Decoding

You can decode audio data independently, without creating an AudioContext, using the exported functions decodeAudioData and decodePCMInBase64.

warning

Decoding on the web has to be done via AudioContext only.

If you already have an audio context, you can decode audio data directly using its decodeAudioData function; the decoded audio will then be automatically resampled to match the context's sampleRate.

caution

Supported file formats:

• flac
• mp3
• ogg
• opus
• wav
• aac
• m4a
• mp4

Last three formats are decoded with ffmpeg on the mobile, see for more info.

decodeAudioData

Decodes audio data from either a file path or an ArrayBuffer. The optional sampleRate parameter lets you resample the decoded audio; if not provided, the original sample rate from the file is used.

Parameter	Type	Description
input	ArrayBuffer	ArrayBuffer with audio data.
	string	Path to remote or local audio file.
	number	Asset module id. Mobile only
sampleRate Optional	number	Target sample rate for the decoded audio.
fetchOptions Optional	RequestInit	Additional headers parameters when passing url to fetch.

Returns Promise<AudioBuffer>.

caution

If you are passing number to decode function, bear in mind that it uses Image component provided by React Native internally. By default only support .mp3, .wav, .mp4, .m4a, .aac audio file formats. If you want to use other types, refer to this section for more info.

Example decoding remote URL

import { decodeAudioData } from 'react-native-audio-api';

const url = ... // url to an audio

const buffer = await decodeAudioData(url);

caution

Internally decoding local files uses Image component to retrieve asset uri, but it does not work on the web platform. You can use expo-asset library for this purpose or retrieve ArrayBuffer on your own and pass it to decoding function.

Example using expo-asset library

import { Asset } from 'expo-asset';
import { AudioContext } from 'react-native-audio-api';

const uri = await Asset.fromModule(require('@/assets/music/example.mp3'))
  .downloadAsync()
  .then((asset) =>  {
    if (!asset.localUri) {
      console.error('Failed to load audio asset');
    }
    return asset.localUri;
  })

const context = new AudioContext();
if (uri) {
  const buffer = await fetch(uri)
  .then((response) => response.arrayBuffer())
  .then((arrayBuffer) => context.decodeAudioData(arrayBuffer));
  console.log('Audio buffer loaded:', buffer);
}

decodePCMInBase64

Decodes base64-encoded PCM audio data.

Parameter	Type	Description
base64String	string	Base64-encoded PCM audio data.
inputSampleRate	number	Sample rate of the input PCM data.
inputChannelCount	number	Number of channels in the input PCM data.
isInterleaved Optional	boolean	Whether the PCM data is interleaved. Default is true.

Returns Promise<AudioBuffer>

Example decoding with data in base64 format

const data = ... // data encoded in base64 string
// data is interleaved (Channel1, Channel2, Channel1, Channel2, ...)
const buffer = await decodeAudioData(data, 4800, 2, true);