File concatenation

Mobile only

You can concatenate existing audio files without creating an AudioContext using the exported concatAudioFiles function.

This is useful when recording with the rotateIntervalBytes option. Rotation keeps long recordings split into smaller files while recording, and concatAudioFiles can join those files back into one file after the recording is finished.

warning

concatAudioFiles is not supported on web.

caution

M4A and WAV concatenation is only supported.

M4A format requires FFmpeg to be available in the native build. WAV concatenation uses miniaudio and does not require FFmpeg.

concatAudioFiles

Concatenates compatible local audio files into a single output file.

Parameter	Type	Description
inputPaths	string[]	Local filesystem paths or file:// URLs to concatenate, in output order.
outputPath	string	Local filesystem path or file:// URL where the joined audio file should be written.

Returns Promise<string>.

The promise resolves with the provided outputPath when concatenation completes.

Compatibility

All input files must use compatible audio parameters. In practice, files should come from the same recorder configuration:

• the same container format,
• the same audio codec,
• the same sample rate,
• the same channel layout,
• compatible codec parameters.

Use an output path with an extension that matches the input files, for example joining .m4a segments into an .m4a output file or .wav segments into a .wav output file.

Example usage with rotated recordings

import { AudioRecorder, FileDirectory, FileFormat, concatAudioFiles } from 'react-native-audio-api';

const audioRecorder = new AudioRecorder();

audioRecorder.enableFileOutput({
  directory: FileDirectory.Cache,
  fileNamePrefix: 'meeting',
  format: FileFormat.M4A,
  rotateIntervalBytes: 8 * 1024 * 1024,
});

// Start and stop the recorder as usual.
const result = audioRecorder.stop();

if (result.status === 'success') {
  const outputPath = result.paths[0].replace(/[^/]+$/, 'meeting-complete.m4a');

  await concatAudioFiles(result.paths, outputPath);
}

Example usage with explicit paths

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

const outputPath = '/path/to/session.m4a';

await concatAudioFiles(
  ['/path/to/session-001.m4a', '/path/to/session-002.m4a', '/path/to/session-003.m4a'],
  outputPath
);