List all available audio devices

Question

I want to list all available audio devices in swift to provide a selection for input and output. My application should listen on a audio channel and "write" to another. I do not want the system default!

let devices = AVCaptureDevice.devices(for: .audio)

print(devices.count)

for device in devices {
    print(device.localizedName)
}

The Code lists 0 devices. But I expect at least the internal output.

Some links to CoreAudio, AudioToolbox and AVFoundation that explain the audio source selection would be nice.

Answer 1

Here's some Swift 5 code that will enumerate all the audio devices.

You can use the uid with AVAudioPlayer's currentDevice property to output to a specific device.

import Cocoa
import AVFoundation

class AudioDevice {
    var audioDeviceID:AudioDeviceID

    init(deviceID:AudioDeviceID) {
        self.audioDeviceID = deviceID
    }

    var hasOutput: Bool {
        get {
            var address:AudioObjectPropertyAddress = AudioObjectPropertyAddress(
                mSelector:AudioObjectPropertySelector(kAudioDevicePropertyStreamConfiguration),
                mScope:AudioObjectPropertyScope(kAudioDevicePropertyScopeOutput),
                mElement:0)

            var propsize:UInt32 = UInt32(MemoryLayout<CFString?>.size);
            var result:OSStatus = AudioObjectGetPropertyDataSize(self.audioDeviceID, &address, 0, nil, &propsize);
            if (result != 0) {
                return false;
            }

            let bufferList = UnsafeMutablePointer<AudioBufferList>.allocate(capacity:Int(propsize))
            result = AudioObjectGetPropertyData(self.audioDeviceID, &address, 0, nil, &propsize, bufferList);
            if (result != 0) {
                return false
            }

            let buffers = UnsafeMutableAudioBufferListPointer(bufferList)
            for bufferNum in 0..<buffers.count {
                if buffers[bufferNum].mNumberChannels > 0 {
                    return true
                }
            }

            return false
        }
    }

    var uid:String? {
        get {
            var address:AudioObjectPropertyAddress = AudioObjectPropertyAddress(
                mSelector:AudioObjectPropertySelector(kAudioDevicePropertyDeviceUID),
                mScope:AudioObjectPropertyScope(kAudioObjectPropertyScopeGlobal),
                mElement:AudioObjectPropertyElement(kAudioObjectPropertyElementMaster))

            var name:CFString? = nil
            var propsize:UInt32 = UInt32(MemoryLayout<CFString?>.size)
            let result:OSStatus = AudioObjectGetPropertyData(self.audioDeviceID, &address, 0, nil, &propsize, &name)
            if (result != 0) {
                return nil
            }

            return name as String?
        }
    }

    var name:String? {
        get {
            var address:AudioObjectPropertyAddress = AudioObjectPropertyAddress(
                mSelector:AudioObjectPropertySelector(kAudioDevicePropertyDeviceNameCFString),
                mScope:AudioObjectPropertyScope(kAudioObjectPropertyScopeGlobal),
                mElement:AudioObjectPropertyElement(kAudioObjectPropertyElementMaster))

            var name:CFString? = nil
            var propsize:UInt32 = UInt32(MemoryLayout<CFString?>.size)
            let result:OSStatus = AudioObjectGetPropertyData(self.audioDeviceID, &address, 0, nil, &propsize, &name)
            if (result != 0) {
                return nil
            }

            return name as String?
        }
    }
}


class AudioDeviceFinder {
    static func findDevices() {
        var propsize:UInt32 = 0

        var address:AudioObjectPropertyAddress = AudioObjectPropertyAddress(
            mSelector:AudioObjectPropertySelector(kAudioHardwarePropertyDevices),
            mScope:AudioObjectPropertyScope(kAudioObjectPropertyScopeGlobal),
            mElement:AudioObjectPropertyElement(kAudioObjectPropertyElementMaster))

        var result:OSStatus = AudioObjectGetPropertyDataSize(AudioObjectID(kAudioObjectSystemObject), &address, UInt32(MemoryLayout<AudioObjectPropertyAddress>.size), nil, &propsize)

        if (result != 0) {
            print("Error \(result) from AudioObjectGetPropertyDataSize")
            return
        }

        let numDevices = Int(propsize / UInt32(MemoryLayout<AudioDeviceID>.size))

        var devids = [AudioDeviceID]()
        for _ in 0..<numDevices {
            devids.append(AudioDeviceID())
        }

        result = AudioObjectGetPropertyData(AudioObjectID(kAudioObjectSystemObject), &address, 0, nil, &propsize, &devids);
        if (result != 0) {
            print("Error \(result) from AudioObjectGetPropertyData")
            return
        }

        for i in 0..<numDevices {
            let audioDevice = AudioDevice(deviceID:devids[i])
            if (audioDevice.hasOutput) {
                if let name = audioDevice.name,
                    let uid = audioDevice.uid {
                    print("Found device \"\(name)\", uid=\(uid)")
                }
            }
        }
    }
}