AudioManager.cs

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

namespace VideoPlayerController
{
    /// <summary>
    /// Controls audio using the Windows CoreAudio API
    /// from: http://stackoverflow.com/questions/14306048/controling-volume-mixer
    /// and: http://netcoreaudio.codeplex.com/
    /// </summary>
    public static class AudioManager
    {
        #region Master Volume Manipulation

        /// <summary>
        /// Gets the current master volume in scalar values (percentage)
        /// </summary>
        /// <returns>-1 in case of an error, if successful the value will be between 0 and 100</returns>
        public static float GetMasterVolume()
        {
            IAudioEndpointVolume masterVol = null;
            try
            {
                masterVol = GetMasterVolumeObject();
                if (masterVol == null)
                    return -1;

                float volumeLevel;
                masterVol.GetMasterVolumeLevelScalar(out volumeLevel);
                return volumeLevel*100;
            }
            finally
            {
                if (masterVol != null)
                    Marshal.ReleaseComObject(masterVol);
            }
        }

        /// <summary>
        /// Gets the mute state of the master volume. 
        /// While the volume can be muted the <see cref="GetMasterVolume"/> will still return the pre-muted volume value.
        /// </summary>
        /// <returns>false if not muted, true if volume is muted</returns>
        public static bool GetMasterVolumeMute()
        {
            IAudioEndpointVolume masterVol = null;
            try
            {
                masterVol = GetMasterVolumeObject();
                if (masterVol == null)
                    return false;

                bool isMuted;
                masterVol.GetMute(out isMuted);
                return isMuted;
            }
            finally
            {
                if (masterVol != null)
                    Marshal.ReleaseComObject(masterVol);
            }
        }

        /// <summary>
        /// Sets the master volume to a specific level
        /// </summary>
        /// <param name="newLevel">Value between 0 and 100 indicating the desired scalar value of the volume</param>
        public static void SetMasterVolume(float newLevel)
        {
            IAudioEndpointVolume masterVol = null;
            try
            {
                masterVol = GetMasterVolumeObject();
                if (masterVol == null)
                    return;

                masterVol.SetMasterVolumeLevelScalar(newLevel/100, Guid.Empty);
            }
            finally
            {
                if (masterVol != null)
                    Marshal.ReleaseComObject(masterVol);
            }
        }

        /// <summary>
        /// Increments or decrements the current volume level by the <see cref="stepAmount"/>.
        /// </summary>
        /// <param name="stepAmount">Value between -100 and 100 indicating the desired step amount. Use negative numbers to decrease
        /// the volume and positive numbers to increase it.</param>
        /// <returns>the new volume level assigned</returns>
        public static float StepMasterVolume(float stepAmount)
        {
            IAudioEndpointVolume masterVol = null;
            try
            {
                masterVol = GetMasterVolumeObject();
                if (masterVol == null)
                    return -1;

                float stepAmountScaled = stepAmount/100;

                // Get the level
                float volumeLevel;
                masterVol.GetMasterVolumeLevelScalar(out volumeLevel);

                // Calculate the new level
                float newLevel = volumeLevel + stepAmountScaled;
                newLevel = Math.Min(1, newLevel);
                newLevel = Math.Max(0, newLevel);

                masterVol.SetMasterVolumeLevelScalar(newLevel, Guid.Empty);

                // Return the new volume level that was set
                return newLevel*100;
            }
            finally
            {
                if (masterVol != null)
                    Marshal.ReleaseComObject(masterVol);
            }
        }

        /// <summary>
        /// Mute or unmute the master volume
        /// </summary>
        /// <param name="isMuted">true to mute the master volume, false to unmute</param>
        public static void SetMasterVolumeMute(bool isMuted)
        {
            IAudioEndpointVolume masterVol = null;
            try
            {
                masterVol = GetMasterVolumeObject();
                if (masterVol == null)
                    return;

                masterVol.SetMute(isMuted, Guid.Empty);
            }
            finally
            {
                if (masterVol != null)
                    Marshal.ReleaseComObject(masterVol);
            }
        }

        /// <summary>
        /// Switches between the master volume mute states depending on the current state
        /// </summary>
        /// <returns>the current mute state, true if the volume was muted, false if unmuted</returns>
        public static bool ToggleMasterVolumeMute()
        {
            IAudioEndpointVolume masterVol = null;
            try
            {
                masterVol = GetMasterVolumeObject();
                if (masterVol == null)
                    return false;

                bool isMuted;
                masterVol.GetMute(out isMuted);
                masterVol.SetMute(!isMuted, Guid.Empty);

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

        private static IAudioEndpointVolume GetMasterVolumeObject()
        {
            IMMDeviceEnumerator deviceEnumerator = null;
            IMMDevice speakers = null;
            try
            {
                deviceEnumerator = (IMMDeviceEnumerator) (new MMDeviceEnumerator());
                deviceEnumerator.GetDefaultAudioEndpoint(EDataFlow.eRender, ERole.eMultimedia, out speakers);

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

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

        #endregion
        
        #region Individual Application Volume Manipulation

        public static float? GetApplicationVolume(int pid)
        {
            ISimpleAudioVolume volume = GetVolumeObject(pid);
            if (volume == null)
                return null;

            float level;
            volume.GetMasterVolume(out level);
            Marshal.ReleaseComObject(volume);
            return level*100;
        }

        public static bool? GetApplicationMute(int pid)
        {
            ISimpleAudioVolume volume = GetVolumeObject(pid);
            if (volume == null)
                return null;

            bool mute;
            volume.GetMute(out mute);
            Marshal.ReleaseComObject(volume);
            return mute;
        }

        public static void SetApplicationVolume(int pid, float level)
        {
            ISimpleAudioVolume volume = GetVolumeObject(pid);
            if (volume == null)
                return;

            Guid guid = Guid.Empty;
            volume.SetMasterVolume(level/100, ref guid);
            Marshal.ReleaseComObject(volume);
        }

        public static void SetApplicationMute(int pid, bool mute)
        {
            ISimpleAudioVolume volume = GetVolumeObject(pid);
            if (volume == null)
                return;

            Guid guid = Guid.Empty;
            volume.SetMute(mute, ref guid);
            Marshal.ReleaseComObject(volume);
        }

        private static ISimpleAudioVolume GetVolumeObject(int pid)
        {
            IMMDeviceEnumerator deviceEnumerator = null;
            IAudioSessionEnumerator sessionEnumerator = null;
            IAudioSessionManager2 mgr = null;
            IMMDevice speakers = null;
            try
            {
                // get the speakers (1st render + multimedia) device
                deviceEnumerator = (IMMDeviceEnumerator) (new MMDeviceEnumerator());
                deviceEnumerator.GetDefaultAudioEndpoint(EDataFlow.eRender, ERole.eMultimedia, out speakers);

                // activate the session manager. we need the enumerator
                Guid IID_IAudioSessionManager2 = typeof (IAudioSessionManager2).GUID;
                object o;
                speakers.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 (speakers != null) Marshal.ReleaseComObject(speakers);
                if (deviceEnumerator != null) Marshal.ReleaseComObject(deviceEnumerator);
            }
        }

        #endregion

    }

    #region Abstracted COM interfaces from Windows CoreAudio API

    [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
}

I was just looking for a way to change the system volume, this is working great for me so far, thanks.

Perfect, work on Windows 10!!

I'm currently trying to get it running in one project. The whole thing runs on .NET-6 but I always get the exception (see above).
I don't know what could be the problem. I used it successfully under .NET 4.8 before. I didn't change anything, I copied the code and executed it...