Expo Video Audio Extractor

On-device audio-only export for React-Native & Expo

No FFmpeg • No GPL • Just the platform media APIs — AVAssetExportSession (iOS) & MediaExtractor / MediaMuxer / MediaCodec (Android)

Table of Contents

• Expo Video Audio Extractor
  • Table of Contents
  • Features
  • Installation
  • Usage
    • API
  • Troubleshooting
  • Contributing
  • License

Features

• Offline – runs entirely on-device, no upload required
• Clean audio export – grab the soundtrack from any local video
• Trim & resample – optional start / duration, sample-rate & channel overrides
• M4A / WAV output – lightweight presets accepted everywhere
• Classic & New Architecture – works if the host app opts into TurboModule/Fabric later

Installation

Supported React-Native versions: 0.79 (Expo SDK 53). Older versions may compile but are not tested.

npx expo install expo-video-audio-extractor

That’s it — run a development build or EAS production build and the native module is ready.

Local testing: run npx expo run:ios or npx expo run:android after installing the library; Expo Go will not include the native code.

Usage

import { extractAudio } from 'expo-video-audio-extractor';
import * as FileSystem from 'expo-file-system';

const videoUri  = FileSystem.cacheDirectory + 'screen-recording.mov';
const outputUri = FileSystem.documentDirectory + 'speech.m4a';

await extractAudio({
  // Required
  video:  videoUri,
  output: outputUri,

  // Optional controls ↓
  format: 'm4a',      // 'm4a' (default) or 'wav'
  start:  2,          // begin 2 s into the video
  duration: 10,       // export 10 s of audio
  volume: 0.9,        // 90 % volume (linear gain)
  channels: 1,        // force mono (wav only)
  sampleRate: 16000,  // override sample-rate (wav only)
});

console.log('Audio saved at', outputUri);

API

| Option | Type | Default | Description | | ------------ | ----------------------- | -------- | ---------------------------------------------------------------------- | | video | string | — | Absolute/local URI to the input video | | output | string | — | Absolute path for the output audio (overwritten if already exists) | | format | 'm4a' \| 'wav' | m4a | Output container/codec | | start | number (seconds) | 0 | Offset into the video to begin extraction | | duration | number (seconds) | to end | Length of audio to export. Omit to export through the end of the video | | volume | number (0‒1) | 1 | Linear gain applied to the exported track | | channels | 1 \| 2 (WAV only) | input | Force mono or stereo output when exporting WAV | | sampleRate | number (Hz, WAV only) | input | Override sample-rate when exporting WAV |

Returns: Promise<string> — absolute file URI of the saved audio.

⚠️ m4a exports are passthrough — the original audio codec (usually AAC) is copied without re-encoding. If you need uniform sample rates or channel layouts, use wav.

Troubleshooting

| Problem | Fix | | ------------------------------ | --------------------------------------------------------------------------------------------------- | | Native module not linked | Rebuild the dev client (eas build --profile development) or run npx expo run-android / run-ios. | | Unsupported format error | Only 'm4a' & 'wav' are currently implemented. | | Audio length mismatch | Check start & duration values; ensure they reside within the video length. | | iOS < 12 crash | The podspec targets iOS 12+. Older OS versions are not supported. |

Contributing

PRs are welcome! See CONTRIBUTING.md for details.

License

MIT © 2025 Elliot Fleming

See LICENSE for details.