I try to play an audio file with AVAudioEngine and AVAudioPlayerNode to an USB device (DAC). When I set the device in Hog Mode, the sound is not played but it works great without Hog Mode.
I also try with AVAudioPlayer, and it doesn't work either.
Does anyone know why and how to solve the problem?
If I set a device ADI-2 to Hog mode, the system set default device to another device Meridian and play sound on it. I can't find a way to play sound on device in hog mode ADI-2 (see images below).
import Cocoa
import AVFoundation
class ViewController: NSViewController {
let audioEngine = AVAudioEngine()
let playerNode = AVAudioPlayerNode()
override func viewDidLoad() {
super.viewDidLoad()
do {
let outputDevice = AudioDevice.defaultOutputDevice()
guard let url = Bundle.main.url(forResource: "file", withExtension: "mp3") else { return }
let audioFile = try AVAudioFile(forReading: url)
outputDevice.setHogMode() // without this line, audio file is played.
audioEngine.attach(playerNode)
audioEngine.connect(playerNode, to: audioEngine.mainMixerNode, format: audioFile.processingFormat)
try audioEngine.start()
playerNode.scheduleFile(audioFile, at: nil, completionHandler: nil)
playerNode.play()
} catch let error {
print(error.localizedDescription)
}
}
}
class AudioDevice {
var id: AudioDeviceID
init(deviceID: AudioDeviceID) {
self.id = deviceID
}
func setHogMode() -> Bool {
guard hogModePID() != pid_t(ProcessInfo.processInfo.processIdentifier) else { return false }
return toggleHogMode()
}
func unsetHogMode() -> Bool {
guard hogModePID() == pid_t(ProcessInfo.processInfo.processIdentifier) else { return false }
return toggleHogMode()
}
private func toggleHogMode() -> Bool {
let address = AudioObject.address(selector: kAudioDevicePropertyHogMode)
var newValue: UInt32 = 1
let status = AudioObject.setPropertyData(id, address: address, andValue: &newValue)
return noErr == status
}
private func hogModePID() -> pid_t? {
let address = AudioObject.address(selector: kAudioDevicePropertyHogMode)
var pid = pid_t()
let status = AudioObject.getPropertyData(id, address: address, andValue: &pid)
return noErr == status ? pid : nil
}
}
extension AudioDevice {
class func defaultOutputDevice() -> AudioDevice {
let address = AudioObject.address(selector: kAudioHardwarePropertyDefaultSystemOutputDevice)
var deviceId = AudioDeviceID()
let status = AudioObject.getPropertyData(AudioObjectID(kAudioObjectSystemObject), address: address, andValue: &deviceId)
if status != noErr {
print("OSStatus error \(status) (defaultOutputDevice)")
}
return AudioDevice(deviceID: deviceId)
}
}
class AudioObject {
class func address(selector: AudioObjectPropertySelector, scope: AudioObjectPropertyScope = kAudioObjectPropertyScopeGlobal, element: AudioObjectPropertyElement = kAudioObjectPropertyElementMaster) -> AudioObjectPropertyAddress {
return AudioObjectPropertyAddress(mSelector: selector, mScope: scope, mElement: element)
}
class func getPropertyData<T>(_ objectID: AudioObjectID, address: AudioObjectPropertyAddress, andValue value: inout T) -> OSStatus {
var theAddress = address
var size = UInt32(MemoryLayout<T>.size)
let status = AudioObjectGetPropertyData(objectID, &theAddress, UInt32(0), nil, &size, &value)
return status
}
class func getPropertyDataSize<Q>(_ objectID: AudioObjectID, address: AudioObjectPropertyAddress, qualifierDataSize: UInt32?, qualifierData: inout [Q], andSize size: inout UInt32) -> (OSStatus) {
var theAddress = address
return AudioObjectGetPropertyDataSize(objectID, &theAddress, qualifierDataSize ?? UInt32(0), &qualifierData, &size)
}
class func getPropertyDataSize<Q>(_ objectID: AudioObjectID, address: AudioObjectPropertyAddress, qualifierDataSize: UInt32?, qualifierData: inout Q, andSize size: inout UInt32) -> (OSStatus) {
var theAddress = address
return AudioObjectGetPropertyDataSize(objectID, &theAddress, qualifierDataSize ?? UInt32(0), &qualifierData, &size)
}
class func getPropertyDataSize(_ objectID: AudioObjectID, address: AudioObjectPropertyAddress, andSize size: inout UInt32) -> (OSStatus) {
var nilValue: ExpressibleByNilLiteral?
return getPropertyDataSize(objectID, address: address, qualifierDataSize: nil, qualifierData: &nilValue, andSize: &size)
}
class func getPropertyDataArray<T, Q>(_ objectID: AudioObjectID, address: AudioObjectPropertyAddress, qualifierDataSize: UInt32?, qualifierData: inout Q, value: inout [T], andDefaultValue defaultValue: T) -> OSStatus {
var size = UInt32(0)
let sizeStatus = getPropertyDataSize(objectID, address: address, qualifierDataSize: qualifierDataSize, qualifierData: &qualifierData, andSize: &size)
if noErr == sizeStatus {
value = [T](repeating: defaultValue, count: Int(size) / MemoryLayout<T>.size)
} else {
return sizeStatus
}
var theAddress = address
let status = AudioObjectGetPropertyData(objectID, &theAddress, qualifierDataSize ?? UInt32(0), &qualifierData, &size, &value)
return status
}
class func getPropertyDataArray<T, Q>(_ objectID: AudioObjectID, address: AudioObjectPropertyAddress, qualifierDataSize: UInt32?, qualifierData: inout [Q], value: inout [T], andDefaultValue defaultValue: T) -> OSStatus {
var size = UInt32(0)
let sizeStatus = getPropertyDataSize(objectID, address: address, qualifierDataSize: qualifierDataSize, qualifierData: &qualifierData, andSize: &size)
if noErr == sizeStatus {
value = [T](repeating: defaultValue, count: Int(size) / MemoryLayout<T>.size)
} else {
return sizeStatus
}
var theAddress = address
let status = AudioObjectGetPropertyData(objectID, &theAddress, qualifierDataSize ?? UInt32(0), &qualifierData, &size, &value)
return status
}
class func getPropertyDataArray<T>(_ objectID: AudioObjectID, address: AudioObjectPropertyAddress, value: inout [T], andDefaultValue defaultValue: T) -> OSStatus {
var nilValue: ExpressibleByNilLiteral?
return getPropertyDataArray(objectID, address: address, qualifierDataSize: nil, qualifierData: &nilValue, value: &value, andDefaultValue: defaultValue)
}
class func setPropertyData<T>(_ objectID: AudioObjectID, address: AudioObjectPropertyAddress, andValue value: inout T) -> OSStatus {
var theAddress = address
let size = UInt32(MemoryLayout<T>.size)
let status = AudioObjectSetPropertyData(objectID, &theAddress, UInt32(0), nil, size, &value)
return status
}
}
So I've never actually used AVAudioEngine myself, but I would guess that if you want it to use a specific device, you need to configure it to do so (I don't see that in the code)
I believe the behavior you are seeing is that:
AVAudioEngine will use the system default deviceLooks like there's a similar question that may help (though the answers are Objective-C): Set AVAudioEngine Input and Output Devices
As far as hog mode goes, it may not be considered very user friendly (and may be intended primarily when you need to work with a non-mixable format).