AudioBuffer: getChannelData() method
The getChannelData()
method of the AudioBuffer
Interface returns a Float32Array
containing the PCM data associated with the channel, defined by the channel parameter (with 0 representing the first channel).
Syntax
js
getChannelData(channel)
Parameters
channel
-
The channel property is an index representing the particular channel to get data for. An index value of 0 represents the first channel. If the
channel
index value is greater than of equal toAudioBuffer.numberOfChannels
, anINDEX_SIZE_ERR
exception will be thrown.
Return value
A Float32Array
.
Examples
In the following example we create a two second buffer, fill it with white noise, and then play it via an AudioBufferSourceNode
. The comments should clearly explain what is going on. You can also run the code live, or view the source.
js
const audioCtx = new (window.AudioContext || window.webkitAudioContext)();
const button = document.querySelector("button");
const pre = document.querySelector("pre");
const myScript = document.querySelector("script");
pre.innerHTML = myScript.innerHTML;
// Stereo
const channels = 2;
// Create an empty two second stereo buffer at the
// sample rate of the AudioContext
const frameCount = audioCtx.sampleRate * 2.0;
const myArrayBuffer = audioCtx.createBuffer(2, frameCount, audioCtx.sampleRate);
button.onclick = () => {
// Fill the buffer with white noise;
//just random values between -1.0 and 1.0
for (let channel = 0; channel < channels; channel++) {
// This gives us the actual ArrayBuffer that contains the data
const nowBuffering = myArrayBuffer.getChannelData(channel);
for (let 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
const 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();
};
Specifications
Specification |
---|
Web Audio API # dom-audiobuffer-getchanneldata |
Browser compatibility
BCD tables only load in the browser