WaveShaperNode.oversample

WaveShaperNode 接口的 oversample 属性是一个指示过采样是否必须使用的枚举值。 过采样是一个用于在将畸变应用到音频信号之前创建更多的采样(上采样)的技术。

一旦被应用, 采样的数值会被还原为初始的数值。 这将通过避免一些混淆现象从而导致更好的结果, 代价则是在畸变曲线上会有较低的精确度。

 可用的oversample 值有:

Value Effect
'none' 不使用过采样。
'2x' 在应用畸变曲线前将采样的数量翻倍。
'4x' 在应用畸变曲线前将采样的数量翻4倍。

语法

distortion.oversample = enumeratedValue;

  • 畸变是一个WaveShaperNode.
  • 枚举值'none''2x', 或 '4x'

示例

The following example shows basic usage of an AudioContext to create a wave shaper node. For applied examples/information, check out our Voice-change-O-matic demo (see app.js for relevant code).

Note: Sigmoid functions are commonly used for distortion curves because of their natural properties. Their S-shape, for instance, helps create a smoother sounding result. We found the below distortion curve code on Stack Overflow.

var audioCtx = new (window.AudioContext || window.webkitAudioContext)();
var distortion = audioCtx.createWaveShaper();

  ...

function makeDistortionCurve(amount) {
  var k = typeof amount === 'number' ? amount : 50,
    n_samples = 44100,
    curve = new Float32Array(n_samples),
    deg = Math.PI / 180,
    i = 0,
    x;
  for ( ; i < n_samples; ++i ) {
    x = i * 2 / n_samples - 1;
    curve[i] = ( 3 + k ) * x * 20 * deg / ( Math.PI + k * Math.abs(x) );
  }
  return curve;
};

  ...

distortion.curve = makeDistortionCurve(400);
distortion.oversample = '4x';

规范

Specification Status Comment
Web Audio API
oversample
Working Draft  

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参考链接