Audio Output

The IAudioOutputDevices service tells you where the music is going — the built-in speaker, wired or USB headphones, a Bluetooth speaker, the car, HDMI or AirPlay — and raises an event when that route changes, such as when the user unplugs their headphones or a Bluetooth speaker connects.

It is registered by AddShinyMusic(), so resolve it from DI like any other service:

public class NowPlayingViewModel(IAudioOutputDevices outputs, IMusicPlayer player)
{
    // ...
}

Note

This is output only and read-only. Capture devices (microphones) are out of scope for a music library, and choosing the output route is the user’s job — through the OS route picker, Control Center, or the system audio settings. No permission is required.

The Current Route

Current returns the route music is playing through, or null when the platform reports none:

var current = outputs.Current;

if (current != null)
    Console.WriteLine($"Playing on {current.Name} ({current.Type})");
    // e.g. "Playing on JBL Flip 5 (BluetoothA2dp)"

Each route is an AudioOutputDevice:

Property	Type	Description
Id	string	Stable platform identifier (Apple port UID / Android AudioDeviceInfo.Id)
Name	string	Human-friendly name, e.g. "JBL Flip 5" or "Speaker"
Type	AudioOutputType	Normalized route type
IsCurrent	bool	Whether this is the route in use right now

AudioOutputType normalizes what each platform reports into one set of values:

Unknown, BuiltInSpeaker, BuiltInReceiver, WiredHeadphones, WiredHeadset, Bluetooth (hands-free HFP/SCO/LE), BluetoothA2dp (stereo — the normal music route), Usb, CarAudio, Hdmi, AirPlay.

Classifying the Route

Rather than switching on every AudioOutputType value, use the helpers in AudioOutputExtensions. Each has an overload for both AudioOutputDevice and AudioOutputType:

Method	true for	Use it for
IsWired()	WiredHeadphones, WiredHeadset, Usb	”is something plugged in”
IsBluetooth()	Bluetooth, BluetoothA2dp	showing a Bluetooth badge
IsBuiltIn()	BuiltInSpeaker, BuiltInReceiver	nothing is plugged in or paired
IsHeadphones()	wired or Bluetooth headphones/headsets	”audio is private to the user”
IsExternalSystem()	CarAudio, Hdmi, AirPlay	playback has left the device

var current = outputs.Current;

if (current?.IsBluetooth() == true)
    ShowBluetoothIcon();
else if (current?.IsWired() == true)
    ShowWiredIcon();
else
    ShowSpeakerIcon();

Tip

IsWired() includes Usb on purpose: on handsets with no 3.5 mm jack, the wired option is USB-C. The trade-off is that a USB audio interface or DAC also answers true — use IsHeadphones() when you specifically mean something worn on the head, at the cost of missing USB-C earbuds.

Reacting to Route Changes

Changed fires whenever the active output route changes. The argument is the new Current value, which may be null:

outputs.Changed += (sender, device) =>
{
    // Classic behavior: the user yanked the headphones out and audio fell back
    // to the loudspeaker — pause rather than blast the room.
    if (device?.IsBuiltIn() == true)
        MainThread.BeginInvokeOnMainThread(_player.Pause);
};

Caution

Changed is raised on whatever thread the OS delivers the route notification on. Marshal to the UI thread (MainThread.BeginInvokeOnMainThread) before touching UI state.

Listing Routes

GetOutputs() returns the output routes the OS reports, with IsCurrent set on the active one:

foreach (var device in outputs.GetOutputs())
    Console.WriteLine($"{device.Name} — {device.Type}{(device.IsCurrent ? " (current)" : "")}");

What this contains differs by platform — see below. It is not a device picker: no platform here lets an app switch the route.

Platform Behavior

Android

GetOutputs() returns every connected output from AudioManager.GetDevices(Outputs).

Android’s AudioDeviceInfo carries no “active” flag, so Current is a derived value: the connected outputs are ranked the way the platform’s own media routing policy does and the winner is reported.

Priority	Route
1	Bluetooth A2DP
2	Bluetooth hands-free (SCO/LE)
3	Wired headset
4	Wired headphones
5	USB
6	Car audio (Automotive bus)
7	HDMI
8	Built-in speaker
9	Earpiece

That’s a very good approximation for media playback — but it is derived, not a platform guarantee. Route changes come from an AudioDeviceCallback registered on the first Changed subscription.

iOS and Mac Catalyst

Current comes straight from AVAudioSession.CurrentRoute — the OS reports the active route directly, so nothing is inferred.

The OS exposes only the active route’s ports; discovering every reachable AirPlay or Bluetooth destination is owned by the system route picker (AVRoutePickerView / Control Center). So GetOutputs() returns the current route — usually a single entry — rather than a full list of destinations.

A mic-equipped wired headset reports as WiredHeadphones, because Apple only surfaces the headset microphone on the input side. Use IsWired() or IsHeadphones() instead of testing for WiredHeadset directly.

Route changes come from the AVAudioSession route-change notification, observed on the first Changed subscription.

Note

Route detection needs a physical device. Simulators and emulators report a single built-in route and never raise a change.