src/controller/timeline-controller.ts
import { Events } from '../events';
import Cea608Parser, { CaptionScreen } from '../utils/cea-608-parser';
import OutputFilter from '../utils/output-filter';
import { parseWebVTT } from '../utils/webvtt-parser';
import {
sendAddTrackEvent,
clearCurrentCues,
addCueToTrack,
removeCuesInRange,
} from '../utils/texttrack-utils';
import { parseIMSC1, IMSC1_CODEC } from '../utils/imsc1-ttml-parser';
import { PlaylistLevelType } from '../types/loader';
import Fragment from '../loader/fragment';
import {
FragParsingUserdataData,
FragLoadedData,
FragDecryptedData,
MediaAttachingData,
ManifestLoadedData,
InitPTSFoundData,
SubtitleTracksUpdatedData,
BufferFlushingData,
FragLoadingData,
} from '../types/events';
import { logger } from '../utils/logger';
import type Hls from '../hls';
import type { ComponentAPI } from '../types/component-api';
import type { HlsConfig } from '../config';
import type { CuesInterface } from '../utils/cues';
import type { MediaPlaylist } from '../types/media-playlist';
import type { VTTCCs } from '../types/vtt';
type TrackProperties = {
label: string;
languageCode: string;
media?: MediaPlaylist;
};
type NonNativeCaptionsTrack = {
_id?: string;
label: string;
kind: string;
default: boolean;
closedCaptions?: MediaPlaylist;
subtitleTrack?: MediaPlaylist;
};
export class TimelineController implements ComponentAPI {
private hls: Hls;
private media: HTMLMediaElement | null = null;
private config: HlsConfig;
private enabled: boolean = true;
private Cues: CuesInterface;
private textTracks: Array<TextTrack> = [];
private tracks: Array<MediaPlaylist> = [];
private initPTS: Array<number> = [];
private timescale: Array<number> = [];
private unparsedVttFrags: Array<FragLoadedData | FragDecryptedData> = [];
private captionsTracks: Record<string, TextTrack> = {};
private nonNativeCaptionsTracks: Record<string, NonNativeCaptionsTrack> = {};
private readonly cea608Parser1!: Cea608Parser;
private readonly cea608Parser2!: Cea608Parser;
private lastSn: number = -1;
private prevCC: number = -1;
private vttCCs: VTTCCs = newVTTCCs();
private captionsProperties: {
textTrack1: TrackProperties;
textTrack2: TrackProperties;
textTrack3: TrackProperties;
textTrack4: TrackProperties;
};
constructor(hls: Hls) {
this.hls = hls;
this.config = hls.config;
this.Cues = hls.config.cueHandler;
this.captionsProperties = {
textTrack1: {
label: this.config.captionsTextTrack1Label,
languageCode: this.config.captionsTextTrack1LanguageCode,
},
textTrack2: {
label: this.config.captionsTextTrack2Label,
languageCode: this.config.captionsTextTrack2LanguageCode,
},
textTrack3: {
label: this.config.captionsTextTrack3Label,
languageCode: this.config.captionsTextTrack3LanguageCode,
},
textTrack4: {
label: this.config.captionsTextTrack4Label,
languageCode: this.config.captionsTextTrack4LanguageCode,
},
};
if (this.config.enableCEA708Captions) {
const channel1 = new OutputFilter(this, 'textTrack1');
const channel2 = new OutputFilter(this, 'textTrack2');
const channel3 = new OutputFilter(this, 'textTrack3');
const channel4 = new OutputFilter(this, 'textTrack4');
this.cea608Parser1 = new Cea608Parser(1, channel1, channel2);
this.cea608Parser2 = new Cea608Parser(3, channel3, channel4);
}
this._registerListeners();
}
private _registerListeners(): void {
const { hls } = this;
hls.on(Events.MEDIA_ATTACHING, this.onMediaAttaching, this);
hls.on(Events.MEDIA_DETACHING, this.onMediaDetaching, this);
hls.on(Events.MANIFEST_LOADING, this.onManifestLoading, this);
hls.on(Events.MANIFEST_LOADED, this.onManifestLoaded, this);
hls.on(Events.SUBTITLE_TRACKS_UPDATED, this.onSubtitleTracksUpdated, this);
hls.on(Events.FRAG_LOADING, this.onFragLoading, this);
hls.on(Events.FRAG_LOADED, this.onFragLoaded, this);
hls.on(Events.FRAG_PARSING_USERDATA, this.onFragParsingUserdata, this);
hls.on(Events.FRAG_DECRYPTED, this.onFragDecrypted, this);
hls.on(Events.INIT_PTS_FOUND, this.onInitPtsFound, this);
hls.on(Events.SUBTITLE_TRACKS_CLEARED, this.onSubtitleTracksCleared, this);
hls.on(Events.BUFFER_FLUSHING, this.onBufferFlushing, this);
}
private _unregisterListeners(): void {
const { hls } = this;
hls.off(Events.MEDIA_ATTACHING, this.onMediaAttaching, this);
hls.off(Events.MEDIA_DETACHING, this.onMediaDetaching, this);
hls.off(Events.MANIFEST_LOADING, this.onManifestLoading, this);
hls.off(Events.MANIFEST_LOADED, this.onManifestLoaded, this);
hls.off(Events.SUBTITLE_TRACKS_UPDATED, this.onSubtitleTracksUpdated, this);
hls.off(Events.FRAG_LOADING, this.onFragLoading, this);
hls.off(Events.FRAG_LOADED, this.onFragLoaded, this);
hls.off(Events.FRAG_PARSING_USERDATA, this.onFragParsingUserdata, this);
hls.off(Events.FRAG_DECRYPTED, this.onFragDecrypted, this);
hls.off(Events.INIT_PTS_FOUND, this.onInitPtsFound, this);
hls.off(Events.SUBTITLE_TRACKS_CLEARED, this.onSubtitleTracksCleared, this);
hls.off(Events.BUFFER_FLUSHING, this.onBufferFlushing, this);
}
public addCues(
trackName: string,
startTime: number,
endTime: number,
screen: CaptionScreen,
cueRanges: Array<[number, number]>
) {
// skip cues which overlap more than 50% with previously parsed time ranges
let merged = false;
for (let i = cueRanges.length; i--; ) {
const cueRange = cueRanges[i];
const overlap = intersection(
cueRange[0],
cueRange[1],
startTime,
endTime
);
if (overlap >= 0) {
cueRange[0] = Math.min(cueRange[0], startTime);
cueRange[1] = Math.max(cueRange[1], endTime);
merged = true;
if (overlap / (endTime - startTime) > 0.5) {
return;
}
}
}
if (!merged) {
cueRanges.push([startTime, endTime]);
}
if (this.config.renderTextTracksNatively) {
const track = this.captionsTracks[trackName];
this.Cues.newCue(track, startTime, endTime, screen);
} else {
const cues = this.Cues.newCue(null, startTime, endTime, screen);
this.hls.trigger(Events.CUES_PARSED, {
type: 'captions',
cues,
track: trackName,
});
}
}
// Triggered when an initial PTS is found; used for synchronisation of WebVTT.
private onInitPtsFound(
event: Events.INIT_PTS_FOUND,
{ frag, id, initPTS, timescale }: InitPTSFoundData
) {
const { unparsedVttFrags } = this;
if (id === 'main') {
this.initPTS[frag.cc] = initPTS;
this.timescale[frag.cc] = timescale;
}
// Due to asynchronous processing, initial PTS may arrive later than the first VTT fragments are loaded.
// Parse any unparsed fragments upon receiving the initial PTS.
if (unparsedVttFrags.length) {
this.unparsedVttFrags = [];
unparsedVttFrags.forEach((frag) => {
this.onFragLoaded(Events.FRAG_LOADED, frag as FragLoadedData);
});
}
}
private getExistingTrack(trackName: string): TextTrack | null {
const { media } = this;
if (media) {
for (let i = 0; i < media.textTracks.length; i++) {
const textTrack = media.textTracks[i];
if (textTrack[trackName]) {
return textTrack;
}
}
}
return null;
}
public createCaptionsTrack(trackName: string) {
if (this.config.renderTextTracksNatively) {
this.createNativeTrack(trackName);
} else {
this.createNonNativeTrack(trackName);
}
}
private createNativeTrack(trackName: string) {
if (this.captionsTracks[trackName]) {
return;
}
const { captionsProperties, captionsTracks, media } = this;
const { label, languageCode } = captionsProperties[trackName];
// Enable reuse of existing text track.
const existingTrack = this.getExistingTrack(trackName);
if (!existingTrack) {
const textTrack = this.createTextTrack('captions', label, languageCode);
if (textTrack) {
// Set a special property on the track so we know it's managed by Hls.js
textTrack[trackName] = true;
captionsTracks[trackName] = textTrack;
}
} else {
captionsTracks[trackName] = existingTrack;
clearCurrentCues(captionsTracks[trackName]);
sendAddTrackEvent(captionsTracks[trackName], media as HTMLMediaElement);
}
}
private createNonNativeTrack(trackName: string) {
if (this.nonNativeCaptionsTracks[trackName]) {
return;
}
// Create a list of a single track for the provider to consume
const trackProperties: TrackProperties = this.captionsProperties[trackName];
if (!trackProperties) {
return;
}
const label = trackProperties.label as string;
const track = {
_id: trackName,
label,
kind: 'captions',
default: trackProperties.media ? !!trackProperties.media.default : false,
closedCaptions: trackProperties.media,
};
this.nonNativeCaptionsTracks[trackName] = track;
this.hls.trigger(Events.NON_NATIVE_TEXT_TRACKS_FOUND, { tracks: [track] });
}
private createTextTrack(
kind: TextTrackKind,
label: string,
lang?: string
): TextTrack | undefined {
const media = this.media;
if (!media) {
return;
}
return media.addTextTrack(kind, label, lang);
}
public destroy() {
this._unregisterListeners();
}
private onMediaAttaching(
event: Events.MEDIA_ATTACHING,
data: MediaAttachingData
) {
this.media = data.media;
this._cleanTracks();
}
private onMediaDetaching() {
const { captionsTracks } = this;
Object.keys(captionsTracks).forEach((trackName) => {
clearCurrentCues(captionsTracks[trackName]);
delete captionsTracks[trackName];
});
this.nonNativeCaptionsTracks = {};
}
private onManifestLoading() {
this.lastSn = -1; // Detect discontinuity in fragment parsing
this.prevCC = -1;
this.vttCCs = newVTTCCs(); // Detect discontinuity in subtitle manifests
this._cleanTracks();
this.tracks = [];
this.captionsTracks = {};
this.nonNativeCaptionsTracks = {};
this.textTracks = [];
this.unparsedVttFrags = this.unparsedVttFrags || [];
this.initPTS = [];
this.timescale = [];
if (this.cea608Parser1 && this.cea608Parser2) {
this.cea608Parser1.reset();
this.cea608Parser2.reset();
}
}
private _cleanTracks() {
// clear outdated subtitles
const { media } = this;
if (!media) {
return;
}
const textTracks = media.textTracks;
if (textTracks) {
for (let i = 0; i < textTracks.length; i++) {
clearCurrentCues(textTracks[i]);
}
}
}
private onSubtitleTracksUpdated(
event: Events.SUBTITLE_TRACKS_UPDATED,
data: SubtitleTracksUpdatedData
) {
this.textTracks = [];
const tracks: Array<MediaPlaylist> = data.subtitleTracks || [];
const hasIMSC1 = tracks.some((track) => track.textCodec === IMSC1_CODEC);
if (this.config.enableWebVTT || (hasIMSC1 && this.config.enableIMSC1)) {
const sameTracks =
this.tracks && tracks && this.tracks.length === tracks.length;
this.tracks = tracks || [];
if (this.config.renderTextTracksNatively) {
const inUseTracks = this.media ? this.media.textTracks : [];
this.tracks.forEach((track, index) => {
let textTrack: TextTrack | undefined;
if (index < inUseTracks.length) {
let inUseTrack: TextTrack | null = null;
for (let i = 0; i < inUseTracks.length; i++) {
if (canReuseVttTextTrack(inUseTracks[i], track)) {
inUseTrack = inUseTracks[i];
break;
}
}
// Reuse tracks with the same label, but do not reuse 608/708 tracks
if (inUseTrack) {
textTrack = inUseTrack;
}
}
if (textTrack) {
clearCurrentCues(textTrack);
} else {
textTrack = this.createTextTrack(
'subtitles',
track.name,
track.lang
);
if (textTrack) {
textTrack.mode = 'disabled';
}
}
if (textTrack) {
(textTrack as any).groupId = track.groupId;
this.textTracks.push(textTrack);
}
});
} else if (!sameTracks && this.tracks && this.tracks.length) {
// Create a list of tracks for the provider to consume
const tracksList = this.tracks.map((track) => {
return {
label: track.name,
kind: track.type.toLowerCase(),
default: track.default,
subtitleTrack: track,
};
});
this.hls.trigger(Events.NON_NATIVE_TEXT_TRACKS_FOUND, {
tracks: tracksList,
});
}
}
}
private onManifestLoaded(
event: Events.MANIFEST_LOADED,
data: ManifestLoadedData
) {
if (this.config.enableCEA708Captions && data.captions) {
data.captions.forEach((captionsTrack) => {
const instreamIdMatch = /(?:CC|SERVICE)([1-4])/.exec(
captionsTrack.instreamId as string
);
if (!instreamIdMatch) {
return;
}
const trackName = `textTrack${instreamIdMatch[1]}`;
const trackProperties: TrackProperties = this.captionsProperties[
trackName
];
if (!trackProperties) {
return;
}
trackProperties.label = captionsTrack.name;
if (captionsTrack.lang) {
// optional attribute
trackProperties.languageCode = captionsTrack.lang;
}
trackProperties.media = captionsTrack;
});
}
}
private onFragLoading(event: Events.FRAG_LOADING, data: FragLoadingData) {
const { cea608Parser1, cea608Parser2, lastSn } = this;
if (!this.enabled || !(cea608Parser1 && cea608Parser2)) {
return;
}
// if this frag isn't contiguous, clear the parser so cues with bad start/end times aren't added to the textTrack
if (data.frag.type === PlaylistLevelType.MAIN) {
const sn = data.frag.sn;
if (sn !== lastSn + 1) {
if (cea608Parser1 && cea608Parser2) {
cea608Parser1.reset();
cea608Parser2.reset();
}
}
this.lastSn = sn as number;
}
}
private onFragLoaded(event: Events.FRAG_LOADED, data: FragLoadedData) {
const { frag, payload } = data;
const { initPTS, unparsedVttFrags } = this;
if (frag.type === PlaylistLevelType.SUBTITLE) {
// If fragment is subtitle type, parse as WebVTT.
if (payload.byteLength) {
// We need an initial synchronisation PTS. Store fragments as long as none has arrived.
if (!Number.isFinite(initPTS[frag.cc])) {
unparsedVttFrags.push(data);
if (initPTS.length) {
// finish unsuccessfully, otherwise the subtitle-stream-controller could be blocked from loading new frags.
this.hls.trigger(Events.SUBTITLE_FRAG_PROCESSED, {
success: false,
frag,
error: new Error('Missing initial subtitle PTS'),
});
}
return;
}
const decryptData = frag.decryptdata;
// If the subtitles are not encrypted, parse VTTs now. Otherwise, we need to wait.
if (
decryptData == null ||
decryptData.key == null ||
decryptData.method !== 'AES-128'
) {
const trackPlaylistMedia = this.tracks[frag.level];
const vttCCs = this.vttCCs;
if (!vttCCs[frag.cc]) {
vttCCs[frag.cc] = {
start: frag.start,
prevCC: this.prevCC,
new: true,
};
this.prevCC = frag.cc;
}
if (
trackPlaylistMedia &&
trackPlaylistMedia.textCodec === IMSC1_CODEC
) {
this._parseIMSC1(frag, payload);
} else {
this._parseVTTs(frag, payload, vttCCs);
}
}
} else {
// In case there is no payload, finish unsuccessfully.
this.hls.trigger(Events.SUBTITLE_FRAG_PROCESSED, {
success: false,
frag,
error: new Error('Empty subtitle payload'),
});
}
}
}
private _parseIMSC1(frag: Fragment, payload: ArrayBuffer) {
const hls = this.hls;
parseIMSC1(
payload,
this.initPTS[frag.cc],
this.timescale[frag.cc],
(cues) => {
this._appendCues(cues, frag.level);
hls.trigger(Events.SUBTITLE_FRAG_PROCESSED, {
success: true,
frag: frag,
});
},
(error) => {
logger.log(`Failed to parse IMSC1: ${error}`);
hls.trigger(Events.SUBTITLE_FRAG_PROCESSED, {
success: false,
frag: frag,
error,
});
}
);
}
private _parseVTTs(frag: Fragment, payload: ArrayBuffer, vttCCs: any) {
const hls = this.hls;
// Parse the WebVTT file contents.
parseWebVTT(
payload,
this.initPTS[frag.cc],
this.timescale[frag.cc],
vttCCs,
frag.cc,
frag.start,
(cues) => {
this._appendCues(cues, frag.level);
hls.trigger(Events.SUBTITLE_FRAG_PROCESSED, {
success: true,
frag: frag,
});
},
(error) => {
this._fallbackToIMSC1(frag, payload);
// Something went wrong while parsing. Trigger event with success false.
logger.log(`Failed to parse VTT cue: ${error}`);
hls.trigger(Events.SUBTITLE_FRAG_PROCESSED, {
success: false,
frag: frag,
error,
});
}
);
}
private _fallbackToIMSC1(frag: Fragment, payload: ArrayBuffer) {
// If textCodec is unknown, try parsing as IMSC1. Set textCodec based on the result
const trackPlaylistMedia = this.tracks[frag.level];
if (!trackPlaylistMedia.textCodec) {
parseIMSC1(
payload,
this.initPTS[frag.cc],
this.timescale[frag.cc],
() => {
trackPlaylistMedia.textCodec = IMSC1_CODEC;
this._parseIMSC1(frag, payload);
},
() => {
trackPlaylistMedia.textCodec = 'wvtt';
}
);
}
}
private _appendCues(cues: VTTCue[], fragLevel: number) {
const hls = this.hls;
if (this.config.renderTextTracksNatively) {
const textTrack = this.textTracks[fragLevel];
// WebVTTParser.parse is an async method and if the currently selected text track mode is set to "disabled"
// before parsing is done then don't try to access currentTrack.cues.getCueById as cues will be null
// and trying to access getCueById method of cues will throw an exception
// Because we check if the mode is disabled, we can force check `cues` below. They can't be null.
if (textTrack.mode === 'disabled') {
return;
}
cues.forEach((cue) => addCueToTrack(textTrack, cue));
} else {
const currentTrack = this.tracks[fragLevel];
const track = currentTrack.default ? 'default' : 'subtitles' + fragLevel;
hls.trigger(Events.CUES_PARSED, { type: 'subtitles', cues, track });
}
}
private onFragDecrypted(
event: Events.FRAG_DECRYPTED,
data: FragDecryptedData
) {
const { frag } = data;
if (frag.type === PlaylistLevelType.SUBTITLE) {
if (!Number.isFinite(this.initPTS[frag.cc])) {
this.unparsedVttFrags.push((data as unknown) as FragLoadedData);
return;
}
this.onFragLoaded(
Events.FRAG_LOADED,
(data as unknown) as FragLoadedData
);
}
}
private onSubtitleTracksCleared() {
this.tracks = [];
this.captionsTracks = {};
}
private onFragParsingUserdata(
event: Events.FRAG_PARSING_USERDATA,
data: FragParsingUserdataData
) {
const { cea608Parser1, cea608Parser2 } = this;
if (!this.enabled || !(cea608Parser1 && cea608Parser2)) {
return;
}
// If the event contains captions (found in the bytes property), push all bytes into the parser immediately
// It will create the proper timestamps based on the PTS value
for (let i = 0; i < data.samples.length; i++) {
const ccBytes = data.samples[i].bytes;
if (ccBytes) {
const ccdatas = this.extractCea608Data(ccBytes);
cea608Parser1.addData(data.samples[i].pts, ccdatas[0]);
cea608Parser2.addData(data.samples[i].pts, ccdatas[1]);
}
}
}
onBufferFlushing(
event: Events.BUFFER_FLUSHING,
{ startOffset, endOffset, type }: BufferFlushingData
) {
// Clear 608 CC cues from the back buffer
// Forward cues are never removed because we can loose streamed 608 content from recent fragments
if (!type || type === 'video') {
const { media } = this;
if (!media || media.currentTime < endOffset) {
return;
}
const { captionsTracks } = this;
Object.keys(captionsTracks).forEach((trackName) =>
removeCuesInRange(captionsTracks[trackName], startOffset, endOffset)
);
}
}
private extractCea608Data(byteArray: Uint8Array): number[][] {
const count = byteArray[0] & 31;
let position = 2;
const actualCCBytes: number[][] = [[], []];
for (let j = 0; j < count; j++) {
const tmpByte = byteArray[position++];
const ccbyte1 = 0x7f & byteArray[position++];
const ccbyte2 = 0x7f & byteArray[position++];
const ccValid = (4 & tmpByte) !== 0;
const ccType = 3 & tmpByte;
if (ccbyte1 === 0 && ccbyte2 === 0) {
continue;
}
if (ccValid) {
if (ccType === 0 || ccType === 1) {
actualCCBytes[ccType].push(ccbyte1);
actualCCBytes[ccType].push(ccbyte2);
}
}
}
return actualCCBytes;
}
}
function canReuseVttTextTrack(inUseTrack, manifestTrack): boolean {
return (
inUseTrack &&
inUseTrack.label === manifestTrack.name &&
!(inUseTrack.textTrack1 || inUseTrack.textTrack2)
);
}
function intersection(x1: number, x2: number, y1: number, y2: number): number {
return Math.min(x2, y2) - Math.max(x1, y1);
}
function newVTTCCs(): VTTCCs {
return {
ccOffset: 0,
presentationOffset: 0,
0: {
start: 0,
prevCC: -1,
new: false,
},
};
}
