CYCho

Based on the posts by @Danyfirex and @careca , I created the following example code. If this code is compiled and executed, it shows the results of SetVolume, GetVolume, SetMute and GetMute commands of ISimpleAudioVolume interface. With this, I would consider my problem SOLVED. Thank you everyone for your kind support.
Edit: The code was revised to work in uncompiled script. too.
; File name: VolumeControlForProcess_Example.au3 #AutoIt3Wrapper_Outfile=VolumeControlForProcess_Example.exe #include-once #include <WinAPIProc.au3> #include <Array.au3> #include <Misc.au3> #include <Sound.au3> Global Const $sCLSID_MMDeviceEnumerator = "{BCDE0395-E52F-467C-8E3D-C4579291692E}" Global Const $sIID_IMMDeviceEnumerator = "{A95664D2-9614-4F35-A746-DE8DB63617E6}" Global Const $sTagIMMDeviceEnumerator = _ "EnumAudioEndpoints hresult(int;dword;ptr*);" & _ "GetDefaultAudioEndpoint hresult(int;int;ptr*);" & _ "GetDevice hresult(wstr;ptr*);" & _ "RegisterEndpointNotificationCallback hresult(ptr);" & _ "UnregisterEndpointNotificationCallback hresult(ptr)" Global Const $sIID_IMMDevice = "{D666063F-1587-4E43-81F1-B948E807363F}" Global Const $sTagIMMDevice = _ "Activate hresult(struct*;dword;ptr;ptr*);" & _ "OpenPropertyStore hresult(dword;ptr*);" & _ "GetId hresult(wstr*);" & _ "GetState hresult(dword*)" Global Const $sIID_IAudioSessionManager2 = "{77aa99a0-1bd6-484f-8bc7-2c654c9a9b6f}" Global Const $sTagIAudioSessionManager = "GetAudioSessionControl hresult(ptr;dword;ptr*);" & _ "GetSimpleAudioVolume hresult(ptr;dword;ptr*);" Global Const $sTagIAudioSessionManager2 = $sTagIAudioSessionManager & "GetSessionEnumerator hresult(ptr*);" & _ "RegisterSessionNotification hresult(ptr);" & _ "UnregisterSessionNotification hresult(ptr);" & _ "RegisterDuckNotification hresult(wstr;ptr);" & _ "UnregisterDuckNotification hresult(ptr)" Global Const $sIID_IAudioSessionEnumerator = "{e2f5bb11-0570-40ca-acdd-3aa01277dee8}" Global Const $sTagIAudioSessionEnumerator = "GetCount hresult(int*);GetSession hresult(int;ptr*)" Global Const $sIID_IAudioSessionControl = "{f4b1a599-7266-4319-a8ca-e70acb11e8cd}" Global Const $sTagIAudioSessionControl = "GetState hresult(int*);GetDisplayName hresult(ptr);" & _ "SetDisplayName hresult(wstr);GetIconPath hresult(ptr);" & _ "SetIconPath hresult(wstr;ptr);GetGroupingParam hresult(ptr*);" & _ "SetGroupingParam hresult(ptr;ptr);RegisterAudioSessionNotification hresult(ptr);" & _ "UnregisterAudioSessionNotification hresult(ptr);" Global Const $sIID_IAudioSessionControl2 = "{bfb7ff88-7239-4fc9-8fa2-07c950be9c6d}" Global Const $sTagIAudioSessionControl2 = $sTagIAudioSessionControl & "GetSessionIdentifier hresult(ptr)" & _ "GetSessionInstanceIdentifier hresult(ptr);" & _ "GetProcessId hresult(dword*);IsSystemSoundsSession hresult();" & _ "SetDuckingPreferences hresult(bool);" ; http://answers.awesomium.com/questions/3398/controlling-the-sound-using-pinvoke-the-volume-mix.html Global Const $sIID_ISimpleAudioVolume = "{87CE5498-68D6-44E5-9215-6DA47EF883D8}" Global Const $sTagISimpleAudioVolume = _ "SetMasterVolume hresult(float;ptr);" & _ "GetMasterVolume hresult(float*);" & _ "SetMute hresult(int;ptr);" & _ "GetMute hresult(int*)" Global $__oIAudioSessionManager2, $gPID = @AutoItPID, $muteState Opt("WinTitleMatchMode", 2) $sFile = "D:\Music\Phone\Pops\Adele - Hello.mp3" ; full path of your mp3 file $aSound = _SoundOpen($sFile) If @error Then MsgBox(0, 'Open Error', "The file cannot be opened.") Exit EndIf ProcessClose("sndvol.exe") Run(@SystemDir &"\sndvol.exe") $hWnd = WinWaitActive(" Mixer - ") Sleep(3000) _SoundPlay($aSound) Sleep(5000) $muteState = _Audio_Action("GetMute", $gPID, "") If $muteState <> 0 Then _Audio_Action("SetMute", $gPID, False) EndIf _Audio_Action("SetVolume", $gPID, 50/100) $iVolume = Round(_Audio_Action("GetVolume", $gPID, "")*100) MsgBox(0, '', "Initial Volume: " & $iVolume) _Audio_Action("SetVolume", $gPID, 100/100) $iVolume = Round(_Audio_Action("GetVolume", $gPID, "")*100) MsgBox(0, '', "Final Volume: " & $iVolume) _Audio_Action("SetMute", $gPID, True) $muteState = _Audio_Action("GetMute", $gPID, "") ; 1 if muted, 0 if unmuted ; 0 if unmuted, 1 if muted via Mixer, -1 if muted via SetMute If $muteState = 0 Then $muteState = "Unmuted" ElseIf $muteState = -1 Then $muteState = "Muted" EndIf MsgBox(0, '', "Result of GetMute Command: " & $muteState) _Audio_Action("SetMute", $gPID, False) $muteState = _Audio_Action("GetMute", $gPID, "") ; 0 if unmuted, 1 if muted via Mixer, -1 if muted via SetMute If $muteState = 0 Then $muteState = "Unmuted" ElseIf $muteState = -1 Then $muteState = "Muted" EndIf MsgBox(0, '', "Result of GetMute Command: " & $muteState) Sleep(5000) _SoundClose($aSound) Func _Audio_Action($action, $pid, $value) ; Each action takes about 6 milliseconds If Not IsObj($__oIAudioSessionManager2) Then $__oIAudioSessionManager2 = Audio_GetIAudioSessionManager2() EndIf If Not IsObj($__oIAudioSessionManager2) Then Return Local $pIAudioSessionEnumerator, $oIAudioSessionEnumerator If $__oIAudioSessionManager2.GetSessionEnumerator($pIAudioSessionEnumerator) < 0 Then Return $oIAudioSessionEnumerator = ObjCreateInterface($pIAudioSessionEnumerator, $sIID_IAudioSessionEnumerator, $sTagIAudioSessionEnumerator) If Not IsObj($oIAudioSessionEnumerator) Then Return SetError(1) Local $i, $nSessions, $pIAudioSessionControl2, $oIAudioSessionControl2 Local $ProcessID, $oISimpleAudioVolume Local $bMute = 0, $error = 1 If $oIAudioSessionEnumerator.GetCount($nSessions) >= 0 Then For $i = 0 To $nSessions - 1 If $oIAudioSessionEnumerator.GetSession($i, $pIAudioSessionControl2) >= 0 Then $oIAudioSessionControl2 = ObjCreateInterface($pIAudioSessionControl2, $sIID_IAudioSessionControl2, $sTagIAudioSessionControl2) If @error Then ContinueLoop $oIAudioSessionControl2.GetProcessId($ProcessID) If $ProcessID = $pid Then $oISimpleAudioVolume = ObjCreateInterface($pIAudioSessionControl2, $sIID_ISimpleAudioVolume, $sTagISimpleAudioVolume) If @error Then ContinueLoop $oIAudioSessionControl2.AddRef() ;stabilize Switch $action Case "SetVolume" If $oISimpleAudioVolume.SetMasterVolume($value, 0) >= 0 Then $error = 0 ExitLoop EndIf Case "GetVolume" If $oISimpleAudioVolume.GetMasterVolume($value) >= 0 Then $error = 0 ExitLoop EndIf Case "SetMute" If $oISimpleAudioVolume.SetMute($value, Null) >= 0 Then $error = 0 ExitLoop EndIf Case "GetMute" If $oISimpleAudioVolume.GetMute($value) >= 0 Then $error = 0 ExitLoop EndIf EndSwitch EndIf EndIf Next EndIf $oISimpleAudioVolume = 0 $oIAudioSessionControl2 = 0 $oIAudioSessionEnumerator = 0 Return SetError($error, 0, $value) EndFunc ;==>_Audio_Action Func Audio_GetIAudioSessionManager2() Local $oIAudioSessionManager2 = 0 Local Const $eMultimedia = 1, $CLSCTX_INPROC_SERVER = 0x01 Local $pIMMDevice, $oMMDevice, $pIAudioSessionManager2 Local $oMMDeviceEnumerator = ObjCreateInterface($sCLSID_MMDeviceEnumerator, $sIID_IMMDeviceEnumerator, $sTagIMMDeviceEnumerator) If IsObj($oMMDeviceEnumerator) Then If $oMMDeviceEnumerator.GetDefaultAudioEndpoint(0, $eMultimedia, $pIMMDevice) >= 0 Then $oMMDevice = ObjCreateInterface($pIMMDevice, $sIID_IMMDevice, $sTagIMMDevice) If IsObj($oMMDevice) Then If $oMMDevice.Activate(_CLSIDFromString($sIID_IAudioSessionManager2), $CLSCTX_INPROC_SERVER, 0, $pIAudioSessionManager2) >= 0 Then $oIAudioSessionManager2 = ObjCreateInterface($pIAudioSessionManager2, $sIID_IAudioSessionManager2, $sTagIAudioSessionManager2) EndIf $oMMDevice = 0 EndIf EndIf $oMMDeviceEnumerator = 0 EndIf If IsObj($oIAudioSessionManager2) Then Return $oIAudioSessionManager2 EndIf EndFunc ;==>Audio_GetIAudioSessionManager2 Func _CLSIDFromString($sGUID) Local $tGUID = DllStructCreate("ulong Data1;ushort Data2;ushort Data3;byte Data4[8]") DllCall("ole32.dll", "long", "CLSIDFromString", "wstr", $sGUID, "struct*", $tGUID) Return $tGUID EndFunc ;==>CLSIDFromString