MacIntercom

Bidirectional computer ↔ Bluetooth audio routing for macOS.

Development status: early release. Hardware compatibility and audio pipeline improvements are ongoing.

Features

• Bidirectional computer ↔ Bluetooth audio routing
• Automatic hardware format detection
• Integrated Bluetooth microphone support
• USB & analog microphone support
• Media-aware operation (enabled by default)
• Optional standalone always-on intercom mode
• Optional Software-Defined Radio (SDR) dual-method squelch mode
• Test tone diagnostics
• Low-latency, high-quality streaming audio pipeline
• Integrated AGC and WebRTC Voice Activity Detection (VAD)
  • WebRTC VAD enabled by default for intelligent voice-gating
  • Replaces legacy envelope follower (toggleable via DebugFlags) to significantly reduce false triggers from room noise
  • Lightweight, zero external dependency footprint

Requirements

• macOS Catalina (10.15) or later
• Bluetooth HFP/HSP audio device
• Microphone permission granted to Terminal (or the GUI app in future releases)

Installation (macOS)

MacIntercom is distributed as a pre-compiled, ad-hoc signed universal binary.

Because it is signed ad-hoc (rather than using an official Apple Developer account), macOS will block its initial execution with a security prompt.

To run the binary immediately:

1. Download the macintercom-macos-universal-...zip file from the latest Release and extract it.
2. Open your terminal and navigate to the folder containing the extracted file.
3. Remove the macOS quarantine attribute by running:

   xattr -d com.apple.quarantine ./macintercom
   

4. Run the application normally:

   ./macintercom
   

Running MacIntercom

MacIntercom supports several operation modes depending on how you want to handle media integration, test tones, or Software-Defined Radio (SDR) inputs.

• Media-Aware Mode (Default): Run ./macintercom. The intercom automatically yields to media playback, pausing/resuming media when toggled.
• Standalone Mode: Run ./macintercom --s. The intercom ignores media playback and stays active continuously until closed with Ctrl-C.
• SDR Squelch Mode: Run ./macintercom --sdr. Mutes the Bluetooth microphone return path for SDR inputs (e.g., routed via Soundflower), supporting two squelch methods:
  • WebRTC VAD: Automatically detects human voice activity in the noise floor.
  • CTCSS Tone Squelch: Pass -tone <frequency> (e.g., ./macintercom --sdr -tone 100.0) to trigger the gate strictly using standard sub-audible EIA/TIA tones via an optimized Goertzel filter.
• Test Tone Mode: Run ./macintercom --t. Simultaneously plays a 220 Hz tone through the computer output and a 440 Hz tone through the Bluetooth speaker.

Notes on Audio Quality

• Universal 48 kHz Sample Rate: To ensure the cleanest audio pipeline and lowest latency, set all active input and output devices (USB microphones, Line-In, Line-Out, and virtual routing tools like Soundflower) to a fixed 48 kHz sample rate in macOS Audio MIDI Setup.

• Bluetooth and SDR Mode: When running macintercom in standard intercom mode, macOS forces Bluetooth speakers with integrated microphones, and headsets, into a lower-quality telephony profile (HFP) to use the microphone. However, because --sdr mode uses a virtual system input instead of your Bluetooth mic, you can route the output to any Bluetooth speaker or headset and it will remain in crisp, full-fidelity A2DP (e.g., 32-bit/48kHz).

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Current status

Current development focuses on:

• stabilizing the 0.1.x series before GUI work begins

Roadmap

v0.1.9

• Stabilization and regression testing

v0.2

• GUI
• Device selection
• Runtime settings
• PA Mode

Future Ideas

• Multiple simultaneous Bluetooth endpoints
• Network intercom
• Push-to-talk over keyboard
• Audio recording
• Optional echo cancellation backend
• Optional AUVoiceProcessingIO backend
• MacPorts & Homebrew packages

Tested Hardware

Bluetooth

• Bluetooth speaker with integrated microphone (HFP in Media-Aware & Standalone Modes, A2DP in SDR Squelch Mode)

Computer Inputs

• USB UAC microphone
• 3.5 mm analog lavalier microphone (battery-powered)
• Mixer line input (48V-powered & unpowered microphones)
• Soundflower v2.0b2

Computer Outputs

• 3.5 mm analog headphone/line level out
• Soundflower v2.0b2

Licensing

MacIntercom is free and open-source software licensed under the GNU General Public License v3.0.

You are free to use, modify, and redistribute MacIntercom under the terms of the GPL-3.0 license.

Organizations requiring proprietary integration, closed-source distribution, commercial hardware bundling, custom development, or dedicated support may contact the author regarding commercial licensing.

Contact: tbz.one/contact

Third-Party Components

MacIntercom incorporates Voice Activity Detection (VAD) algorithms from the WebRTC project. Please refer to the THIRD_PARTY_LICENSES.md file for complete copyright notices and redistribution terms.