tsdemuxer.js

/**
 * A stream-based mp2ts to mp4 converter. This utility is used to
 * deliver mp4s to a SourceBuffer on platforms that support native
 * Media Source Extensions.
 */

 import Event           from '../events';
 import ExpGolomb       from './exp-golomb';
// import Hex             from '../utils/hex';
 import MP4             from '../remux/mp4-generator';
 import observer        from '../observer';
 import {logger}        from '../utils/logger';
 import {ErrorTypes,ErrorDetails} from '../errors';

 class TSDemuxer {

  constructor() {
    this.lastCC = 0;
  }

  switchLevel() {
    this.pmtParsed = false;
    this._pmtId = this._avcId = this._aacId = -1;
    this._avcTrack = {type : 'video', sequenceNumber : 0};
    this._aacTrack = {type : 'audio', sequenceNumber : 0};
    this._avcSamples = [];
    this._avcSamplesLength = 0;
    this._avcSamplesNbNalu = 0;
    this._aacSamples = [];
    this._aacSamplesLength = 0;
    this._initSegGenerated = false;
  }

  insertDiscontinuity() {
    this.switchLevel();
    this._initPTS = this._initDTS = undefined;
  }

  // feed incoming data to the front of the parsing pipeline
  push(data,audioCodec, videoCodec,timeOffset,cc,level,duration) {
    var avcData,aacData,start,len = data.length,stt,pid,atf,offset;
    this.audioCodec = audioCodec;
    this.videoCodec = videoCodec;
    this.timeOffset = timeOffset;
    this._duration = duration;
    if(cc !== this.lastCC) {
      logger.log(`discontinuity detected`);
      this.insertDiscontinuity();
      this.lastCC = cc;
    } else if(level !== this.lastLevel) {
      logger.log(`level switch detected`);
      this.switchLevel();
      this.lastLevel = level;
    }
    var pmtParsed=this.pmtParsed,avcId=this._avcId,aacId=this._aacId;

    // loop through TS packets
    for(start = 0; start < len ; start += 188) {
      if(data[start] === 0x47) {
        stt = !!(data[start+1] & 0x40);
        // pid is a 13-bit field starting at the last bit of TS[1]
        pid = ((data[start+1] & 0x1f) << 8) + data[start+2];
        atf = (data[start+3] & 0x30) >> 4;
        // if an adaption field is present, its length is specified by the fifth byte of the TS packet header.
        if(atf > 1) {
          offset = start+5+data[start+4];
          // continue if there is only adaptation field
          if(offset === (start+188)) {
            continue;
          }
        } else {
          offset = start+4;
        }
        if(pmtParsed) {
          if(pid === avcId) {
            if(stt) {
              if(avcData) {
                this._parseAVCPES(this._parsePES(avcData));
              }
              avcData = {data: [],size: 0};
            }
            avcData.data.push(data.subarray(offset,start+188));
            avcData.size+=start+188-offset;
          } else if(pid === aacId) {
            if(stt) {
              if(aacData) {
                this._parseAACPES(this._parsePES(aacData));
              }
              aacData = {data: [],size: 0};
            }
            aacData.data.push(data.subarray(offset,start+188));
            aacData.size+=start+188-offset;
          }
        } else {
          if(stt) {
            offset += data[offset] + 1;
          }
          if(pid === 0) {
            this._parsePAT(data,offset);
          } else if(pid === this._pmtId) {
            this._parsePMT(data,offset);
            pmtParsed = this.pmtParsed = true;
            avcId = this._avcId;
            aacId = this._aacId;
          }
        }
      } else {
        observer.trigger(Event.ERROR, { type : ErrorTypes.MEDIA_ERROR, details : ErrorDetails.FRAG_PARSING_ERROR, fatal:false, reason : 'TS packet did not start with 0x47'});
      }
    }
  // parse last PES packet
    if(avcData) {
      this._parseAVCPES(this._parsePES(avcData));
    }
    if(aacData) {
      this._parseAACPES(this._parsePES(aacData));
    }
  }

  end() {
    //logger.log('nb AVC samples:' + this._avcSamples.length);
    if(this._avcSamples.length) {
      this._flushAVCSamples();
    }
    //logger.log('nb AAC samples:' + this._aacSamples.length);
    if(this._aacSamples.length) {
      this._flushAACSamples();
    }
    //notify end of parsing
    observer.trigger(Event.FRAG_PARSED);
  }

  destroy() {
    this.switchLevel();
    this._initPTS = this._initDTS = undefined;
    this._duration = 0;
  }

  _parsePAT(data,offset) {
    // skip the PSI header and parse the first PMT entry
    this._pmtId  = (data[offset+10] & 0x1F) << 8 | data[offset+11];
    //logger.log('PMT PID:'  + this._pmtId);
  }

  _parsePMT(data,offset) {
    var sectionLength,tableEnd,programInfoLength,pid;
    sectionLength = (data[offset+1] & 0x0f) << 8 | data[offset+2];
    tableEnd = offset + 3 + sectionLength - 4;
    // to determine where the table is, we have to figure out how
    // long the program info descriptors are
    programInfoLength = (data[offset+10] & 0x0f) << 8 | data[offset+11];

    // advance the offset to the first entry in the mapping table
    offset += 12 + programInfoLength;
    while (offset < tableEnd) {
      pid = (data[offset + 1] & 0x1F) << 8 | data[offset + 2];
      switch(data[offset]) {
        // ISO/IEC 13818-7 ADTS AAC (MPEG-2 lower bit-rate audio)
        case 0x0f:
        //logger.log('AAC PID:'  + pid);
          this._aacId = pid;
          this._aacTrack.id = pid;
        break;
        // ITU-T Rec. H.264 and ISO/IEC 14496-10 (lower bit-rate video)
        case 0x1b:
        //logger.log('AVC PID:'  + pid);
        this._avcId = pid;
        this._avcTrack.id = pid;
        break;
        default:
        logger.log('unkown stream type:'  + data[offset]);
        break;
      }
      // move to the next table entry
      // skip past the elementary stream descriptors, if present
      offset += ((data[offset + 3] & 0x0F) << 8 | data[offset + 4]) + 5;
    }
  }

  _parsePES(stream) {
    var i = 0,frag,pesFlags,pesPrefix,pesLen,pesHdrLen,pesData,pesPts,pesDts,payloadStartOffset;
    //retrieve PTS/DTS from first fragment
    frag = stream.data[0];
    pesPrefix = (frag[0] << 16) + (frag[1] << 8) + frag[2];
    if(pesPrefix === 1) {
      pesLen = (frag[4] << 8) + frag[5];
      pesFlags = frag[7];
      if (pesFlags & 0xC0) {
        /* PES header described here : http://dvd.sourceforge.net/dvdinfo/pes-hdr.html
            as PTS / DTS is 33 bit we cannot use bitwise operator in JS,
            as Bitwise operators treat their operands as a sequence of 32 bits */
        pesPts = (frag[9] & 0x0E)*536870912 // 1 << 29
          + (frag[10] & 0xFF)*4194304 // 1 << 22
          + (frag[11] & 0xFE)*16384 // 1 << 14
          + (frag[12] & 0xFF)*128 // 1 << 7
          + (frag[13] & 0xFE)/2;
          // check if greater than 2^32 -1
          if (pesPts > 4294967295) {
              // decrement 2^33
              pesPts -= 8589934592;
          }
        if (pesFlags & 0x40) {
          pesDts = (frag[14] & 0x0E )*536870912 // 1 << 29
            + (frag[15] & 0xFF )*4194304 // 1 << 22
            + (frag[16] & 0xFE )*16384 // 1 << 14
            + (frag[17] & 0xFF )*128 // 1 << 7
            + (frag[18] & 0xFE )/2;
          // check if greater than 2^32 -1
          if (pesDts > 4294967295) {
              // decrement 2^33
              pesDts -= 8589934592;
          }
        } else {
          pesDts = pesPts;
        }
      }
      pesHdrLen = frag[8];
      payloadStartOffset = pesHdrLen+9;
      // trim PES header
      stream.data[0] = stream.data[0].subarray(payloadStartOffset);
      stream.size -= payloadStartOffset;
      //reassemble PES packet
      pesData = new Uint8Array(stream.size);
      // reassemble the packet
      while (stream.data.length) {
        frag = stream.data.shift();
        pesData.set(frag, i);
        i += frag.byteLength;
      }
      return { data : pesData, pts : pesPts, dts : pesDts, len : pesLen};
    } else {
      return null;
    }
  }

  _parseAVCPES(pes) {
    var units,track = this._avcTrack,avcSample,key = false;
    units = this._parseAVCNALu(pes.data);
    //free pes.data to save up some memory
    pes.data = null;
    units.units.forEach(unit => {
      switch(unit.type) {
        //IDR
        case 5:
          key = true;
          break;
        //SPS
        case 7:
          if(!track.sps) {
            var expGolombDecoder = new ExpGolomb(unit.data);
            var config = expGolombDecoder.readSequenceParameterSet();
            track.width = config.width;
            track.height = config.height;
            track.profileIdc = config.profileIdc;
            track.profileCompatibility = config.profileCompatibility;
            track.levelIdc = config.levelIdc;
            track.sps = [unit.data];
            track.duration = 90000*this._duration;
            var codecarray = unit.data.subarray(1,4);
            var codecstring  = 'avc1.';
            for(var i = 0; i < 3; i++) {
                var h = codecarray[i].toString(16);
                if (h.length < 2) {
                    h = '0' + h;
                }
                codecstring += h;
            }
            track.codec = codecstring;
          }
          break;
        //PPS
        case 8:
          if(!track.pps) {
            track.pps = [unit.data];
          }
          break;
        default:
          break;
      }
    });
    //build sample from PES
    // Annex B to MP4 conversion to be done
    avcSample = { units : units, pts : pes.pts, dts : pes.dts , key : key};
    this._avcSamples.push(avcSample);
    this._avcSamplesLength += units.length;
    this._avcSamplesNbNalu += units.units.length;
    // generate Init Segment if needed
    if(!this._initSegGenerated) {
      this._generateInitSegment();
    }
  }


  _flushAVCSamples() {
    var view,i=8,avcSample,mp4Sample,mp4SampleLength,unit,track = this._avcTrack,
        lastSampleDTS,mdat,moof,firstPTS,firstDTS,pts,dts,ptsnorm,dtsnorm,samples = [];

    /* concatenate the video data and construct the mdat in place
      (need 8 more bytes to fill length and mpdat type) */
    mdat = new Uint8Array(this._avcSamplesLength + (4 * this._avcSamplesNbNalu)+8);
    view = new DataView(mdat.buffer);
    view.setUint32(0,mdat.byteLength);
    mdat.set(MP4.types.mdat,4);
    while(this._avcSamples.length) {
      avcSample = this._avcSamples.shift();
      mp4SampleLength = 0;

      // convert NALU bitstream to MP4 format (prepend NALU with size field)
      while(avcSample.units.units.length) {
        unit = avcSample.units.units.shift();
        view.setUint32(i, unit.data.byteLength);
        i += 4;
        mdat.set(unit.data, i);
        i += unit.data.byteLength;
        mp4SampleLength+=4+unit.data.byteLength;
      }
      pts = avcSample.pts - this._initDTS;
      dts = avcSample.dts - this._initDTS;
      //logger.log('Video/PTS/DTS:' + avcSample.pts + '/' + avcSample.dts);

      if(lastSampleDTS !== undefined) {
        ptsnorm = this._PTSNormalize(pts,lastSampleDTS);
        dtsnorm = this._PTSNormalize(dts,lastSampleDTS);

        mp4Sample.duration = dtsnorm - lastSampleDTS;
        if(mp4Sample.duration < 0) {
          //logger.log('invalid sample duration at PTS/DTS::' + avcSample.pts + '/' + avcSample.dts + ':' + mp4Sample.duration);
          mp4Sample.duration = 0;
        }
      } else {
        ptsnorm = this._PTSNormalize(pts,this.nextAvcPts);
        dtsnorm = this._PTSNormalize(dts,this.nextAvcPts);
        // check if fragments are contiguous (i.e. no missing frames between fragment)
        if(this.nextAvcPts) {
          var delta = Math.round((ptsnorm - this.nextAvcPts)/90),absdelta=Math.abs(delta);
          //logger.log('absdelta/avcSample.pts:' + absdelta + '/' + avcSample.pts);
          // if delta is less than 300 ms, next loaded fragment is assumed to be contiguous with last one
          if(absdelta < 300) {
            //logger.log('Video next PTS:' + this.nextAvcPts);
            if(delta > 1) {
              logger.log(`AVC:${delta} ms hole between fragments detected,filling it`);
            } else if (delta < -1) {
              logger.log(`AVC:${(-delta)} ms overlapping between fragments detected`);
            }
            // set PTS to next PTS
            ptsnorm = this.nextAvcPts;
            // offset DTS as well, ensure that DTS is smaller or equal than new PTS
            dtsnorm = Math.max(dtsnorm-delta, this.lastAvcDts);
           // logger.log('Video/PTS/DTS adjusted:' + avcSample.pts + '/' + avcSample.dts);
          }
        }
        // remember first PTS of our avcSamples, ensure value is positive
        firstPTS = Math.max(0,ptsnorm);
        firstDTS = Math.max(0,dtsnorm);
      }
      console.log(`PTS/DTS/initDTS/normPTS/normDTS/relative PTS : ${avcSample.pts}/${avcSample.dts}/${this._initDTS}/${ptsnorm}/${dtsnorm}/${(avcSample.pts/4294967296).toFixed(3)}`);

      mp4Sample = {
        size: mp4SampleLength,
        duration : 0,
        cts: ptsnorm - dtsnorm,
        flags: {
          isLeading: 0,
          isDependedOn: 0,
          hasRedundancy: 0,
          degradPrio: 0
        }
      };

      if(avcSample.key === true) {
        // the current sample is a key frame
        mp4Sample.flags.dependsOn = 2;
        mp4Sample.flags.isNonSync = 0;
      } else {
        mp4Sample.flags.dependsOn = 1;
        mp4Sample.flags.isNonSync = 1;
      }
      samples.push(mp4Sample);
      lastSampleDTS = dtsnorm;
    }
    if(samples.length >=2) {
      mp4Sample.duration = samples[samples.length-2].duration;
    }
    this.lastAvcDts = dtsnorm;
    // next AVC sample PTS should be equal to last sample PTS + duration
    this.nextAvcPts = ptsnorm + mp4Sample.duration;
    //logger.log('Video/lastAvcDts/nextAvcPts:' + this.lastAvcDts + '/' + this.nextAvcPts);

    this._avcSamplesLength = 0;
    this._avcSamplesNbNalu = 0;

    track.samples = samples;
    moof = MP4.moof(track.sequenceNumber++,firstDTS,track);
    track.samples = [];
    observer.trigger(Event.FRAG_PARSING_DATA,{
      moof: moof,
      mdat: mdat,
      startPTS : firstPTS/90000,
      endPTS : this.nextAvcPts/90000,
      startDTS : firstDTS/90000,
      endDTS : (dtsnorm + mp4Sample.duration)/90000,
      type : 'video',
      nb : samples.length
    });
  }

  _parseAVCNALu(array) {
    var i = 0,len = array.byteLength,value,overflow,state = 0;
    var units = [], unit, unitType, lastUnitStart,lastUnitType,length = 0;
    //logger.log('PES:' + Hex.hexDump(array));

    while(i< len) {
      value = array[i++];
      // finding 3 or 4-byte start codes (00 00 01 OR 00 00 00 01)
      switch(state) {
        case 0:
          if(value === 0) {
            state = 1;
          }
          break;
        case 1:
          if(value === 0) {
            state = 2;
          } else {
            state = 0;
          }
          break;
        case 2:
        case 3:
          if(value === 0) {
            state = 3;
          } else if(value === 1) {
            unitType = array[i] & 0x1f;
            //logger.log('find NALU @ offset:' + i + ',type:' + unitType);
            if(lastUnitStart) {
              unit = { data : array.subarray(lastUnitStart,i-state-1), type : lastUnitType};
              length+=i-state-1-lastUnitStart;
              //logger.log('pushing NALU, type/size:' + unit.type + '/' + unit.data.byteLength);
              units.push(unit);
            } else {
              // If NAL units are not starting right at the beginning of the PES packet, push preceding data into previous NAL unit.
              overflow  = i - state - 1;
              if (overflow) {
                  //logger.log('first NALU found with overflow:' + overflow);
                  if(this._avcSamples.length) {
                    var lastavcSample = this._avcSamples[this._avcSamples.length-1];
                    var lastUnit = lastavcSample.units.units[lastavcSample.units.units.length-1];
                    var tmp = new Uint8Array(lastUnit.data.byteLength+overflow);
                    tmp.set(lastUnit.data,0);
                    tmp.set(array.subarray(0,overflow),lastUnit.data.byteLength);
                    lastUnit.data = tmp;
                    lastavcSample.units.length+=overflow;
                    this._avcSamplesLength+=overflow;
                  }
              }
            }
            lastUnitStart = i;
            lastUnitType = unitType;
            if(unitType === 1 || unitType === 5) {
              // OPTI !!! if IDR/NDR unit, consider it is last NALu
              i = len;
            }
            state = 0;
          } else {
            state = 0;
          }
          break;
        default:
          break;
      }
    }
    if(lastUnitStart) {
      unit = { data : array.subarray(lastUnitStart,len), type : lastUnitType};
      length+=len-lastUnitStart;
      units.push(unit);
      //logger.log('pushing NALU, type/size:' + unit.type + '/' + unit.data.byteLength);
    }
    return { units : units , length : length};
  }

  _PTSNormalize(value,reference) {
    var offset;
    if (reference < value) {
        // - 2^33
        offset = -8589934592;
    } else {
        // + 2^33
        offset = 8589934592;
    }
    /* PTS is 33bit (from 0 to 2^33 -1)
      if diff between value and reference is bigger than half of the amplitude (2^32) then it means that
      PTS looping occured. fill the gap */
    while (Math.abs(value - reference) > 4294967296) {
        value += offset;
    }
    return value;
  }

  _parseAACPES(pes) {
    var track = this._aacTrack,aacSample,data = pes.data,config,adtsFrameSize,adtsStartOffset,adtsHeaderLen,stamp,nbSamples,len;
    if(this.aacOverFlow) {
      var tmp = new Uint8Array(this.aacOverFlow.byteLength+data.byteLength);
      tmp.set(this.aacOverFlow,0);
      tmp.set(data,this.aacOverFlow.byteLength);
      data = tmp;
    }
    // look for ADTS header (0xFFFx)
    for(adtsStartOffset = 0, len = data.length; adtsStartOffset<len-1; adtsStartOffset++) {
      if((data[adtsStartOffset] === 0xff) && (data[adtsStartOffset+1] & 0xf0) === 0xf0) {
        break;
      }
    }
    // if ADTS header does not start straight from the beginning of the PES payload, raise an error
    if(adtsStartOffset) {
      var reason,fatal;
      if(adtsStartOffset < len - 1) {
        reason = `AAC PES did not start with ADTS header,offset:${adtsStartOffset}`;
        fatal = false;
      } else {
        reason = `no ADTS header found in AAC PES`;
        fatal = true;
      }
      observer.trigger(Event.ERROR, { type : ErrorTypes.MEDIA_ERROR, details : ErrorDetails.FRAG_PARSING_ERROR, fatal:fatal, reason : reason});
      if(fatal) {
        return;
      }
    }

    if(!track.audiosamplerate) {
      config = this._ADTStoAudioConfig(data,adtsStartOffset,this.audioCodec);
      track.config = config.config;
      track.audiosamplerate = config.samplerate;
      track.channelCount = config.channelCount;
      track.codec = config.codec;
      track.duration = 90000*this._duration;
      console.log(`parsed   codec:${track.codec},rate:${config.samplerate},nb channel:${config.channelCount}`);
    }
    nbSamples = 0;
    while((adtsStartOffset + 5) < len) {
      // retrieve frame size
      adtsFrameSize = ((data[adtsStartOffset+3] & 0x03) << 11);
      // byte 4
      adtsFrameSize |= (data[adtsStartOffset+4] << 3);
      // byte 5
      adtsFrameSize |= ((data[adtsStartOffset+5] & 0xE0) >>> 5);
      adtsHeaderLen = (!!(data[adtsStartOffset+1] & 0x01) ? 7 : 9);
      adtsFrameSize -= adtsHeaderLen;
      stamp = Math.round(pes.pts + nbSamples*1024*90000/track.audiosamplerate);
      //stamp = pes.pts;
      //console.log('AAC frame, offset/length/pts:' + (adtsStartOffset+7) + '/' + adtsFrameSize + '/' + stamp.toFixed(0));
      if(adtsStartOffset+adtsHeaderLen+adtsFrameSize <= len) {
        aacSample = { unit : data.subarray(adtsStartOffset+adtsHeaderLen,adtsStartOffset+adtsHeaderLen+adtsFrameSize) , pts : stamp, dts : stamp};
        this._aacSamples.push(aacSample);
        this._aacSamplesLength += adtsFrameSize;
        adtsStartOffset+=adtsFrameSize+adtsHeaderLen;
        nbSamples++;
      } else {
        break;
      }
    }

    if(!this._initSegGenerated) {
      this._generateInitSegment();
    }
    if(adtsStartOffset < len) {
      this.aacOverFlow = data.subarray(adtsStartOffset,len);
    } else {
      this.aacOverFlow = null;
    }
  }

  _flushAACSamples() {
    var view,i=8,aacSample,mp4Sample,unit,track = this._aacTrack,
        lastSampleDTS,mdat,moof,firstPTS,firstDTS,pts,dts,ptsnorm,dtsnorm,samples = [];

    /* concatenate the audio data and construct the mdat in place
      (need 8 more bytes to fill length and mpdat type) */
    mdat = new Uint8Array(this._aacSamplesLength+8);
    view = new DataView(mdat.buffer);
    view.setUint32(0,mdat.byteLength);
    mdat.set(MP4.types.mdat,4);
    while(this._aacSamples.length) {
      aacSample = this._aacSamples.shift();
      unit = aacSample.unit;
      mdat.set(unit, i);
      i += unit.byteLength;

      pts = aacSample.pts - this._initDTS;
      dts = aacSample.dts - this._initDTS;

      //logger.log('Audio/PTS:' + aacSample.pts.toFixed(0));
      if(lastSampleDTS !== undefined) {
        ptsnorm = this._PTSNormalize(pts,lastSampleDTS);
        dtsnorm = this._PTSNormalize(dts,lastSampleDTS);
        // we use DTS to compute sample duration, but we use PTS to compute initPTS which is used to sync audio and video
        mp4Sample.duration = dtsnorm - lastSampleDTS;
        if(mp4Sample.duration < 0) {
          //logger.log('invalid sample duration at PTS/DTS::' + avcSample.pts + '/' + avcSample.dts + ':' + mp4Sample.duration);
          mp4Sample.duration = 0;
        }
      } else {
        ptsnorm = this._PTSNormalize(pts,this.nextAacPts);
        dtsnorm = this._PTSNormalize(dts,this.nextAacPts);
        // check if fragments are contiguous (i.e. no missing frames between fragment)
        if(this.nextAacPts && this.nextAacPts !== ptsnorm) {
          //logger.log('Audio next PTS:' + this.nextAacPts);
          var delta = Math.round((ptsnorm - this.nextAacPts)/90);
          // if delta is less than 300 ms, next loaded fragment is assumed to be contiguous with last one
          if(Math.abs(delta) > 1 && Math.abs(delta) < 300) {
            if(delta > 0) {
              logger.log(`AAC:${delta} ms hole between fragments detected,filling it`);
              // set PTS to next PTS, and ensure PTS is greater or equal than last DTS
              ptsnorm = Math.max(this.nextAacPts, this.lastAacDts);
              dtsnorm = ptsnorm;
              //logger.log('Audio/PTS/DTS adjusted:' + aacSample.pts + '/' + aacSample.dts);
            } else {
              logger.log(`AAC:${(-delta)} ms overlapping between fragments detected`);
            }
          }
        }
        // remember first PTS of our aacSamples, ensure value is positive
        firstPTS = Math.max(0,ptsnorm);
        firstDTS = Math.max(0,dtsnorm);
      }
      console.log(`PTS/DTS/initDTS/normPTS/normDTS/relative PTS : ${aacSample.pts}/${aacSample.dts}/${this._initDTS}/${ptsnorm}/${dtsnorm}/${(aacSample.pts/4294967296).toFixed(3)}`);
      mp4Sample = {
        size: unit.byteLength,
        cts: 0,
        duration:0,
        flags: {
          isLeading: 0,
          isDependedOn: 0,
          hasRedundancy: 0,
          degradPrio: 0,
          dependsOn : 1,
        }
      };
      samples.push(mp4Sample);
      lastSampleDTS = dtsnorm;
    }
    //set last sample duration as being identical to previous sample
    if(samples.length >=2) {
      mp4Sample.duration = samples[samples.length-2].duration;
    }
    this.lastAacDts = dtsnorm;
    // next aac sample PTS should be equal to last sample PTS + duration
    this.nextAacPts = ptsnorm + mp4Sample.duration;
    //logger.log('Audio/PTS/PTSend:' + aacSample.pts.toFixed(0) + '/' + this.nextAacDts.toFixed(0));

    this._aacSamplesLength = 0;
    track.samples = samples;
    moof = MP4.moof(track.sequenceNumber++,firstDTS,track);
    track.samples = [];
    observer.trigger(Event.FRAG_PARSING_DATA,{
      moof: moof,
      mdat: mdat,
      startPTS : firstPTS/90000,
      endPTS : this.nextAacPts/90000,
      startDTS : firstDTS/90000,
      endDTS : (dtsnorm + mp4Sample.duration)/90000,
      type : 'audio',
      nb : samples.length
    });
  }

  _ADTStoAudioConfig(data,offset,audioCodec) {
    var adtsObjectType, // :int
        adtsSampleingIndex, // :int
        adtsExtensionSampleingIndex, // :int
        adtsChanelConfig, // :int
        config,
        userAgent = navigator.userAgent.toLowerCase(),
        adtsSampleingRates = [
            96000, 88200,
            64000, 48000,
            44100, 32000,
            24000, 22050,
            16000, 12000
          ];

    // byte 2
    adtsObjectType = ((data[offset+2] & 0xC0) >>> 6) + 1;
    adtsSampleingIndex = ((data[offset+2] & 0x3C) >>> 2);
    adtsChanelConfig = ((data[offset+2] & 0x01) << 2);
    // byte 3
    adtsChanelConfig |= ((data[offset+3] & 0xC0) >>> 6);

    console.log(`manifest codec:${audioCodec},ADTS data:type:${adtsObjectType},sampleingIndex:${adtsSampleingIndex}[${adtsSampleingRates[adtsSampleingIndex]}kHz],channelConfig:${adtsChanelConfig}`);


    // firefox: freq less than 24kHz = AAC SBR (HE-AAC)
    if(userAgent.indexOf('firefox') !== -1) {
      if(adtsSampleingIndex >=6) {
        adtsObjectType = 5;
        config = new Array(4);
        // HE-AAC uses SBR (Spectral Band Replication) , high frequencies are constructed from low frequencies
        // there is a factor 2 between frame sample rate and output sample rate
        // multiply frequency by 2 (see table below, equivalent to substract 3)
        adtsExtensionSampleingIndex = adtsSampleingIndex-3;
      } else {
        adtsObjectType = 2;
        config = new Array(2);
        adtsExtensionSampleingIndex = adtsSampleingIndex;
      }
      // Android : always use AAC
    } else if(userAgent.indexOf('android') !== -1) {
      adtsObjectType = 2;
      config = new Array(2);
      adtsExtensionSampleingIndex = adtsSampleingIndex;
    } else {
      /*  for other browsers (chrome ...)
          always force audio type to be HE-AAC SBR, as some browsers do not support audio codec switch properly (like Chrome ...)
      */
        adtsObjectType = 5;
        config = new Array(4);
       // if (manifest codec is HE-AAC) OR (manifest codec not specified AND frequency less than 24kHz)
      if((audioCodec && audioCodec.indexOf('mp4a.40.5') !==-1) || (!audioCodec && adtsSampleingIndex >=6))  {
        // HE-AAC uses SBR (Spectral Band Replication) , high frequencies are constructed from low frequencies
        // there is a factor 2 between frame sample rate and output sample rate
        // multiply frequency by 2 (see table below, equivalent to substract 3)
        adtsExtensionSampleingIndex = adtsSampleingIndex - 3;
      } else {
      // if (manifest codec is AAC) AND (frequency less than 24kHz OR nb channel is 1)
        if(audioCodec && audioCodec.indexOf('mp4a.40.2') !==-1 && (adtsSampleingIndex >= 6 || adtsChanelConfig ===1)) {
          adtsObjectType = 2;
          config = new Array(2);
        }
        adtsExtensionSampleingIndex = adtsSampleingIndex;
      }
    }
  /* refer to http://wiki.multimedia.cx/index.php?title=MPEG-4_Audio#Audio_Specific_Config
      ISO 14496-3 (AAC).pdf - Table 1.13 — Syntax of AudioSpecificConfig()
    Audio Profile / Audio Object Type
    0: Null
    1: AAC Main
    2: AAC LC (Low Complexity)
    3: AAC SSR (Scalable Sample Rate)
    4: AAC LTP (Long Term Prediction)
    5: SBR (Spectral Band Replication)
    6: AAC Scalable
   sampling freq
    0: 96000 Hz
    1: 88200 Hz
    2: 64000 Hz
    3: 48000 Hz
    4: 44100 Hz
    5: 32000 Hz
    6: 24000 Hz
    7: 22050 Hz
    8: 16000 Hz
    9: 12000 Hz
    10: 11025 Hz
    11: 8000 Hz
    12: 7350 Hz
    13: Reserved
    14: Reserved
    15: frequency is written explictly
    Channel Configurations
    These are the channel configurations:
    0: Defined in AOT Specifc Config
    1: 1 channel: front-center
    2: 2 channels: front-left, front-right
  */
    // audioObjectType = profile => profile, the MPEG-4 Audio Object Type minus 1
    config[0] = adtsObjectType << 3;
    // samplingFrequencyIndex
    config[0] |= (adtsSampleingIndex & 0x0E) >> 1;
    config[1] |= (adtsSampleingIndex & 0x01) << 7;
    // channelConfiguration
    config[1] |= adtsChanelConfig << 3;
    if(adtsObjectType === 5) {
      // adtsExtensionSampleingIndex
      config[1] |= (adtsExtensionSampleingIndex & 0x0E) >> 1;
      config[2] = (adtsExtensionSampleingIndex & 0x01) << 7;
      // adtsObjectType (force to 2, chrome is checking that object type is less than 5 ???
      //    https://chromium.googlesource.com/chromium/src.git/+/master/media/formats/mp4/aac.cc
      config[2] |= 2 << 2;
      config[3] = 0;
    }
    return { config : config, samplerate : adtsSampleingRates[adtsSampleingIndex], channelCount : adtsChanelConfig, codec : ('mp4a.40.' + adtsObjectType)};
  }

  _generateInitSegment() {
    if(this._avcId === -1) {
      //audio only
      if(this._aacTrack.config) {
         observer.trigger(Event.FRAG_PARSING_INIT_SEGMENT,{
          audioMoov: MP4.initSegment([this._aacTrack]),
          audioCodec : this._aacTrack.codec,
          audioChannelCount : this._aacTrack.channelCount
        });
        this._initSegGenerated = true;
      }
      if(this._initPTS === undefined) {
        // remember first PTS of this demuxing context
        this._initPTS = this._aacSamples[0].pts - 90000*this.timeOffset;
        this._initDTS = this._aacSamples[0].dts - 90000*this.timeOffset;
      }
    } else
    if(this._aacId === -1) {
      //video only
      if(this._avcTrack.sps && this._avcTrack.pps) {
         observer.trigger(Event.FRAG_PARSING_INIT_SEGMENT,{
          videoMoov: MP4.initSegment([this._avcTrack]),
          videoCodec : this._avcTrack.codec,
          videoWidth : this._avcTrack.width,
          videoHeight : this._avcTrack.height
        });
        this._initSegGenerated = true;
        if(this._initPTS === undefined) {
          // remember first PTS of this demuxing context
          this._initPTS = this._avcSamples[0].pts - 90000*this.timeOffset;
          this._initDTS = this._avcSamples[0].dts - 90000*this.timeOffset;
        }
      }
    } else {
      //audio and video
      if(this._aacTrack.config && this._avcTrack.sps && this._avcTrack.pps) {
         observer.trigger(Event.FRAG_PARSING_INIT_SEGMENT,{
          audioMoov: MP4.initSegment([this._aacTrack]),
          audioCodec : this._aacTrack.codec,
          audioChannelCount : this._aacTrack.channelCount,
          videoMoov: MP4.initSegment([this._avcTrack]),
          videoCodec : this._avcTrack.codec,
          videoWidth : this._avcTrack.width,
          videoHeight : this._avcTrack.height
        });
        this._initSegGenerated = true;
        if(this._initPTS === undefined) {
          // remember first PTS of this demuxing context
          this._initPTS = Math.min(this._avcSamples[0].pts,this._aacSamples[0].pts) - 90000*this.timeOffset;
          this._initDTS = Math.min(this._avcSamples[0].dts,this._aacSamples[0].dts) - 90000*this.timeOffset;
        }
      }
    }
  }
}

export default TSDemuxer;