jtBaseApp/node_modules/mux.js/cjs/codecs/adts.js

/**
 * mux.js
 *
 * Copyright (c) Brightcove
 * Licensed Apache-2.0 https://github.com/videojs/mux.js/blob/master/LICENSE
 */
'use strict';

var Stream = require('../utils/stream.js');

var ONE_SECOND_IN_TS = require('../utils/clock').ONE_SECOND_IN_TS;

var _AdtsStream;

var ADTS_SAMPLING_FREQUENCIES = [96000, 88200, 64000, 48000, 44100, 32000, 24000, 22050, 16000, 12000, 11025, 8000, 7350];
/*
 * Accepts a ElementaryStream and emits data events with parsed
 * AAC Audio Frames of the individual packets. Input audio in ADTS
 * format is unpacked and re-emitted as AAC frames.
 *
 * @see http://wiki.multimedia.cx/index.php?title=ADTS
 * @see http://wiki.multimedia.cx/?title=Understanding_AAC
 */

_AdtsStream = function AdtsStream(handlePartialSegments) {
  var buffer,
      frameNum = 0;

  _AdtsStream.prototype.init.call(this);

  this.skipWarn_ = function (start, end) {
    this.trigger('log', {
      level: 'warn',
      message: "adts skiping bytes " + start + " to " + end + " in frame " + frameNum + " outside syncword"
    });
  };

  this.push = function (packet) {
    var i = 0,
        frameLength,
        protectionSkipBytes,
        frameEnd,
        oldBuffer,
        sampleCount,
        adtsFrameDuration;

    if (!handlePartialSegments) {
      frameNum = 0;
    }

    if (packet.type !== 'audio') {
      // ignore non-audio data
      return;
    } // Prepend any data in the buffer to the input data so that we can parse
    // aac frames the cross a PES packet boundary


    if (buffer && buffer.length) {
      oldBuffer = buffer;
      buffer = new Uint8Array(oldBuffer.byteLength + packet.data.byteLength);
      buffer.set(oldBuffer);
      buffer.set(packet.data, oldBuffer.byteLength);
    } else {
      buffer = packet.data;
    } // unpack any ADTS frames which have been fully received
    // for details on the ADTS header, see http://wiki.multimedia.cx/index.php?title=ADTS


    var skip; // We use i + 7 here because we want to be able to parse the entire header.
    // If we don't have enough bytes to do that, then we definitely won't have a full frame.

    while (i + 7 < buffer.length) {
      // Look for the start of an ADTS header..
      if (buffer[i] !== 0xFF || (buffer[i + 1] & 0xF6) !== 0xF0) {
        if (typeof skip !== 'number') {
          skip = i;
        } // If a valid header was not found,  jump one forward and attempt to
        // find a valid ADTS header starting at the next byte


        i++;
        continue;
      }

      if (typeof skip === 'number') {
        this.skipWarn_(skip, i);
        skip = null;
      } // The protection skip bit tells us if we have 2 bytes of CRC data at the
      // end of the ADTS header


      protectionSkipBytes = (~buffer[i + 1] & 0x01) * 2; // Frame length is a 13 bit integer starting 16 bits from the
      // end of the sync sequence
      // NOTE: frame length includes the size of the header

      frameLength = (buffer[i + 3] & 0x03) << 11 | buffer[i + 4] << 3 | (buffer[i + 5] & 0xe0) >> 5;
      sampleCount = ((buffer[i + 6] & 0x03) + 1) * 1024;
      adtsFrameDuration = sampleCount * ONE_SECOND_IN_TS / ADTS_SAMPLING_FREQUENCIES[(buffer[i + 2] & 0x3c) >>> 2]; // If we don't have enough data to actually finish this ADTS frame,
      // then we have to wait for more data

      if (buffer.byteLength - i < frameLength) {
        break;
      } // Otherwise, deliver the complete AAC frame


      this.trigger('data', {
        pts: packet.pts + frameNum * adtsFrameDuration,
        dts: packet.dts + frameNum * adtsFrameDuration,
        sampleCount: sampleCount,
        audioobjecttype: (buffer[i + 2] >>> 6 & 0x03) + 1,
        channelcount: (buffer[i + 2] & 1) << 2 | (buffer[i + 3] & 0xc0) >>> 6,
        samplerate: ADTS_SAMPLING_FREQUENCIES[(buffer[i + 2] & 0x3c) >>> 2],
        samplingfrequencyindex: (buffer[i + 2] & 0x3c) >>> 2,
        // assume ISO/IEC 14496-12 AudioSampleEntry default of 16
        samplesize: 16,
        // data is the frame without it's header
        data: buffer.subarray(i + 7 + protectionSkipBytes, i + frameLength)
      });
      frameNum++;
      i += frameLength;
    }

    if (typeof skip === 'number') {
      this.skipWarn_(skip, i);
      skip = null;
    } // remove processed bytes from the buffer.


    buffer = buffer.subarray(i);
  };

  this.flush = function () {
    frameNum = 0;
    this.trigger('done');
  };

  this.reset = function () {
    buffer = void 0;
    this.trigger('reset');
  };

  this.endTimeline = function () {
    buffer = void 0;
    this.trigger('endedtimeline');
  };
};

_AdtsStream.prototype = new Stream();
module.exports = _AdtsStream;