webcodecs-flv/src/pcm-player.js

webcodecs decode flv

function PCMPlayer(option, onAudioFramePlaybackEnd, player) {
  this.init(option, onAudioFramePlaybackEnd, player);
}

PCMPlayer.prototype.init = function (option, onAudioFramePlaybackEnd, player) {
  var defaults = {
    encoding: '16bitInt',
    channels: 1,
    sampleRate: 8000,
    flushingTime: 1000,
  };
  this.playbackRate = 1.0;
  this.player = player;
  this.onAudioFramePlaybackEnd = onAudioFramePlaybackEnd;
  this.option = Object.assign({}, defaults, option);
  this.samples = new Float32Array();
  // this.flush = this.flush.bind(this);
  // this.interval = setInterval(this.flush, this.option.flushingTime);
  this.maxValue = this.getMaxValue();
  this.typedArray = this.getTypedArray();
  this.createContext();
  this.timestampBuffer = [];
};

PCMPlayer.prototype.getMaxValue = function () {
  var encodings = {
    '8bitInt': 128,
    '16bitInt': 32768,
    '32bitInt': 2147483648,
    '32bitFloat': 1,
  };

  return encodings[this.option.encoding]
    ? encodings[this.option.encoding]
    : encodings['16bitInt'];
};

PCMPlayer.prototype.getTypedArray = function () {
  var typedArrays = {
    '8bitInt': Int8Array,
    '16bitInt': Int16Array,
    '32bitInt': Int32Array,
    '32bitFloat': Float32Array,
  };

  return typedArrays[this.option.encoding]
    ? typedArrays[this.option.encoding]
    : typedArrays['16bitInt'];
};

PCMPlayer.prototype.createContext = function () {
  this.audioCtx = new (window.AudioContext || window.webkitAudioContext)();
  this.gainNode = this.audioCtx.createGain();
  this.gainNode.gain.value = 1;
  this.gainNode.connect(this.audioCtx.destination);
  this.startTime = this.audioCtx.currentTime;
};

PCMPlayer.prototype.isTypedArray = function (data) {
  return (
    data.byteLength && data.buffer && data.buffer.constructor == ArrayBuffer
  );
};

PCMPlayer.prototype.feed = function (data, timestamp, playbackRate) {
  if (!this.isTypedArray(data)) return;
  data = this.getFormatedValue(data);
  var tmp = new Float32Array(this.samples.length + data.length);
  tmp.set(this.samples, 0);
  tmp.set(data, this.samples.length);
  this.samples = tmp;
  this.playbackRate = playbackRate;
  this.timestampBuffer.push(timestamp);
};

PCMPlayer.prototype.getFormatedValue = function (data) {
  var data = new this.typedArray(data.buffer),
    float32 = new Float32Array(data.length),
    i;

  for (i = 0; i < data.length; i++) {
    float32[i] = data[i] / this.maxValue;
  }
  return float32;
};

PCMPlayer.prototype.volume = function (volume) {
  this.gainNode.gain.value = volume;
};

PCMPlayer.prototype.destroy = function () {
  if (this.interval) {
    clearInterval(this.interval);
  }
  this.samples = null;
  this.audioCtx.close();
  this.audioCtx = null;
};

PCMPlayer.prototype.flush = function () {
  if (!this.samples.length) return;
  var bufferSource = this.audioCtx.createBufferSource(),
    length = this.samples.length / this.option.channels,
    audioBuffer = this.audioCtx.createBuffer(
      this.option.channels,
      length,
      this.option.sampleRate
    ),
    audioData,
    channel,
    offset,
    i,
    decrement;

  for (channel = 0; channel < this.option.channels; channel++) {
    audioData = audioBuffer.getChannelData(channel);
    offset = channel;
    decrement = 50;
    for (i = 0; i < length; i++) {
      audioData[i] = this.samples[offset];
      /* fadein */
      if (i < 50) {
        audioData[i] = (audioData[i] * i) / 50;
      }
      /* fadeout*/
      if (i >= length - 51) {
        audioData[i] = (audioData[i] * decrement--) / 50;
      }
      offset += this.option.channels;
    }
  }

  if (this.startTime < this.audioCtx.currentTime) {
    this.startTime = this.audioCtx.currentTime;
  }
  //console.log('start vs current '+this.startTime+' vs '+this.audioCtx.currentTime+' duration: '+audioBuffer.duration);
  if (this.timestampBuffer.length > 0) {
    bufferSource.timestamp = this.timestampBuffer[0];
    this.timestampBuffer.shift();
  }
  bufferSource.playbackRate.value = this.playbackRate;
  bufferSource.buffer = audioBuffer;
  bufferSource.connect(this.gainNode);
  bufferSource.start(this.startTime);
  var that = this;
  bufferSource.onended = function (info) {
    that.onAudioFramePlaybackEnd(info, that.player);
    that.bufferSources.shift();
  };
  this.startTime += audioBuffer.duration;
  this.samples = new Float32Array();
};

PCMPlayer.prototype.getTimestamp = function () {
  if (this.audioCtx) {
    return this.audioCtx.currentTime;
  } else {
    return 0;
  }
};

PCMPlayer.prototype.play = function (
  data,
  playbackRate,
  timestamp,
  state,
  onend,
  player
) {
  if (!this.isTypedArray(data)) {
    return;
  }

  data = this.getFormatedValue(data);
  if (!data.length) {
    return;
  }

  var bufferSource = this.audioCtx.createBufferSource(),
    length = data.length / this.option.channels,
    audioBuffer = this.audioCtx.createBuffer(
      this.option.channels,
      length,
      this.option.sampleRate
    ),
    audioData,
    channel,
    offset,
    i,
    decrement;

  for (channel = 0; channel < this.option.channels; channel++) {
    audioData = audioBuffer.getChannelData(channel);
    offset = channel;
    decrement = 50;
    for (i = 0; i < length; i++) {
      audioData[i] = data[offset];
      // /* fadein */
      // if (i < 50) {
      //     audioData[i] = (audioData[i] * i) / 50;
      // }
      // /* fadeout*/
      // if (i >= (length - 51)) {
      //     audioData[i] = (audioData[i] * decrement--) / 50;
      // }
      offset += this.option.channels;
    }
  }

  if (this.startTime < this.audioCtx.currentTime) {
    this.startTime = this.audioCtx.currentTime;
  }

  // console.log('start vs current '+this.startTime+' vs '+this.audioCtx.currentTime+' duration: '+audioBuffer.duration);
  bufferSource.state = state;
  bufferSource.timestamp = timestamp;
  bufferSource.buffer = audioBuffer;
  // bufferSource.msg = "测试TAG";
  bufferSource.connect(this.gainNode);
  bufferSource.playbackRate.value = playbackRate;
  var that = this;
  // console.log("bufferSource.playbackRate.value = " + playbackRate);
  bufferSource.onended = function (info) {
    onend(info, player);
  };
  bufferSource.start(this.startTime);
  this.startTime += audioBuffer.duration / playbackRate;

  return audioBuffer.duration;
};

PCMPlayer.prototype.pause = function () {
  if (this.audioCtx.state === 'running') {
    this.audioCtx.suspend();
  }
  var u = navigator.userAgent;
  var isiOS = !!u.match(/\(i[^;]+;( U;)? CPU.+Mac OS X/); //ios终端
  if (!isiOS) {
    this.audioCtx.close();
  }
  console.log(
    'line 222, PCMPlayer.prototype.pause-> this.audioCtx.state: ',
    this.audioCtx.state
  );
};

PCMPlayer.prototype.resume = function () {
  // console.log("PCMPlayer.prototype.resume-> this.audioCtx.state: ", this.audioCtx.state);
  // if(this.audioCtx)
  // {
  //     this.audioCtx.suspend();
  //     this.audioCtx.close();
  // }
  if (this.audioCtx.state === 'closed') {
    this.createContext();
  }
  if (this.audioCtx.state === 'suspended') {
    console.log(
      'PCMPlayer.prototype.resume-> this.audioCtx.state: ',
      this.audioCtx.state
    );
    this.audioCtx.resume();
  }
};

PCMPlayer.prototype.status = function () {
  if (this.audioCtx) {
    return this.audioCtx.state;
  } else {
    return 'suspended';
  }
};

export default PCMPlayer;