@tianfeng98/hls.js/src/controller/audio-track-controller.ts

HLS.js is a JavaScript library that supports playing MPEG-TS and HEVC encoded HLS streams in browsers with support for MSE.

import BasePlaylistController from './base-playlist-controller';
import { Events } from '../events';
import { ErrorTypes, ErrorDetails } from '../errors';
import { PlaylistContextType } from '../types/loader';
import { mediaAttributesIdentical } from '../utils/media-option-attributes';
import type Hls from '../hls';
import type { MediaPlaylist } from '../types/media-playlist';
import type { HlsUrlParameters } from '../types/level';
import type {
  ManifestParsedData,
  AudioTracksUpdatedData,
  ErrorData,
  LevelLoadingData,
  AudioTrackLoadedData,
  LevelSwitchingData,
} from '../types/events';

class AudioTrackController extends BasePlaylistController {
  private tracks: MediaPlaylist[] = [];
  private groupIds: (string | undefined)[] | null = null;
  private tracksInGroup: MediaPlaylist[] = [];
  private trackId: number = -1;
  private currentTrack: MediaPlaylist | null = null;
  private selectDefaultTrack: boolean = true;

  constructor(hls: Hls) {
    super(hls, '[audio-track-controller]');
    this.registerListeners();
  }

  private registerListeners() {
    const { hls } = this;
    hls.on(Events.MANIFEST_LOADING, this.onManifestLoading, this);
    hls.on(Events.MANIFEST_PARSED, this.onManifestParsed, this);
    hls.on(Events.LEVEL_LOADING, this.onLevelLoading, this);
    hls.on(Events.LEVEL_SWITCHING, this.onLevelSwitching, this);
    hls.on(Events.AUDIO_TRACK_LOADED, this.onAudioTrackLoaded, this);
    hls.on(Events.ERROR, this.onError, this);
  }

  private unregisterListeners() {
    const { hls } = this;
    hls.off(Events.MANIFEST_LOADING, this.onManifestLoading, this);
    hls.off(Events.MANIFEST_PARSED, this.onManifestParsed, this);
    hls.off(Events.LEVEL_LOADING, this.onLevelLoading, this);
    hls.off(Events.LEVEL_SWITCHING, this.onLevelSwitching, this);
    hls.off(Events.AUDIO_TRACK_LOADED, this.onAudioTrackLoaded, this);
    hls.off(Events.ERROR, this.onError, this);
  }

  public destroy() {
    this.unregisterListeners();
    this.tracks.length = 0;
    this.tracksInGroup.length = 0;
    this.currentTrack = null;
    super.destroy();
  }

  protected onManifestLoading(): void {
    this.tracks = [];
    this.tracksInGroup = [];
    this.groupIds = null;
    this.currentTrack = null;
    this.trackId = -1;
    this.selectDefaultTrack = true;
  }

  protected onManifestParsed(
    event: Events.MANIFEST_PARSED,
    data: ManifestParsedData,
  ): void {
    this.tracks = data.audioTracks || [];
  }

  protected onAudioTrackLoaded(
    event: Events.AUDIO_TRACK_LOADED,
    data: AudioTrackLoadedData,
  ): void {
    const { id, groupId, details } = data;
    const trackInActiveGroup = this.tracksInGroup[id];

    if (!trackInActiveGroup || trackInActiveGroup.groupId !== groupId) {
      this.warn(
        `Audio track with id:${id} and group:${groupId} not found in active group ${trackInActiveGroup?.groupId}`,
      );
      return;
    }

    const curDetails = trackInActiveGroup.details;
    trackInActiveGroup.details = data.details;
    this.log(
      `Audio track ${id} "${trackInActiveGroup.name}" lang:${trackInActiveGroup.lang} group:${groupId} loaded [${details.startSN}-${details.endSN}]`,
    );

    if (id === this.trackId) {
      this.playlistLoaded(id, data, curDetails);
    }
  }

  protected onLevelLoading(
    event: Events.LEVEL_LOADING,
    data: LevelLoadingData,
  ): void {
    this.switchLevel(data.level);
  }

  protected onLevelSwitching(
    event: Events.LEVEL_SWITCHING,
    data: LevelSwitchingData,
  ): void {
    this.switchLevel(data.level);
  }

  private switchLevel(levelIndex: number) {
    const levelInfo = this.hls.levels[levelIndex];
    if (!levelInfo) {
      return;
    }
    const audioGroups = levelInfo.audioGroups || null;
    const currentGroups = this.groupIds;
    const currentTrack = this.currentTrack;
    if (
      !audioGroups ||
      currentGroups?.length !== audioGroups?.length ||
      audioGroups?.some((groupId) => currentGroups?.indexOf(groupId) === -1)
    ) {
      this.groupIds = audioGroups;
      this.trackId = -1;
      this.currentTrack = null;

      const audioTracks = this.tracks.filter(
        (track): boolean =>
          !audioGroups || audioGroups.indexOf(track.groupId) !== -1,
      );
      if (audioTracks.length) {
        // Disable selectDefaultTrack if there are no default tracks
        if (
          this.selectDefaultTrack &&
          !audioTracks.some((track) => track.default)
        ) {
          this.selectDefaultTrack = false;
        }
        // track.id should match hls.audioTracks index
        audioTracks.forEach((track, i) => {
          track.id = i;
        });
      } else if (!currentTrack && !this.tracksInGroup.length) {
        // Do not dispatch AUDIO_TRACKS_UPDATED when there were and are no tracks
        return;
      }

      this.tracksInGroup = audioTracks;
      let trackId = this.findTrackId(currentTrack);
      if (trackId === -1 && currentTrack) {
        trackId = this.findTrackId(null);
      }

      const audioTracksUpdated: AudioTracksUpdatedData = { audioTracks };
      this.log(
        `Updating audio tracks, ${
          audioTracks.length
        } track(s) found in group(s): ${audioGroups?.join(',')}`,
      );
      this.hls.trigger(Events.AUDIO_TRACKS_UPDATED, audioTracksUpdated);

      const selectedTrackId = this.trackId;
      if (trackId !== -1 && selectedTrackId === -1) {
        this.setAudioTrack(trackId);
      } else if (audioTracks.length && selectedTrackId === -1) {
        const error = new Error(
          `No audio track selected for current audio group-ID(s): ${this.groupIds?.join(
            ',',
          )} track count: ${audioTracks.length}`,
        );
        this.warn(error.message);

        this.hls.trigger(Events.ERROR, {
          type: ErrorTypes.MEDIA_ERROR,
          details: ErrorDetails.AUDIO_TRACK_LOAD_ERROR,
          fatal: true,
          error,
        });
      }
    } else if (this.shouldReloadPlaylist(currentTrack)) {
      // Retry playlist loading if no playlist is or has been loaded yet
      this.setAudioTrack(this.trackId);
    }
  }

  protected onError(event: Events.ERROR, data: ErrorData): void {
    if (data.fatal || !data.context) {
      return;
    }

    if (
      data.context.type === PlaylistContextType.AUDIO_TRACK &&
      data.context.id === this.trackId &&
      (!this.groupIds || this.groupIds.indexOf(data.context.groupId) !== -1)
    ) {
      this.requestScheduled = -1;
      this.checkRetry(data);
    }
  }

  get allAudioTracks(): MediaPlaylist[] {
    return this.tracks;
  }

  get audioTracks(): MediaPlaylist[] {
    return this.tracksInGroup;
  }

  get audioTrack(): number {
    return this.trackId;
  }

  set audioTrack(newId: number) {
    // If audio track is selected from API then don't choose from the manifest default track
    this.selectDefaultTrack = false;
    this.setAudioTrack(newId);
  }

  private setAudioTrack(newId: number): void {
    const tracks = this.tracksInGroup;

    // check if level idx is valid
    if (newId < 0 || newId >= tracks.length) {
      this.warn(`Invalid audio track id: ${newId}`);
      return;
    }

    // stopping live reloading timer if any
    this.clearTimer();

    this.selectDefaultTrack = false;
    const lastTrack = this.currentTrack;
    const track = tracks[newId];
    const trackLoaded = track.details && !track.details.live;
    if (newId === this.trackId && track === lastTrack && trackLoaded) {
      return;
    }
    this.log(
      `Switching to audio-track ${newId} "${track.name}" lang:${track.lang} group:${track.groupId}`,
    );
    this.trackId = newId;
    this.currentTrack = track;
    this.hls.trigger(Events.AUDIO_TRACK_SWITCHING, { ...track });
    // Do not reload track unless live
    if (trackLoaded) {
      return;
    }
    const hlsUrlParameters = this.switchParams(track.url, lastTrack?.details);
    this.loadPlaylist(hlsUrlParameters);
  }

  private findTrackId(currentTrack: MediaPlaylist | null): number {
    const audioTracks = this.tracksInGroup;
    for (let i = 0; i < audioTracks.length; i++) {
      const track = audioTracks[i];
      if (this.selectDefaultTrack && !track.default) {
        continue;
      }
      if (
        !currentTrack ||
        mediaAttributesIdentical(currentTrack.attrs, track.attrs)
      ) {
        return track.id;
      }
      if (
        mediaAttributesIdentical(currentTrack.attrs, track.attrs, [
          'LANGUAGE',
          'ASSOC-LANGUAGE',
          'CHARACTERISTICS',
        ])
      ) {
        return track.id;
      }
      if (
        mediaAttributesIdentical(currentTrack.attrs, track.attrs, ['LANGUAGE'])
      ) {
        return track.id;
      }
    }
    return -1;
  }

  protected loadPlaylist(hlsUrlParameters?: HlsUrlParameters): void {
    const audioTrack = this.currentTrack;
    if (this.shouldLoadPlaylist(audioTrack) && audioTrack) {
      super.loadPlaylist();
      const id = audioTrack.id;
      const groupId = audioTrack.groupId as string;
      let url = audioTrack.url;
      if (hlsUrlParameters) {
        try {
          url = hlsUrlParameters.addDirectives(url);
        } catch (error) {
          this.warn(
            `Could not construct new URL with HLS Delivery Directives: ${error}`,
          );
        }
      }
      // track not retrieved yet, or live playlist we need to (re)load it
      this.log(
        `loading audio-track playlist ${id} "${audioTrack.name}" lang:${audioTrack.lang} group:${groupId}`,
      );
      this.clearTimer();
      this.hls.trigger(Events.AUDIO_TRACK_LOADING, {
        url,
        id,
        groupId,
        deliveryDirectives: hlsUrlParameters || null,
      });
    }
  }
}

export default AudioTrackController;