MicRouter

MicRouter is a low-latency tool that transforms your Android device into a high-quality microphone for your Windows PC. It routes audio from your phone's microphone to your PC via a USB connection with minimal latency.

Prebuilt Releases

For most users, it is recommended to download the latest prebuilt binaries from the GitHub Releases page. This is the easiest way to get started with MicRouter.

The project is configured with a CI/CD workflow that automatically builds and releases new versions of the Android and Windows applications whenever changes are pushed to the master branch.

Architecture Overview

The MicRouter system consists of three main components that work together:

1. Android App (android/): A native Android application that runs as a foreground service. It captures raw audio from the microphone, can apply audio effects, and streams the data over a TCP socket.
2. PC Backend (desktop/backend/): A Python server that listens for a connection from the Flutter UI and the Android app. It forwards commands from the UI, receives the audio stream, applies a digital gain, and plays the audio through a selected sound device on the PC.
3. PC Frontend (desktop/frontend/): A Flutter desktop application for Windows that provides a user interface for controlling the system. It allows the user to select an output device, start/stop the stream, and adjust the digital gain.

The communication flow is as follows:

• The Android app starts a TCP server (default port 6000) and waits for a connection.
• The PC Backend starts a TCP server for the UI (default port 5000).
• When the user clicks "Start" in the PC Frontend, it sends a start command to the PC Backend.
• The PC Backend then uses adb forward to create a connection to the Android app over USB and connects to its TCP server.
• The Android app sends the raw audio data to the PC Backend, which processes it and plays it on the PC.

Features

• Low Latency Streaming: Audio is sent as a raw PCM stream over a TCP socket created via adb for high speed.
• Background Operation: The Android app runs as a foreground service, allowing it to work even when the app is in the background or the screen is off.
• Digital Effects & Processing:
  • Digital Gain: Boost the microphone volume from the PC client.
  • Hardware Noise Suppression: Utilizes the device's built-in noise suppressor for cleaner audio (if available).
  • Hardware Echo Cancellation: Utilizes the device's built-in acoustic echo canceler (if available).
• AI Noise Cancellation: The PC backend uses RNNoise (Recurrent Neural Network for Audio Noise Reduction) to eliminate background noise in real-time.
• Real-time Monitoring: The PC client provides a real-time audio visualizer and status updates.

Prerequisites

1. Android Device: With USB Debugging enabled.
2. Windows PC:
   • Python 3.10+ installed.
   • Flutter SDK installed.
3. ADB: Must be installed and accessible from your system's PATH.
4. (Optional) VB-Audio Cable: To route the audio as a virtual microphone input to other applications.

Development Setup

To run this project in a development environment, you need to set up and run the Android app, the Python backend, and the Flutter frontend separately.

1. Android App

1. Open the android/ directory in Android Studio.
2. Build and run the project on your connected Android device.
3. Alternatively, you can install it using Gradle:

   cd android && ./gradlew installDebug

4. Launch the app and grant the required microphone permissions. You can also configure audio settings from within the app.

2. PC Application (Desktop)

A. Run the Backend (Python):

1. Install the required Python packages:

   pip install -r desktop/backend/requirements.txt

2. Start the backend server:

   python desktop/backend/backend.py

   The backend will start and wait for a connection from the Flutter frontend.

B. Run the Frontend (Flutter):

1. Navigate to the frontend directory:

   cd desktop/frontend

2. Install the Flutter dependencies:

   flutter pub get

3. Run the Flutter application on Windows:

   flutter run -d windows

The Flutter app will launch and automatically connect to the running Python backend.

Configuration

Android App Settings

The Android app provides a settings screen where you can configure the following:

• Server Port: The TCP port for the audio stream (default: 6000).
• Sample Rate: The audio sample rate in Hz (default: 48000).
• Mic Source: Select the Android audio source (Default, Microphone, Voice Recognition, Voice Communication).
• Enable HW Suppressor: Toggle hardware noise suppression (default: true).

PC Backend API

The Python backend communicates with the Flutter frontend via JSON commands on port 5000.

• {"command": "get_devices"}: Requests a list of available audio output devices on the PC. The backend responds with a {"type": "devices", "payload": [...]} message.

• {"command": "start", "device_name": "...", "port": 6000}: Tells the backend to start the audio stream. It requires the name of the target output device and the port for the Android app.

• {"command": "stop"}: Stops the audio stream.

• {"command": "set_gain", "value": 1.5}: Sets the digital gain (volume multiplier).

• {"command": "toggle_rnnoise", "value": true}: Enables or disables the AI noise cancellation (RNNoise).