Audio Recorder (Nuxt Module)

Audio Recorder is a powerful Nuxt.js module that provides advanced audio recording, processing, and management capabilities for web applications. This module includes Vue components, composables, and utilities for seamless audio recording integration with client-side storage and audio format conversion.

Features

• Audio Recording: Web-based audio recording with AudioWorklet and PCM capture
• Audio Visualization: Real-time audio visualization during recording
• Session Management: Persistent audio session storage with IndexedDB
• Audio Conversion: FFmpeg integration for PCM to MP3 conversion and concatenation
• Chunked Recording: Configurable chunk intervals for efficient storage management
• Storage Services: Client-side audio chunk storage with ArrayBuffer for optimal performance
• Session Explorer: Browse and manage recorded audio sessions
• Abandoned Recording Recovery: Automatic detection and recovery of interrupted recordings
• iOS Support: Improved background recording support for iOS devices
• Internationalization: Built-in i18n support (English and German)

Technology Stack

• Framework: Nuxt.js module with Vue 3
• Package Manager: Bun
• Audio Processing: FFmpeg WebAssembly
• Database: Dexie for IndexedDB management
• Animation: Motion-V for smooth UI transitions
• Testing: Playwright for e2e testing

Setup

Prerequisites

• Node.js 18+
• Bun package manager
• Modern browser with MediaRecorder API support

Installation

Install the module to your Nuxt application:

Using Bun

bun add @dcc-bs/audio-recorder.bs.js

Using NPM

npm i @dcc-bs/audio-recorder.bs.js

Using Yarn

yarn add @dcc-bs/audio-recorder.bs.js

Configuration

Add it to your nuxt.config.ts:

export default defineNuxtConfig({
    modules: [
        '@dcc-bs/audio-recorder.bs.js',
    ],
})

under the vite config in nuxt.config.ts configure dexie:

vite: {
    resolve: {
        alias: {
            dexie: "dexie/dist/dexie.mjs",
        },
    },
}

add the following line to your main CSS file:

@import '@dcc-bs/audio-recorder.bs.js';

Usage

Basic Audio Recording

<template>
  <div>
    <AudioRecorder 
      :show-result="true"
      :auto-start="false"
      :store-to-db-interval="30"
      :logger="customLogger"
      @recording-started="onRecordingStarted"
      @recording-stopped="onRecordingStopped"
    />
  </div>
</template>

<script setup>
function customLogger(message) {
  console.log('[AudioRecorder]:', message)
}

function onRecordingStarted(stream) {
  console.log('Recording started:', stream)
}

function onRecordingStopped(audioBlob, audioUrl) {
  console.log('Recording stopped:', { audioBlob, audioUrl })
}
</script>

Using Audio Recording Composable

<script setup>
import { useAudioRecording, useAudioSessions } from '@dcc-bs/audio-recorder.bs.js'

const { 
  startRecording, 
  stopRecording, 
  recordingTime,
  isRecording,
  audioUrl,
  error
} = useAudioRecording({
  storeToDbInterval: 30, // Store chunks every 30 seconds
  logger: console.log,
  onRecordingStarted: (stream) => {
    console.log('Recording started')
  },
  onRecordingStopped: (audioBlob, audioUrl) => {
    console.log('Recording completed')
  },
  onError: (error) => {
    console.error('Recording error:', error)
  }
})

const { getMp3Blob, abandonedRecording, deleteAbandonedRecording } = useAudioSessions({
  deleteOldSessionsDaysInterval: 7,
  logger: console.log
})

// Start recording
await startRecording()

// Stop recording
await stopRecording()

// Download recorded audio as MP3 from a session
async function downloadAudio(sessionId) {
  const blob = await getMp3Blob(sessionId)
  if (blob) {
    const url = URL.createObjectURL(blob)
    const a = document.createElement('a')
    a.href = url
    a.download = `recording-${Date.now()}.mp3`
    a.click()
    URL.revokeObjectURL(url)
  }
}
</script>

Audio Session Explorer

<template>
  <AudioSessionExplorer />
</template>

Components

AudioRecorder

The main recording component with start/stop controls and audio visualization.

Props

Property	Type	Default	Description
showResult	boolean	true	Whether to show the playback section after recording is complete
autoStart	boolean	false	Automatically start recording when the component is mounted
storeToDbInterval	number	5	Interval in seconds to store audio chunks to IndexedDB (e.g., 30 for 30 seconds)
logger	(msg: string) => void	undefined	Optional custom logging function for debugging

Events

Event	Parameters	Description
recording-started	stream: MediaStream	Emitted when recording starts successfully
recording-stopped	audioBlob: Blob, audioUrl: string	Emitted when recording stops with the audio data

Exposed Methods & Properties

The component exposes the following methods and reactive properties via template refs:

Property/Method	Type	Description
isRecording	Ref<boolean>	Reactive boolean indicating if recording is in progress
startRecording	() => Promise<void>	Method to start audio recording
stopRecording	() => Promise<void>	Method to stop audio recording
recordingTime	Ref<number>	Recording time in seconds
formattedRecordingTime	ComputedRef<string>	Formatted recording time as "MM:SS"
error	Ref<string | null>	Current error message, if any
audioUrl	Ref<string | null>	URL of the recorded audio blob

Usage with Template Ref

<script setup lang="ts">
import { ref, computed } from 'vue';
import type { AudioRecorder } from '#components';

const recorderRef = ref<typeof AudioRecorder>()

const isRecording = computed(() => recorderRef.value?.isRecording)
const formattedTime = computed(() => recorderRef.value?.formattedRecordingTime)

function startRecording() {
  recorderRef.value?.startRecording()
}

function stopRecording() {
  recorderRef.value?.stopRecording()
}
</script>

<template>
  <div>
    <AudioRecorder ref="recorderRef" />
    <button @click="startRecording">Start</button>
    <button @click="stopRecording">Stop</button>
    <p>Recording: {{ isRecording }}</p>
    <p>Time: {{ formattedTime }}</p>
  </div>
</template>

AudioVisualizer

Real-time audio waveform visualization component that displays frequency data as animated bars.

Props

Property	Type	Required	Description
stream	MediaStream | undefined	Yes	The audio stream to visualize
isRecording	boolean	Yes	Whether recording is currently active (controls visualization updates)

Events

This component does not emit any events.

Exposed Methods & Properties

This component does not expose any methods or properties via defineExpose.

Usage

<script setup lang="ts">
import { ref } from 'vue'

const audioStream = ref<MediaStream>()
const recordingState = ref(false)

// Get stream from getUserMedia or other source
navigator.mediaDevices.getUserMedia({ audio: true })
  .then(stream => {
    audioStream.value = stream
    recordingState.value = true
  })
</script>

<template>
  <div>
    <AudioVisualizer 
      :stream="audioStream" 
      :is-recording="recordingState" 
    />
  </div>
</template>

Technical Details

• Uses Web Audio API with AudioContext and AnalyserNode
• FFT size: 256 for frequency analysis
• Updates visualization every 50ms when recording
• Displays 25 frequency bars (mirrored for visual symmetry)
• Automatically cleans up audio context when recording stops
• Responsive design with bars scaling based on frequency amplitude

AudioSessionExplorer

Browse and manage audio sessions component with customizable actions.

Props

Property	Type	Default	Description
showDownloadButton	boolean	true	Whether to show the default download button
showDeleteButton	boolean	true	Whether to show the default delete button
customActions	CustomAction[]	[]	Array of custom action buttons to display before the download button

CustomAction Interface

interface CustomAction {
  label: string           // Button text
  icon?: string          // Icon name (e.g., 'i-lucide-upload')
  color?: string         // Button color (default: 'primary')
  variant?: string       // Button variant (default: 'soft')
  loading?: boolean      // External loading state
  disabled?: boolean     // External disabled state
  handler: (
    sessionId: string,
    mp3Blob: Blob,
    deleteSession: () => Promise<void>
  ) => void | Promise<void>
}

Slots

Slot	Props	Description
actions	session, getMp3Blob, deleteSession	Custom action buttons slot for maximum flexibility

Usage Examples

Basic usage:

<template>
  <AudioSessionExplorer />
</template>

With custom actions:

<script setup lang="ts">
import type { CustomAction } from '@dcc-bs/audio-recorder.bs.js'

const customActions: CustomAction[] = [
  {
    label: 'Upload',
    icon: 'i-lucide-upload',
    color: 'blue',
    handler: async (sessionId, mp3Blob, deleteSession) => {
      // Upload the blob to your server
      await uploadToServer(mp3Blob)
      
      // Optionally delete the session after successful upload
      await deleteSession()
    }
  },
  {
    label: 'Share',
    icon: 'i-lucide-share',
    color: 'green',
    variant: 'outline',
    handler: async (sessionId, mp3Blob) => {
      // Share the audio blob
      await shareAudio(mp3Blob)
      // Session is kept (no deleteSession call)
    }
  }
]
</script>

<template>
  <AudioSessionExplorer :custom-actions="customActions" />
</template>

Hide default buttons and use custom actions only:

<script setup>
const customActions = [
  {
    label: 'Process',
    icon: 'i-lucide-cog',
    handler: async (sessionId, mp3Blob, deleteSession) => {
      const processed = await processAudio(mp3Blob)
      if (processed) {
        await deleteSession()
      }
    }
  }
]
</script>

<template>
  <AudioSessionExplorer
    :custom-actions="customActions"
    :show-download-button="false"
    :show-delete-button="false"
  />
</template>

Using the actions slot for maximum control:

<template>
  <AudioSessionExplorer>
    <template #actions="{ session, getMp3Blob, deleteSession }">
      <UButton
        @click="async () => {
          const blob = await getMp3Blob()
          await customProcessing(blob, session.id)
        }"
        color="purple"
        icon="i-lucide-sparkles"
      >
        Custom Action
      </UButton>
    </template>
  </AudioSessionExplorer>
</template>

Combining custom actions with slot:

<script setup>
const customActions = [
  {
    label: 'Quick Upload',
    icon: 'i-lucide-upload',
    handler: async (sessionId, mp3Blob, deleteSession) => {
      await quickUpload(mp3Blob)
      await deleteSession()
    }
  }
]
</script>

<template>
  <AudioSessionExplorer :custom-actions="customActions">
    <template #actions="{ session, getMp3Blob }">
      <!-- Additional custom button via slot -->
      <UButton @click="specialAction(session)">
        Special
      </UButton>
    </template>
  </AudioSessionExplorer>
</template>

Features

• Session List: Displays all recorded audio sessions with metadata
• Download: Export sessions as MP3 files (can be disabled)
• Delete: Remove sessions from storage (can be disabled)
• Custom Actions: Add custom buttons with access to the MP3 blob and delete functionality
• Loading States: Automatic loading indicators for all actions
• Animations: Smooth transitions using Motion-V
• Empty State: User-friendly message when no sessions exist

Development

Start the development playground:

bun dev

Build the module:

bun dev:build

Prepare the development environment:

bun dev:prepare

Testing

Run unit tests:

bun test

Run tests with coverage:

bun test:coverage

Run end-to-end tests:

bun test:e2e

Run tests in watch mode:

bun test:watch

Code Quality

Format code with Biome:

bun lint

Run linting and fixes:

bun check

Architecture

Recording Pipeline

The module uses a modern AudioWorklet-based architecture for high-quality PCM audio capture:

1. AudioWorklet PCM Capture: Raw PCM audio data is captured using a custom AudioWorkletProcessor (pcm-recorder-worklet.js)
2. Chunked Storage: PCM data is accumulated in memory and periodically converted to MP3 chunks using FFmpeg.wasm
3. IndexedDB Persistence: MP3 chunks are stored as ArrayBuffers in IndexedDB for efficient storage
4. Final Concatenation: On recording completion, all MP3 chunks are concatenated into a single MP3 file

This architecture provides:

• Lower memory footprint compared to MediaRecorder blob accumulation
• Better iOS compatibility with AudioWorklet support
• Flexible chunk intervals for customizable storage patterns
• Direct MP3 output without intermediate WebM files

Database Schema

AudioSession: Tracks recording metadata

• id, name, createdAt, chunkCount, totalSize
• chunkIds: Array maintaining chunk order
• sampleRate, numChannels: PCM metadata for reconstruction

AudioChunk: Stores MP3 audio chunks

• id, sessionId, createdAt
• buffer: ArrayBuffer containing MP3 data

Project Structure

• src/: Main module source code
  • module.ts: Nuxt module entry point
  • runtime/: Runtime components and composables
    • assets/: AudioWorklet processor files
    • components/: Vue components for audio recording
    • composables/: Audio recording composables and FFmpeg integration
    • services/: Audio storage and database services
    • utils/: Utility functions for microphone handling and PCM processing
    • lang/: Internationalization files
• playground/: Development playground and examples
• tests/: Unit and integration tests
  • e2e/: End-to-end tests with Playwright
  • nuxt/: Nuxt-specific tests

Release

To release a new version:

bun release

This will run linting, tests, build the module, generate changelog, and push with tags.

License

MIT © Data Competence Center Basel-Stadt

Datenwissenschaften und KI
Developed with ❤️ by DCC - Data Competence Center