/*! @license * Shaka Player * Copyright 2016 Google LLC * SPDX-License-Identifier: Apache-2.0 */goog.provide('shaka.util.PeriodCombiner');goog.require('goog.asserts');goog.require('shaka.log');goog.require('shaka.media.DrmEngine');goog.require('shaka.media.MetaSegmentIndex');goog.require('shaka.media.SegmentIndex');goog.require('shaka.util.Error');goog.require('shaka.util.IReleasable');goog.require('shaka.util.LanguageUtils');goog.require('shaka.util.ManifestParserUtils');goog.require('shaka.util.MimeUtils');/** * A utility to combine streams across periods. * * @implements {shaka.util.IReleasable} * @final * @export */shaka.util.PeriodCombiner = class { /** */ constructor() { /** @private {!Array.<shaka.extern.Variant>} */ this.variants_ = []; /** @private {!Array.<shaka.extern.Stream>} */ this.audioStreams_ = []; /** @private {!Array.<shaka.extern.Stream>} */ this.videoStreams_ = []; /** @private {!Array.<shaka.extern.Stream>} */ this.textStreams_ = []; /** @private {!Array.<shaka.extern.Stream>} */ this.imageStreams_ = []; /** @private {boolean} */ this.multiTypeVariantsAllowed_ = false; /** @private {boolean} */ this.useStreamOnce_ = false; /** * The IDs of the periods we have already used to generate streams. * This helps us identify the periods which have been added when a live * stream is updated. * * @private {!Set.<string>} */ this.usedPeriodIds_ = new Set(); } /** @override */ release() { const allStreams = this.audioStreams_.concat(this.videoStreams_, this.textStreams_, this.imageStreams_); for (const stream of allStreams) { if (stream.segmentIndex) { stream.segmentIndex.release(); } } this.audioStreams_ = []; this.videoStreams_ = []; this.textStreams_ = []; this.imageStreams_ = []; this.variants_ = []; } /** * @return {!Array.<shaka.extern.Variant>} * * @export */ getVariants() { return this.variants_; } /** * @return {!Array.<shaka.extern.Stream>} * * @export */ getTextStreams() { // Return a copy of the array because makeTextStreamsForClosedCaptions // may make changes to the contents of the array. Those changes should not // propagate back to the PeriodCombiner. return this.textStreams_.slice(); } /** * @return {!Array.<shaka.extern.Stream>} * * @export */ getImageStreams() { return this.imageStreams_; } /** * Returns an object that contains arrays of streams by type * @param {!Array<shaka.extern.Period>} periods * @param {boolean} addDummy * @return {{ * audioStreamsPerPeriod: !Array<!Map<string, shaka.extern.Stream>>, * videoStreamsPerPeriod: !Array<!Map<string, shaka.extern.Stream>>, * textStreamsPerPeriod: !Array<!Map<string, shaka.extern.Stream>>, * imageStreamsPerPeriod: !Array<!Map<string, shaka.extern.Stream>> * }} * @private */ getStreamsPerPeriod_(periods, addDummy) { const ContentType = shaka.util.ManifestParserUtils.ContentType; const PeriodCombiner = shaka.util.PeriodCombiner; const audioStreamsPerPeriod = []; const videoStreamsPerPeriod = []; const textStreamsPerPeriod = []; const imageStreamsPerPeriod = []; for (const period of periods) { const audioMap = new Map(period.audioStreams.map((s) => [PeriodCombiner.generateAudioKey_(s), s])); const videoMap = new Map(period.videoStreams.map((s) => [PeriodCombiner.generateVideoKey_(s), s])); const textMap = new Map(period.textStreams.map((s) => [PeriodCombiner.generateTextKey_(s), s])); const imageMap = new Map(period.imageStreams.map((s) => [PeriodCombiner.generateImageKey_(s), s])); // It's okay to have a period with no text or images, but our algorithm // fails on any period without matching streams. So we add dummy streams // to each period. Since we combine text streams by language and image // streams by resolution, we might need a dummy even in periods with these // streams already. if (addDummy) { const dummyText = PeriodCombiner.dummyStream_(ContentType.TEXT); textMap.set(PeriodCombiner.generateTextKey_(dummyText), dummyText); const dummyImage = PeriodCombiner.dummyStream_(ContentType.IMAGE); imageMap.set(PeriodCombiner.generateImageKey_(dummyImage), dummyImage); } audioStreamsPerPeriod.push(audioMap); videoStreamsPerPeriod.push(videoMap); textStreamsPerPeriod.push(textMap); imageStreamsPerPeriod.push(imageMap); } return { audioStreamsPerPeriod, videoStreamsPerPeriod, textStreamsPerPeriod, imageStreamsPerPeriod, }; } /** * @param {!Array.<shaka.extern.Period>} periods * @param {boolean} isDynamic * @param {boolean=} isPatchUpdate * @return {!Promise} * * @export */ async combinePeriods(periods, isDynamic, isPatchUpdate = false) { const ContentType = shaka.util.ManifestParserUtils.ContentType; // Optimization: for single-period VOD, do nothing. This makes sure // single-period DASH content will be 100% accurately represented in the // output. if (!isDynamic && periods.length == 1) { // We need to filter out duplicates, so call getStreamsPerPeriod() // so it will do that by usage of Map. const { audioStreamsPerPeriod, videoStreamsPerPeriod, textStreamsPerPeriod, imageStreamsPerPeriod, } = this.getStreamsPerPeriod_(periods, /* addDummy= */ false); this.audioStreams_ = Array.from(audioStreamsPerPeriod[0].values()); this.videoStreams_ = Array.from(videoStreamsPerPeriod[0].values()); this.textStreams_ = Array.from(textStreamsPerPeriod[0].values()); this.imageStreams_ = Array.from(imageStreamsPerPeriod[0].values()); } else { // How many periods we've seen before which are not included in this call. const periodsMissing = isPatchUpdate ? this.usedPeriodIds_.size : 0; // Find the first period we haven't seen before. Tag all the periods we // see now as "used". let firstNewPeriodIndex = -1; for (let i = 0; i < periods.length; i++) { const period = periods[i]; if (this.usedPeriodIds_.has(period.id)) { // This isn't new. } else { // This one _is_ new. this.usedPeriodIds_.add(period.id); if (firstNewPeriodIndex == -1) { // And it's the _first_ new one. firstNewPeriodIndex = i; } } } if (firstNewPeriodIndex == -1) { // Nothing new? Nothing to do. return; } const { audioStreamsPerPeriod, videoStreamsPerPeriod, textStreamsPerPeriod, imageStreamsPerPeriod, } = this.getStreamsPerPeriod_(periods, /* addDummy= */ true); await Promise.all([ this.combine_( this.audioStreams_, audioStreamsPerPeriod, firstNewPeriodIndex, shaka.util.PeriodCombiner.cloneStream_, shaka.util.PeriodCombiner.concatenateStreams_, periodsMissing), this.combine_( this.videoStreams_, videoStreamsPerPeriod, firstNewPeriodIndex, shaka.util.PeriodCombiner.cloneStream_, shaka.util.PeriodCombiner.concatenateStreams_, periodsMissing), this.combine_( this.textStreams_, textStreamsPerPeriod, firstNewPeriodIndex, shaka.util.PeriodCombiner.cloneStream_, shaka.util.PeriodCombiner.concatenateStreams_, periodsMissing), this.combine_( this.imageStreams_, imageStreamsPerPeriod, firstNewPeriodIndex, shaka.util.PeriodCombiner.cloneStream_, shaka.util.PeriodCombiner.concatenateStreams_, periodsMissing), ]); } // Create variants for all audio/video combinations. let nextVariantId = 0; const variants = []; if (!this.videoStreams_.length || !this.audioStreams_.length) { // For audio-only or video-only content, just give each stream its own // variant. const streams = this.videoStreams_.length ? this.videoStreams_ : this.audioStreams_; for (const stream of streams) { const id = nextVariantId++; variants.push({ id, language: stream.language, disabledUntilTime: 0, primary: stream.primary, audio: stream.type == ContentType.AUDIO ? stream : null, video: stream.type == ContentType.VIDEO ? stream : null, bandwidth: stream.bandwidth || 0, drmInfos: stream.drmInfos, allowedByApplication: true, allowedByKeySystem: true, decodingInfos: [], }); } } else { for (const audio of this.audioStreams_) { for (const video of this.videoStreams_) { const commonDrmInfos = shaka.media.DrmEngine.getCommonDrmInfos( audio.drmInfos, video.drmInfos); if (audio.drmInfos.length && video.drmInfos.length && !commonDrmInfos.length) { shaka.log.warning( 'Incompatible DRM in audio & video, skipping variant creation.', audio, video); continue; } const id = nextVariantId++; variants.push({ id, language: audio.language, disabledUntilTime: 0, primary: audio.primary, audio, video, bandwidth: (audio.bandwidth || 0) + (video.bandwidth || 0), drmInfos: commonDrmInfos, allowedByApplication: true, allowedByKeySystem: true, decodingInfos: [], }); } } } this.variants_ = variants; } /** * Stitch together DB streams across periods, taking a mix of stream types. * The offline database does not separate these by type. * * Unlike the DASH case, this does not need to maintain any state for manifest * updates. * * @param {!Array.<!Array.<shaka.extern.StreamDB>>} streamDbsPerPeriod * @return {!Promise.<!Array.<shaka.extern.StreamDB>>} */ static async combineDbStreams(streamDbsPerPeriod) { const ContentType = shaka.util.ManifestParserUtils.ContentType; const PeriodCombiner = shaka.util.PeriodCombiner; // Optimization: for single-period content, do nothing. This makes sure // single-period DASH or any HLS content stored offline will be 100% // accurately represented in the output. if (streamDbsPerPeriod.length == 1) { return streamDbsPerPeriod[0]; } const audioStreamDbsPerPeriod = streamDbsPerPeriod.map( (streams) => new Map(streams .filter((s) => s.type === ContentType.AUDIO) .map((s) => [PeriodCombiner.generateAudioKey_(s), s]))); const videoStreamDbsPerPeriod = streamDbsPerPeriod.map( (streams) => new Map(streams .filter((s) => s.type === ContentType.VIDEO) .map((s) => [PeriodCombiner.generateVideoKey_(s), s]))); const textStreamDbsPerPeriod = streamDbsPerPeriod.map( (streams) => new Map(streams .filter((s) => s.type === ContentType.TEXT) .map((s) => [PeriodCombiner.generateTextKey_(s), s]))); const imageStreamDbsPerPeriod = streamDbsPerPeriod.map( (streams) => new Map(streams .filter((s) => s.type === ContentType.IMAGE) .map((s) => [PeriodCombiner.generateImageKey_(s), s]))); // It's okay to have a period with no text or images, but our algorithm // fails on any period without matching streams. So we add dummy streams to // each period. Since we combine text streams by language and image streams // by resolution, we might need a dummy even in periods with these streams // already. for (const textStreams of textStreamDbsPerPeriod) { const dummy = PeriodCombiner.dummyStreamDB_(ContentType.TEXT); textStreams.set(PeriodCombiner.generateTextKey_(dummy), dummy); } for (const imageStreams of imageStreamDbsPerPeriod) { const dummy = PeriodCombiner.dummyStreamDB_(ContentType.IMAGE); imageStreams.set(PeriodCombiner.generateImageKey_(dummy), dummy); } const periodCombiner = new shaka.util.PeriodCombiner(); const combinedAudioStreamDbs = await periodCombiner.combine_( /* outputStreams= */ [], audioStreamDbsPerPeriod, /* firstNewPeriodIndex= */ 0, shaka.util.PeriodCombiner.cloneStreamDB_, shaka.util.PeriodCombiner.concatenateStreamDBs_, /* periodsMissing= */ 0); const combinedVideoStreamDbs = await periodCombiner.combine_( /* outputStreams= */ [], videoStreamDbsPerPeriod, /* firstNewPeriodIndex= */ 0, shaka.util.PeriodCombiner.cloneStreamDB_, shaka.util.PeriodCombiner.concatenateStreamDBs_, /* periodsMissing= */ 0); const combinedTextStreamDbs = await periodCombiner.combine_( /* outputStreams= */ [], textStreamDbsPerPeriod, /* firstNewPeriodIndex= */ 0, shaka.util.PeriodCombiner.cloneStreamDB_, shaka.util.PeriodCombiner.concatenateStreamDBs_, /* periodsMissing= */ 0); const combinedImageStreamDbs = await periodCombiner.combine_( /* outputStreams= */ [], imageStreamDbsPerPeriod, /* firstNewPeriodIndex= */ 0, shaka.util.PeriodCombiner.cloneStreamDB_, shaka.util.PeriodCombiner.concatenateStreamDBs_, /* periodsMissing= */ 0); // Recreate variantIds from scratch in the output. // HLS content is always single-period, so the early return at the top of // this method would catch all HLS content. DASH content stored with v3.0 // will already be flattened before storage. Therefore the only content // that reaches this point is multi-period DASH content stored before v3.0. // Such content always had variants generated from all combinations of audio // and video, so we can simply do that now without loss of correctness. let nextVariantId = 0; if (!combinedVideoStreamDbs.length || !combinedAudioStreamDbs.length) { // For audio-only or video-only content, just give each stream its own // variant ID. const combinedStreamDbs = combinedVideoStreamDbs.concat(combinedAudioStreamDbs); for (const stream of combinedStreamDbs) { stream.variantIds = [nextVariantId++]; } } else { for (const audio of combinedAudioStreamDbs) { for (const video of combinedVideoStreamDbs) { const id = nextVariantId++; video.variantIds.push(id); audio.variantIds.push(id); } } } return combinedVideoStreamDbs .concat(combinedAudioStreamDbs) .concat(combinedTextStreamDbs) .concat(combinedImageStreamDbs); } /** * Combine input Streams per period into flat output Streams. * Templatized to handle both DASH Streams and offline StreamDBs. * * @param {!Array.<T>} outputStreams A list of existing output streams, to * facilitate updates for live DASH content. Will be modified and returned. * @param {!Array<!Map<string, T>>} streamsPerPeriod A list of maps of Streams * from each period. * @param {number} firstNewPeriodIndex An index into streamsPerPeriod which * represents the first new period that hasn't been processed yet. * @param {function(T):T} clone Make a clone of an input stream. * @param {function(T, T)} concat Concatenate the second stream onto the end * of the first. * @param {number} periodsMissing The number of periods missing * * @return {!Promise.<!Array.<T>>} The same array passed to outputStreams, * modified to include any newly-created streams. * * @template T * Accepts either a StreamDB or Stream type. * * @private */ async combine_( outputStreams, streamsPerPeriod, firstNewPeriodIndex, clone, concat, periodsMissing) { const unusedStreamsPerPeriod = []; for (let i = 0; i < streamsPerPeriod.length; i++) { if (i >= firstNewPeriodIndex) { // This periods streams are all new. unusedStreamsPerPeriod.push(new Set(streamsPerPeriod[i].values())); } else { // This period's streams have all been used already. unusedStreamsPerPeriod.push(new Set()); } } // First, extend all existing output Streams into the new periods. for (const outputStream of outputStreams) { // eslint-disable-next-line no-await-in-loop const ok = await this.extendExistingOutputStream_( outputStream, streamsPerPeriod, firstNewPeriodIndex, concat, unusedStreamsPerPeriod, periodsMissing); if (!ok) { // This output Stream was not properly extended to include streams from // the new period. This is likely a bug in our algorithm, so throw an // error. throw new shaka.util.Error( shaka.util.Error.Severity.CRITICAL, shaka.util.Error.Category.MANIFEST, shaka.util.Error.Code.PERIOD_FLATTENING_FAILED); } // This output stream is now complete with content from all known // periods. } // for (const outputStream of outputStreams) for (const unusedStreams of unusedStreamsPerPeriod) { for (const stream of unusedStreams) { // Create a new output stream which includes this input stream. const outputStream = this.createNewOutputStream_( stream, streamsPerPeriod, clone, concat, unusedStreamsPerPeriod); if (outputStream) { outputStreams.push(outputStream); } else { // This is not a stream we can build output from, but it may become // part of another output based on another period's stream. } } // for (const stream of unusedStreams) } // for (const unusedStreams of unusedStreamsPerPeriod) for (const unusedStreams of unusedStreamsPerPeriod) { for (const stream of unusedStreams) { if (shaka.util.PeriodCombiner.isDummy_(stream)) { // This is one of our dummy streams, so ignore it. We may not use // them all, and that's fine. continue; } // If this stream has a different codec/MIME than any other stream, // then we can't play it. const hasCodec = outputStreams.some((s) => { return this.areAVStreamsCompatible_(stream, s); }); if (!hasCodec) { continue; } // Any other unused stream is likely a bug in our algorithm, so throw // an error. shaka.log.error('Unused stream in period-flattening!', stream, outputStreams); throw new shaka.util.Error( shaka.util.Error.Severity.CRITICAL, shaka.util.Error.Category.MANIFEST, shaka.util.Error.Code.PERIOD_FLATTENING_FAILED); } } return outputStreams; } /** * @param {T} outputStream An existing output stream which needs to be * extended into new periods. * @param {!Array<!Map<string, T>>} streamsPerPeriod A list of maps of Streams * from each period. * @param {number} firstNewPeriodIndex An index into streamsPerPeriod which * represents the first new period that hasn't been processed yet. * @param {function(T, T)} concat Concatenate the second stream onto the end * of the first. * @param {!Array.<!Set.<T>>} unusedStreamsPerPeriod An array of sets of * unused streams from each period. * @param {number} periodsMissing How many periods are missing in this update. * * @return {!Promise.<boolean>} * * @template T * Should only be called with a Stream type in practice, but has call sites * from other templated functions that also accept a StreamDB. * * @private */ async extendExistingOutputStream_( outputStream, streamsPerPeriod, firstNewPeriodIndex, concat, unusedStreamsPerPeriod, periodsMissing) { this.findMatchesInAllPeriods_(streamsPerPeriod, outputStream, periodsMissing > 0); // This only exists where T == Stream, and this should only ever be called // on Stream types. StreamDB should not have pre-existing output streams. goog.asserts.assert(outputStream.createSegmentIndex, 'outputStream should be a Stream type!'); if (!outputStream.matchedStreams) { // We were unable to extend this output stream. shaka.log.error('No matches extending output stream!', outputStream, streamsPerPeriod); return false; } // We need to create all the per-period segment indexes and append them to // the output's MetaSegmentIndex. if (outputStream.segmentIndex) { await shaka.util.PeriodCombiner.extendOutputSegmentIndex_(outputStream, firstNewPeriodIndex + periodsMissing); } shaka.util.PeriodCombiner.extendOutputStream_(outputStream, firstNewPeriodIndex, concat, unusedStreamsPerPeriod, periodsMissing); return true; } /** * Creates the segment indexes for an array of input streams, and append them * to the output stream's segment index. * * @param {shaka.extern.Stream} outputStream * @param {number} firstNewPeriodIndex An index into streamsPerPeriod which * represents the first new period that hasn't been processed yet. * @private */ static async extendOutputSegmentIndex_(outputStream, firstNewPeriodIndex) { const operations = []; const streams = outputStream.matchedStreams; goog.asserts.assert(streams, 'matched streams should be valid'); for (const stream of streams) { operations.push(stream.createSegmentIndex()); if (stream.trickModeVideo && !stream.trickModeVideo.segmentIndex) { operations.push(stream.trickModeVideo.createSegmentIndex()); } } await Promise.all(operations); // Concatenate the new matches onto the stream, starting at the first new // period. // Satisfy the compiler about the type. // Also checks if the segmentIndex is still valid after the async // operations, to make sure we stop if the active stream has changed. if (outputStream.segmentIndex instanceof shaka.media.MetaSegmentIndex) { for (let i = firstNewPeriodIndex; i < streams.length; i++) { const match = streams[i]; goog.asserts.assert(match.segmentIndex, 'stream should have a segmentIndex.'); if (match.segmentIndex) { outputStream.segmentIndex.appendSegmentIndex(match.segmentIndex); } } } } /** * Create a new output Stream based on a particular input Stream. Locates * matching Streams in all other periods and combines them into an output * Stream. * Templatized to handle both DASH Streams and offline StreamDBs. * * @param {T} stream An input stream on which to base the output stream. * @param {!Array<!Map<string, T>>} streamsPerPeriod A list of maps of Streams * from each period. * @param {function(T):T} clone Make a clone of an input stream. * @param {function(T, T)} concat Concatenate the second stream onto the end * of the first. * @param {!Array.<!Set.<T>>} unusedStreamsPerPeriod An array of sets of * unused streams from each period. * * @return {?T} A newly-created output Stream, or null if matches * could not be found.` * * @template T * Accepts either a StreamDB or Stream type. * * @private */ createNewOutputStream_( stream, streamsPerPeriod, clone, concat, unusedStreamsPerPeriod) { // Check do we want to create output stream from dummy stream // and if so, return quickly. if (shaka.util.PeriodCombiner.isDummy_(stream)) { return null; } // Start by cloning the stream without segments, key IDs, etc. const outputStream = clone(stream); // Find best-matching streams in all periods. this.findMatchesInAllPeriods_(streamsPerPeriod, outputStream); // This only exists where T == Stream. if (outputStream.createSegmentIndex) { // Override the createSegmentIndex function of the outputStream. outputStream.createSegmentIndex = async () => { if (!outputStream.segmentIndex) { outputStream.segmentIndex = new shaka.media.MetaSegmentIndex(); await shaka.util.PeriodCombiner.extendOutputSegmentIndex_( outputStream, /* firstNewPeriodIndex= */ 0); } }; // For T == Stream, we need to create all the per-period segment indexes // in advance. concat() will add them to the output's MetaSegmentIndex. } if (!outputStream.matchedStreams || !outputStream.matchedStreams.length) { // This is not a stream we can build output from, but it may become part // of another output based on another period's stream. return null; } shaka.util.PeriodCombiner.extendOutputStream_(outputStream, /* firstNewPeriodIndex= */ 0, concat, unusedStreamsPerPeriod, /* periodsMissing= */ 0); return outputStream; } /** * @param {T} outputStream An existing output stream which needs to be * extended into new periods. * @param {number} firstNewPeriodIndex An index into streamsPerPeriod which * represents the first new period that hasn't been processed yet. * @param {function(T, T)} concat Concatenate the second stream onto the end * of the first. * @param {!Array.<!Set.<T>>} unusedStreamsPerPeriod An array of sets of * unused streams from each period. * @param {number} periodsMissing How many periods are missing in this update * * @template T * Accepts either a StreamDB or Stream type. * * @private */ static extendOutputStream_( outputStream, firstNewPeriodIndex, concat, unusedStreamsPerPeriod, periodsMissing) { const ContentType = shaka.util.ManifestParserUtils.ContentType; const LanguageUtils = shaka.util.LanguageUtils; const matches = outputStream.matchedStreams; // Assure the compiler that matches didn't become null during the async // operation before. goog.asserts.assert(outputStream.matchedStreams, 'matchedStreams should be non-null'); // Concatenate the new matches onto the stream, starting at the first new // period. const start = firstNewPeriodIndex + periodsMissing; for (let i = start; i < matches.length; i++) { const match = matches[i]; concat(outputStream, match); // We only consider an audio stream "used" if its language is related to // the output language. There are scenarios where we want to generate // separate tracks for each language, even when we are forced to connect // unrelated languages across periods. let used = true; if (outputStream.type == ContentType.AUDIO) { const relatedness = LanguageUtils.relatedness( outputStream.language, match.language); if (relatedness == 0) { used = false; } } if (used) { unusedStreamsPerPeriod[i - periodsMissing].delete(match); // Add the full mimetypes to the stream. if (match.fullMimeTypes) { for (const fullMimeType of match.fullMimeTypes.values()) { outputStream.fullMimeTypes.add(fullMimeType); } } } } } /** * Clone a Stream to make an output Stream for combining others across * periods. * * @param {shaka.extern.Stream} stream * @return {shaka.extern.Stream} * @private */ static cloneStream_(stream) { const clone = /** @type {shaka.extern.Stream} */(Object.assign({}, stream)); // These are wiped out now and rebuilt later from the various per-period // streams that match this output. clone.originalId = null; clone.createSegmentIndex = () => Promise.resolve(); clone.closeSegmentIndex = () => { if (clone.segmentIndex) { clone.segmentIndex.release(); clone.segmentIndex = null; } // Close the segment index of the matched streams. if (clone.matchedStreams) { for (const match of clone.matchedStreams) { if (match.segmentIndex) { match.segmentIndex.release(); match.segmentIndex = null; } } } }; // Clone roles array so this output stream can own it. clone.roles = clone.roles.slice(); clone.segmentIndex = null; clone.emsgSchemeIdUris = []; clone.keyIds = new Set(); clone.closedCaptions = null; clone.trickModeVideo = null; return clone; } /** * Clone a StreamDB to make an output stream for combining others across * periods. * * @param {shaka.extern.StreamDB} streamDb * @return {shaka.extern.StreamDB} * @private */ static cloneStreamDB_(streamDb) { const clone = /** @type {shaka.extern.StreamDB} */(Object.assign( {}, streamDb)); // Clone roles array so this output stream can own it. clone.roles = clone.roles.slice(); // These are wiped out now and rebuilt later from the various per-period // streams that match this output. clone.keyIds = new Set(); clone.segments = []; clone.variantIds = []; clone.closedCaptions = null; return clone; } /** * Combine the various fields of the input Stream into the output. * * @param {shaka.extern.Stream} output * @param {shaka.extern.Stream} input * @private */ static concatenateStreams_(output, input) { // We keep the original stream's bandwidth, resolution, frame rate, // sample rate, and channel count to ensure that it's properly // matched with similar content in other periods further down // the line. // Combine arrays, keeping only the unique elements const combineArrays = (output, input) => { if (!output) { output = []; } for (const item of input) { if (!output.includes(item)) { output.push(item); } } return output; }; output.roles = combineArrays(output.roles, input.roles); if (input.emsgSchemeIdUris) { output.emsgSchemeIdUris = combineArrays( output.emsgSchemeIdUris, input.emsgSchemeIdUris); } for (const keyId of input.keyIds) { output.keyIds.add(keyId); } if (output.originalId == null) { output.originalId = input.originalId; } else { output.originalId += ',' + (input.originalId || ''); } const commonDrmInfos = shaka.media.DrmEngine.getCommonDrmInfos( output.drmInfos, input.drmInfos); if (input.drmInfos.length && output.drmInfos.length && !commonDrmInfos.length) { throw new shaka.util.Error( shaka.util.Error.Severity.CRITICAL, shaka.util.Error.Category.MANIFEST, shaka.util.Error.Code.INCONSISTENT_DRM_ACROSS_PERIODS); } output.drmInfos = commonDrmInfos; // The output is encrypted if any input was encrypted. output.encrypted = output.encrypted || input.encrypted; // Combine the closed captions maps. if (input.closedCaptions) { if (!output.closedCaptions) { output.closedCaptions = new Map(); } for (const [key, value] of input.closedCaptions) { output.closedCaptions.set(key, value); } } // Combine trick-play video streams, if present. if (input.trickModeVideo) { if (!output.trickModeVideo) { // Create a fresh output stream for trick-mode playback. output.trickModeVideo = shaka.util.PeriodCombiner.cloneStream_( input.trickModeVideo); // TODO: fix the createSegmentIndex function for trickModeVideo. // The trick-mode tracks in multi-period content should have trick-mode // segment indexes whenever available, rather than only regular-mode // segment indexes. output.trickModeVideo.createSegmentIndex = () => { // Satisfy the compiler about the type. goog.asserts.assert( output.segmentIndex instanceof shaka.media.MetaSegmentIndex, 'The stream should have a MetaSegmentIndex.'); output.trickModeVideo.segmentIndex = output.segmentIndex.clone(); return Promise.resolve(); }; } // Concatenate the trick mode input onto the trick mode output. shaka.util.PeriodCombiner.concatenateStreams_( output.trickModeVideo, input.trickModeVideo); } else if (output.trickModeVideo) { // We have a trick mode output, but no input from this Period. Fill it in // from the standard input Stream. shaka.util.PeriodCombiner.concatenateStreams_( output.trickModeVideo, input); } } /** * Combine the various fields of the input StreamDB into the output. * * @param {shaka.extern.StreamDB} output * @param {shaka.extern.StreamDB} input * @private */ static concatenateStreamDBs_(output, input) { // Combine arrays, keeping only the unique elements const combineArrays = (output, input) => { if (!output) { output = []; } for (const item of input) { if (!output.includes(item)) { output.push(item); } } return output; }; output.roles = combineArrays(output.roles, input.roles); for (const keyId of input.keyIds) { output.keyIds.add(keyId); } // The output is encrypted if any input was encrypted. output.encrypted = output.encrypted && input.encrypted; // Concatenate segments without de-duping. output.segments.push(...input.segments); // Combine the closed captions maps. if (input.closedCaptions) { if (!output.closedCaptions) { output.closedCaptions = new Map(); } for (const [key, value] of input.closedCaptions) { output.closedCaptions.set(key, value); } } } /** * Finds streams in all periods which match the output stream. * * @param {!Array<!Map<string, T>>} streamsPerPeriod * @param {T} outputStream * @param {boolean=} shouldAppend * * @template T * Accepts either a StreamDB or Stream type. * * @private */ findMatchesInAllPeriods_(streamsPerPeriod, outputStream, shouldAppend = false) { const matches = shouldAppend ? outputStream.matchedStreams : []; for (const streams of streamsPerPeriod) { const match = this.findBestMatchInPeriod_(streams, outputStream); if (!match) { return; } matches.push(match); } outputStream.matchedStreams = matches; } /** * Find the best match for the output stream. * * @param {!Map<string, T>} streams * @param {T} outputStream * @return {?T} Returns null if no match can be found. * * @template T * Accepts either a StreamDB or Stream type. * * @private */ findBestMatchInPeriod_(streams, outputStream) { const getKey = { 'audio': shaka.util.PeriodCombiner.generateAudioKey_, 'video': shaka.util.PeriodCombiner.generateVideoKey_, 'text': shaka.util.PeriodCombiner.generateTextKey_, 'image': shaka.util.PeriodCombiner.generateImageKey_, }[outputStream.type]; let best = null; const key = getKey(outputStream); if (streams.has(key)) { // We've found exact match by hashing. best = streams.get(key); } else { // We haven't found exact match, try to find the best one via // linear search. const areCompatible = { 'audio': (os, s) => this.areAVStreamsCompatible_(os, s), 'video': (os, s) => this.areAVStreamsCompatible_(os, s), 'text': shaka.util.PeriodCombiner.areTextStreamsCompatible_, 'image': shaka.util.PeriodCombiner.areImageStreamsCompatible_, }[outputStream.type]; const isBetterMatch = { 'audio': shaka.util.PeriodCombiner.isAudioStreamBetterMatch_, 'video': shaka.util.PeriodCombiner.isVideoStreamBetterMatch_, 'text': shaka.util.PeriodCombiner.isTextStreamBetterMatch_, 'image': shaka.util.PeriodCombiner.isImageStreamBetterMatch_, }[outputStream.type]; for (const stream of streams.values()) { if (!areCompatible(outputStream, stream)) { continue; } if (outputStream.fastSwitching != stream.fastSwitching) { continue; } if (!best || isBetterMatch(outputStream, best, stream)) { best = stream; } } } // Remove just found stream if configured to, so possible future linear // searches can be faster. if (this.useStreamOnce_ && !shaka.util.PeriodCombiner.isDummy_(best)) { streams.delete(getKey(best)); } return best; } /** * @param {T} a * @param {T} b * @return {boolean} * * @template T * Accepts either a StreamDB or Stream type. * * @private */ static areAVStreamsExactMatch_(a, b) { if (a.mimeType != b.mimeType) { return false; } /** * @param {string} codecs * @return {string} */ const getCodec = (codecs) => { if (!shaka.util.PeriodCombiner.memoizedCodecs.has(codecs)) { const normalizedCodec = shaka.util.MimeUtils.getNormalizedCodec(codecs); shaka.util.PeriodCombiner.memoizedCodecs.set(codecs, normalizedCodec); } return shaka.util.PeriodCombiner.memoizedCodecs.get(codecs); }; return getCodec(a.codecs) == getCodec(b.codecs); } /** * @param {boolean} allowed If set to true, multi-mimeType or multi-codec * variants will be allowed. * @export */ setAllowMultiTypeVariants(allowed) { this.multiTypeVariantsAllowed_ = allowed; } /** * @param {boolean} useOnce if true, stream will be used only once in period * flattening algoritnm. * @export */ setUseStreamOnce(useOnce) { this.useStreamOnce_ = useOnce; } /** * @param {T} outputStream An audio or video output stream * @param {T} candidate A candidate stream to be combined with the output * @return {boolean} True if the candidate could be combined with the * output stream * * @template T * Accepts either a StreamDB or Stream type. * * @private */ areAVStreamsCompatible_(outputStream, candidate) { // Check for an exact match. if (!shaka.util.PeriodCombiner.areAVStreamsExactMatch_( outputStream, candidate)) { // It's not an exact match. See if we can do multi-codec or multi-mimeType // stream instead, using SourceBuffer.changeType. if (!this.multiTypeVariantsAllowed_) { return false; } } // This field is only available on Stream, not StreamDB. if (outputStream.drmInfos) { // Check for compatible DRM systems. Note that clear streams are // implicitly compatible with any DRM and with each other. if (!shaka.media.DrmEngine.areDrmCompatible(outputStream.drmInfos, candidate.drmInfos)) { return false; } } return true; } /** * @param {T} outputStream A text output stream * @param {T} candidate A candidate stream to be combined with the output * @return {boolean} True if the candidate could be combined with the * output * * @template T * Accepts either a StreamDB or Stream type. * * @private */ static areTextStreamsCompatible_(outputStream, candidate) { const LanguageUtils = shaka.util.LanguageUtils; // For text, we don't care about MIME type or codec. We can always switch // between text types. // If the candidate is a dummy, then it is compatible, and we could use it // if nothing else matches. if (!candidate.language) { return true; } // Forced subtitles should be treated as unique streams if (outputStream.forced !== candidate.forced) { return false; } const languageRelatedness = LanguageUtils.relatedness( outputStream.language, candidate.language); // We will strictly avoid combining text across languages or "kinds" // (caption vs subtitle). if (languageRelatedness == 0 || candidate.kind != outputStream.kind) { return false; } return true; } /** * @param {T} outputStream A image output stream * @param {T} candidate A candidate stream to be combined with the output * @return {boolean} True if the candidate could be combined with the * output * * @template T * Accepts either a StreamDB or Stream type. * * @private */ static areImageStreamsCompatible_(outputStream, candidate) { // For image, we don't care about MIME type. We can always switch // between image types. return true; } /** * @param {T} outputStream An audio output stream * @param {T} best The best match so far for this period * @param {T} candidate A candidate stream which might be better * @return {boolean} True if the candidate is a better match * * @template T * Accepts either a StreamDB or Stream type. * * @private */ static isAudioStreamBetterMatch_(outputStream, best, candidate) { const LanguageUtils = shaka.util.LanguageUtils; const {BETTER, EQUAL, WORSE} = shaka.util.PeriodCombiner.BetterOrWorse; // An exact match is better than a non-exact match. const bestIsExact = shaka.util.PeriodCombiner.areAVStreamsExactMatch_( outputStream, best); const candidateIsExact = shaka.util.PeriodCombiner.areAVStreamsExactMatch_( outputStream, candidate); if (bestIsExact && !candidateIsExact) { return false; } if (!bestIsExact && candidateIsExact) { return true; } // The most important thing is language. In some cases, we will accept a // different language across periods when we must. const bestRelatedness = LanguageUtils.relatedness( outputStream.language, best.language); const candidateRelatedness = LanguageUtils.relatedness( outputStream.language, candidate.language); if (candidateRelatedness > bestRelatedness) { return true; } if (candidateRelatedness < bestRelatedness) { return false; } // If language-based differences haven't decided this, look at labels. // If available options differ, look does any matches with output stream. if (best.label !== candidate.label) { if (outputStream.label === best.label) { return false; } if (outputStream.label === candidate.label) { return true; } } // If label-based differences haven't decided this, look at roles. If // the candidate has more roles in common with the output, upgrade to the // candidate. if (outputStream.roles.length) { const bestRoleMatches = best.roles.filter((role) => outputStream.roles.includes(role)); const candidateRoleMatches = candidate.roles.filter((role) => outputStream.roles.includes(role)); if (candidateRoleMatches.length > bestRoleMatches.length) { return true; } else if (candidateRoleMatches.length < bestRoleMatches.length) { return false; } else { // Both streams have the same role overlap with the outputStream // If this is the case, choose the stream with the fewer roles overall. // Streams that match best together tend to be streams with the same // roles, e g stream1 with roles [r1, r2] is likely a better match // for stream2 with roles [r1, r2] vs stream3 with roles // [r1, r2, r3, r4]. // If we match stream1 with stream3 due to the same role overlap, // stream2 is likely to be left unmatched and error out later. // See https://github.com/shaka-project/shaka-player/issues/2542 for // more details. return candidate.roles.length < best.roles.length; } } else if (!candidate.roles.length && best.roles.length) { // If outputStream has no roles, and only one of the streams has no roles, // choose the one with no roles. return true; } else if (candidate.roles.length && !best.roles.length) { return false; } // If the language doesn't match, but the candidate is the "primary" // language, then that should be preferred as a fallback. if (!best.primary && candidate.primary) { return true; } if (best.primary && !candidate.primary) { return false; } // If language-based and role-based features are equivalent, take the audio // with the closes channel count to the output. const channelsBetterOrWorse = shaka.util.PeriodCombiner.compareClosestPreferLower( outputStream.channelsCount, best.channelsCount, candidate.channelsCount); if (channelsBetterOrWorse == BETTER) { return true; } else if (channelsBetterOrWorse == WORSE) { return false; } // If channels are equal, take the closest sample rate to the output. const sampleRateBetterOrWorse = shaka.util.PeriodCombiner.compareClosestPreferLower( outputStream.audioSamplingRate, best.audioSamplingRate, candidate.audioSamplingRate); if (sampleRateBetterOrWorse == BETTER) { return true; } else if (sampleRateBetterOrWorse == WORSE) { return false; } if (outputStream.bandwidth) { // Take the audio with the closest bandwidth to the output. const bandwidthBetterOrWorse = shaka.util.PeriodCombiner.compareClosestPreferMinimalAbsDiff_( outputStream.bandwidth, best.bandwidth, candidate.bandwidth); if (bandwidthBetterOrWorse == BETTER) { return true; } else if (bandwidthBetterOrWorse == WORSE) { return false; } } // If the result of each comparison was inconclusive, default to false. return false; } /** * @param {T} outputStream A video output stream * @param {T} best The best match so far for this period * @param {T} candidate A candidate stream which might be better * @return {boolean} True if the candidate is a better match * * @template T * Accepts either a StreamDB or Stream type. * * @private */ static isVideoStreamBetterMatch_(outputStream, best, candidate) { const {BETTER, EQUAL, WORSE} = shaka.util.PeriodCombiner.BetterOrWorse; // An exact match is better than a non-exact match. const bestIsExact = shaka.util.PeriodCombiner.areAVStreamsExactMatch_( outputStream, best); const candidateIsExact = shaka.util.PeriodCombiner.areAVStreamsExactMatch_( outputStream, candidate); if (bestIsExact && !candidateIsExact) { return false; } if (!bestIsExact && candidateIsExact) { return true; } // Take the video with the closest resolution to the output. const resolutionBetterOrWorse = shaka.util.PeriodCombiner.compareClosestPreferLower( outputStream.width * outputStream.height, best.width * best.height, candidate.width * candidate.height); if (resolutionBetterOrWorse == BETTER) { return true; } else if (resolutionBetterOrWorse == WORSE) { return false; } // We may not know the frame rate for the content, in which case this gets // skipped. if (outputStream.frameRate) { // Take the video with the closest frame rate to the output. const frameRateBetterOrWorse = shaka.util.PeriodCombiner.compareClosestPreferLower( outputStream.frameRate, best.frameRate, candidate.frameRate); if (frameRateBetterOrWorse == BETTER) { return true; } else if (frameRateBetterOrWorse == WORSE) { return false; } } if (outputStream.bandwidth) { // Take the video with the closest bandwidth to the output. const bandwidthBetterOrWorse = shaka.util.PeriodCombiner.compareClosestPreferMinimalAbsDiff_( outputStream.bandwidth, best.bandwidth, candidate.bandwidth); if (bandwidthBetterOrWorse == BETTER) { return true; } else if (bandwidthBetterOrWorse == WORSE) { return false; } } // If the result of each comparison was inconclusive, default to false. return false; } /** * @param {T} outputStream A text output stream * @param {T} best The best match so far for this period * @param {T} candidate A candidate stream which might be better * @return {boolean} True if the candidate is a better match * * @template T * Accepts either a StreamDB or Stream type. * * @private */ static isTextStreamBetterMatch_(outputStream, best, candidate) { const LanguageUtils = shaka.util.LanguageUtils; // The most important thing is language. In some cases, we will accept a // different language across periods when we must. const bestRelatedness = LanguageUtils.relatedness( outputStream.language, best.language); const candidateRelatedness = LanguageUtils.relatedness( outputStream.language, candidate.language); if (candidateRelatedness > bestRelatedness) { return true; } if (candidateRelatedness < bestRelatedness) { return false; } // If the language doesn't match, but the candidate is the "primary" // language, then that should be preferred as a fallback. if (!best.primary && candidate.primary) { return true; } if (best.primary && !candidate.primary) { return false; } // If language-based differences haven't decided this, look at labels. // If available options differ, look does any matches with output stream. if (best.label !== candidate.label) { if (outputStream.label === best.label) { return false; } if (outputStream.label === candidate.label) { return true; } } // If the candidate has more roles in common with the output, upgrade to the // candidate. if (outputStream.roles.length) { const bestRoleMatches = best.roles.filter((role) => outputStream.roles.includes(role)); const candidateRoleMatches = candidate.roles.filter((role) => outputStream.roles.includes(role)); if (candidateRoleMatches.length > bestRoleMatches.length) { return true; } if (candidateRoleMatches.length < bestRoleMatches.length) { return false; } } else if (!candidate.roles.length && best.roles.length) { // If outputStream has no roles, and only one of the streams has no roles, // choose the one with no roles. return true; } else if (candidate.roles.length && !best.roles.length) { return false; } // If the candidate has the same MIME type and codec, upgrade to the // candidate. It's not required that text streams use the same format // across periods, but it's a helpful signal. Some content in our demo app // contains the same languages repeated with two different text formats in // each period. This condition ensures that all text streams are used. // Otherwise, we wind up with some one stream of each language left unused, // triggering a failure. if (candidate.mimeType == outputStream.mimeType && candidate.codecs == outputStream.codecs && (best.mimeType != outputStream.mimeType || best.codecs != outputStream.codecs)) { return true; } // If the result of each comparison was inconclusive, default to false. return false; } /** * @param {T} outputStream A image output stream * @param {T} best The best match so far for this period * @param {T} candidate A candidate stream which might be better * @return {boolean} True if the candidate is a better match * * @template T * Accepts either a StreamDB or Stream type. * * @private */ static isImageStreamBetterMatch_(outputStream, best, candidate) { const {BETTER, EQUAL, WORSE} = shaka.util.PeriodCombiner.BetterOrWorse; // Take the image with the closest resolution to the output. const resolutionBetterOrWorse = shaka.util.PeriodCombiner.compareClosestPreferLower( outputStream.width * outputStream.height, best.width * best.height, candidate.width * candidate.height); if (resolutionBetterOrWorse == BETTER) { return true; } else if (resolutionBetterOrWorse == WORSE) { return false; } // If the result of each comparison was inconclusive, default to false. return false; } /** * Create a dummy StreamDB to fill in periods that are missing a certain type, * to avoid failing the general flattening algorithm. This won't be used for * audio or video, since those are strictly required in all periods if they * exist in any period. * * @param {shaka.util.ManifestParserUtils.ContentType} type * @return {shaka.extern.StreamDB} * @private */ static dummyStreamDB_(type) { return { id: 0, originalId: '', groupId: null, primary: false, type, mimeType: '', codecs: '', language: '', originalLanguage: null, label: null, width: null, height: null, encrypted: false, keyIds: new Set(), segments: [], variantIds: [], roles: [], forced: false, channelsCount: null, audioSamplingRate: null, spatialAudio: false, closedCaptions: null, external: false, fastSwitching: false, }; } /** * Create a dummy Stream to fill in periods that are missing a certain type, * to avoid failing the general flattening algorithm. This won't be used for * audio or video, since those are strictly required in all periods if they * exist in any period. * * @param {shaka.util.ManifestParserUtils.ContentType} type * @return {shaka.extern.Stream} * @private */ static dummyStream_(type) { return { id: 0, originalId: '', groupId: null, createSegmentIndex: () => Promise.resolve(), segmentIndex: new shaka.media.SegmentIndex([]), mimeType: '', codecs: '', encrypted: false, drmInfos: [], keyIds: new Set(), language: '', originalLanguage: null, label: null, type, primary: false, trickModeVideo: null, emsgSchemeIdUris: null, roles: [], forced: false, channelsCount: null, audioSamplingRate: null, spatialAudio: false, closedCaptions: null, accessibilityPurpose: null, external: false, fastSwitching: false, fullMimeTypes: new Set(), }; } /** * Compare the best value so far with the candidate value and the output * value. Decide if the candidate is better, equal, or worse than the best * so far. Any value less than or equal to the output is preferred over a * larger value, and closer to the output is better than farther. * * This provides us a generic way to choose things that should match as * closely as possible, like resolution, frame rate, audio channels, or * sample rate. If we have to go higher to make a match, we will. But if * the user selects 480p, for example, we don't want to surprise them with * 720p and waste bandwidth if there's another choice available to us. * * @param {number} outputValue * @param {number} bestValue * @param {number} candidateValue * @return {shaka.util.PeriodCombiner.BetterOrWorse} */ static compareClosestPreferLower(outputValue, bestValue, candidateValue) { const {BETTER, EQUAL, WORSE} = shaka.util.PeriodCombiner.BetterOrWorse; // If one is the exact match for the output value, and the other isn't, // prefer the one that is the exact match. if (bestValue == outputValue && outputValue != candidateValue) { return WORSE; } else if (candidateValue == outputValue && outputValue != bestValue) { return BETTER; } if (bestValue > outputValue) { if (candidateValue <= outputValue) { // Any smaller-or-equal-to-output value is preferable to a // bigger-than-output value. return BETTER; } // Both "best" and "candidate" are greater than the output. Take // whichever is closer. if (candidateValue - outputValue < bestValue - outputValue) { return BETTER; } else if (candidateValue - outputValue > bestValue - outputValue) { return WORSE; } } else { // The "best" so far is less than or equal to the output. If the // candidate is bigger than the output, we don't want it. if (candidateValue > outputValue) { return WORSE; } // Both "best" and "candidate" are less than or equal to the output. // Take whichever is closer. if (outputValue - candidateValue < outputValue - bestValue) { return BETTER; } else if (outputValue - candidateValue > outputValue - bestValue) { return WORSE; } } return EQUAL; } /** * @param {number} outputValue * @param {number} bestValue * @param {number} candidateValue * @return {shaka.util.PeriodCombiner.BetterOrWorse} * @private */ static compareClosestPreferMinimalAbsDiff_( outputValue, bestValue, candidateValue) { const {BETTER, EQUAL, WORSE} = shaka.util.PeriodCombiner.BetterOrWorse; const absDiffBest = Math.abs(outputValue - bestValue); const absDiffCandidate = Math.abs(outputValue - candidateValue); if (absDiffCandidate < absDiffBest) { return BETTER; } else if (absDiffBest < absDiffCandidate) { return WORSE; } return EQUAL; } /** * @param {T} stream * @return {boolean} * @template T * Accepts either a StreamDB or Stream type. * @private */ static isDummy_(stream) { const ContentType = shaka.util.ManifestParserUtils.ContentType; switch (stream.type) { case ContentType.TEXT: return !stream.language; case ContentType.IMAGE: return !stream.tilesLayout; default: return false; } } /** * @param {T} v * @return {string} * @template T * Accepts either a StreamDB or Stream type. * @private */ static generateVideoKey_(v) { return shaka.util.PeriodCombiner.generateKey_([ v.fastSwitching, v.width, v.frameRate, v.codecs, v.mimeType, v.label, v.roles, v.closedCaptions ? Array.from(v.closedCaptions.entries()) : null, v.bandwidth, ]); } /** * @param {T} a * @return {string} * @template T * Accepts either a StreamDB or Stream type. * @private */ static generateAudioKey_(a) { return shaka.util.PeriodCombiner.generateKey_([ a.fastSwitching, a.channelsCount, a.language, a.bandwidth, a.label, a.codecs, a.mimeType, a.roles, a.audioSamplingRate, a.primary, ]); } /** * @param {T} t * @return {string} * @template T * Accepts either a StreamDB or Stream type. * @private */ static generateTextKey_(t) { return shaka.util.PeriodCombiner.generateKey_([ t.language, t.label, t.codecs, t.mimeType, t.bandwidth, t.roles, ]); } /** * @param {T} i * @return {string} * @template T * Accepts either a StreamDB or Stream type. * @private */ static generateImageKey_(i) { return shaka.util.PeriodCombiner.generateKey_([ i.width, i.codecs, i.mimeType, ]); } /** * @param {!Array<*>} values * @return {string} * @private */ static generateKey_(values) { return JSON.stringify(values); }};/** * @enum {number} */shaka.util.PeriodCombiner.BetterOrWorse = { BETTER: 1, EQUAL: 0, WORSE: -1,};/** * @private {Map<string, string>} */shaka.util.PeriodCombiner.memoizedCodecs = new Map();