src/loader/fragment.ts

import { buildAbsoluteURL } from 'url-toolkit';
import { LevelKey } from './level-key';
import { LoadStats } from './load-stats';
import { AttrList } from '../utils/attr-list';
import type {
  FragmentLoaderContext,
  KeyLoaderContext,
  Loader,
  PlaylistLevelType,
} from '../types/loader';
import type { KeySystemFormats } from '../utils/mediakeys-helper';
 
export enum ElementaryStreamTypes {
  AUDIO = 'audio',
  VIDEO = 'video',
  AUDIOVIDEO = 'audiovideo',
}
 
export interface ElementaryStreamInfo {
  startPTS: number;
  endPTS: number;
  startDTS: number;
  endDTS: number;
  partial?: boolean;
}
 
export type ElementaryStreams = Record<
  ElementaryStreamTypes,
  ElementaryStreamInfo | null
>;
 
export class BaseSegment {
  private _byteRange: number[] | null = null;
  private _url: string | null = null;
 
  // baseurl is the URL to the playlist
  public readonly baseurl: string;
  // relurl is the portion of the URL that comes from inside the playlist.
  public relurl?: string;
  // Holds the types of data this fragment supports
  public elementaryStreams: ElementaryStreams = {
    [ElementaryStreamTypes.AUDIO]: null,
    [ElementaryStreamTypes.VIDEO]: null,
    [ElementaryStreamTypes.AUDIOVIDEO]: null,
  };
 
  constructor(baseurl: string) {
    this.baseurl = baseurl;
  }
 
  // setByteRange converts a EXT-X-BYTERANGE attribute into a two element array
  setByteRange(value: string, previous?: BaseSegment) {
    const params = value.split('@', 2);
    const byteRange: number[] = [];
    if (params.length === 1) {
      byteRange[0] = previous ? previous.byteRangeEndOffset : 0;
    } else {
      byteRange[0] = parseInt(params[1]);
    }
    byteRange[1] = parseInt(params[0]) + byteRange[0];
    this._byteRange = byteRange;
  }
 
  get byteRange(): number[] {
    if (!this._byteRange) {
      return [];
    }
 
    return this._byteRange;
  }
 
  get byteRangeStartOffset(): number {
    return this.byteRange[0];
  }
 
  get byteRangeEndOffset(): number {
    return this.byteRange[1];
  }
 
  get url(): string {
    if (!this._url && this.baseurl && this.relurl) {
      this._url = buildAbsoluteURL(this.baseurl, this.relurl, {
        alwaysNormalize: true,
      });
    }
    return this._url || '';
  }
 
  set url(value: string) {
    this._url = value;
  }
}
 
export class Fragment extends BaseSegment {
  private _decryptdata: LevelKey | null = null;
 
  public rawProgramDateTime: string | null = null;
  public programDateTime: number | null = null;
  public tagList: Array<string[]> = [];
 
  // EXTINF has to be present for a m3u8 to be considered valid
  public duration: number = 0;
  // sn notates the sequence number for a segment, and if set to a string can be 'initSegment'
  public sn: number | 'initSegment' = 0;
  // levelkeys are the EXT-X-KEY tags that apply 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 levelkeys?: { [key: string]: LevelKey };
  // A string representing the fragment type
  public readonly type: PlaylistLevelType;
  // A reference to the loader. Set while the fragment is loading, and removed afterwards. Used to abort fragment loading
  public loader: Loader<FragmentLoaderContext> | null = null;
  // A reference to the key loader. Set while the key is loading, and removed afterwards. Used to abort key loading
  public keyLoader: Loader<KeyLoaderContext> | null = null;
  // The level/track index to which the fragment belongs
  public level: number = -1;
  // The continuity counter of the fragment
  public cc: number = 0;
  // The starting Presentation Time Stamp (PTS) of the fragment. Set after transmux complete.
  public startPTS?: number;
  // The ending Presentation Time Stamp (PTS) of the fragment. Set after transmux complete.
  public endPTS?: number;
  // The latest Presentation Time Stamp (PTS) appended to the buffer.
  public appendedPTS?: number;
  // The starting Decode Time Stamp (DTS) of the fragment. Set after transmux complete.
  public startDTS!: number;
  // The ending Decode Time Stamp (DTS) of the fragment. Set after transmux complete.
  public endDTS!: number;
  // The start time of the fragment, as listed in the manifest. Updated after transmux complete.
  public start: number = 0;
  // Set by `updateFragPTSDTS` in level-helper
  public deltaPTS?: number;
  // The maximum starting Presentation Time Stamp (audio/video PTS) of the fragment. Set after transmux complete.
  public maxStartPTS?: number;
  // The minimum ending Presentation Time Stamp (audio/video PTS) of the fragment. Set after transmux complete.
  public minEndPTS?: number;
  // Load/parse timing information
  public stats: LoadStats = new LoadStats();
  public urlId: number = 0;
  public data?: Uint8Array;
  // A flag indicating whether the segment was downloaded in order to test bitrate, and was not buffered
  public bitrateTest: boolean = false;
  // #EXTINF  segment title
  public title: string | null = null;
  // The Media Initialization Section for this segment
  public initSegment: Fragment | null = null;
  // Fragment is the last fragment in the media playlist
  public endList?: boolean;
 
  constructor(type: PlaylistLevelType, baseurl: string) {
    super(baseurl);
    this.type = type;
  }
 
  get decryptdata(): LevelKey | null {
    const { levelkeys } = this;
    if (!levelkeys && !this._decryptdata) {
      return null;
    }
 
    if (!this._decryptdata && this.levelkeys && !this.levelkeys.NONE) {
      const key = this.levelkeys.identity;
      if (key) {
        this._decryptdata = key.getDecryptData(this.sn);
      } else {
        const keyFormats = Object.keys(this.levelkeys);
        if (keyFormats.length === 1) {
          return (this._decryptdata = this.levelkeys[
            keyFormats[0]
          ].getDecryptData(this.sn));
        } else {
          // Multiple keys. key-loader to call Fragment.setKeyFormat based on selected key-system.
        }
      }
    }
 
    return this._decryptdata;
  }
 
  get end(): number {
    return this.start + this.duration;
  }
 
  get endProgramDateTime() {
    if (this.programDateTime === null) {
      return null;
    }
 
    if (!Number.isFinite(this.programDateTime)) {
      return null;
    }
 
    const duration = !Number.isFinite(this.duration) ? 0 : this.duration;
 
    return this.programDateTime + duration * 1000;
  }
 
  get encrypted() {
    // At the m3u8-parser level we need to add support for manifest signalled keyformats
    // when we want the fragment to start reporting that it is encrypted.
    // Currently, keyFormat will only be set for identity keys
    if (this._decryptdata?.encrypted) {
      return true;
    } else if (this.levelkeys) {
      const keyFormats = Object.keys(this.levelkeys);
      const len = keyFormats.length;
      if (len > 1 || (len === 1 && this.levelkeys[keyFormats[0]].encrypted)) {
        return true;
      }
    }
 
    return false;
  }
 
  setKeyFormat(keyFormat: KeySystemFormats) {
    if (this.levelkeys) {
      const key = this.levelkeys[keyFormat];
      if (key && !this._decryptdata) {
        this._decryptdata = key.getDecryptData(this.sn);
      }
    }
  }
 
  abortRequests(): void {
    this.loader?.abort();
    this.keyLoader?.abort();
  }
 
  setElementaryStreamInfo(
    type: ElementaryStreamTypes,
    startPTS: number,
    endPTS: number,
    startDTS: number,
    endDTS: number,
    partial: boolean = false
  ) {
    const { elementaryStreams } = this;
    const info = elementaryStreams[type];
    if (!info) {
      elementaryStreams[type] = {
        startPTS,
        endPTS,
        startDTS,
        endDTS,
        partial,
      };
      return;
    }
 
    info.startPTS = Math.min(info.startPTS, startPTS);
    info.endPTS = Math.max(info.endPTS, endPTS);
    info.startDTS = Math.min(info.startDTS, startDTS);
    info.endDTS = Math.max(info.endDTS, endDTS);
  }
 
  clearElementaryStreamInfo() {
    const { elementaryStreams } = this;
    elementaryStreams[ElementaryStreamTypes.AUDIO] = null;
    elementaryStreams[ElementaryStreamTypes.VIDEO] = null;
    elementaryStreams[ElementaryStreamTypes.AUDIOVIDEO] = null;
  }
}
 
export class Part extends BaseSegment {
  public readonly fragOffset: number = 0;
  public readonly duration: number = 0;
  public readonly gap: boolean = false;
  public readonly independent: boolean = false;
  public readonly relurl: string;
  public readonly fragment: Fragment;
  public readonly index: number;
  public stats: LoadStats = new LoadStats();
 
  constructor(
    partAttrs: AttrList,
    frag: Fragment,
    baseurl: string,
    index: number,
    previous?: Part
  ) {
    super(baseurl);
    this.duration = partAttrs.decimalFloatingPoint('DURATION');
    this.gap = partAttrs.bool('GAP');
    this.independent = partAttrs.bool('INDEPENDENT');
    this.relurl = partAttrs.enumeratedString('URI') as string;
    this.fragment = frag;
    this.index = index;
    const byteRange = partAttrs.enumeratedString('BYTERANGE');
    if (byteRange) {
      this.setByteRange(byteRange, previous);
    }
    if (previous) {
      this.fragOffset = previous.fragOffset + previous.duration;
    }
  }
 
  get start(): number {
    return this.fragment.start + this.fragOffset;
  }
 
  get end(): number {
    return this.start + this.duration;
  }
 
  get loaded(): boolean {
    const { elementaryStreams } = this;
    return !!(
      elementaryStreams.audio ||
      elementaryStreams.video ||
      elementaryStreams.audiovideo
    );
  }
}