winapi - How can I mute/unmute my sound from PowerShell

Question

Trying to write a PowerShell cmdlet that will mute the sound at start, unless already muted, and un-mute it at the end (only if it wasn't muted to begin with). Couldn't find any PoweShell or WMI object I could use. I was toying with using Win32 functions like auxGetVolume or auxSetVolume, but couldn't quite get it to work (how to read the values from an IntPtr?).

I'm using V2 CTP2. Any ideas folks?

Thanks!

Answer 1

Starting with Vista you have to use the Core Audio API to control the system volume. It's a COM API that doesn't support automation and thus requires a lot of boilerplate to use from .NET and PowerShell.

Anyways the code bellow let you access the [Audio]::Volume and [Audio]::Mute properties from PowerShell. This also work on a remote computer which could be useful. Just copy-paste the code in your PowerShell window.

Add-Type -TypeDefinition @'
using System.Runtime.InteropServices;

[Guid("5CDF2C82-841E-4546-9722-0CF74078229A"), InterfaceType(ComInterfaceType.InterfaceIsIUnknown)]
interface IAudioEndpointVolume {
  // f(), g(), ... are unused COM method slots. Define these if you care
  int f(); int g(); int h(); int i();
  int SetMasterVolumeLevelScalar(float fLevel, System.Guid pguidEventContext);
  int j();
  int GetMasterVolumeLevelScalar(out float pfLevel);
  int k(); int l(); int m(); int n();
  int SetMute([MarshalAs(UnmanagedType.Bool)] bool bMute, System.Guid pguidEventContext);
  int GetMute(out bool pbMute);
}
[Guid("D666063F-1587-4E43-81F1-B948E807363F"), InterfaceType(ComInterfaceType.InterfaceIsIUnknown)]
interface IMMDevice {
  int Activate(ref System.Guid id, int clsCtx, int activationParams, out IAudioEndpointVolume aev);
}
[Guid("A95664D2-9614-4F35-A746-DE8DB63617E6"), InterfaceType(ComInterfaceType.InterfaceIsIUnknown)]
interface IMMDeviceEnumerator {
  int f(); // Unused
  int GetDefaultAudioEndpoint(int dataFlow, int role, out IMMDevice endpoint);
}
[ComImport, Guid("BCDE0395-E52F-467C-8E3D-C4579291692E")] class MMDeviceEnumeratorComObject { }

public class Audio {
  static IAudioEndpointVolume Vol() {
    var enumerator = new MMDeviceEnumeratorComObject() as IMMDeviceEnumerator;
    IMMDevice dev = null;
    Marshal.ThrowExceptionForHR(enumerator.GetDefaultAudioEndpoint(/*eRender*/ 0, /*eMultimedia*/ 1, out dev));
    IAudioEndpointVolume epv = null;
    var epvid = typeof(IAudioEndpointVolume).GUID;
    Marshal.ThrowExceptionForHR(dev.Activate(ref epvid, /*CLSCTX_ALL*/ 23, 0, out epv));
    return epv;
  }
  public static float Volume {
    get {float v = -1; Marshal.ThrowExceptionForHR(Vol().GetMasterVolumeLevelScalar(out v)); return v;}
    set {Marshal.ThrowExceptionForHR(Vol().SetMasterVolumeLevelScalar(value, System.Guid.Empty));}
  }
  public static bool Mute {
    get { bool mute; Marshal.ThrowExceptionForHR(Vol().GetMute(out mute)); return mute; }
    set { Marshal.ThrowExceptionForHR(Vol().SetMute(value, System.Guid.Empty)); }
  }
}
'@

Usage sample:

PS C:> [Audio]::Volume         # Check current volume (now about 10%)
0,09999999
PS C:> [Audio]::Mute           # See if speaker is muted
False
PS C:> [Audio]::Mute = $true   # Mute speaker
PS C:> [Audio]::Volume = 0.75  # Set volume to 75%
PS C:> [Audio]::Volume         # Check that the changes are applied
0,75
PS C:> [Audio]::Mute
True
PS C:>

There are more comprehensive .NET wrappers out there for the Core Audio API if you need one but I'm not aware of a set of PowerShell friendly cmdlets.

P.S. Diogo answer seems clever but it doesn't work for me.