MeetsAudioRec

macOS application that records system audio and microphone input simultaneously, mixed into a single M4A file.

Features

• System Audio Capture: Records all system audio using ScreenCaptureKit
• Microphone Input: Captures microphone audio with device selection (supports various formats)
• Real-time Mixing: Combines both sources with adjustable volume balance
• Live Controls: Adjust volume and toggle sources during recording
• Level Meters: Visual feedback for system, mic, and mixed audio levels
• M4A Output: High-quality AAC encoding at 256kbps, 48kHz stereo

Requirements

• macOS 13.0 (Ventura) or later
• Screen Recording permission (for system audio)
• Microphone permission

Building

Prerequisites

• Xcode 15.0+
• XcodeGen (optional, for project generation)

Generate Xcode Project

# Install xcodegen if not already installed
brew install xcodegen
# Generate .xcodeprojcd MeetsAudioRec
xcodegen generate

Build and Run

1. Open MeetsAudioRec.xcodeproj in Xcode
2. Select your development team in Signing & Capabilities
3. Build and run (⌘R)

Build for Distribution

# Development build
./scripts/build.sh
# Release build
./scripts/build.sh Release
# Create notarized DMG (requires Apple Developer account)
./scripts/package_dmg.sh

First-time Setup for Notarization

Store your Apple credentials in Keychain:

xcrun notarytool store-credentials "notarytool-profile" \
--apple-id YOUR_APPLE_ID@example.com \
--team-id YOUR_TEAM_ID

Usage

1. Launch the app
2. Grant required permissions when prompted
3. Select your microphone device from the dropdown
4. Adjust volume sliders and enable/disable sources as needed
5. Click "Record" to begin
6. Adjust volumes or toggle sources in real-time during recording
7. Click "Stop" to finish
8. Recording is saved to ~/Documents/MeetsAudioRec/

Permissions

Screen Recording

Required to capture system audio. Grant in: System Settings → Privacy & Security → Screen Recording

Microphone

Required to capture microphone input. The app will prompt for permission on first use.

Architecture

┌─────────────────────────────────────────────────────────────┐
│ AudioCaptureManager │
├─────────────────────────────────────────────────────────────┤
│ ┌─────────────────┐ ┌─────────────────┐ │
│ │ SystemAudio │ │ Microphone │ │
│ │ Capture │ │ Capture │ │
│ │ (ScreenCapture │ │ (AVCapture │ │
│ │ Kit) │ │ Session) │ │
│ └────────┬────────┘ └────────┬────────┘ │
│ │ │ │
│ └──────────┬───────────┘ │
│ ▼ │
│ ┌─────────────────┐ │
│ │ AudioMixer │ │
│ │ - Ring buffers │ │
│ │ - Mix & volume │ │
│ │ - Level calc │ │
│ └────────┬────────┘ │
│ ▼ │
│ ┌─────────────────┐ │
│ │ AVAudioFile │ │
│ │ (M4A/AAC) │ │
│ └─────────────────┘ │
└─────────────────────────────────────────────────────────────┘

Technical Notes

Audio Format Handling

• System audio: Float32, 48kHz, stereo (from ScreenCaptureKit)
• Microphone: Various formats supported (auto-converted to Float32 48kHz stereo)
  • Handles interleaved and non-interleaved formats
  • Supports Float32, Int16, Int32 input formats
• Output: AAC 256kbps, 48kHz stereo

State Management

• AudioCaptureManager: Single source of truth for recording state and audio levels
• RecordingState: UI preferences (volumes, device selection, output directory)

License

MIT License