shaka-player
Version:
DASH/EME video player library
582 lines (512 loc) • 21.8 kB
JavaScript
/*! @license
* Shaka Player
* Copyright 2016 Google LLC
* SPDX-License-Identifier: Apache-2.0
*/
goog.provide('shaka.dash.SegmentTemplate');
goog.require('goog.asserts');
goog.require('shaka.dash.MpdUtils');
goog.require('shaka.dash.SegmentBase');
goog.require('shaka.log');
goog.require('shaka.media.InitSegmentReference');
goog.require('shaka.media.SegmentIndex');
goog.require('shaka.media.SegmentReference');
goog.require('shaka.util.Error');
goog.require('shaka.util.Iterables');
goog.require('shaka.util.ManifestParserUtils');
goog.require('shaka.util.ObjectUtils');
goog.requireType('shaka.dash.DashParser');
/**
* @summary A set of functions for parsing SegmentTemplate elements.
*/
shaka.dash.SegmentTemplate = class {
/**
* Creates a new StreamInfo object.
* Updates the existing SegmentIndex, if any.
*
* @param {shaka.dash.DashParser.Context} context
* @param {shaka.dash.DashParser.RequestInitSegmentCallback}
* requestInitSegment
* @param {!Object.<string, !shaka.media.SegmentIndex>} segmentIndexMap
* @param {boolean} isUpdate True if the manifest is being updated.
* @param {number} segmentLimit The maximum number of segments to generate for
* a SegmentTemplate with fixed duration.
* @return {shaka.dash.DashParser.StreamInfo}
*/
static createStreamInfo(
context, requestInitSegment, segmentIndexMap, isUpdate,
segmentLimit) {
goog.asserts.assert(context.representation.segmentTemplate,
'Should only be called with SegmentTemplate');
const SegmentTemplate = shaka.dash.SegmentTemplate;
const initSegmentReference = SegmentTemplate.createInitSegment_(context);
const info = SegmentTemplate.parseSegmentTemplateInfo_(context);
SegmentTemplate.checkSegmentTemplateInfo_(context, info);
// Direct fields of context will be reassigned by the parser before
// generateSegmentIndex is called. So we must make a shallow copy first,
// and use that in the generateSegmentIndex callbacks.
const shallowCopyOfContext =
shaka.util.ObjectUtils.shallowCloneObject(context);
if (info.indexTemplate) {
shaka.dash.SegmentBase.checkSegmentIndexSupport(
context, initSegmentReference);
return {
generateSegmentIndex: () => {
return SegmentTemplate.generateSegmentIndexFromIndexTemplate_(
shallowCopyOfContext, requestInitSegment, initSegmentReference,
info);
},
};
} else if (info.segmentDuration) {
if (!isUpdate) {
context.presentationTimeline.notifyMaxSegmentDuration(
info.segmentDuration);
context.presentationTimeline.notifyMinSegmentStartTime(
context.periodInfo.start);
}
return {
generateSegmentIndex: () => {
return SegmentTemplate.generateSegmentIndexFromDuration_(
shallowCopyOfContext, info, segmentLimit, initSegmentReference);
},
};
} else {
/** @type {shaka.media.SegmentIndex} */
let segmentIndex = null;
let id = null;
if (context.period.id && context.representation.id) {
// Only check/store the index if period and representation IDs are set.
id = context.period.id + ',' + context.representation.id;
segmentIndex = segmentIndexMap[id];
}
const references = SegmentTemplate.createFromTimeline_(
shallowCopyOfContext, info, initSegmentReference);
const periodStart = context.periodInfo.start;
const periodEnd = context.periodInfo.duration ?
context.periodInfo.start + context.periodInfo.duration : Infinity;
// Don't fit live content, since it might receive more segments.
// Unless that live content is multi-period; it's safe to fit every period
// but the last one, since only the last period might receive new
// segments.
const shouldFit = periodEnd != Infinity;
if (segmentIndex) {
if (shouldFit) {
// Fit the new references before merging them, so that the merge
// algorithm has a more accurate view of their start and end times.
const wrapper = new shaka.media.SegmentIndex(references);
wrapper.fit(periodStart, periodEnd);
}
segmentIndex.merge(references);
segmentIndex.evict(
context.presentationTimeline.getSegmentAvailabilityStart());
} else {
context.presentationTimeline.notifySegments(references);
segmentIndex = new shaka.media.SegmentIndex(references);
if (id && context.dynamic) {
segmentIndexMap[id] = segmentIndex;
}
}
if (shouldFit) {
segmentIndex.fit(periodStart, periodEnd);
}
return {
generateSegmentIndex: () => Promise.resolve(segmentIndex),
};
}
}
/**
* @param {?shaka.dash.DashParser.InheritanceFrame} frame
* @return {Element}
* @private
*/
static fromInheritance_(frame) {
return frame.segmentTemplate;
}
/**
* Parses a SegmentTemplate element into an info object.
*
* @param {shaka.dash.DashParser.Context} context
* @return {shaka.dash.SegmentTemplate.SegmentTemplateInfo}
* @private
*/
static parseSegmentTemplateInfo_(context) {
const SegmentTemplate = shaka.dash.SegmentTemplate;
const MpdUtils = shaka.dash.MpdUtils;
const segmentInfo =
MpdUtils.parseSegmentInfo(context, SegmentTemplate.fromInheritance_);
const media = MpdUtils.inheritAttribute(
context, SegmentTemplate.fromInheritance_, 'media');
const index = MpdUtils.inheritAttribute(
context, SegmentTemplate.fromInheritance_, 'index');
return {
segmentDuration: segmentInfo.segmentDuration,
timescale: segmentInfo.timescale,
startNumber: segmentInfo.startNumber,
scaledPresentationTimeOffset: segmentInfo.scaledPresentationTimeOffset,
unscaledPresentationTimeOffset:
segmentInfo.unscaledPresentationTimeOffset,
timeline: segmentInfo.timeline,
mediaTemplate: media,
indexTemplate: index,
};
}
/**
* Verifies a SegmentTemplate info object.
*
* @param {shaka.dash.DashParser.Context} context
* @param {shaka.dash.SegmentTemplate.SegmentTemplateInfo} info
* @private
*/
static checkSegmentTemplateInfo_(context, info) {
let n = 0;
n += info.indexTemplate ? 1 : 0;
n += info.timeline ? 1 : 0;
n += info.segmentDuration ? 1 : 0;
if (n == 0) {
shaka.log.error(
'SegmentTemplate does not contain any segment information:',
'the SegmentTemplate must contain either an index URL template',
'a SegmentTimeline, or a segment duration.',
context.representation);
throw new shaka.util.Error(
shaka.util.Error.Severity.CRITICAL,
shaka.util.Error.Category.MANIFEST,
shaka.util.Error.Code.DASH_NO_SEGMENT_INFO);
} else if (n != 1) {
shaka.log.warning(
'SegmentTemplate containes multiple segment information sources:',
'the SegmentTemplate should only contain an index URL template,',
'a SegmentTimeline or a segment duration.',
context.representation);
if (info.indexTemplate) {
shaka.log.info('Using the index URL template by default.');
info.timeline = null;
info.segmentDuration = null;
} else {
goog.asserts.assert(info.timeline, 'There should be a timeline');
shaka.log.info('Using the SegmentTimeline by default.');
info.segmentDuration = null;
}
}
if (!info.indexTemplate && !info.mediaTemplate) {
shaka.log.error(
'SegmentTemplate does not contain sufficient segment information:',
'the SegmentTemplate\'s media URL template is missing.',
context.representation);
throw new shaka.util.Error(
shaka.util.Error.Severity.CRITICAL,
shaka.util.Error.Category.MANIFEST,
shaka.util.Error.Code.DASH_NO_SEGMENT_INFO);
}
}
/**
* Generates a SegmentIndex from an index URL template.
*
* @param {shaka.dash.DashParser.Context} context
* @param {shaka.dash.DashParser.RequestInitSegmentCallback}
* requestInitSegment
* @param {shaka.media.InitSegmentReference} init
* @param {shaka.dash.SegmentTemplate.SegmentTemplateInfo} info
* @return {!Promise.<shaka.media.SegmentIndex>}
* @private
*/
static generateSegmentIndexFromIndexTemplate_(
context, requestInitSegment, init, info) {
const MpdUtils = shaka.dash.MpdUtils;
const ManifestParserUtils = shaka.util.ManifestParserUtils;
goog.asserts.assert(info.indexTemplate, 'must be using index template');
const filledTemplate = MpdUtils.fillUriTemplate(
info.indexTemplate, context.representation.id,
null, context.bandwidth || null, null);
const resolvedUris = ManifestParserUtils.resolveUris(
context.representation.baseUris, [filledTemplate]);
return shaka.dash.SegmentBase.generateSegmentIndexFromUris(
context, requestInitSegment, init, resolvedUris, 0, null,
info.scaledPresentationTimeOffset);
}
/**
* Generates a SegmentIndex from fixed-duration segments.
*
* @param {shaka.dash.DashParser.Context} context
* @param {shaka.dash.SegmentTemplate.SegmentTemplateInfo} info
* @param {number} segmentLimit The maximum number of segments to generate.
* @param {shaka.media.InitSegmentReference} initSegmentReference
* @return {!Promise.<shaka.media.SegmentIndex>}
* @private
*/
static generateSegmentIndexFromDuration_(
context, info, segmentLimit, initSegmentReference) {
goog.asserts.assert(info.mediaTemplate,
'There should be a media template with duration');
const MpdUtils = shaka.dash.MpdUtils;
const ManifestParserUtils = shaka.util.ManifestParserUtils;
const presentationTimeline = context.presentationTimeline;
// Capture values that could change as the parsing context moves on to
// other parts of the manifest.
const periodStart = context.periodInfo.start;
const periodDuration = context.periodInfo.duration;
const periodEnd = periodDuration ?
periodStart + periodDuration : Infinity;
const segmentDuration = info.segmentDuration;
goog.asserts.assert(
segmentDuration != null, 'Segment duration must not be null!');
const startNumber = info.startNumber;
const timescale = info.timescale;
const template = info.mediaTemplate;
const bandwidth = context.bandwidth || null;
const id = context.representation.id;
const baseUris = context.representation.baseUris;
const timestampOffset = periodStart - info.scaledPresentationTimeOffset;
// Computes the range of presentation timestamps both within the period and
// available. This is an intersection of the period range and the
// availability window.
const computeAvailablePeriodRange = () => {
return [
Math.max(
presentationTimeline.getSegmentAvailabilityStart(),
periodStart),
Math.min(
presentationTimeline.getSegmentAvailabilityEnd(),
periodEnd),
];
};
// Computes the range of absolute positions both within the period and
// available. The range is inclusive. These are the positions for which we
// will generate segment references.
const computeAvailablePositionRange = () => {
// In presentation timestamps.
const availablePresentationTimes = computeAvailablePeriodRange();
goog.asserts.assert(availablePresentationTimes.every(isFinite),
'Available presentation times must be finite!');
goog.asserts.assert(availablePresentationTimes.every((x) => x >= 0),
'Available presentation times must be positive!');
goog.asserts.assert(segmentDuration != null,
'Segment duration must not be null!');
// In period-relative timestamps.
const availablePeriodTimes =
availablePresentationTimes.map((x) => x - periodStart);
// These may sometimes be reversed ([1] <= [0]) if the period is
// completely unavailable. The logic will still work if this happens,
// because we will simply generate no references.
// In period-relative positions (0-based).
const availablePeriodPositions = [
Math.ceil(availablePeriodTimes[0] / segmentDuration),
Math.ceil(availablePeriodTimes[1] / segmentDuration) - 1,
];
// In absolute positions.
const availablePresentationPositions =
availablePeriodPositions.map((x) => x + startNumber);
return availablePresentationPositions;
};
// For Live, we must limit the initial SegmentIndex in size, to avoid
// consuming too much CPU or memory for content with gigantic
// timeShiftBufferDepth (which can have values up to and including
// Infinity).
const range = computeAvailablePositionRange();
const minPosition = context.dynamic ?
Math.max(range[0], range[1] - segmentLimit + 1) :
range[0];
const maxPosition = range[1];
const references = [];
const createReference = (position) => {
// These inner variables are all scoped to the inner loop, and can be used
// safely in the callback below.
goog.asserts.assert(segmentDuration != null,
'Segment duration must not be null!');
// Relative to the period start.
const positionWithinPeriod = position - startNumber;
const segmentPeriodTime = positionWithinPeriod * segmentDuration;
// What will appear in the actual segment files. The media timestamp is
// what is expected in the $Time$ template.
const segmentMediaTime = segmentPeriodTime +
info.scaledPresentationTimeOffset;
const getUris = () => {
const mediaUri = MpdUtils.fillUriTemplate(
template, id, position, bandwidth,
segmentMediaTime * timescale);
return ManifestParserUtils.resolveUris(baseUris, [mediaUri]);
};
// Relative to the presentation.
const segmentStart = segmentPeriodTime + periodStart;
// Cap the segment end at the period end so that references from the
// next period will fit neatly after it.
const segmentEnd = Math.min(segmentStart + segmentDuration, periodEnd);
// This condition will be true unless the segmentStart was >= periodEnd.
// If we've done the position calculations correctly, this won't happen.
goog.asserts.assert(segmentStart < segmentEnd,
'Generated a segment outside of the period!');
return new shaka.media.SegmentReference(
segmentStart,
segmentEnd,
getUris,
/* startByte= */ 0,
/* endByte= */ null,
initSegmentReference,
timestampOffset,
/* appendWindowStart= */ periodStart,
/* appendWindowEnd= */ periodEnd);
};
for (let position = minPosition; position <= maxPosition; ++position) {
const reference = createReference(position);
references.push(reference);
}
/** @type {shaka.media.SegmentIndex} */
const segmentIndex = new shaka.media.SegmentIndex(references);
// If the availability timeline currently ends before the period, we will
// need to add references over time.
if (presentationTimeline.getSegmentAvailabilityEnd() < periodEnd) {
// The period continues to get longer over time, so check for new
// references once every |segmentDuration| seconds.
// We clamp to |minPosition| in case the initial range was reversed and no
// references were generated. Otherwise, the update would start creating
// negative positions for segments in periods which begin in the future.
let nextPosition = Math.max(minPosition, maxPosition + 1);
segmentIndex.updateEvery(segmentDuration, () => {
// Evict any references outside the window.
segmentIndex.evict(presentationTimeline.getSegmentAvailabilityStart());
// Compute any new references that need to be added.
const [_, maxPosition] = computeAvailablePositionRange();
const references = [];
while (nextPosition <= maxPosition) {
const reference = createReference(nextPosition);
references.push(reference);
nextPosition++;
}
if (presentationTimeline.getSegmentAvailabilityEnd() >= periodEnd &&
!references.length) {
// Signal stop.
return null;
}
return references;
});
}
return Promise.resolve(segmentIndex);
}
/**
* Creates segment references from a timeline.
*
* @param {shaka.dash.DashParser.Context} context
* @param {shaka.dash.SegmentTemplate.SegmentTemplateInfo} info
* @param {shaka.media.InitSegmentReference} initSegmentReference
* @return {!Array.<!shaka.media.SegmentReference>}
* @private
*/
static createFromTimeline_(context, info, initSegmentReference) {
const MpdUtils = shaka.dash.MpdUtils;
const ManifestParserUtils = shaka.util.ManifestParserUtils;
const periodStart = context.periodInfo.start;
const periodDuration = context.periodInfo.duration;
const timestampOffset = periodStart - info.scaledPresentationTimeOffset;
const appendWindowStart = periodStart;
const appendWindowEnd = periodDuration ?
periodStart + periodDuration : Infinity;
/** @type {!Array.<!shaka.media.SegmentReference>} */
const references = [];
const enum_ = (it) => shaka.util.Iterables.enumerate(it);
for (const {i, item: {start, unscaledStart, end}} of enum_(info.timeline)) {
// Note: i = k - 1, where k indicates the k'th segment listed in the MPD.
// (See section 5.3.9.5.3 of the DASH spec.)
const segmentReplacement = i + info.startNumber;
// Consider the presentation time offset in segment uri computation
const timeReplacement = unscaledStart +
info.unscaledPresentationTimeOffset;
const repId = context.representation.id;
const bandwidth = context.bandwidth || null;
const mediaTemplate = info.mediaTemplate;
const baseUris = context.representation.baseUris;
// This callback must not capture any non-local
// variables, such as info, context, etc. Make
// sure any values you reference here have
// been assigned to local variables within the
// loop, or else we will end up with a leak.
const createUris =
() => {
goog.asserts.assert(
mediaTemplate,
'There should be a media template with a timeline');
const mediaUri = MpdUtils.fillUriTemplate(
mediaTemplate, repId,
segmentReplacement, bandwidth || null, timeReplacement);
return ManifestParserUtils
.resolveUris(baseUris, [mediaUri])
.map((g) => {
return g.toString();
});
};
references.push(new shaka.media.SegmentReference(
periodStart + start,
periodStart + end,
createUris,
/* startByte= */ 0,
/* endByte= */ null,
initSegmentReference,
timestampOffset,
appendWindowStart,
appendWindowEnd));
}
return references;
}
/**
* Creates an init segment reference from a context object.
*
* @param {shaka.dash.DashParser.Context} context
* @return {shaka.media.InitSegmentReference}
* @private
*/
static createInitSegment_(context) {
const MpdUtils = shaka.dash.MpdUtils;
const ManifestParserUtils = shaka.util.ManifestParserUtils;
const SegmentTemplate = shaka.dash.SegmentTemplate;
const initialization = MpdUtils.inheritAttribute(
context, SegmentTemplate.fromInheritance_, 'initialization');
if (!initialization) {
return null;
}
const repId = context.representation.id;
const bandwidth = context.bandwidth || null;
const baseUris = context.representation.baseUris;
const getUris = () => {
goog.asserts.assert(initialization, 'Should have returned earler');
const filledTemplate = MpdUtils.fillUriTemplate(
initialization, repId, null, bandwidth, null);
const resolvedUris = ManifestParserUtils.resolveUris(
baseUris, [filledTemplate]);
return resolvedUris;
};
return new shaka.media.InitSegmentReference(getUris, 0, null);
}
};
/**
* @typedef {{
* timescale: number,
* segmentDuration: ?number,
* startNumber: number,
* scaledPresentationTimeOffset: number,
* unscaledPresentationTimeOffset: number,
* timeline: Array.<shaka.dash.MpdUtils.TimeRange>,
* mediaTemplate: ?string,
* indexTemplate: ?string
* }}
* @private
*
* @description
* Contains information about a SegmentTemplate.
*
* @property {number} timescale
* The time-scale of the representation.
* @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.dash.MpdUtils.TimeRange>} timeline
* The timeline of the representation, if given. Times in seconds.
* @property {?string} mediaTemplate
* The media URI template, if given.
* @property {?string} indexTemplate
* The index URI template, if given.
*/
shaka.dash.SegmentTemplate.SegmentTemplateInfo;