID":',
uriTemplate);
widthStr = undefined;
}
if (name == 'Time') {
if (typeof value != 'bigint') {
goog.asserts.assert(typeof value == 'number',
'Time value should be a number or bigint!');
if (Math.abs(value - Math.round(value)) >= 0.2) {
shaka.log.alwaysWarn(
'Calculated $Time$ values must be close to integers');
}
value = Math.round(value);
}
}
/** @type {string} */
let valueString;
switch (format) {
case undefined: // Happens if there is no format specifier.
case 'd':
case 'i':
case 'u':
valueString = value.toString();
break;
case 'o':
valueString = value.toString(8);
break;
case 'x':
valueString = value.toString(16);
break;
case 'X':
valueString = value.toString(16).toUpperCase();
break;
default:
goog.asserts.assert(false, 'Unhandled format specifier');
valueString = value.toString();
break;
}
// Create a padding string.
const width = window.parseInt(widthStr, 10) || 1;
const paddingSize = Math.max(0, width - valueString.length);
const padding = (new Array(paddingSize + 1)).join('0');
return padding + valueString;
});
return uri;
}
/**
* Expands a SegmentTimeline into an array-based timeline. The results are in
* seconds.
*
* @param {Array<!shaka.extern.xml.Node>} timePoints
* @param {number} timescale
* @param {number} unscaledPresentationTimeOffset
* @param {number} periodDuration The Period's duration in seconds.
* Infinity indicates that the Period continues indefinitely.
* @param {number} startNumber
* @return {!Array<shaka.media.PresentationTimeline.TimeRange>}
*/
static createTimeline(
timePoints, timescale, unscaledPresentationTimeOffset,
periodDuration, startNumber) {
goog.asserts.assert(
timescale > 0 && timescale < Infinity,
'timescale must be a positive, finite integer');
goog.asserts.assert(
periodDuration > 0, 'period duration must be a positive integer');
// Alias.
const TXml = shaka.util.TXml;
/** @type {!Array<shaka.media.PresentationTimeline.TimeRange>} */
const timeline = [];
let lastEndTime = -unscaledPresentationTimeOffset;
for (let i = 0; i < timePoints.length; ++i) {
const timePoint = timePoints[i];
const next = timePoints[i + 1];
let t = TXml.parseAttr(timePoint, 't', TXml.parseNonNegativeInt);
const d =
TXml.parseAttr(timePoint, 'd', TXml.parseNonNegativeInt);
const r = TXml.parseAttr(timePoint, 'r', TXml.parseInt);
const k = TXml.parseAttr(timePoint, 'k', TXml.parseInt);
const partialSegments = k || 0;
// Adjust the start time to account for the presentation time offset.
if (t != null) {
t -= unscaledPresentationTimeOffset;
}
if (!d) {
shaka.log.warning(
'"S" element must have a duration: ignoring this element.',
timePoint);
continue;
}
let startTime = t != null ? t : lastEndTime;
let repeat = r || 0;
if (repeat < 0) {
if (next) {
const nextStartTime =
TXml.parseAttr(next, 't', TXml.parseNonNegativeInt);
if (nextStartTime == null) {
shaka.log.warning(
'An "S" element cannot have a negative repeat',
'if the next "S" element does not have a valid start time:',
'ignoring the remaining "S" elements.', timePoint);
return timeline;
} else if (startTime >= nextStartTime) {
shaka.log.warning(
'An "S" element cannot have a negative repeat if its start ',
'time exceeds the next "S" element\'s start time:',
'ignoring the remaining "S" elements.', timePoint);
return timeline;
}
repeat = Math.ceil((nextStartTime - startTime) / d) - 1;
} else {
if (periodDuration == Infinity) {
// The DASH spec. actually allows the last "S" element to have a
// negative repeat value even when the Period has an infinite
// duration. No one uses this feature and no one ever should,
// ever.
shaka.log.warning(
'The last "S" element cannot have a negative repeat',
'if the Period has an infinite duration:',
'ignoring the last "S" element.', timePoint);
return timeline;
} else if (startTime / timescale >= periodDuration) {
shaka.log.warning(
'The last "S" element cannot have a negative repeat',
'if its start time exceeds the Period\'s duration:',
'ignoring the last "S" element.', timePoint);
return timeline;
}
repeat = Math.ceil((periodDuration * timescale - startTime) / d) - 1;
}
}
// The end of the last segment may be before the start of the current
// segment (a gap) or after the start of the current segment (an
// overlap). If there is a gap/overlap then stretch/compress the end of
// the last segment to the start of the current segment.
//
// Note: it is possible to move the start of the current segment to the
// end of the last segment, but this would complicate the computation of
// the $Time$ placeholder later on.
if ((timeline.length > 0) && (startTime != lastEndTime)) {
const delta = startTime - lastEndTime;
if (Math.abs(delta / timescale) >=
shaka.util.ManifestParserUtils.GAP_OVERLAP_TOLERANCE_SECONDS) {
shaka.log.warning(
'SegmentTimeline contains a large gap/overlap:',
'the content may have errors in it.', timePoint);
}
timeline[timeline.length - 1].end = startTime / timescale;
}
for (let j = 0; j <= repeat; ++j) {
const endTime = startTime + d;
const item = {
start: startTime / timescale,
end: endTime / timescale,
unscaledStart: startTime,
partialSegments: partialSegments,
segmentPosition: timeline.length + startNumber,
};
timeline.push(item);
startTime = endTime;
lastEndTime = endTime;
}
}
return timeline;
}
/**
* Parses common segment info for SegmentList and SegmentTemplate.
*
* @param {shaka.dash.DashParser.Context} context
* @param {function(?shaka.dash.DashParser.InheritanceFrame):
* ?shaka.extern.xml.Node} callback
* Gets the element that contains the segment info.
* @return {shaka.dash.MpdUtils.SegmentInfo}
*/
static parseSegmentInfo(context, callback) {
goog.asserts.assert(
callback(context.representation),
'There must be at least one element of the given type.');
const MpdUtils = shaka.dash.MpdUtils;
const TXml = shaka.util.TXml;
const timescaleStr =
MpdUtils.inheritAttribute(context, callback, 'timescale');
let timescale = 1;
if (timescaleStr) {
timescale = TXml.parsePositiveInt(timescaleStr) || 1;
}
const durationStr =
MpdUtils.inheritAttribute(context, callback, 'duration');
const unscaledSegmentDuration = TXml.parsePositiveInt(durationStr || '');
const segmentDuration = unscaledSegmentDuration ?
unscaledSegmentDuration / timescale : null;
const startNumberStr =
MpdUtils.inheritAttribute(context, callback, 'startNumber');
const unscaledPresentationTimeOffset =
Number(MpdUtils.inheritAttribute(context, callback,
'presentationTimeOffset')) || 0;
let startNumber = TXml.parseNonNegativeInt(startNumberStr || '');
if (startNumberStr == null || startNumber == null) {
startNumber = 1;
}
/** @type {Array<shaka.media.PresentationTimeline.TimeRange>} */
let timeline = null;
const timelineNode =
MpdUtils.inheritChild(context, callback, 'SegmentTimeline');
if (timelineNode) {
const timePoints = TXml.findChildren(timelineNode, 'S');
timeline = MpdUtils.createTimeline(
timePoints, timescale, unscaledPresentationTimeOffset,
context.periodInfo.duration || Infinity, startNumber);
}
const scaledPresentationTimeOffset =
(unscaledPresentationTimeOffset / timescale) || 0;
return {
timescale: timescale,
unscaledSegmentDuration: unscaledSegmentDuration,
segmentDuration: segmentDuration,
startNumber: startNumber,
scaledPresentationTimeOffset: scaledPresentationTimeOffset,
unscaledPresentationTimeOffset: unscaledPresentationTimeOffset,
timeline: timeline,
};
}
/**
* Parses common attributes for Representation, AdaptationSet, and Period.
* @param {shaka.dash.DashParser.Context} context
* @param {function(?shaka.dash.DashParser.InheritanceFrame):
* ?shaka.extern.xml.Node} callback
* @return {!Array<!shaka.extern.xml.Node>}
*/
static getNodes(context, callback) {
const Functional = shaka.util.Functional;
goog.asserts.assert(
callback(context.representation),
'There must be at least one element of the given type.',
);
return [
callback(context.representation),
callback(context.adaptationSet),
callback(context.period),
].filter(Functional.isNotNull);
}
/**
* Searches the inheritance for a Segment* with the given attribute.
*
* @param {shaka.dash.DashParser.Context} context
* @param {function(?shaka.dash.DashParser.InheritanceFrame):
* ?shaka.extern.xml.Node} callback
* Gets the Element that contains the attribute to inherit.
* @param {string} attribute
* @return {?string}
*/
static inheritAttribute(context, callback, attribute) {
const MpdUtils = shaka.dash.MpdUtils;
const nodes = MpdUtils.getNodes(context, callback);
let result = null;
for (const node of nodes) {
result = node.attributes[attribute];
if (result) {
break;
}
}
return result;
}
/**
* Searches the inheritance for a Segment* with the given child.
*
* @param {shaka.dash.DashParser.Context} context
* @param {function(?shaka.dash.DashParser.InheritanceFrame):
* ?shaka.extern.xml.Node} callback
* Gets the Element that contains the child to inherit.
* @param {string} child
* @return {?shaka.extern.xml.Node}
*/
static inheritChild(context, callback, child) {
const MpdUtils = shaka.dash.MpdUtils;
const nodes = MpdUtils.getNodes(context, callback);
const TXml = shaka.util.TXml;
let result = null;
for (const node of nodes) {
result = TXml.findChild(node, child);
if (result) {
break;
}
}
return result;
}
/**
* Follow the xlink link contained in the given element.
* It also strips the xlink properties off of the element,
* even if the process fails.
*
* @param {!shaka.extern.xml.Node} element
* @param {!shaka.extern.RetryParameters} retryParameters
* @param {boolean} failGracefully
* @param {string} baseUri
* @param {!shaka.net.NetworkingEngine} networkingEngine
* @param {number} linkDepth
* @return {!shaka.util.AbortableOperation.<!shaka.extern.xml.Node>}
* @private
*/
static handleXlinkInElement_(
element, retryParameters, failGracefully, baseUri, networkingEngine,
linkDepth) {
const MpdUtils = shaka.dash.MpdUtils;
const TXml = shaka.util.TXml;
const Error = shaka.util.Error;
const ManifestParserUtils = shaka.util.ManifestParserUtils;
const NS = MpdUtils.XlinkNamespaceUri_;
const xlinkHref = TXml.getAttributeNS(element, NS, 'href');
const xlinkActuate =
TXml.getAttributeNS(element, NS, 'actuate') || 'onRequest';
// Remove the xlink properties, so it won't download again
// when re-processed.
for (const key of Object.keys(element.attributes)) {
const segments = key.split(':');
const namespace = shaka.util.TXml.getKnownNameSpace(NS);
if (segments[0] == namespace) {
delete element.attributes[key];
}
}
if (linkDepth >= 5) {
return shaka.util.AbortableOperation.failed(new Error(
Error.Severity.CRITICAL, Error.Category.MANIFEST,
Error.Code.DASH_XLINK_DEPTH_LIMIT));
}
if (xlinkActuate != 'onLoad') {
// Only xlink:actuate="onLoad" is supported.
// When no value is specified, the assumed value is "onRequest".
return shaka.util.AbortableOperation.failed(new Error(
Error.Severity.CRITICAL, Error.Category.MANIFEST,
Error.Code.DASH_UNSUPPORTED_XLINK_ACTUATE));
}
// Resolve the xlink href, in case it's a relative URL.
const uris = ManifestParserUtils.resolveUris([baseUri], [xlinkHref]);
// Load in the linked elements.
const requestType = shaka.net.NetworkingEngine.RequestType.MANIFEST;
const request =
shaka.net.NetworkingEngine.makeRequest(uris, retryParameters);
const requestOperation = networkingEngine.request(requestType, request);
// The interface is abstract, but we know it was implemented with the
// more capable internal class.
goog.asserts.assert(
requestOperation instanceof shaka.util.AbortableOperation,
'Unexpected implementation of IAbortableOperation!');
// Satisfy the compiler with a cast.
const networkOperation =
/** @type {!shaka.util.AbortableOperation.<shaka.extern.Response>} */ (
requestOperation);
// Chain onto that operation.
return networkOperation.chain(
(response) => {
// This only supports the case where the loaded xml has a single
// top-level element. If there are multiple roots, it will be
// rejected.
const rootElem =
TXml.parseXml(response.data, element.tagName);
if (!rootElem) {
// It was not valid XML.
return shaka.util.AbortableOperation.failed(new Error(
Error.Severity.CRITICAL, Error.Category.MANIFEST,
Error.Code.DASH_INVALID_XML, xlinkHref));
}
// Now that there is no other possibility of the process erroring,
// the element can be changed further.
// Remove the current contents of the node.
element.children = [];
// Move the children of the loaded xml into the current element.
while (rootElem.children.length) {
const child = rootElem.children.shift();
element.children.push(child);
}
// Move the attributes of the loaded xml into the current element.
for (const key of Object.keys(rootElem.attributes)) {
element.attributes[key] = rootElem.attributes[key];
}
return shaka.dash.MpdUtils.processXlinks(
element, retryParameters, failGracefully, uris[0],
networkingEngine, linkDepth + 1);
});
}
/**
* Filter the contents of a node recursively, replacing xlink links
* with their associated online data.
*
* @param {!shaka.extern.xml.Node} element
* @param {!shaka.extern.RetryParameters} retryParameters
* @param {boolean} failGracefully
* @param {string} baseUri
* @param {!shaka.net.NetworkingEngine} networkingEngine
* @param {number=} linkDepth default set to 0
* @return {!shaka.util.AbortableOperation.<!shaka.extern.xml.Node>}
*/
static processXlinks(
element, retryParameters,
failGracefully, baseUri, networkingEngine,
linkDepth = 0) {
const MpdUtils = shaka.dash.MpdUtils;
const TXml = shaka.util.TXml;
const NS = MpdUtils.XlinkNamespaceUri_;
if (TXml.getAttributeNS(element, NS, 'href')) {
let handled = MpdUtils.handleXlinkInElement_(
element, retryParameters, failGracefully,
baseUri, networkingEngine, linkDepth);
if (failGracefully) {
// Catch any error and go on.
handled = handled.chain(undefined, (error) => {
// handleXlinkInElement_ strips the xlink properties off of the
// element even if it fails, so calling processXlinks again will
// handle whatever contents the element natively has.
return MpdUtils.processXlinks(
element, retryParameters, failGracefully, baseUri,
networkingEngine, linkDepth);
});
}
return handled;
}
const childOperations = [];
for (const child of shaka.util.TXml.getChildNodes(element)) {
const resolveToZeroString = 'urn:mpeg:dash:resolve-to-zero:2013';
if (TXml.getAttributeNS(child, NS, 'href') == resolveToZeroString) {
// This is a 'resolve to zero' code; it means the element should
// be removed, as specified by the mpeg-dash rules for xlink.
element.children = element.children.filter(
(elem) => elem !== child);
} else if (child.tagName != 'SegmentTimeline') {
// Don't recurse into a SegmentTimeline since xlink attributes
// aren't valid in there and looking at each segment can take a long
// time with larger manifests.
// Replace the child with its processed form.
childOperations.push(shaka.dash.MpdUtils.processXlinks(
/** @type {!shaka.extern.xml.Node} */ (child),
retryParameters, failGracefully,
baseUri, networkingEngine, linkDepth));
}
}
return shaka.util.AbortableOperation.all(childOperations).chain(() => {
return element;
});
}
};
/**
* @typedef {{
* timescale: number,
* unscaledSegmentDuration: ?number,
* segmentDuration: ?number,
* startNumber: number,
* scaledPresentationTimeOffset: number,
* unscaledPresentationTimeOffset: number,
* timeline: Array<shaka.media.PresentationTimeline.TimeRange>
* }}
*
* @description
* Contains common information between SegmentList and SegmentTemplate items.
*
* @property {number} timescale
* The time-scale of the representation.
* @property {?number} unscaledSegmentDuration
* The duration of the segments in timescale units, if given.
* @property {?number} segmentDuration
* The duration of the segments in seconds, if given.
* @property {number} startNumber
* The start number of the segments; 1 or greater.
* @property {number} scaledPresentationTimeOffset
* The presentation time offset of the representation, in seconds.
* @property {number} unscaledPresentationTimeOffset
* The presentation time offset of the representation, in timescale units.
* @property {Array<shaka.media.PresentationTimeline.TimeRange>} timeline
* The timeline of the representation, if given. Times in seconds.
*/
shaka.dash.MpdUtils.SegmentInfo;
/**
* @const {string}
* @private
*/
shaka.dash.MpdUtils.XlinkNamespaceUri_ = 'http://www.w3.org/1999/xlink';