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index.md
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---
title: "AudioBuffer: getChannelData() method"
short-title: getChannelData()
slug: Web/API/AudioBuffer/getChannelData
page-type: web-api-instance-method
browser-compat: api.AudioBuffer.getChannelData
---
{{ APIRef("Web Audio API") }}
The **`getChannelData()`** method of the {{ domxref("AudioBuffer") }} Interface returns a {{jsxref("Float32Array")}} containing the PCM data associated with the channel, defined by the channel parameter (with 0 representing the first channel).
## Syntax
```js-nolint
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 to {{domxref("AudioBuffer.numberOfChannels")}}, an `INDEX_SIZE_ERR` exception will be thrown.
### Return value
A {{jsxref("Float32Array")}}.
## Examples
In the following example we create a two second buffer, fill it with white noise, and then play it via an {{ domxref("AudioBufferSourceNode") }}. The comments should clearly explain what is going on. You can also [run the code live](https://mdn.github.io/webaudio-examples/audio-buffer/), or [view the source](https://github.com/mdn/webaudio-examples).
```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
{{Specifications}}
## Browser compatibility
{{Compat}}
## See also
- [Using the Web Audio API](/en-US/docs/Web/API/Web_Audio_API/Using_Web_Audio_API)