AudioBuffer.getChannelData()
AudioBuffer
接口的 getChannelData() 方法返回一Float32Array
(en-US) ,其中包含与通道关联的 PCM 数据,通道参数定义 (0 表示第一个通道)。
语法
var myArrayBuffer = audioCtx.createBuffer(2, frameCount, audioCtx.sampleRate);
var nowBuffering = myArrayBuffer.getChannelData(channel);
参数
- channel
-
channel 属性是要获取特定通道数据的索引。0 代表第一个通道。如果索引值大于或等于
AudioBuffer.numberOfChannels
, 会抛出一个索引大小异常(INDEX_SIZE_ERR
)的错误。
返回值
例子
在下例中,我们创建一个 2 秒钟的缓冲区,用白噪声填充它,然后通过AudioBufferSourceNode
来播放它。评论应该会清楚的解释发生的事情。你也可以实时运行代码,或者查看源代码。
var audioCtx = new (window.AudioContext || window.webkitAudioContext)();
var button = document.querySelector('button');
var pre = document.querySelector('pre');
var myScript = document.querySelector('script');
pre.innerHTML = myScript.innerHTML;
// Stereo
var channels = 2;
// Create an empty two second stereo buffer at the
// sample rate of the AudioContext
var frameCount = audioCtx.sampleRate * 2.0;
var myArrayBuffer = audioCtx.createBuffer(2, frameCount, audioCtx.sampleRate);
button.onclick = function() {
// Fill the buffer with white noise;
//just random values between -1.0 and 1.0
for (var channel = 0; channel < channels; channel++) {
// This gives us the actual ArrayBuffer that contains the data
var nowBuffering = myArrayBuffer.getChannelData(channel);
for (var i = 0; i < frameCount; i++) {
// Math.random() is in [0; 1.0]
// audio needs to be in [-1.0; 1.0]
nowBuffering[i] = Math.random() * 2 - 1;
}
}
// Get an AudioBufferSourceNode.
// This is the AudioNode to use when we want to play an AudioBuffer
var source = audioCtx.createBufferSource();
// set the buffer in the AudioBufferSourceNode
source.buffer = myArrayBuffer;
// connect the AudioBufferSourceNode to the
// destination so we can hear the sound
source.connect(audioCtx.destination);
// start the source playing
source.start();
}
Specification
Specification |
---|
Web Audio API # dom-audiobuffer-getchanneldata |
Browser compatibility
BCD tables only load in the browser