audio_io 0.3.0

Very simple interface to provide a stream of audio data for processing/visualising in Flutter

audio_io

A Flutter plugin for cross-platform real-time audio streaming. Provides low-latency audio input/output with simple Stream-based API for audio processing, recording, and visualization.

Features

• Real-time audio streaming from microphone to Flutter
• Audio output/playback through speakers
• Cross-platform support (iOS, macOS, Android, Web, Linux, Windows)
• Simple Stream-based API
• Configurable audio latency modes
• Consistent data format across all platforms (Float64, 48kHz, mono)
• Low-latency audio processing
• Volume level monitoring

Platform Support

Platform	Status	Implementation
iOS	✅ Supported	Native (AVAudioEngine)
macOS	✅ Supported	Native (AVAudioEngine)
Android	✅ Supported	FFI (miniaudio)
Web	✅ Supported	Web Audio API
Linux	✅ Supported	FFI (miniaudio)
Windows	✅ Supported	FFI (miniaudio)

Getting Started

Installation

Add audio_io to your pubspec.yaml:

dependencies:
  audio_io: ^0.3.0

iOS Setup

Add microphone usage description to your Info.plist:

<key>NSMicrophoneUsageDescription</key>
<string>This app needs access to the microphone for audio processing.</string>

macOS Setup

1. Add microphone usage description to your macos/Runner/Info.plist:

<key>NSMicrophoneUsageDescription</key>
<string>This app needs access to the microphone for audio processing.</string>

2. Enable audio input in your entitlements files:
   • macos/Runner/DebugProfile.entitlements
   • macos/Runner/Release.entitlements

<key>com.apple.security.device.audio-input</key>
<true/>

Android Setup

Add microphone permission to your android/app/src/main/AndroidManifest.xml:

<uses-permission android:name="android.permission.RECORD_AUDIO" />

The plugin will automatically request the permission at runtime when needed.

Usage

import 'package:audio_io/audio_io.dart';

// Get the audio instance
final audioIo = AudioIo.instance;

// Configure latency (optional)
await audioIo.requestLatency(AudioIoLatency.Balanced);

// Start audio processing
await audioIo.start();

// Listen to input audio stream
audioIo.input.listen((audioData) {
  // Process audio data (List<double>)
  print('Received ${audioData.length} samples');
  
  // Calculate volume level (RMS)
  final sum = audioData.fold<double>(
    0.0, (sum, sample) => sum + sample * sample);
  final rms = sqrt(sum / audioData.length);
});

// Send audio to output (echo example)
audioIo.input.listen((data) {
  audioIo.output.add(data);
});

// Stop audio processing
await audioIo.stop();

Latency Configuration

The plugin supports three latency modes:

enum AudioIoLatency {
  Realtime,  // Lowest latency (~1.5ms buffer)
  Balanced,  // Balanced latency/CPU (~3ms buffer)
  Powersave, // Lower CPU usage (~6ms buffer)
}

// Set before starting audio
await audioIo.requestLatency(AudioIoLatency.Realtime);

Audio Format

All platforms use a consistent audio format:

• Sample Rate: 48kHz (may adapt to device capabilities)
• Channels: Mono (1 channel)
• Data Type: Double precision floats (Float64/double)
• Stream Format: Chunks of audio samples as List<double>
• Internal Processing: Platform-specific (Float32 on native platforms)

Requirements

• Dart SDK: >=3.0.0 <4.0.0
• Flutter: >=3.10.0
• iOS: 12.0 or higher
• macOS: 10.15 or higher

License

See LICENSE file for details.