# All files / src/controller audio-stream-controller.js

5.66% Statements 25/442
3.06% Branches 10/327
22.58% Functions 7/31
5.75% Lines 25/435

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     /*
     * Audio Stream Controller
    */

    import BinarySearch from '../utils/binary-search';
    import { BufferHelper } from '../utils/buffer-helper';
    import Demuxer from '../demux/demuxer';
    import Event from '../events';
    import * as LevelHelper from './level-helper';
    import TimeRanges from '../utils/time-ranges';
    import { ErrorTypes, ErrorDetails } from '../errors';
    import { logger } from '../utils/logger';
    import { findFragWithCC } from '../utils/discontinuities';
    import TaskLoop from '../task-loop';
    import { FragmentState } from './fragment-tracker';
    import Fragment from '../loader/fragment';

    const { performance } = window;

    const State = {
      STOPPED: 'STOPPED',
      STARTING: 'STARTING',
      IDLE: 'IDLE',
      PAUSED: 'PAUSED',
      KEY_LOADING: 'KEY_LOADING',
      FRAG_LOADING: 'FRAG_LOADING',
      FRAG_LOADING_WAITING_RETRY: 'FRAG_LOADING_WAITING_RETRY',
      WAITING_TRACK: 'WAITING_TRACK',
      PARSING: 'PARSING',
      PARSED: 'PARSED',
      BUFFER_FLUSHING: 'BUFFER_FLUSHING',
      ENDED: 'ENDED',
      ERROR: 'ERROR',
      WAITING_INIT_PTS: 'WAITING_INIT_PTS'
    };

    class AudioStreamController extends TaskLoop {
      constructor (hls, fragmentTracker) {
        super(hls,
          Event.MEDIA_ATTACHED,
          Event.MEDIA_DETACHING,
          Event.AUDIO_TRACKS_UPDATED,
          Event.AUDIO_TRACK_SWITCHING,
          Event.AUDIO_TRACK_LOADED,
          Event.KEY_LOADED,
          Event.FRAG_LOADED,
          Event.FRAG_PARSING_INIT_SEGMENT,
          Event.FRAG_PARSING_DATA,
          Event.FRAG_PARSED,
          Event.ERROR,
          Event.BUFFER_RESET,
          Event.BUFFER_CREATED,
          Event.BUFFER_APPENDED,
          Event.BUFFER_FLUSHED,
          Event.INIT_PTS_FOUND);
        this.fragmentTracker = fragmentTracker;
        this.config = hls.config;
        this.audioCodecSwap = false;
        this._state = State.STOPPED;
        this.initPTS = [];
        this.waitingFragment = null;
        this.videoTrackCC = null;
      }

      onHandlerDestroying () {
        this.stopLoad();
        super.onHandlerDestroying();
      }

      onHandlerDestroyed () {
        this.state = State.STOPPED;
        this.fragmentTracker = null;
        super.onHandlerDestroyed();
      }

      // Signal that video PTS was found
      onInitPtsFound (data) {
        let demuxerId = data.id, cc = data.frag.cc, initPTS = data.initPTS;
        if (demuxerId === 'main') {
          // Always update the new INIT PTS
          // Can change due level switch
          this.initPTS[cc] = initPTS;
          this.videoTrackCC = cc;
          logger.log(`InitPTS for cc: ${cc} found from video track: ${initPTS}`);

          // If we are waiting we need to demux/remux the waiting frag
          // With the new initPTS
          if (this.state === State.WAITING_INIT_PTS) {
            this.tick();
          }
        }
      }

      startLoad (startPosition) {
        Iif (this.tracks) {
          let lastCurrentTime = this.lastCurrentTime;
          this.stopLoad();
          this.setInterval(100);
          this.fragLoadError = 0;
          if (lastCurrentTime > 0 && startPosition === -1) {
            logger.log(`audio:override startPosition with lastCurrentTime @${lastCurrentTime.toFixed(3)}`);
            this.state = State.IDLE;
          } else {
            this.lastCurrentTime = this.startPosition ? this.startPosition : startPosition;
            this.state = State.STARTING;
          }
          this.nextLoadPosition = this.startPosition = this.lastCurrentTime;
          this.tick();
        } else {
          this.startPosition = startPosition;
          this.state = State.STOPPED;
        }
      }

      stopLoad () {
        let frag = this.fragCurrent;
        if (frag) {
          if (frag.loader) {
            frag.loader.abort();
          }

          this.fragmentTracker.removeFragment(frag);
          this.fragCurrent = null;
        }
        this.fragPrevious = null;
        if (this.demuxer) {
          this.demuxer.destroy();
          this.demuxer = null;
        }
        this.state = State.STOPPED;
      }

      set state (nextState) {
        Iif (this.state !== nextState) {
          const previousState = this.state;
          this._state = nextState;
          logger.log(`audio stream:${previousState}->${nextState}`);
        }
      }

      get state () {
        return this._state;
      }

      doTick () {
        let pos, track, trackDetails, hls = this.hls, config = hls.config;
        // logger.log('audioStream:' + this.state);
        switch (this.state) {
        case State.ERROR:
          // don't do anything in error state to avoid breaking further ...
        case State.PAUSED:
          // don't do anything in paused state either ...
        case State.BUFFER_FLUSHING:
          break;
        case State.STARTING:
          this.state = State.WAITING_TRACK;
          this.loadedmetadata = false;
          break;
        case State.IDLE:
          const tracks = this.tracks;
          // audio tracks not received => exit loop
          if (!tracks) {
            break;
          }

          // if video not attached AND
          // start fragment already requested OR start frag prefetch disable
          // exit loop
          // => if media not attached but start frag prefetch is enabled and start frag not requested yet, we will not exit loop
          if (!this.media &&
              (this.startFragRequested || !config.startFragPrefetch)) {
            break;
          }

          // determine next candidate fragment to be loaded, based on current position and
          //  end of buffer position
          // if we have not yet loaded any fragment, start loading from start position
          if (this.loadedmetadata) {
            pos = this.media.currentTime;
          } else {
            pos = this.nextLoadPosition;
            if (pos === undefined) {
              break;
            }
          }
          let media = this.mediaBuffer ? this.mediaBuffer : this.media,
            videoBuffer = this.videoBuffer ? this.videoBuffer : this.media,
            bufferInfo = BufferHelper.bufferInfo(media, pos, config.maxBufferHole),
            mainBufferInfo = BufferHelper.bufferInfo(videoBuffer, pos, config.maxBufferHole),
            bufferLen = bufferInfo.len,
            bufferEnd = bufferInfo.end,
            fragPrevious = this.fragPrevious,
            // ensure we buffer at least config.maxBufferLength (default 30s) or config.maxMaxBufferLength (default: 600s)
            // whichever is smaller.
            // once we reach that threshold, don't buffer more than video (mainBufferInfo.len)
            maxConfigBuffer = Math.min(config.maxBufferLength, config.maxMaxBufferLength),
            maxBufLen = Math.max(maxConfigBuffer, mainBufferInfo.len),
            audioSwitch = this.audioSwitch,
            trackId = this.trackId;

            // if buffer length is less than maxBufLen try to load a new fragment
          if ((bufferLen < maxBufLen || audioSwitch) && trackId < tracks.length) {
            trackDetails = tracks[trackId].details;
            // if track info not retrieved yet, switch state and wait for track retrieval
            if (typeof trackDetails === 'undefined') {
              this.state = State.WAITING_TRACK;
              break;
            }

            // check if we need to finalize media stream
            // we just got done loading the final fragment and there is no other buffered range after ...
            // rationale is that in case there are any buffered ranges after, it means that there are unbuffered portion in between
            // so we should not switch to ENDED in that case, to be able to buffer them
            if (!audioSwitch && !trackDetails.live && fragPrevious && fragPrevious.sn === trackDetails.endSN && !bufferInfo.nextStart) {
              // if we are not seeking or if we are seeking but everything (almost) til the end is buffered, let's signal eos
              // we don't compare exactly media.duration === bufferInfo.end as there could be some subtle media duration difference when switching
              // between different renditions. using half frag duration should help cope with these cases.
              if (!this.media.seeking || (this.media.duration - bufferEnd) < fragPrevious.duration / 2) {
                // Finalize the media stream
                this.hls.trigger(Event.BUFFER_EOS, { type: 'audio' });
                this.state = State.ENDED;
                break;
              }
            }

            // find fragment index, contiguous with end of buffer position
            let fragments = trackDetails.fragments,
              fragLen = fragments.length,
              start = fragments[0].start,
              end = fragments[fragLen - 1].start + fragments[fragLen - 1].duration,
              frag;

              // When switching audio track, reload audio as close as possible to currentTime
            if (audioSwitch) {
              if (trackDetails.live && !trackDetails.PTSKnown) {
                logger.log('switching audiotrack, live stream, unknown PTS,load first fragment');
                bufferEnd = 0;
              } else {
                bufferEnd = pos;
                // if currentTime (pos) is less than alt audio playlist start time, it means that alt audio is ahead of currentTime
                if (trackDetails.PTSKnown && pos < start) {
                  // if everything is buffered from pos to start or if audio buffer upfront, let's seek to start
                  if (bufferInfo.end > start || bufferInfo.nextStart) {
                    logger.log('alt audio track ahead of main track, seek to start of alt audio track');
                    this.media.currentTime = start + 0.05;
                  } else {
                    return;
                  }
                }
              }
            }
            if (trackDetails.initSegment && !trackDetails.initSegment.data) {
              frag = trackDetails.initSegment;
            } // eslint-disable-line brace-style
            // if bufferEnd before start of playlist, load first fragment
            else if (bufferEnd <= start) {
              frag = fragments[0];
              if (this.videoTrackCC !== null && frag.cc !== this.videoTrackCC) {
                // Ensure we find a fragment which matches the continuity of the video track
                frag = findFragWithCC(fragments, this.videoTrackCC);
              }
              if (trackDetails.live && frag.loadIdx && frag.loadIdx === this.fragLoadIdx) {
                // we just loaded this first fragment, and we are still lagging behind the start of the live playlist
                // let's force seek to start
                const nextBuffered = bufferInfo.nextStart ? bufferInfo.nextStart : start;
                logger.log(`no alt audio available @currentTime:${this.media.currentTime}, seeking @${nextBuffered + 0.05}`);
                this.media.currentTime = nextBuffered + 0.05;
                return;
              }
            } else {
              let foundFrag;
              let maxFragLookUpTolerance = config.maxFragLookUpTolerance;
              const fragNext = fragPrevious ? fragments[fragPrevious.sn - fragments[0].sn + 1] : undefined;
              let fragmentWithinToleranceTest = (candidate) => {
                // offset should be within fragment boundary - config.maxFragLookUpTolerance
                // this is to cope with situations like
                // bufferEnd = 9.991
                // frag[Ø] : [0,10]
                // frag[1] : [10,20]
                // bufferEnd is within frag[0] range ... although what we are expecting is to return frag[1] here
                //              frag start               frag start+duration
                //                  |-----------------------------|
                //              <--->                         <--->
                //  ...--------><-----------------------------><---------....
                // previous frag         matching fragment         next frag
                //  return -1             return 0                 return 1
                // logger.log(`level/sn/start/end/bufEnd:${level}/${candidate.sn}/${candidate.start}/${(candidate.start+candidate.duration)}/${bufferEnd}`);
                // Set the lookup tolerance to be small enough to detect the current segment - ensures we don't skip over very small segments
                let candidateLookupTolerance = Math.min(maxFragLookUpTolerance, candidate.duration);
                if ((candidate.start + candidate.duration - candidateLookupTolerance) <= bufferEnd) {
                  return 1;
                } else if (candidate.start - candidateLookupTolerance > bufferEnd && candidate.start) {
                  // if maxFragLookUpTolerance will have negative value then don't return -1 for first element
                  return -1;
                }

                return 0;
              };

              if (bufferEnd < end) {
                if (bufferEnd > end - maxFragLookUpTolerance) {
                  maxFragLookUpTolerance = 0;
                }

                // Prefer the next fragment if it's within tolerance
                if (fragNext && !fragmentWithinToleranceTest(fragNext)) {
                  foundFrag = fragNext;
                } else {
                  foundFrag = BinarySearch.search(fragments, fragmentWithinToleranceTest);
                }
              } else {
                // reach end of playlist
                foundFrag = fragments[fragLen - 1];
              }
              if (foundFrag) {
                frag = foundFrag;
                start = foundFrag.start;
                // logger.log('find SN matching with pos:' +  bufferEnd + ':' + frag.sn);
                if (fragPrevious && frag.level === fragPrevious.level && frag.sn === fragPrevious.sn) {
                  if (frag.sn < trackDetails.endSN) {
                    frag = fragments[frag.sn + 1 - trackDetails.startSN];
                    logger.log(`SN just loaded, load next one: ${frag.sn}`);
                  } else {
                    frag = null;
                  }
                }
              }
            }
            if (frag) {
              // logger.log('      loading frag ' + i +',pos/bufEnd:' + pos.toFixed(3) + '/' + bufferEnd.toFixed(3));
              if (frag.encrypted) {
                logger.log(`Loading key for ${frag.sn} of [${trackDetails.startSN} ,${trackDetails.endSN}],track ${trackId}`);
                this.state = State.KEY_LOADING;
                hls.trigger(Event.KEY_LOADING, { frag: frag });
              } else {
                logger.log(`Loading ${frag.sn}, cc: ${frag.cc} of [${trackDetails.startSN} ,${trackDetails.endSN}],track ${trackId}, currentTime:${pos},bufferEnd:${bufferEnd.toFixed(3)}`);
                // only load if fragment is not loaded or if in audio switch
                // we force a frag loading in audio switch as fragment tracker might not have evicted previous frags in case of quick audio switch
                if (audioSwitch || this.fragmentTracker.getState(frag) === FragmentState.NOT_LOADED) {
                  this.fragCurrent = frag;
                  this.startFragRequested = true;
                  if (!isNaN(frag.sn)) {
                    this.nextLoadPosition = frag.start + frag.duration;
                  }

                  hls.trigger(Event.FRAG_LOADING, { frag });
                  this.state = State.FRAG_LOADING;
                }
              }
            }
          }
          break;
        case State.WAITING_TRACK:
          track = this.tracks[this.trackId];
          // check if playlist is already loaded
          if (track && track.details) {
            this.state = State.IDLE;
          }

          break;
        case State.FRAG_LOADING_WAITING_RETRY:
          var now = performance.now();
          var retryDate = this.retryDate;
          media = this.media;
          var isSeeking = media && media.seeking;
          // if current time is gt than retryDate, or if media seeking let's switch to IDLE state to retry loading
          if (!retryDate || (now >= retryDate) || isSeeking) {
            logger.log('audioStreamController: retryDate reached, switch back to IDLE state');
            this.state = State.IDLE;
          }
          break;
        case State.WAITING_INIT_PTS:
          const videoTrackCC = this.videoTrackCC;
          if (this.initPTS[videoTrackCC] === undefined) {
            break;
          }

          // Ensure we don't get stuck in the WAITING_INIT_PTS state if the waiting frag CC doesn't match any initPTS
          const waitingFrag = this.waitingFragment;
          if (waitingFrag) {
            const waitingFragCC = waitingFrag.frag.cc;
            if (videoTrackCC !== waitingFragCC) {
              track = this.tracks[this.trackId];
              if (track.details && track.details.live) {
                logger.warn(`Waiting fragment CC (${waitingFragCC}) does not match video track CC (${videoTrackCC})`);
                this.waitingFragment = null;
                this.state = State.IDLE;
              }
            } else {
              this.state = State.FRAG_LOADING;
              this.onFragLoaded(this.waitingFragment);
              this.waitingFragment = null;
            }
          } else {
            this.state = State.IDLE;
          }

          break;
        case State.STOPPED:
        case State.FRAG_LOADING:
        case State.PARSING:
        case State.PARSED:
        case State.ENDED:
          break;
        default:
          break;
        }
      }

      onMediaAttached (data) {
        let media = this.media = this.mediaBuffer = data.media;
        this.onvseeking = this.onMediaSeeking.bind(this);
        this.onvended = this.onMediaEnded.bind(this);
        media.addEventListener('seeking', this.onvseeking);
        media.addEventListener('ended', this.onvended);
        let config = this.config;
        if (this.tracks && config.autoStartLoad) {
          this.startLoad(config.startPosition);
        }
      }

      onMediaDetaching () {
        let media = this.media;
        if (media && media.ended) {
          logger.log('MSE detaching and video ended, reset startPosition');
          this.startPosition = this.lastCurrentTime = 0;
        }

        // remove video listeners
        if (media) {
          media.removeEventListener('seeking', this.onvseeking);
          media.removeEventListener('ended', this.onvended);
          this.onvseeking = this.onvseeked = this.onvended = null;
        }
        this.media = this.mediaBuffer = this.videoBuffer = null;
        this.loadedmetadata = false;
        this.stopLoad();
      }

      onMediaSeeking () {
        if (this.state === State.ENDED) {
          // switch to IDLE state to check for potential new fragment
          this.state = State.IDLE;
        }
        if (this.media) {
          this.lastCurrentTime = this.media.currentTime;
        }

        // tick to speed up processing
        this.tick();
      }

      onMediaEnded () {
        // reset startPosition and lastCurrentTime to restart playback @ stream beginning
        this.startPosition = this.lastCurrentTime = 0;
      }

      onAudioTracksUpdated (data) {
        logger.log('audio tracks updated');
        this.tracks = data.audioTracks;
      }

      onAudioTrackSwitching (data) {
        // if any URL found on new audio track, it is an alternate audio track
        let altAudio = !!data.url;
        this.trackId = data.id;

        this.fragCurrent = null;
        this.state = State.PAUSED;
        this.waitingFragment = null;
        // destroy useless demuxer when switching audio to main
        if (!altAudio) {
          if (this.demuxer) {
            this.demuxer.destroy();
            this.demuxer = null;
          }
        } else {
          // switching to audio track, start timer if not already started
          this.setInterval(100);
        }

        // should we switch tracks ?
        if (altAudio) {
          this.audioSwitch = true;
          // main audio track are handled by stream-controller, just do something if switching to alt audio track
          this.state = State.IDLE;
        }
        this.tick();
      }

      onAudioTrackLoaded (data) {
        let newDetails = data.details,
          trackId = data.id,
          track = this.tracks[trackId],
          duration = newDetails.totalduration,
          sliding = 0;

        logger.log(`track ${trackId} loaded [${newDetails.startSN},${newDetails.endSN}],duration:${duration}`);

        if (newDetails.live) {
          let curDetails = track.details;
          if (curDetails && newDetails.fragments.length > 0) {
            // we already have details for that level, merge them
            LevelHelper.mergeDetails(curDetails, newDetails);
            sliding = newDetails.fragments[0].start;
            // TODO
            // this.liveSyncPosition = this.computeLivePosition(sliding, curDetails);
            if (newDetails.PTSKnown) {
              logger.log(`live audio playlist sliding:${sliding.toFixed(3)}`);
            } else {
              logger.log('live audio playlist - outdated PTS, unknown sliding');
            }
          } else {
            newDetails.PTSKnown = false;
            logger.log('live audio playlist - first load, unknown sliding');
          }
        } else {
          newDetails.PTSKnown = false;
        }
        track.details = newDetails;

        // compute start position
        if (!this.startFragRequested) {
        // compute start position if set to -1. use it straight away if value is defined
          if (this.startPosition === -1) {
            // first, check if start time offset has been set in playlist, if yes, use this value
            let startTimeOffset = newDetails.startTimeOffset;
            if (!isNaN(startTimeOffset)) {
              logger.log(`start time offset found in playlist, adjust startPosition to ${startTimeOffset}`);
              this.startPosition = startTimeOffset;
            } else {
              this.startPosition = 0;
            }
          }
          this.nextLoadPosition = this.startPosition;
        }
        // only switch batck to IDLE state if we were waiting for track to start downloading a new fragment
        if (this.state === State.WAITING_TRACK) {
          this.state = State.IDLE;
        }

        // trigger handler right now
        this.tick();
      }

      onKeyLoaded () {
        if (this.state === State.KEY_LOADING) {
          this.state = State.IDLE;
          this.tick();
        }
      }

      onFragLoaded (data) {
        let fragCurrent = this.fragCurrent,
          fragLoaded = data.frag;
        Iif (this.state === State.FRAG_LOADING &&
            fragCurrent &&
            fragLoaded.type === 'audio' &&
            fragLoaded.level === fragCurrent.level &&
            fragLoaded.sn === fragCurrent.sn) {
          let track = this.tracks[this.trackId],
            details = track.details,
            duration = details.totalduration,
            trackId = fragCurrent.level,
            sn = fragCurrent.sn,
            cc = fragCurrent.cc,
            audioCodec = this.config.defaultAudioCodec || track.audioCodec || 'mp4a.40.2',
            stats = this.stats = data.stats;
          if (sn === 'initSegment') {
            this.state = State.IDLE;

            stats.tparsed = stats.tbuffered = performance.now();
            details.initSegment.data = data.payload;
            this.hls.trigger(Event.FRAG_BUFFERED, { stats: stats, frag: fragCurrent, id: 'audio' });
            this.tick();
          } else {
            this.state = State.PARSING;
            // transmux the MPEG-TS data to ISO-BMFF segments
            this.appended = false;
            if (!this.demuxer) {
              this.demuxer = new Demuxer(this.hls, 'audio');
            }

            // Check if we have video initPTS
            // If not we need to wait for it
            let initPTS = this.initPTS[cc];
            let initSegmentData = details.initSegment ? details.initSegment.data : [];
            if (details.initSegment || initPTS !== undefined) {
              this.pendingBuffering = true;
              logger.log(`Demuxing ${sn} of [${details.startSN} ,${details.endSN}],track ${trackId}`);
              // time Offset is accurate if level PTS is known, or if playlist is not sliding (not live)
              let accurateTimeOffset = false; // details.PTSKnown || !details.live;
              this.demuxer.push(data.payload, initSegmentData, audioCodec, null, fragCurrent, duration, accurateTimeOffset, initPTS);
            } else {
              logger.log(`unknown video PTS for continuity counter ${cc}, waiting for video PTS before demuxing audio frag ${sn} of [${details.startSN} ,${details.endSN}],track ${trackId}`);
              this.waitingFragment = data;
              this.state = State.WAITING_INIT_PTS;
            }
          }
        }
        this.fragLoadError = 0;
      }

      onFragParsingInitSegment (data) {
        const fragCurrent = this.fragCurrent;
        const fragNew = data.frag;
        if (fragCurrent &&
            data.id === 'audio' &&
            fragNew.sn === fragCurrent.sn &&
            fragNew.level === fragCurrent.level &&
            this.state === State.PARSING) {
          let tracks = data.tracks, track;

          // delete any video track found on audio demuxer
          if (tracks.video) {
            delete tracks.video;
          }

          // include levelCodec in audio and video tracks
          track = tracks.audio;
          if (track) {
            track.levelCodec = track.codec;
            track.id = data.id;
            this.hls.trigger(Event.BUFFER_CODECS, tracks);
            logger.log(`audio track:audio,container:${track.container},codecs[level/parsed]=[${track.levelCodec}/${track.codec}]`);
            let initSegment = track.initSegment;
            if (initSegment) {
              let appendObj = { type: 'audio', data: initSegment, parent: 'audio', content: 'initSegment' };
              if (this.audioSwitch) {
                this.pendingData = [appendObj];
              } else {
                this.appended = true;
                // arm pending Buffering flag before appending a segment
                this.pendingBuffering = true;
                this.hls.trigger(Event.BUFFER_APPENDING, appendObj);
              }
            }
            // trigger handler right now
            this.tick();
          }
        }
      }

      onFragParsingData (data) {
        const fragCurrent = this.fragCurrent;
        const fragNew = data.frag;
        if (fragCurrent &&
            data.id === 'audio' &&
            data.type === 'audio' &&
            fragNew.sn === fragCurrent.sn &&
            fragNew.level === fragCurrent.level &&
            this.state === State.PARSING) {
          let trackId = this.trackId,
            track = this.tracks[trackId],
            hls = this.hls;

          if (isNaN(data.endPTS)) {
            data.endPTS = data.startPTS + fragCurrent.duration;
            data.endDTS = data.startDTS + fragCurrent.duration;
          }

          fragCurrent.addElementaryStream(Fragment.ElementaryStreamTypes.AUDIO);

          logger.log(`parsed ${data.type},PTS:[${data.startPTS.toFixed(3)},${data.endPTS.toFixed(3)}],DTS:[${data.startDTS.toFixed(3)}/${data.endDTS.toFixed(3)}],nb:${data.nb}`);
          LevelHelper.updateFragPTSDTS(track.details, fragCurrent, data.startPTS, data.endPTS);

          let audioSwitch = this.audioSwitch, media = this.media, appendOnBufferFlush = false;
          // Only flush audio from old audio tracks when PTS is known on new audio track
          if (audioSwitch && media) {
            if (media.readyState) {
              let currentTime = media.currentTime;
              logger.log('switching audio track : currentTime:' + currentTime);
              if (currentTime >= data.startPTS) {
                logger.log('switching audio track : flushing all audio');
                this.state = State.BUFFER_FLUSHING;
                hls.trigger(Event.BUFFER_FLUSHING, { startOffset: 0, endOffset: Number.POSITIVE_INFINITY, type: 'audio' });
                appendOnBufferFlush = true;
                // Lets announce that the initial audio track switch flush occur
                this.audioSwitch = false;
                hls.trigger(Event.AUDIO_TRACK_SWITCHED, { id: trackId });
              }
            } else {
              // Lets announce that the initial audio track switch flush occur
              this.audioSwitch = false;
              hls.trigger(Event.AUDIO_TRACK_SWITCHED, { id: trackId });
            }
          }

          let pendingData = this.pendingData;

          if (!pendingData) {
            console.warn('Apparently attempt to enqueue media payload without codec initialization data upfront');
            hls.trigger(Event.ERROR, { type: ErrorTypes.MEDIA_ERROR, details: null, fatal: true });
            return;
          }

          if (!this.audioSwitch) {
            [data.data1, data.data2].forEach(buffer => {
              if (buffer && buffer.length) {
                pendingData.push({ type: data.type, data: buffer, parent: 'audio', content: 'data' });
              }
            });
            if (!appendOnBufferFlush && pendingData.length) {
              pendingData.forEach(appendObj => {
                // only append in PARSING state (rationale is that an appending error could happen synchronously on first segment appending)
                // in that case it is useless to append following segments
                if (this.state === State.PARSING) {
                  // arm pending Buffering flag before appending a segment
                  this.pendingBuffering = true;
                  this.hls.trigger(Event.BUFFER_APPENDING, appendObj);
                }
              });
              this.pendingData = [];
              this.appended = true;
            }
          }
          // trigger handler right now
          this.tick();
        }
      }

      onFragParsed (data) {
        const fragCurrent = this.fragCurrent;
        const fragNew = data.frag;
        if (fragCurrent &&
            data.id === 'audio' &&
            fragNew.sn === fragCurrent.sn &&
            fragNew.level === fragCurrent.level &&
            this.state === State.PARSING) {
          this.stats.tparsed = performance.now();
          this.state = State.PARSED;
          this._checkAppendedParsed();
        }
      }

      onBufferReset () {
        // reset reference to sourcebuffers
        this.mediaBuffer = this.videoBuffer = null;
        this.loadedmetadata = false;
      }

      onBufferCreated (data) {
        let audioTrack = data.tracks.audio;
        if (audioTrack) {
          this.mediaBuffer = audioTrack.buffer;
          this.loadedmetadata = true;
        }
        if (data.tracks.video) {
          this.videoBuffer = data.tracks.video.buffer;
        }
      }

      onBufferAppended (data) {
        Iif (data.parent === 'audio') {
          const state = this.state;
          if (state === State.PARSING || state === State.PARSED) {
            // check if all buffers have been appended
            this.pendingBuffering = (data.pending > 0);
            this._checkAppendedParsed();
          }
        }
      }

      _checkAppendedParsed () {
        // trigger handler right now
        if (this.state === State.PARSED && (!this.appended || !this.pendingBuffering)) {
          let frag = this.fragCurrent, stats = this.stats, hls = this.hls;
          if (frag) {
            this.fragPrevious = frag;
            stats.tbuffered = performance.now();
            hls.trigger(Event.FRAG_BUFFERED, { stats: stats, frag: frag, id: 'audio' });
            let media = this.mediaBuffer ? this.mediaBuffer : this.media;
            logger.log(`audio buffered : ${TimeRanges.toString(media.buffered)}`);
            if (this.audioSwitch && this.appended) {
              this.audioSwitch = false;
              hls.trigger(Event.AUDIO_TRACK_SWITCHED, { id: this.trackId });
            }
            this.state = State.IDLE;
          }
          this.tick();
        }
      }

      onError (data) {
        let frag = data.frag;
        // don't handle frag error not related to audio fragment
        if (frag && frag.type !== 'audio') {
          return;
        }

        switch (data.details) {
        case ErrorDetails.FRAG_LOAD_ERROR:
        case ErrorDetails.FRAG_LOAD_TIMEOUT:
          if (!data.fatal) {
            let loadError = this.fragLoadError;
            if (loadError) {
              loadError++;
            } else {
              loadError = 1;
            }

            let config = this.config;
            if (loadError <= config.fragLoadingMaxRetry) {
              this.fragLoadError = loadError;
              // exponential backoff capped to config.fragLoadingMaxRetryTimeout
              let delay = Math.min(Math.pow(2, loadError - 1) * config.fragLoadingRetryDelay, config.fragLoadingMaxRetryTimeout);
              logger.warn(`audioStreamController: frag loading failed, retry in ${delay} ms`);
              this.retryDate = performance.now() + delay;
              // retry loading state
              this.state = State.FRAG_LOADING_WAITING_RETRY;
            } else {
              logger.error(`audioStreamController: ${data.details} reaches max retry, redispatch as fatal ...`);
              // switch error to fatal
              data.fatal = true;
              this.state = State.ERROR;
            }
          }
          break;
        case ErrorDetails.AUDIO_TRACK_LOAD_ERROR:
        case ErrorDetails.AUDIO_TRACK_LOAD_TIMEOUT:
        case ErrorDetails.KEY_LOAD_ERROR:
        case ErrorDetails.KEY_LOAD_TIMEOUT:
          //  when in ERROR state, don't switch back to IDLE state in case a non-fatal error is received
          if (this.state !== State.ERROR) {
            // if fatal error, stop processing, otherwise move to IDLE to retry loading
            this.state = data.fatal ? State.ERROR : State.IDLE;
            logger.warn(`audioStreamController: ${data.details} while loading frag,switch to ${this.state} state ...`);
          }
          break;
        case ErrorDetails.BUFFER_FULL_ERROR:
          // if in appending state
          if (data.parent === 'audio' && (this.state === State.PARSING || this.state === State.PARSED)) {
            const media = this.mediaBuffer,
              currentTime = this.media.currentTime,
              mediaBuffered = media && BufferHelper.isBuffered(media, currentTime) && BufferHelper.isBuffered(media, currentTime + 0.5);
              // reduce max buf len if current position is buffered
            if (mediaBuffered) {
              const config = this.config;
              if (config.maxMaxBufferLength >= config.maxBufferLength) {
                // reduce max buffer length as it might be too high. we do this to avoid loop flushing ...
                config.maxMaxBufferLength /= 2;
                logger.warn(`audio:reduce max buffer length to ${config.maxMaxBufferLength}s`);
              }
              this.state = State.IDLE;
            } else {
              // current position is not buffered, but browser is still complaining about buffer full error
              // this happens on IE/Edge, refer to https://github.com/video-dev/hls.js/pull/708
              // in that case flush the whole audio buffer to recover
              logger.warn('buffer full error also media.currentTime is not buffered, flush audio buffer');
              this.fragCurrent = null;
              // flush everything
              this.state = State.BUFFER_FLUSHING;
              this.hls.trigger(Event.BUFFER_FLUSHING, { startOffset: 0, endOffset: Number.POSITIVE_INFINITY, type: 'audio' });
            }
          }
          break;
        default:
          break;
        }
      }

      onBufferFlushed () {
        let pendingData = this.pendingData;
        if (pendingData && pendingData.length) {
          logger.log('appending pending audio data on Buffer Flushed');
          pendingData.forEach(appendObj => {
            this.hls.trigger(Event.BUFFER_APPENDING, appendObj);
          });
          this.appended = true;
          this.pendingData = [];
          this.state = State.PARSED;
        } else {
          // move to IDLE once flush complete. this should trigger new fragment loading
          this.state = State.IDLE;
          // reset reference to frag
          this.fragPrevious = null;
          this.tick();
        }
      }
    }
    export default AudioStreamController;