麦克风数据采样

Question

我在将麦克风数据采样转换为 16 位 PCM 带符号整数时遇到问题。

我的应用程序是在带有 actionScript 3 的 Adobe AIR 中，但我有使用网络音频的服务演示代码 API 并且它指出：

/**
 * Creates a Blob type: 'audio/l16' with the
 * chunk coming from the microphone.
 */
var exportDataBuffer = function(buffer, bufferSize) {
  var pcmEncodedBuffer = null,
    dataView = null,
    index = 0,
    volume = 0x7FFF; //range from 0 to 0x7FFF to control the volume

  pcmEncodedBuffer = new ArrayBuffer(bufferSize * 2);
  dataView = new DataView(pcmEncodedBuffer);

  /* Explanation for the math: The raw values captured from the Web Audio API are
   * in 32-bit Floating Point, between -1 and 1 (per the specification).
   * The values for 16-bit PCM range between -32768 and +32767 (16-bit signed integer).
   * Multiply to control the volume of the output. We store in little endian.
   */
  for (var i = 0; i < buffer.length; i++) {
    dataView.setInt16(index, buffer[i] * volume, true);
    index += 2;
  }

  // l16 is the MIME type for 16-bit PCM
  return new Blob([dataView], { type: 'audio/l16' });
};

我需要一种方法来以相同的方式转换我的样本。

这是我的，但它似乎不起作用：

function micSampleDataHandler(event:SampleDataEvent):void
    {

        while(event.data.bytesAvailable)
        {
            var sample:Number = event.data.readFloat();
            var integer:int;
            sample = sample * 32768 ;
            if( sample > 32767 ) sample = 32767;
            if( sample < -32768 ) sample = -32768;
            integer = int(sample) ;
            soundBytes.writeInt(integer);
        }

    }

任何建议都会对我有很大帮助，谢谢

编辑：

这是我的 WaveEncoder 函数。这可以用来将样本编码成所需的格式吗：

public function encode( samples:ByteArray, channels:int=2, bits:int=16, rate:int=44100 ):ByteArray
        {
            var data:ByteArray = create( samples );

            _bytes.length = 0;
            _bytes.endian = Endian.LITTLE_ENDIAN;

            _bytes.writeUTFBytes( WaveEncoder.RIFF );
            _bytes.writeInt( uint( data.length + 44 ) );
            _bytes.writeUTFBytes( WaveEncoder.WAVE );
            _bytes.writeUTFBytes( WaveEncoder.FMT );
            _bytes.writeInt( uint( 16 ) );
            _bytes.writeShort( uint( 1 ) );
            _bytes.writeShort( channels );
            _bytes.writeInt( rate );
            _bytes.writeInt( uint( rate * channels * ( bits >> 3 ) ) );
            _bytes.writeShort( uint( channels * ( bits >> 3 ) ) );
            _bytes.writeShort( bits );
            _bytes.writeUTFBytes( WaveEncoder.DATA );
            _bytes.writeInt( data.length );
            _bytes.writeBytes( data );
            _bytes.position = 0;

            return _bytes;
        }

编辑2：

问题似乎出在：dataview.setInt16(byteOffset, value [ littleEndian])

如何在 as3 中设置 byteOffset？

Answer 1

知道了。 writeInt()写32位，你只需要写16位，用writeShort()代替。

soundBytes.writeShort(integer);

麦克风数据采样

Microphone data sampling

air

audio

microphone

actionscript-3