AudioBuffer

The AudioBuffer interface represents a short audio asset, commonly shorter then one minute. It can consists of one or more channels, each one appearing to be 32-bit floating-point linear PCM values with a nominal range of [−1, 1] (but not limited to that range), specific sample rate which is the quantity of frames that will play in one second and length.

It can be created from audio file using decodeAudioData, decodeAudioDataSource or from raw data using constructor. Once you have data in AudioBuffer, audio can be played by passing it to AudioBufferSourceNode.

Constructor

BaseAudioContext.createBuffer(numChannels, length, sampleRate)

Decoding

BaseAudioContext.decodeAudioData

const audioBuffer = await fetch(URL)
      .then((response) => response.arrayBuffer())
      .then((arrayBuffer) =>
        audioContextRef.current!.decodeAudioData(arrayBuffer)
      )

BaseAudioContext.decodeAudioDataSource

import * as FileSystem from 'expo-file-system';

const audioBuffer = await FileSystem.downloadAsync(
      URL,
      `${FileSystem.documentDirectory}/example-music-01.mp3`
    ).then(({ uri }) => audioContext.decodeAudioDataSource(uri));

Properties

Name	Type	Description
sampleRate	number	Float value representing sample rate of the PCM data stored in the buffer.	Read only
length	length	Integer value representing length of the PCM data stored in the buffer.	Read only
duration	number	Double value representing duration, in seconds, of the PCM data stored in the buffer.	Read only
numberOfChannels	number	Integer value representing the number of audio channels of the PCM data stored in the buffer.	Read only

Methods

getChannelData

The above method returns modifiable array with PCM data from given channel.

Parameters	Type	Description
channel	number	Index of the AudioBuffer's channel from which data will be returned.

Errors:

Error type	Description
IndexSizeError	channel specifies unexisting audio channel.

Returns Float32Array.

copyFromChannel

The above method copies data from given channel of the AudioBuffer to an array.

Parameters	Type	Description
destination	Float32Array	The array to which data will be copied.
channelNumber	number	Index of the AudioBuffer's channel from which data will be copied.
startInChannel Optional	number	Channel's offset from which to start copying data.

Errors:

Error type	Description
IndexSizeError	channelNumber specifies unexisting audio channel.
IndexSizeError	startInChannel is greater then the AudioBuffer length.

Returns undefined.

copyToChannel

The above method copies data from given array to specified channel of the AudioBuffer.

Parameters	Type	Description
source	Float32Array	The array from which data will be copied.
channelNumber	number	Index of the AudioBuffer's channel to which data will be copied.
startInChannel Optional	number	Channel's offset from which to start copying data.

Errors:

Error type	Description
IndexSizeError	channelNumber specifies unexisting audio channel.
IndexSizeError	startInChannel is greater then the AudioBuffer length.

Returns undefined.