audiomix

Native module for mixing multiple audio recordings in Expo React Native (Android).
It allows combining a base track with recordings, handling delays (delayMs), and optional monitoring during playback.

Installation

npm install audiomix

Link native module if needed (RN < 0.60):

react-native link audiomix

For RN 0.60+, autolinking handles it.

Usage

Import

import { audioMix } from 'audiomix';

Method: mixRecordings

audioMix(
  recordings: Array<{ id: string; uri: string; delayMs?: number }>,
  selectedIds: string[],
  baseTrack: string | null,
  monitorPlayback: boolean,
  syncValue: number,
)

• recordings: List of recording objects. Each must include id and uri. Optional delayMs in ms.
• selectedIds: Array of IDs from recordings to include in mixing.
• baseTrack: Path/URI of base audio track (can be null).
• monitorPlayback: If true, mixes with base track for monitoring.
• syncValue: Sync adjustment in ms.
• Returns: Promise resolving with the path of the mixed output .wav file (stored in app cache).

Example

const recordings = [
  { id: '1', uri: '/storage/emulated/0/Music/rec1.wav', delayMs: 120 },
  { id: '2', uri: '/storage/emulated/0/Music/rec2.wav', delayMs: 0 },
];

const selectedIds = ['1'];

const baseTrack = '/storage/emulated/0/Music/base.wav';

audioMix(
  recordings,
  selectedIds,
  baseTrack,
  true,    // monitorPlayback
  0        // syncValue
).then(outputPath => {
  console.log('Mixed audio file:', outputPath);
}).catch(err => {
  console.error('Mixing error:', err);
});

Notes

• Output file is generated in the app cache directory with name pattern: mixed_output_<timestamp>.wav

• On error, promise rejects with:

  • MIX_PREP_ERROR: Input or preparation error.
  • MIX_ERROR: Mixing process failed.

License

MIT