GainNode - Web API 接口参考 编辑

GainNode 接口表示音量的变化。它是一个AudioNode音频处理模块，在输出前使用给定增益应用到输入。一个 GainNode 总是只有一个输入和一个输出，两者拥有同样数量的声道。

增益是一个无单位的值，会对所有输入声道的音频进行相应的增加。如果进行了修改，则会立即应用新增益，从而在结果音频中产生奇怪的“咔嗒”声。为了防止这种情况发生，请不要直接更改值，而应在AudioParam接口上使用指数插值方法。

构造函数

GainNode()

创建GainNode对象的新实例。不应手动创建增益节点；而应该使用AudioContext.createGain()方法。

属性

从其父类继承属性AudioNode。

GainNode.gain 只读

是一个a-rateAudioParam表示应用的增益量。必须设置AudioParam.value或者使用AudioParam的方法改变增益效果。

方法

无指定方法；所有方法继承自父类AudioNode.

示例

The following example shows basic usage of an AudioContext to create a GainNode, which is then used to mute and unmute the audio when a Mute button is clicked by changing the gain property value.

The below snippet wouldn't work as is — for a complete working example, check out our Voice-change-O-matic demo (view source.)

<div>
  <button class="mute">Mute button</button>
</div>

var audioCtx = new (window.AudioContext || window.webkitAudioContext)();
var gainNode = audioCtx.createGain();
var mute = document.querySelector('.mute');
var source;

if (navigator.mediaDevices.getUserMedia) {
 navigator.mediaDevices.getUserMedia (
   // constraints - only audio needed for this app
   {
     audio: true
   },

   // Success callback
   function(stream) {
     source = audioCtx.createMediaStreamSource(stream);

   },

   // Error callback
   function(err) {
     console.log('The following gUM error occured: ' + err);
   }
  );
} else {
   console.log('getUserMedia not supported on your browser!');
}

source.connect(gainNode);
gainNode.connect(audioCtx.destination);

  ...

mute.onclick = voiceMute;

function voiceMute() {
  if(mute.id == "") {
    // 0 means mute. If you still hear something, make sure you haven't
    // connected your source into the output in addition to using the GainNode.
    gainNode.gain.setValueAtTime(0, audioCtx.currentTime);
    mute.id = "activated";
    mute.innerHTML = "Unmute";
  } else {
    gainNode.gain.setValueAtTime(1, audioCtx.currentTime);
    mute.id = "";
    mute.innerHTML = "Mute";
  }
}

规范

浏览器兼容

BCD tables only load in the browser

参见

• 使用Web音频API