Record Audio on OSX (AVAudioSession not available)

Question

I am looking to capture audio on OSX. I have IOS working with AVAudioSession, but since it is not supported on OSX, I'm having difficulty finding a simple example on OSX to record audio to a file for subsequent playback.

All the examples I find on stackoverflow have been IOS and or not in Swift.

Any help here would be appreciated. A link to a OSX Swift based simple audio capture sample code would be great.

Thanks Tom

Answer 1

AVAudioSession exists to manage iOS audio constraints. These constraints don't exist on macOS, so you don't need AVAudioSession. Hooray!

You can capture audio to a file with AVAudioEngine and AVAudioFile:

import Cocoa
import AVFoundation

@NSApplicationMain
class AppDelegate: NSObject, NSApplicationDelegate {

    @IBOutlet weak var window: NSWindow!

    let audioEngine = AVAudioEngine()
    var outputFile: AVAudioFile? = nil

    func applicationDidFinishLaunching(_ aNotification: Notification) {
        // If sandboxed, don't forget to turn on Microphone in Capabilities > App Sandbox
        let input = audioEngine.inputNode
        let bus = 0
        let inputFormat = input.inputFormat(forBus: bus)

        let outputURL = FileManager.default.urls(for: .documentDirectory, in: .userDomainMask).first!.appendingPathComponent("out.caf")
        print("writing to \(outputURL)")

        outputFile = try! AVAudioFile(forWriting: outputURL, settings: inputFormat.settings, commonFormat: inputFormat.commonFormat, interleaved: inputFormat.isInterleaved)

        input.installTap(onBus: bus, bufferSize: 512, format: inputFormat) { (buffer, time) in
            try! self.outputFile?.write(from: buffer)
        }

        try! audioEngine.start()

        DispatchQueue.main.asyncAfter(deadline: .now()+5) {
            print("Finish")
            self.audioEngine.stop()
            self.outputFile = nil
        }
    }
}