CoreAudioAPI.cs

using System;
using System.Runtime.InteropServices;
// ReSharper disable SuspiciousTypeConversion.Global
// ReSharper disable InconsistentNaming

//Copied from https://gist.github.com/sverrirs/d099b34b7f72bb4fb386

namespace MediaControls_Plugin
{
    #region Abstracted COM interfaces from Windows CoreAudio API
    internal class Speakers : Direction {
        public EDataFlow Flow => EDataFlow.eRender;
        public ERole Role => ERole.eMultimedia;
    }

    internal class Microphone : Direction {
        public EDataFlow Flow => EDataFlow.eCapture;
        public ERole Role => ERole.eMultimedia;
    }

    internal interface Direction {
        EDataFlow Flow { get; }
        ERole Role { get; }
    }

    internal static class CoreAudioAPI {
        public static IAudioEndpointVolume GetMasterVolumeObject(Direction dir)
        {
            IMMDeviceEnumerator deviceEnumerator = null;
            IMMDevice device = null;
            try
            {
                deviceEnumerator = (IMMDeviceEnumerator)(new MMDeviceEnumerator());
                deviceEnumerator.GetDefaultAudioEndpoint(dir.Flow, dir.Role, out device);

                Guid IID_IAudioEndpointVolume = typeof(IAudioEndpointVolume).GUID;
                object o;
                device.Activate(ref IID_IAudioEndpointVolume, 0, IntPtr.Zero, out o);
                IAudioEndpointVolume masterVol = (IAudioEndpointVolume)o;

                return masterVol;
            }
            finally
            {
                if (device != null) Marshal.ReleaseComObject(device);
                if (deviceEnumerator != null) Marshal.ReleaseComObject(deviceEnumerator);
            }
        }

        public static ISimpleAudioVolume GetVolumeObject(Direction dir, int pid)
        {
            IMMDeviceEnumerator deviceEnumerator = null;
            IAudioSessionEnumerator sessionEnumerator = null;
            IAudioSessionManager2 mgr = null;
            IMMDevice device = null;
            try
            {
                // get the speakers (1st render + multimedia) device
                deviceEnumerator = (IMMDeviceEnumerator)(new MMDeviceEnumerator());
                deviceEnumerator.GetDefaultAudioEndpoint(dir.Flow, dir.Role, out device);

                // activate the session manager. we need the enumerator
                Guid IID_IAudioSessionManager2 = typeof(IAudioSessionManager2).GUID;
                object o;
                device.Activate(ref IID_IAudioSessionManager2, 0, IntPtr.Zero, out o);
                mgr = (IAudioSessionManager2)o;

                // enumerate sessions for on this device
                mgr.GetSessionEnumerator(out sessionEnumerator);
                int count;
                sessionEnumerator.GetCount(out count);

                // search for an audio session with the required process-id
                ISimpleAudioVolume volumeControl = null;
                for (int i = 0; i < count; ++i)
                {
                    IAudioSessionControl2 ctl = null;
                    try
                    {
                        sessionEnumerator.GetSession(i, out ctl);

                        // NOTE: we could also use the app name from ctl.GetDisplayName()
                        int cpid;
                        ctl.GetProcessId(out cpid);

                        if (cpid == pid)
                        {
                            volumeControl = ctl as ISimpleAudioVolume;
                            break;
                        }
                    }
                    finally
                    {
                        if (ctl != null) Marshal.ReleaseComObject(ctl);
                    }
                }

                return volumeControl;
            }
            finally
            {
                if (sessionEnumerator != null) Marshal.ReleaseComObject(sessionEnumerator);
                if (mgr != null) Marshal.ReleaseComObject(mgr);
                if (device != null) Marshal.ReleaseComObject(device);
                if (deviceEnumerator != null) Marshal.ReleaseComObject(deviceEnumerator);
            }
        }
    }

    [ComImport]
    [Guid("BCDE0395-E52F-467C-8E3D-C4579291692E")]
    internal class MMDeviceEnumerator
    {
    }

    internal enum EDataFlow
    {
        eRender,
        eCapture,
        eAll,
        EDataFlow_enum_count
    }

    internal enum ERole
    {
        eConsole,
        eMultimedia,
        eCommunications,
        ERole_enum_count
    }

    [Guid("A95664D2-9614-4F35-A746-DE8DB63617E6"), InterfaceType(ComInterfaceType.InterfaceIsIUnknown)]
    internal interface IMMDeviceEnumerator
    {
        int NotImpl1();

        [PreserveSig]
        int GetDefaultAudioEndpoint(EDataFlow dataFlow, ERole role, out IMMDevice ppDevice);

        // the rest is not implemented
    }

    [Guid("D666063F-1587-4E43-81F1-B948E807363F"), InterfaceType(ComInterfaceType.InterfaceIsIUnknown)]
    internal interface IMMDevice
    {
        [PreserveSig]
        int Activate(ref Guid iid, int dwClsCtx, IntPtr pActivationParams, [MarshalAs(UnmanagedType.IUnknown)] out object ppInterface);

        // the rest is not implemented
    }

    [Guid("77AA99A0-1BD6-484F-8BC7-2C654C9A9B6F"), InterfaceType(ComInterfaceType.InterfaceIsIUnknown)]
    internal interface IAudioSessionManager2
    {
        int NotImpl1();
        int NotImpl2();

        [PreserveSig]
        int GetSessionEnumerator(out IAudioSessionEnumerator SessionEnum);

        // the rest is not implemented
    }

    [Guid("E2F5BB11-0570-40CA-ACDD-3AA01277DEE8"), InterfaceType(ComInterfaceType.InterfaceIsIUnknown)]
    internal interface IAudioSessionEnumerator
    {
        [PreserveSig]
        int GetCount(out int SessionCount);

        [PreserveSig]
        int GetSession(int SessionCount, out IAudioSessionControl2 Session);
    }

    [Guid("87CE5498-68D6-44E5-9215-6DA47EF883D8"), InterfaceType(ComInterfaceType.InterfaceIsIUnknown)]
    internal interface ISimpleAudioVolume
    {
        [PreserveSig]
        int SetMasterVolume(float fLevel, ref Guid EventContext);

        [PreserveSig]
        int GetMasterVolume(out float pfLevel);

        [PreserveSig]
        int SetMute(bool bMute, ref Guid EventContext);

        [PreserveSig]
        int GetMute(out bool pbMute);
    }

    [Guid("bfb7ff88-7239-4fc9-8fa2-07c950be9c6d"), InterfaceType(ComInterfaceType.InterfaceIsIUnknown)]
    internal interface IAudioSessionControl2
    {
        // IAudioSessionControl
        [PreserveSig]
        int NotImpl0();

        [PreserveSig]
        int GetDisplayName([MarshalAs(UnmanagedType.LPWStr)] out string pRetVal);

        [PreserveSig]
        int SetDisplayName([MarshalAs(UnmanagedType.LPWStr)] string Value, [MarshalAs(UnmanagedType.LPStruct)] Guid EventContext);

        [PreserveSig]
        int GetIconPath([MarshalAs(UnmanagedType.LPWStr)] out string pRetVal);

        [PreserveSig]
        int SetIconPath([MarshalAs(UnmanagedType.LPWStr)] string Value, [MarshalAs(UnmanagedType.LPStruct)] Guid EventContext);

        [PreserveSig]
        int GetGroupingParam(out Guid pRetVal);

        [PreserveSig]
        int SetGroupingParam([MarshalAs(UnmanagedType.LPStruct)] Guid Override, [MarshalAs(UnmanagedType.LPStruct)] Guid EventContext);

        [PreserveSig]
        int NotImpl1();

        [PreserveSig]
        int NotImpl2();

        // IAudioSessionControl2
        [PreserveSig]
        int GetSessionIdentifier([MarshalAs(UnmanagedType.LPWStr)] out string pRetVal);

        [PreserveSig]
        int GetSessionInstanceIdentifier([MarshalAs(UnmanagedType.LPWStr)] out string pRetVal);

        [PreserveSig]
        int GetProcessId(out int pRetVal);

        [PreserveSig]
        int IsSystemSoundsSession();

        [PreserveSig]
        int SetDuckingPreference(bool optOut);
    }

    // http://netcoreaudio.codeplex.com/SourceControl/latest#trunk/Code/CoreAudio/Interfaces/IAudioEndpointVolume.cs
    [Guid("5CDF2C82-841E-4546-9722-0CF74078229A"), InterfaceType(ComInterfaceType.InterfaceIsIUnknown)]
    public interface IAudioEndpointVolume
    {
        [PreserveSig]
        int NotImpl1();

        [PreserveSig]
        int NotImpl2();

        /// <summary>
        /// Gets a count of the channels in the audio stream.
        /// </summary>
        /// <param name="channelCount">The number of channels.</param>
        /// <returns>An HRESULT code indicating whether the operation passed of failed.</returns>
        [PreserveSig]
        int GetChannelCount(
            [Out][MarshalAs(UnmanagedType.U4)] out UInt32 channelCount);

        /// <summary>
        /// Sets the master volume level of the audio stream, in decibels.
        /// </summary>
        /// <param name="level">The new master volume level in decibels.</param>
        /// <param name="eventContext">A user context value that is passed to the notification callback.</param>
        /// <returns>An HRESULT code indicating whether the operation passed of failed.</returns>
        [PreserveSig]
        int SetMasterVolumeLevel(
            [In][MarshalAs(UnmanagedType.R4)] float level,
            [In][MarshalAs(UnmanagedType.LPStruct)] Guid eventContext);

        /// <summary>
        /// Sets the master volume level, expressed as a normalized, audio-tapered value.
        /// </summary>
        /// <param name="level">The new master volume level expressed as a normalized value between 0.0 and 1.0.</param>
        /// <param name="eventContext">A user context value that is passed to the notification callback.</param>
        /// <returns>An HRESULT code indicating whether the operation passed of failed.</returns>
        [PreserveSig]
        int SetMasterVolumeLevelScalar(
            [In][MarshalAs(UnmanagedType.R4)] float level,
            [In][MarshalAs(UnmanagedType.LPStruct)] Guid eventContext);

        /// <summary>
        /// Gets the master volume level of the audio stream, in decibels.
        /// </summary>
        /// <param name="level">The volume level in decibels.</param>
        /// <returns>An HRESULT code indicating whether the operation passed of failed.</returns>
        [PreserveSig]
        int GetMasterVolumeLevel(
            [Out][MarshalAs(UnmanagedType.R4)] out float level);

        /// <summary>
        /// Gets the master volume level, expressed as a normalized, audio-tapered value.
        /// </summary>
        /// <param name="level">The volume level expressed as a normalized value between 0.0 and 1.0.</param>
        /// <returns>An HRESULT code indicating whether the operation passed of failed.</returns>
        [PreserveSig]
        int GetMasterVolumeLevelScalar(
            [Out][MarshalAs(UnmanagedType.R4)] out float level);

        /// <summary>
        /// Sets the volume level, in decibels, of the specified channel of the audio stream.
        /// </summary>
        /// <param name="channelNumber">The channel number.</param>
        /// <param name="level">The new volume level in decibels.</param>
        /// <param name="eventContext">A user context value that is passed to the notification callback.</param>
        /// <returns>An HRESULT code indicating whether the operation passed of failed.</returns>
        [PreserveSig]
        int SetChannelVolumeLevel(
            [In][MarshalAs(UnmanagedType.U4)] UInt32 channelNumber,
            [In][MarshalAs(UnmanagedType.R4)] float level,
            [In][MarshalAs(UnmanagedType.LPStruct)] Guid eventContext);

        /// <summary>
        /// Sets the normalized, audio-tapered volume level of the specified channel in the audio stream.
        /// </summary>
        /// <param name="channelNumber">The channel number.</param>
        /// <param name="level">The new master volume level expressed as a normalized value between 0.0 and 1.0.</param>
        /// <param name="eventContext">A user context value that is passed to the notification callback.</param>
        /// <returns>An HRESULT code indicating whether the operation passed of failed.</returns>
        [PreserveSig]
        int SetChannelVolumeLevelScalar(
            [In][MarshalAs(UnmanagedType.U4)] UInt32 channelNumber,
            [In][MarshalAs(UnmanagedType.R4)] float level,
            [In][MarshalAs(UnmanagedType.LPStruct)] Guid eventContext);

        /// <summary>
        /// Gets the volume level, in decibels, of the specified channel in the audio stream.
        /// </summary>
        /// <param name="channelNumber">The zero-based channel number.</param>
		/// <param name="level">The volume level in decibels.</param>
        /// <returns>An HRESULT code indicating whether the operation passed of failed.</returns>
        [PreserveSig]
        int GetChannelVolumeLevel(
            [In][MarshalAs(UnmanagedType.U4)] UInt32 channelNumber,
            [Out][MarshalAs(UnmanagedType.R4)] out float level);

        /// <summary>
        /// Gets the normalized, audio-tapered volume level of the specified channel of the audio stream.
        /// </summary>
        /// <param name="channelNumber">The zero-based channel number.</param>
		/// <param name="level">The volume level expressed as a normalized value between 0.0 and 1.0.</param>
        /// <returns>An HRESULT code indicating whether the operation passed of failed.</returns>
        [PreserveSig]
        int GetChannelVolumeLevelScalar(
            [In][MarshalAs(UnmanagedType.U4)] UInt32 channelNumber,
            [Out][MarshalAs(UnmanagedType.R4)] out float level);

        /// <summary>
        /// Sets the muting state of the audio stream.
        /// </summary>
        /// <param name="isMuted">True to mute the stream, or false to unmute the stream.</param>
        /// <param name="eventContext">A user context value that is passed to the notification callback.</param>
        /// <returns>An HRESULT code indicating whether the operation passed of failed.</returns>
        [PreserveSig]
        int SetMute(
            [In][MarshalAs(UnmanagedType.Bool)] Boolean isMuted,
            [In][MarshalAs(UnmanagedType.LPStruct)] Guid eventContext);

        /// <summary>
        /// Gets the muting state of the audio stream.
        /// </summary>
        /// <param name="isMuted">The muting state. True if the stream is muted, false otherwise.</param>
        /// <returns>An HRESULT code indicating whether the operation passed of failed.</returns>
        [PreserveSig]
        int GetMute(
            [Out][MarshalAs(UnmanagedType.Bool)] out Boolean isMuted);

        /// <summary>
        /// Gets information about the current step in the volume range.
        /// </summary>
        /// <param name="step">The current zero-based step index.</param>
        /// <param name="stepCount">The total number of steps in the volume range.</param>
        /// <returns>An HRESULT code indicating whether the operation passed of failed.</returns>
        [PreserveSig]
        int GetVolumeStepInfo(
            [Out][MarshalAs(UnmanagedType.U4)] out UInt32 step,
            [Out][MarshalAs(UnmanagedType.U4)] out UInt32 stepCount);

        /// <summary>
        /// Increases the volume level by one step.
        /// </summary>
        /// <param name="eventContext">A user context value that is passed to the notification callback.</param>
        /// <returns>An HRESULT code indicating whether the operation passed of failed.</returns>
        [PreserveSig]
        int VolumeStepUp(
            [In][MarshalAs(UnmanagedType.LPStruct)] Guid eventContext);

        /// <summary>
        /// Decreases the volume level by one step.
        /// </summary>
        /// <param name="eventContext">A user context value that is passed to the notification callback.</param>
        /// <returns>An HRESULT code indicating whether the operation passed of failed.</returns>
        [PreserveSig]
        int VolumeStepDown(
            [In][MarshalAs(UnmanagedType.LPStruct)] Guid eventContext);

        /// <summary>
        /// Queries the audio endpoint device for its hardware-supported functions.
        /// </summary>
        /// <param name="hardwareSupportMask">A hardware support mask that indicates the capabilities of the endpoint.</param>
        /// <returns>An HRESULT code indicating whether the operation passed of failed.</returns>
        [PreserveSig]
        int QueryHardwareSupport(
            [Out][MarshalAs(UnmanagedType.U4)] out UInt32 hardwareSupportMask);

        /// <summary>
        /// Gets the volume range of the audio stream, in decibels.
        /// </summary>
		/// <param name="volumeMin">The minimum volume level in decibels.</param>
		/// <param name="volumeMax">The maximum volume level in decibels.</param>
		/// <param name="volumeStep">The volume increment level in decibels.</param>
        /// <returns>An HRESULT code indicating whether the operation passed of failed.</returns>
        [PreserveSig]
        int GetVolumeRange(
            [Out][MarshalAs(UnmanagedType.R4)] out float volumeMin,
            [Out][MarshalAs(UnmanagedType.R4)] out float volumeMax,
            [Out][MarshalAs(UnmanagedType.R4)] out float volumeStep);
    }

    #endregion
}