/
fragment.ts
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/
fragment.ts
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import { buildAbsoluteURL } from 'url-toolkit';
import { logger } from '../utils/logger';
import LevelKey from './level-key';
export enum ElementaryStreamTypes {
AUDIO = 'audio',
VIDEO = 'video',
}
export default class Fragment {
private _url: string | null = null;
private _byteRange: number[] | null = null;
private _decryptdata: LevelKey | null = null;
// Holds the types of data this fragment supports
private _elementaryStreams: Record<ElementaryStreamTypes, boolean> = {
[ElementaryStreamTypes.AUDIO]: false,
[ElementaryStreamTypes.VIDEO]: false
};
public rawProgramDateTime: string | null = null;
public programDateTime: number | null = null;
public tagList: Array<string[]> = [];
// TODO: Move at least baseurl to constructor.
// Currently we do a two-pass construction as use the Fragment class almost like a object for holding parsing state.
// It may make more sense to just use a POJO to keep state during the parsing phase.
// Have Fragment be the representation once we have a known state?
// Something to think on.
// relurl is the portion of the URL that comes from inside the playlist.
public relurl!: string;
// baseurl is the URL to the playlist
public baseurl!: string;
// EXTINF has to be present for a m3u8 to be considered valid
public duration!: number;
// sn notates the sequence number for a segment, and if set to a string can be 'initSegment'
public sn: number | 'initSegment' = 0;
// levelkey is the EXT-X-KEY that applies to this segment for decryption
// core difference from the private field _decryptdata is the lack of the initialized IV
// _decryptdata will set the IV for this segment based on the segment number in the fragment
public levelkey?: LevelKey;
// setByteRange converts a EXT-X-BYTERANGE attribute into a two element array
setByteRange (value: string, previousFrag?: Fragment) {
const params = value.split('@', 2);
const byteRange: number[] = [];
if (params.length === 1) {
byteRange[0] = previousFrag ? previousFrag.byteRangeEndOffset : 0;
} else {
byteRange[0] = parseInt(params[1]);
}
byteRange[1] = parseInt(params[0]) + byteRange[0];
this._byteRange = byteRange;
}
get url () {
if (!this._url && this.relurl) {
this._url = buildAbsoluteURL(this.baseurl, this.relurl, { alwaysNormalize: true });
}
return this._url;
}
set url (value) {
this._url = value;
}
get byteRange (): number[] {
if (!this._byteRange) {
return [];
}
return this._byteRange;
}
/**
* @type {number}
*/
get byteRangeStartOffset () {
return this.byteRange[0];
}
get byteRangeEndOffset () {
return this.byteRange[1];
}
get decryptdata (): LevelKey | null {
if (!this.levelkey && !this._decryptdata) {
return null;
}
if (!this._decryptdata && this.levelkey) {
// TODO look for this warning for 'initSegment' sn getting used in decryption IV
if (typeof this.sn !== 'number') {
logger.warn(`undefined behaviour for sn="${this.sn}" in IV generation`);
}
this._decryptdata = this.fragmentDecryptdataFromLevelkey(this.levelkey, this.sn as number);
}
return this._decryptdata;
}
get endProgramDateTime () {
if (this.programDateTime === null) {
return null;
}
if (!Number.isFinite(this.programDateTime)) {
return null;
}
let duration = !Number.isFinite(this.duration) ? 0 : this.duration;
return this.programDateTime + (duration * 1000);
}
get encrypted () {
return !!((this.decryptdata && this.decryptdata.uri !== null) && (this.decryptdata.key === null));
}
/**
* @param {ElementaryStreamTypes} type
*/
addElementaryStream (type: ElementaryStreamTypes) {
this._elementaryStreams[type] = true;
}
/**
* @param {ElementaryStreamTypes} type
*/
hasElementaryStream (type: ElementaryStreamTypes) {
return this._elementaryStreams[type] === true;
}
/**
* Utility method for parseLevelPlaylist to create an initialization vector for a given segment
* @returns {Uint8Array}
*/
createInitializationVector (segmentNumber: number): Uint8Array {
let uint8View = new Uint8Array(16);
for (let i = 12; i < 16; i++) {
uint8View[i] = (segmentNumber >> 8 * (15 - i)) & 0xff;
}
return uint8View;
}
/**
* Utility method for parseLevelPlaylist to get a fragment's decryption data from the currently parsed encryption key data
* @param levelkey - a playlist's encryption info
* @param segmentNumber - the fragment's segment number
* @returns {*} - an object to be applied as a fragment's decryptdata
*/
fragmentDecryptdataFromLevelkey (levelkey: LevelKey, segmentNumber: number): LevelKey {
let decryptdata = levelkey;
if (levelkey && levelkey.method && levelkey.uri && !levelkey.iv) {
decryptdata = new LevelKey(levelkey.baseuri, levelkey.reluri);
decryptdata.method = levelkey.method;
decryptdata.iv = this.createInitializationVector(segmentNumber);
}
return decryptdata;
}
}