AudioParam.exponentialRampToValueAtTime()

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exponentialRampToValueAtTime() 方法在 AudioParam Interface schedules a gradual exponential change in the value of the AudioParam . The change starts at the time specified for the 上一 event, follows an exponential ramp to the new value given in the value parameter, and reaches the new value at the time given in the endTime 参数。

注意 : Exponential ramps are considered more useful when changing frequencies or playback rates than linear ramps because of the way the human ear works.

句法

var AudioParam = AudioParam.exponentialRampToValueAtTime(value, endTime)

参数

值: A floating point number representing the value the AudioParam will ramp to by the given time.
endTime

A reference to this AudioParam object. In some browsers older implementations of this interface return void.

范例

In this example, we have a media source with two control buttons (see the audio-param repo for the source code, or view the example live .) When these buttons are pressed, exponentialRampToValueAtTime() is used to fade the gain value up to 1.0, and down to 0, respectively. This is pretty useful for fade in/fade out effects:

// create audio context
var AudioContext = window.AudioContext || window.webkitAudioContext;
var audioCtx = new AudioContext();
// set basic variables for example
var myAudio = document.querySelector('audio');
var pre = document.querySelector('pre');
var myScript = document.querySelector('script');
pre.innerHTML = myScript.innerHTML;
var expRampPlus = document.querySelector('.exp-ramp-plus');
var expRampMinus = document.querySelector('.exp-ramp-minus');
// Create a MediaElementAudioSourceNode
// Feed the HTMLMediaElement into it
var source = audioCtx.createMediaElementSource(myAudio);
// Create a gain node and set its gain value to 0.5
var gainNode = audioCtx.createGain();
// connect the AudioBufferSourceNode to the gainNode
// and the gainNode to the destination
gainNode.gain.setValueAtTime(0, audioCtx.currentTime);
source.connect(gainNode);
gainNode.connect(audioCtx.destination);
// set buttons to do something onclick
expRampPlus.onclick = function() {
  gainNode.gain.exponentialRampToValueAtTime(1.0, audioCtx.currentTime + 2);
}
expRampMinus.onclick = function() {
  gainNode.gain.exponentialRampToValueAtTime(0.01, audioCtx.currentTime + 2);
}

注意 : A value of 0.01 was used for the value to ramp down to in the last function rather than 0, as an invalid or illegal string error is thrown if 0 is used — the value needs to be positive.

规范

规范	状态	注释
Web 音频 API The definition of 'exponentialRampToValueAtTime' 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
`exponentialRampToValueAtTime`	Chrome 14	Edge 12	Firefox 部分支持 25 注意事项部分支持 25 注意事项 Does not work (see bug 1171438 and bug 1567777 ).	IE 不支持 No	Opera 15	Safari 6	WebView Android Yes	Chrome Android 部分支持 18 注意事项部分支持 18 注意事项 This sets the target volume at the specified time, but it doesn’t ramp to it, causing this function to behave like `setValueAtTime()` .	Firefox Android 部分支持 26 注意事项部分支持 26 注意事项 Does not work (see bug 1171438 and bug 1567777 ).	Opera Android 14	Safari iOS Yes	Samsung Internet Android 1.0

图例

完整支持
部分支持
不支持

另请参阅

使用 Web 音频 API

元数据

最后修改： May 14, 2020

Web 音频 API
AudioParam
特性
方法
1. cancelAndHoldAtTime()
2. cancelScheduledValues()
3. exponentialRampToValueAtTime()
4. linearRampToValueAtTime()
5. setTargetAtTime()
6. setValueAtTime()
7. setValueCurveAtTime()
Related pages for Web Audio API

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