Baremetal Audio Engine 🚀

A high-performance, lock-free audio DSP engine for Flutter, powered by C++17 and Miniaudio. Designed for real-time visualization, sample-accurate playback, and zero-latency synchronization.

🔥 Features

• ⚡ Zero-Latency FFI Bridge: Direct memory access between C++ and Dart (no MethodChannels).
• 🎤 Real-time FFT Analysis: Built-in Fast Fourier Transform (1024 bins) for high-FPS audio visualization.
• ⏱️ Sample-Accurate Clock: Perfect synchronization for subtitles, lyrics, or rhythm games (drift-free).
• 🛡️ Crash-Proof Architecture: Persistent singleton design with buffer overflow protection (tested on low-end Android devices).
• 🎛️ Dual Mode:
  • Capture Mode: Low-latency microphone input for visualizers.
  • Playback Mode: File playback with auto-resampling (44.1kHz -> 48kHz) and seek support.
• 📉 RMS Metering: Atomic thread-safe volume level monitoring.

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📸 Demo

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🛠️ Installation

Add baremetal_audio to your pubspec.yaml:

dependencies:
  baremetal_audio: ^1.0.2

Android Setup

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

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

iOS Setup

Add this to ios/Runner/Info.plist:

<key>NSMicrophoneUsageDescription</key>
<string>We need access to the microphone for real-time audio analysis.</string>

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💡 Usage

1. Initialize Engine

import 'package:baremetal_audio/baremetal_audio.dart';

// Mode 1: Microphone Capture
BaremetalAudio.init(mode: EngineMode.capture);

// Mode 2: File Playback
BaremetalAudio.init(mode: EngineMode.playback, filePath: "/path/to/song.mp3");

2. Real-time Visualization (60 FPS)

Use a Timer to fetch data directly from C++ memory (Zero-Copy):

Timer.periodic(const Duration(milliseconds: 16), (_) {
  // Get FFT Spectrum (Float32List pointer)
  final ptr = BaremetalAudio.getFftArray();
  if (ptr != nullptr) {
    final spectrum = ptr.asTypedList(512); // Read first 512 bins
    // Draw spectrum...
  }
  
  // Get Volume Level
  final rms = BaremetalAudio.getRmsLevel();
});

3. Subtitle Synchronization

Load an SRT string and get the current line instantly:

// Load subtitles
BaremetalAudio.loadSubtitles(srtContent);

// In your loop:
final currentLine = BaremetalAudio.getCurrentSubtitle();
final time = BaremetalAudio.getMediaTime(); // Accurate to 0.001s

4. Cleanup

BaremetalAudio.stop();

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🧠 How it Works

Unlike standard Flutter audio plugins that rely on platform channels (Java/Obj-C), Baremetal Audio runs a native C++ thread using miniaudio. It writes FFT and RMS data directly to a shared memory block. Dart reads this memory via dart:ffi without any serialization overhead.

• Backend: C++17 (Miniaudio)
• Bridge: Dart FFI (Foreign Function Interface)
• Thread Safety: std::atomic for lock-free communication.

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🤝 Contributing

Pull requests are welcome! For major changes, please open an issue first to discuss what you would like to change.

📄 License

This project is licensed under the Apache 2.0 License - see the LICENSE file for details.