SystemAudioKit

Record the microphone and what the Mac plays, as separate tracks on one timeline. Built for call and meeting recorders.

• System audio through Core Audio process taps (macOS 14.2+): everything the Mac plays, or only selected apps (including their helper processes, which is where browsers play calls). Uses the light "System Audio Recording Only" permission, not Screen Recording.
• ScreenCaptureKit fallback for setups where a tap cannot be used.
• Microphone from the default input or a chosen device.
• Aligned tracks. Each track is written against the host clock, and gaps (a silent app, a paused stream) are filled with silence, so microphone.wav and system.wav always line up. That lets a transcriber label everything on the microphone as you and diarize only the other side.
• Meeting detection: notices when Zoom, Teams, Slack, FaceTime, Discord, Webex, WhatsApp, Signal, Telegram or a browser (for Meet and other web calls) starts using the microphone, and when it stops.
• Mixing to a single M4A or WAV, permission checks, device and process listing.

Documentation: systemaudiokit.lucaspiera.com

Used by EchoPad.

Install

.package(url: "https://github.com/pieralukasz/SystemAudioKit.git", from: "0.1.0")

Your app's Info.plist needs NSMicrophoneUsageDescription and NSAudioCaptureUsageDescription (plus NSScreenCaptureUsageDescription if you use the ScreenCaptureKit backend).

Use

import SystemAudioKit

let recorder = AudioRecorder()
recorder.onLevels = { mic, system in /* 0...1, for meters */ }

try await recorder.start(.init(microphone: .systemDefault, systemAudio: .everything), in: folder)
// …
let recording = await recorder.stop()!
print(recording.microphoneURL!, recording.systemAudioURL!, recording.duration)
try recording.mix(to: folder.appendingPathComponent("call.m4a"))

Only one app:

try await recorder.start(.init(systemAudio: .apps(["us.zoom.xos"])), in: folder)

Meetings:

let detector = MeetingDetector()
detector.onChange = { started, ended in
    for meeting in started { print("\(meeting.appName) call started") }
}
detector.start()

Command line

swift run -c release sysaudio devices
swift run -c release sysaudio processes
swift run -c release sysaudio meetings
swift run -c release sysaudio record 10 ./out            # microphone + everything
swift run -c release sysaudio record 10 ./out --app us.zoom.xos --no-mic

The first recording triggers the macOS permission prompt, and the system track is silent until you allow it.

Notes

• The tap excludes the recording process itself, so your app's own sounds are not recorded.
• The tap is rebuilt when the default output device changes (for example when headphones connect). The gap while it rebuilds is filled with silence, so the tracks stay aligned.

License

MIT