Question

我遇到了将麦克风数据采样转换为16位PCM有符号整数的问题。

我的应用程序位于Adobe AIR中，带有actionScript 3，但我有使用Web Audio API的服务演示代码，并指出：

/**
 * 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' });
};

我需要一种以同样方式转换样本的方法。

这就是我所拥有的，但它似乎没有起作用：

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);
        }

    }

任何建议都会帮助我，谢谢

编辑：

这是我拥有的WaveEncoder功能。可以用它来将样本编码成所需的格式：

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;
        }

EDIT2：

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

我如何在as3中执行byteOffset？

Answer 1

知道了。 writeInt()写入32位，您只需要写入16.请改用writeShort()。

soundBytes.writeShort(integer);

麦克风数据采样

1 个答案: