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AudioNode.connect(AudioParam)

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允许我们将当前节点的一个输出连接到音频参数的一个输入,并允许通过音频信号控制参数。
使AudioNode输出连接到多个AudioParam,并将多个AudioNode输出连接到单个 AudioParam,同时多次调用connect()。因此支持Fan-in and fan-out。
 AudioParam可以从连接到它的任何AudioNode输出获取渲染的音频数据,并通过下混合将其转换为单声道(如果本身不是单声道的话)。然后,它将其他这样的输出和固定参数混合( AudioParam的值通常没有任何连接),包括为参数调度的任何时间的变化。
因此,可以通过将AudioParam的值设置为中心频率来选择AudioParam将要更改的范围,并使用音频源和AudioParam之间的GainNode来调整AudioParam更改的范围。

Syntax

var lfo = audioCtx.createOscillator();
lfo.frequency.value = 2.0; // Hz, two times per second

var lfoGain = audioCtx.createGain();
lfoGain.gain.value = 0.5;

// this is the parameter that is going to be modulated
var gain = audioCtx.createGain();
gain.gain.value = 0.5;

// Oscillators go from -1 to 1
// Make it go from -0.5 to +0.5 by connecting it to a GainNode with a gain value of 0.5
lfo.connect(lfoGain);

// because the value of the gain.gain AudioParam is originaly 0.5, the value is added, and it will go from 0.0 to 1.0
lfoGain.connect(gain.gain);

lfo.connect(gain.gain);

Note: There can only be one connection between an output from one specific AudioNode and an AudioParam. Multiple connections to the same termini are equivalent to a single such connection (the duplicates are ignored).

Returns

Void.

Example

In this example, we will be altering the gain value of a GainNode using an OscillatorNode with a slow frequency value. This technique is know as an LFO-controlled parameter.

var AudioContext = window.AudioContext || window.webkitAudioContext;

var audioCtx = new AudioContext();

// create an normal oscillator to make sound
var oscillator = audioCtx.createOscillator();

// create a second oscillator that will be used as an LFO (Low-frequency
// oscillator), and will control a parameter
var lfo = audioCtx.createOscillator();

// set the frequency of the second oscillator to a low number
lfo.frequency.value = 2.0; // 2Hz: two oscillations par second

// create a gain whose gain AudioParam will be controlled by the LFO
var gain = audioCtx.createGain();

// connect the LFO to the gain AudioParam. This means the value of the LFO
// will not produce any audio, but will change the value of the gain instead
lfo.connect(gain.gain);

// connect the oscillator that will produce audio to the gain
oscillator.connect(gain);

// connect the gain to the destination so we hear sound
gain.connect(audioCtx.destination);

// start the oscillator that will produce audio
oscillator.start();

// start the oscillator that will modify the gain value
lfo.start();

Parameters

Destination
The AudioParam you are connecting to.
Output (optional)
An index describing which output of the current AudioNode you want to connect to the AudioParam. The index numbers are defined according to the number of output channels (see Audio channels.)  If this parameter is out-of-bound, an INDEX_SIZE_ERR exception is thrown.

Specifications

Specification Status Comment
Web Audio API
connect(AudioParam)
Working Draft  

Browser compatibility

Feature Chrome Firefox (Gecko) Internet Explorer Opera Safari (WebKit)
connect(AudioParam) (Yes) webkit (Yes) 未实现 (Yes) 未实现
Feature Android Firefox Mobile (Gecko) Firefox OS (Gecko) IE Phone Opera Mobile Safari Mobile
connect(AudioParam) 未实现 (Yes) (Yes) 未实现 未实现 未实现

See also

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