How to identify the default audio device in Powershell?

Question

I am looking for a solution to get the default audio device via Powershell. In best case, it could work via embedded C#-code to directly use IMMDeviceEnumerator::GetDefaultAudioEndpoint (see here IMMDeviceEnumertor ).

But if it is easier to get this via RegKeys, then this is also OK. I have seen a couple of code-snippets reading the keys from HKLM\\SOFTWARE\\Microsoft\\Windows\\CurrentVersion\\MMDevices\\Audio\\Render or \\Capture, but I still struggle to identify the DEFAULT device.

It seems, when I do modify the order of devices, then I can simply search for active devices (DeviceState=1) and then sort by the values "Level:0", "Level:1" and "Level:2", but the level-values are not available on a system, where the user has not modied the order manually. What is the sort-criteria in such case?

This is the code-snippet to solve it via RegKeys, but as mentioned - not working for all situations:

$regAudio =  "HKLM:\SOFTWARE\Microsoft\Windows\CurrentVersion\MMDevices\Audio"
$nameId = "{b3f8fa53-0004-438e-9003-51a46e139bfc},6"
$classId = "{a45c254e-df1c-4efd-8020-67d146a850e0},2"
$driverDetails = "{83da6326-97a6-4088-9453-a1923f573b29},3"

function get-DefaultDevice($type) {
    $activeDevices = foreach($key in  Get-ChildItem "$regAudio\$type\") {
        foreach($item in Get-ItemProperty $key.PsPath) { 
            if ($item.DeviceState -eq $activeState) {$item}
        }
    }
    $defaultDevice = $activeDevices | Sort-Object -Property "Level:0","Level:1","Level:2" | select -last 1
    $details = Get-ItemProperty "$($defaultDevice.PSPath)\Properties"
    $name = "$($details.$classId) ($($details.$nameId))"
    return @{
        name   = $name
        driver = $details.$driverDetails
    }
}

$OsRender = get-DefaultDevice "Render"
$OsCapture = get-DefaultDevice "Capture"

Is there any way to get this info "in a smart way" (without any external DLLs, of course)?

Answer 1

Finally I figured it out and I am happy to share the working code-snippet:

cls
Add-Type -TypeDefinition @'
using System.Runtime.InteropServices;
[Guid("D666063F-1587-4E43-81F1-B948E807363F"), InterfaceType(ComInterfaceType.InterfaceIsIUnknown)]
interface IMMDevice {
    int a(); int o();
    int GetId([MarshalAs(UnmanagedType.LPWStr)] out string id);
}
[Guid("A95664D2-9614-4F35-A746-DE8DB63617E6"), InterfaceType(ComInterfaceType.InterfaceIsIUnknown)]
interface IMMDeviceEnumerator {
    int f();
    int GetDefaultAudioEndpoint(int dataFlow, int role, out IMMDevice endpoint);
}
[ComImport, Guid("BCDE0395-E52F-467C-8E3D-C4579291692E")] class MMDeviceEnumeratorComObject { }
public class Audio {
    public static string GetDefault (int direction) {
    var enumerator = new MMDeviceEnumeratorComObject() as IMMDeviceEnumerator;
    IMMDevice dev = null;
    Marshal.ThrowExceptionForHR(enumerator.GetDefaultAudioEndpoint(direction, 1, out dev));
    string id = null;
    Marshal.ThrowExceptionForHR(dev.GetId(out id));
    return id;
    }
}
'@

function getFriendlyName($id) {
    $reg = "HKLM:\SYSTEM\CurrentControlSet\Enum\SWD\MMDEVAPI\$id"
    return (get-ItemProperty $reg).FriendlyName
}

$id0 = [audio]::GetDefault(0)
$id1 = [audio]::GetDefault(1)
write-host "Default Speaker: $(getFriendlyName $id0)" 
write-host "Default Micro  : $(getFriendlyName $id1)"