react-ts-audio-recorder

🎙️ Framework-agnostic multi-format audio recorder with MP3 and WAV support. Built on top of Kagami/vmsg for MP3 encoding, with custom PCM→WAV encoder.

✨ Features

• 🎯 Multi-format support: MP3 (vmsg WASM), WAV (PCM→WAV)
• 📦 Zero dependencies: No runtime deps, just Web Audio API
• 🚀 Modern APIs: Uses AudioWorklet (not deprecated ScriptProcessorNode)
• 🎛️ Pitch shift: Built-in pitch adjustment for MP3 format
• 🌐 Browser support: Works in all modern browsers (Chrome, Firefox, Safari, Edge)
• 📱 TypeScript: Full TypeScript support with type definitions
• ⚡ Lightweight: MP3 encoder ~73 KB gzipped, WAV no WASM needed

📦 Install

npm install react-ts-audio-recorder

🚀 Quick Start

Basic Usage with MultiRecorder

import { MultiRecorder } from "react-ts-audio-recorder";
import vmsgWasm from "react-ts-audio-recorder/assets/vmsg.wasm?url";

const recorder = new MultiRecorder({
  format: "mp3", // "mp3" | "wav"
  sampleRate: 48000,
  wasmURL: vmsgWasm, // Only needed for MP3
});

await recorder.init();
await recorder.startRecording();
// ... recording ...
const blob = await recorder.stopRecording();
recorder.close();

React Example

import { useState, useRef } from "react";
import { MultiRecorder, type AudioFormat } from "react-ts-audio-recorder";
import vmsgWasm from "react-ts-audio-recorder/assets/vmsg.wasm?url";

function AudioRecorder() {
  const [isRecording, setIsRecording] = useState(false);
  const recorderRef = useRef<MultiRecorder | null>(null);

  const startRecording = async () => {
    const recorder = new MultiRecorder({
      format: "wav", // or "mp3"
      sampleRate: 48000,
      wasmURL: vmsgWasm,
    });
    
    recorderRef.current = recorder;
    await recorder.init();
    await recorder.startRecording();
    setIsRecording(true);
  };

  const stopRecording = async () => {
    if (!recorderRef.current) return;
    
    const blob = await recorderRef.current.stopRecording();
    recorderRef.current.close();
    recorderRef.current = null;
    setIsRecording(false);
    
    // Use the blob (e.g., create audio URL)
    const url = URL.createObjectURL(blob);
    console.log("Recorded audio:", url);
  };

  return (
    <div>
      <button onClick={isRecording ? stopRecording : startRecording}>
        {isRecording ? "Stop" : "Start"} Recording
      </button>
    </div>
  );
}

📚 API Reference

MultiRecorder

Main class for recording audio in multiple formats.

Constructor

new MultiRecorder(options: MultiRecorderOptions)

Options

Option	Type	Default	Description
format	"mp3" | "wav"	Required	Output audio format
sampleRate	number	48000	Sample rate in Hz
wasmURL	string	"/vmsg.wasm"	URL to vmsg.wasm (MP3 only)
shimURL	string	undefined	WebAssembly polyfill URL (MP3 only)
pitch	number	0	Pitch shift [-1, 1] (MP3 only)
workletURL	string	"/pcm-worklet.js"	PCM worklet URL (WAV only)

Methods

init(): Promise<void>

Initialize the recorder. Must be called before startRecording().

await recorder.init();

startRecording(): Promise<void>

Start recording audio from the microphone.

await recorder.startRecording();

stopRecording(): Promise<Blob>

Stop recording and return the audio blob.

const blob = await recorder.stopRecording();
// blob.type will be:
// - "audio/mpeg" for MP3
// - "audio/wav" for WAV

close(): void

Clean up resources. Always call this when done.

recorder.close();

Format Comparison

Format	Encoder	WASM Required	File Size	Quality	Browser Support
MP3	vmsg (LAME)	✅ Yes	Small	Good	All modern browsers
WAV	Custom PCM→WAV	❌ No	Large	Lossless	All modern browsers

📁 Assets

Importing Assets with Vite

// Import WASM file
import vmsgWasm from "react-ts-audio-recorder/assets/vmsg.wasm?url";

// Import PCM worklet
import pcmWorklet from "react-ts-audio-recorder/assets/pcm-worklet.js?url";

const recorder = new MultiRecorder({
  format: "wav",
  wasmURL: vmsgWasm,
  workletURL: pcmWorklet,
});

Using Constants

import { DEFAULT_VMSG_WASM_URL, PCM_WORKLET_URL, loadPCMWorklet } from "react-ts-audio-recorder";

// Use default URLs
const recorder = new MultiRecorder({
  format: "mp3",
  wasmURL: DEFAULT_VMSG_WASM_URL,
});

// Load worklet manually
const audioContext = new AudioContext();
await loadPCMWorklet(audioContext, PCM_WORKLET_URL);

Static Assets

If not using a bundler, copy assets to your public directory:

public/
  vmsg.wasm
  pcm-worklet.js

Then reference them:

const recorder = new MultiRecorder({
  format: "mp3",
  wasmURL: "/vmsg.wasm",
  workletURL: "/pcm-worklet.js",
});

🎨 Examples

Example: Format Selector

See the full React example in example/vite-demo/:

cd example/vite-demo
npm install
npm run dev

The demo includes:

• Format selector (MP3/WAV)
• Real-time recording timer
• Audio preview and download
• Error handling

🔧 Development

# Install dependencies
npm install

# Build
npm run build

# Watch mode
npm run dev

# Type check
npm run typecheck

📝 Notes

Browser Compatibility

• MP3: Requires WebAssembly support (all modern browsers)
• WAV: Works everywhere (no WASM needed)

Performance

• MP3: Best compression, universal support, requires WASM
• WAV: No compression, largest files, fastest encoding, no WASM needed

AudioWorklet vs ScriptProcessorNode

This library uses AudioWorklet (modern API) instead of deprecated ScriptProcessorNode for better performance and future compatibility.

📄 License

MIT © 2025 ThangDevAlone

The MP3 encoder and CSS originate from Kagami/vmsg (CC0). Please keep attribution when redistributing.

🙏 Credits

• Kagami/vmsg - Original MP3 encoder implementation
• Web Audio API - Modern audio processing