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transmuxer.ts
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transmuxer.ts
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import type { HlsEventEmitter } from '../events';
import { Events } from '../events';
import { ErrorTypes, ErrorDetails } from '../errors';
import Decrypter from '../crypt/decrypter';
import AACDemuxer from '../demux/aacdemuxer';
import MP4Demuxer from '../demux/mp4demuxer';
import TSDemuxer, { TypeSupported } from '../demux/tsdemuxer';
import MP3Demuxer from '../demux/mp3demuxer';
import MP4Remuxer from '../remux/mp4-remuxer';
import PassThroughRemuxer from '../remux/passthrough-remuxer';
import ChunkCache from './chunk-cache';
import { appendUint8Array } from '../utils/mp4-tools';
import { logger } from '../utils/logger';
import type { Demuxer, KeyData } from '../types/demuxer';
import type { Remuxer } from '../types/remuxer';
import type { TransmuxerResult, ChunkMetadata } from '../types/transmuxer';
import type { HlsConfig } from '../config';
import type { LevelKey } from '../loader/level-key';
import type { PlaylistLevelType } from '../types/loader';
let now;
// performance.now() not available on WebWorker, at least on Safari Desktop
try {
now = self.performance.now.bind(self.performance);
} catch (err) {
logger.debug('Unable to use Performance API on this environment');
now = self.Date.now;
}
type MuxConfig =
| { demux: typeof TSDemuxer; remux: typeof MP4Remuxer }
| { demux: typeof MP4Demuxer; remux: typeof PassThroughRemuxer }
| { demux: typeof AACDemuxer; remux: typeof MP4Remuxer }
| { demux: typeof MP3Demuxer; remux: typeof MP4Remuxer };
const muxConfig: MuxConfig[] = [
{ demux: TSDemuxer, remux: MP4Remuxer },
{ demux: MP4Demuxer, remux: PassThroughRemuxer },
{ demux: AACDemuxer, remux: MP4Remuxer },
{ demux: MP3Demuxer, remux: MP4Remuxer },
];
let minProbeByteLength = 1024;
muxConfig.forEach(({ demux }) => {
minProbeByteLength = Math.max(minProbeByteLength, demux.minProbeByteLength);
});
export default class Transmuxer {
private observer: HlsEventEmitter;
private typeSupported: TypeSupported;
private config: HlsConfig;
private vendor: string;
private id: PlaylistLevelType;
private demuxer?: Demuxer;
private remuxer?: Remuxer;
private decrypter?: Decrypter;
private probe!: Function;
private decryptionPromise: Promise<TransmuxerResult> | null = null;
private transmuxConfig!: TransmuxConfig;
private currentTransmuxState!: TransmuxState;
private cache: ChunkCache = new ChunkCache();
constructor(
observer: HlsEventEmitter,
typeSupported: TypeSupported,
config: HlsConfig,
vendor: string,
id: PlaylistLevelType
) {
this.observer = observer;
this.typeSupported = typeSupported;
this.config = config;
this.vendor = vendor;
this.id = id;
}
configure(transmuxConfig: TransmuxConfig) {
this.transmuxConfig = transmuxConfig;
if (this.decrypter) {
this.decrypter.reset();
}
}
push(
data: ArrayBuffer,
decryptdata: LevelKey | null,
chunkMeta: ChunkMetadata,
state?: TransmuxState
): TransmuxerResult | Promise<TransmuxerResult> {
const stats = chunkMeta.transmuxing;
stats.executeStart = now();
let uintData: Uint8Array = new Uint8Array(data);
const { cache, config, currentTransmuxState, transmuxConfig } = this;
if (state) {
this.currentTransmuxState = state;
}
const keyData = getEncryptionType(uintData, decryptdata);
if (keyData && keyData.method === 'AES-128') {
const decrypter = this.getDecrypter();
// Software decryption is synchronous; webCrypto is not
if (config.enableSoftwareAES) {
// Software decryption is progressive. Progressive decryption may not return a result on each call. Any cached
// data is handled in the flush() call
const decryptedData = decrypter.softwareDecrypt(
uintData,
keyData.key.buffer,
keyData.iv.buffer
);
if (!decryptedData) {
stats.executeEnd = now();
return emptyResult(chunkMeta);
}
uintData = new Uint8Array(decryptedData);
} else {
this.decryptionPromise = decrypter
.webCryptoDecrypt(uintData, keyData.key.buffer, keyData.iv.buffer)
.then((decryptedData): TransmuxerResult => {
// Calling push here is important; if flush() is called while this is still resolving, this ensures that
// the decrypted data has been transmuxed
const result = this.push(
decryptedData,
null,
chunkMeta
) as TransmuxerResult;
this.decryptionPromise = null;
return result;
});
return this.decryptionPromise!;
}
}
const {
contiguous,
discontinuity,
trackSwitch,
accurateTimeOffset,
timeOffset,
} = state || currentTransmuxState;
const {
audioCodec,
videoCodec,
defaultInitPts,
duration,
initSegmentData,
} = transmuxConfig;
// Reset muxers before probing to ensure that their state is clean, even if flushing occurs before a successful probe
if (discontinuity || trackSwitch) {
this.resetInitSegment(initSegmentData, audioCodec, videoCodec, duration);
}
if (discontinuity) {
this.resetInitialTimestamp(defaultInitPts);
}
if (!contiguous) {
this.resetContiguity();
}
if (this.needsProbing(uintData, discontinuity, trackSwitch)) {
if (cache.dataLength) {
const cachedData = cache.flush();
uintData = appendUint8Array(cachedData, uintData);
}
this.configureTransmuxer(uintData, transmuxConfig);
}
const result = this.transmux(
uintData,
keyData,
timeOffset,
accurateTimeOffset,
chunkMeta
);
const currentState = this.currentTransmuxState;
currentState.contiguous = true;
currentState.discontinuity = false;
currentState.trackSwitch = false;
stats.executeEnd = now();
return result;
}
// Due to data caching, flush calls can produce more than one TransmuxerResult (hence the Array type)
flush(
chunkMeta: ChunkMetadata
): TransmuxerResult[] | Promise<TransmuxerResult[]> {
const stats = chunkMeta.transmuxing;
stats.executeStart = now();
const { decrypter, cache, currentTransmuxState, decryptionPromise } = this;
if (decryptionPromise) {
// Upon resolution, the decryption promise calls push() and returns its TransmuxerResult up the stack. Therefore
// only flushing is required for async decryption
return decryptionPromise.then(() => {
return this.flush(chunkMeta);
});
}
const transmuxResults: Array<TransmuxerResult> = [];
const { timeOffset } = currentTransmuxState;
if (decrypter) {
// The decrypter may have data cached, which needs to be demuxed. In this case we'll have two TransmuxResults
// This happens in the case that we receive only 1 push call for a segment (either for non-progressive downloads,
// or for progressive downloads with small segments)
const decryptedData = decrypter.flush();
if (decryptedData) {
// Push always returns a TransmuxerResult if decryptdata is null
transmuxResults.push(
this.push(decryptedData, null, chunkMeta) as TransmuxerResult
);
}
}
const bytesSeen = cache.dataLength;
cache.reset();
const { demuxer, remuxer } = this;
if (!demuxer || !remuxer) {
// If probing failed, and each demuxer saw enough bytes to be able to probe, then Hls.js has been given content its not able to handle
if (bytesSeen >= minProbeByteLength) {
this.observer.emit(Events.ERROR, Events.ERROR, {
type: ErrorTypes.MEDIA_ERROR,
details: ErrorDetails.FRAG_PARSING_ERROR,
fatal: true,
reason: 'no demux matching with content found',
});
}
stats.executeEnd = now();
return [emptyResult(chunkMeta)];
}
const demuxResultOrPromise = demuxer.flush(timeOffset);
if (isPromise(demuxResultOrPromise)) {
// Decrypt final SAMPLE-AES samples
return demuxResultOrPromise.then((demuxResult) => {
this.flushRemux(transmuxResults, demuxResult, chunkMeta);
return transmuxResults;
});
}
this.flushRemux(transmuxResults, demuxResultOrPromise, chunkMeta);
return transmuxResults;
}
private flushRemux(transmuxResults, demuxResult, chunkMeta) {
const { audioTrack, avcTrack, id3Track, textTrack } = demuxResult;
const { accurateTimeOffset, timeOffset } = this.currentTransmuxState;
logger.log(
`[transmuxer.ts]: Flushed fragment ${chunkMeta.sn}${
chunkMeta.part > -1 ? ' p: ' + chunkMeta.part : ''
} of level ${chunkMeta.level}`
);
const remuxResult = this.remuxer!.remux(
audioTrack,
avcTrack,
id3Track,
textTrack,
timeOffset,
accurateTimeOffset,
true,
this.id
);
transmuxResults.push({
remuxResult,
chunkMeta,
});
chunkMeta.transmuxing.executeEnd = now();
}
resetInitialTimestamp(defaultInitPts: number | undefined) {
const { demuxer, remuxer } = this;
if (!demuxer || !remuxer) {
return;
}
demuxer.resetTimeStamp(defaultInitPts);
remuxer.resetTimeStamp(defaultInitPts);
}
resetContiguity() {
const { demuxer, remuxer } = this;
if (!demuxer || !remuxer) {
return;
}
demuxer.resetContiguity();
remuxer.resetNextTimestamp();
}
resetInitSegment(
initSegmentData: Uint8Array | undefined,
audioCodec: string | undefined,
videoCodec: string | undefined,
duration: number
) {
const { demuxer, remuxer } = this;
if (!demuxer || !remuxer) {
return;
}
demuxer.resetInitSegment(audioCodec, videoCodec, duration);
remuxer.resetInitSegment(initSegmentData, audioCodec, videoCodec);
}
destroy(): void {
if (this.demuxer) {
this.demuxer.destroy();
this.demuxer = undefined;
}
if (this.remuxer) {
this.remuxer.destroy();
this.remuxer = undefined;
}
}
private transmux(
data: Uint8Array,
keyData: KeyData | null,
timeOffset: number,
accurateTimeOffset: boolean,
chunkMeta: ChunkMetadata
): TransmuxerResult | Promise<TransmuxerResult> {
let result: TransmuxerResult | Promise<TransmuxerResult>;
if (keyData && keyData.method === 'SAMPLE-AES') {
result = this.transmuxSampleAes(
data,
keyData,
timeOffset,
accurateTimeOffset,
chunkMeta
);
} else {
result = this.transmuxUnencrypted(
data,
timeOffset,
accurateTimeOffset,
chunkMeta
);
}
return result;
}
private transmuxUnencrypted(
data: Uint8Array,
timeOffset: number,
accurateTimeOffset: boolean,
chunkMeta: ChunkMetadata
): TransmuxerResult {
const { audioTrack, avcTrack, id3Track, textTrack } = (
this.demuxer as Demuxer
).demux(data, timeOffset, false, !this.config.progressive);
const remuxResult = this.remuxer!.remux(
audioTrack,
avcTrack,
id3Track,
textTrack,
timeOffset,
accurateTimeOffset,
false,
this.id
);
return {
remuxResult,
chunkMeta,
};
}
private transmuxSampleAes(
data: Uint8Array,
decryptData: KeyData,
timeOffset: number,
accurateTimeOffset: boolean,
chunkMeta: ChunkMetadata
): Promise<TransmuxerResult> {
return (this.demuxer as Demuxer)
.demuxSampleAes(data, decryptData, timeOffset)
.then((demuxResult) => {
const remuxResult = this.remuxer!.remux(
demuxResult.audioTrack,
demuxResult.avcTrack,
demuxResult.id3Track,
demuxResult.textTrack,
timeOffset,
accurateTimeOffset,
false,
this.id
);
return {
remuxResult,
chunkMeta,
};
});
}
private configureTransmuxer(
data: Uint8Array,
transmuxConfig: TransmuxConfig
) {
const { config, observer, typeSupported, vendor } = this;
const {
audioCodec,
defaultInitPts,
duration,
initSegmentData,
videoCodec,
} = transmuxConfig;
// probe for content type
let mux;
for (let i = 0, len = muxConfig.length; i < len; i++) {
if (muxConfig[i].demux.probe(data)) {
mux = muxConfig[i];
break;
}
}
if (!mux) {
// If probing previous configs fail, use mp4 passthrough
logger.warn(
'Failed to find demuxer by probing frag, treating as mp4 passthrough'
);
mux = { demux: MP4Demuxer, remux: PassThroughRemuxer };
}
// so let's check that current remuxer and demuxer are still valid
const demuxer = this.demuxer;
const remuxer = this.remuxer;
const Remuxer: MuxConfig['remux'] = mux.remux;
const Demuxer: MuxConfig['demux'] = mux.demux;
if (!remuxer || !(remuxer instanceof Remuxer)) {
this.remuxer = new Remuxer(observer, config, typeSupported, vendor);
}
if (!demuxer || !(demuxer instanceof Demuxer)) {
this.demuxer = new Demuxer(observer, config, typeSupported);
this.probe = Demuxer.probe;
}
// Ensure that muxers are always initialized with an initSegment
this.resetInitSegment(initSegmentData, audioCodec, videoCodec, duration);
this.resetInitialTimestamp(defaultInitPts);
}
private needsProbing(
data: Uint8Array,
discontinuity: boolean,
trackSwitch: boolean
): boolean {
// in case of continuity change, or track switch
// we might switch from content type (AAC container to TS container, or TS to fmp4 for example)
return !this.demuxer || !this.remuxer || discontinuity || trackSwitch;
}
private getDecrypter(): Decrypter {
let decrypter = this.decrypter;
if (!decrypter) {
decrypter = this.decrypter = new Decrypter(this.observer, this.config);
}
return decrypter;
}
}
function getEncryptionType(
data: Uint8Array,
decryptData: LevelKey | null
): KeyData | null {
let encryptionType: KeyData | null = null;
if (
data.byteLength > 0 &&
decryptData != null &&
decryptData.key != null &&
decryptData.iv !== null &&
decryptData.method != null
) {
encryptionType = decryptData as KeyData;
}
return encryptionType;
}
const emptyResult = (chunkMeta): TransmuxerResult => ({
remuxResult: {},
chunkMeta,
});
export function isPromise<T>(p: Promise<T> | any): p is Promise<T> {
return 'then' in p && p.then instanceof Function;
}
export class TransmuxConfig {
public audioCodec?: string;
public videoCodec?: string;
public initSegmentData?: Uint8Array;
public duration: number;
public defaultInitPts?: number;
constructor(
audioCodec: string | undefined,
videoCodec: string | undefined,
initSegmentData: Uint8Array | undefined,
duration: number,
defaultInitPts?: number
) {
this.audioCodec = audioCodec;
this.videoCodec = videoCodec;
this.initSegmentData = initSegmentData;
this.duration = duration;
this.defaultInitPts = defaultInitPts;
}
}
export class TransmuxState {
public discontinuity: boolean;
public contiguous: boolean;
public accurateTimeOffset: boolean;
public trackSwitch: boolean;
public timeOffset: number;
constructor(
discontinuity: boolean,
contiguous: boolean,
accurateTimeOffset: boolean,
trackSwitch: boolean,
timeOffset: number
) {
this.discontinuity = discontinuity;
this.contiguous = contiguous;
this.accurateTimeOffset = accurateTimeOffset;
this.trackSwitch = trackSwitch;
this.timeOffset = timeOffset;
}
}