PeriodicWave | Web API

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构造函数
特性
方法
范例
规范
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PeriodicWave interface defines a periodic waveform that can be used to shape the output of an OscillatorNode .

PeriodicWave has no inputs or outputs; it is used to define custom oscillators when calling OscillatorNode.setPeriodicWave() 。 PeriodicWave itself is created/returned by AudioContext.createPeriodicWave() .

构造函数

PeriodicWave.PeriodicWave(): 创建新的 PeriodicWave object instance using the default values for all properties. If you wish to establish custom property values at the outset, use the AudioContext.createPeriodicWave() factory method instead.

特性

None; also, PeriodicWave doesn't inherit any properties.

方法

None; also, PeriodicWave doesn't inherit any methods.

范例

The following example illustrates simple usage of createPeriodicWave() ，要创建 PeriodicWave object containing a simple sine wave.

var real = new Float32Array(2);
var imag = new Float32Array(2);
var ac = new AudioContext();
var osc = ac.createOscillator();
real[0] = 0;
imag[0] = 0;
real[1] = 1;
imag[1] = 0;
var wave = ac.createPeriodicWave(real, imag, {disableNormalization: true});
osc.setPeriodicWave(wave);
osc.connect(ac.destination);
osc.start();
osc.stop(2);

This works because a sound that contains only a fundamental tone is by definition a sine wave

Here, we create a PeriodicWave with two values. The first value is the DC offset, which is the value at which the oscillator starts. 0 is good here, because we want to start the curve at the middle of the [-1.0; 1.0] range.

The second and subsequent values are sine and cosine components. You can think of it as the result of a Fourier transform, where you get frequency domain values from time domain value. Here, with createPeriodicWave() , you specify the frequencies, and the browser performs an inverse Fourier transform to get a time domain buffer for the frequency of the oscillator. Here, we only set one component at full volume (1.0) on the fundamental tone, so we get a sine wave.

The coefficients of the Fourier transform should be given in ascending order (i.e. $\left(a+bi\right)e^{i} , \left(c+di\right)e^{2i} , \left(f+gi\right)e^{3i}$ etc.) and can be positive or negative. A simple way of manually obtaining such coefficients (though not the best) is to use a graphing calculator.

规范

规范	状态	注释
Web 音频 API The definition of 'PeriodicWave' in that specification.	工作草案

浏览器兼容性

The compatibility table on this page is generated from structured data. If you'd like to contribute to the data, please check out https://github.com/mdn/browser-compat-data and send us a pull request. 更新 GitHub 上的兼容性数据

	桌面						移动
	Chrome	Edge	Firefox	Internet Explorer	Opera	Safari	Android webview	Chrome for Android	Firefox for Android	Opera for Android	Safari on iOS	Samsung Internet
`PeriodicWave`	Chrome 14	Edge ≤18	Firefox 25	IE 不支持 No	Opera 15	Safari 6	WebView Android Yes	Chrome Android 18	Firefox Android 26	Opera Android 14	Safari iOS Yes	Samsung Internet Android 1.0
`PeriodicWave()` 构造函数	Chrome 55	Edge ≤79	Firefox 53	IE 不支持 No	Opera 42	Safari ?	WebView Android 55 注意事项 55 注意事项 Before Chrome 59, the default values were not supported.	Chrome Android 55 注意事项 55 注意事项 Before Chrome 59, the default values were not supported.	Firefox Android 53	Opera Android 42	Safari iOS ?	Samsung Internet Android 6.0 注意事项 6.0 注意事项 Before Samsung Internet 7.0, the default values were not supported.

图例

完整支持
不支持
兼容性未知 ?

另请参阅

使用 Web 音频 API

元数据

最后修改： Mar 28, 2020

在此页

构造函数

特性

方法

范例

规范

浏览器兼容性

图例

另请参阅

相关话题