Here is the code :
public class AudioMixerHelper
{
public const int MMSYSERR_NOERROR = 0;
public const int MAXPNAMELEN = 32;
public const int MIXER_LONG_NAME_CHARS = 64;
public const int MIXER_SHORT_NAME_CHARS = 16;
public const int MIXER_GETLINEINFOF_COMPONENTTYPE = 0x3;
public const int MIXER_GETCONTROLDETAILSF_VALUE = 0x0;
public const int MIXER_GETLINECONTROLSF_ONEBYTYPE = 0x2;
public const int MIXER_SETCONTROLDETAILSF_VALUE = 0x0;
public const int MIXERLINE_COMPONENTTYPE_DST_FIRST = 0x0;
public const int MIXERLINE_COMPONENTTYPE_SRC_FIRST = 0x1000;
public const int MIXERLINE_COMPONENTTYPE_DST_SPEAKERS =
(MIXERLINE_COMPONENTTYPE_DST_FIRST + 4);
public const int MIXERLINE_COMPONENTTYPE_SRC_MICROPHONE =
(MIXERLINE_COMPONENTTYPE_SRC_FIRST + 3);
public const int MIXERLINE_COMPONENTTYPE_SRC_LINE =
(MIXERLINE_COMPONENTTYPE_SRC_FIRST + 2);
public const int MIXERCONTROL_CT_CLASS_FADER = 0x50000000;
public const int MIXERCONTROL_CT_UNITS_UNSIGNED = 0x30000;
public const int MIXERCONTROL_CONTROLTYPE_FADER =
(MIXERCONTROL_CT_CLASS_FADER | MIXERCONTROL_CT_UNITS_UNSIGNED);
public const int MIXERCONTROL_CONTROLTYPE_VOLUME =
(MIXERCONTROL_CONTROLTYPE_FADER + 1);
[ DllImport( "winmm.dll", CharSet=CharSet.Ansi )]
private static extern int mixerClose (int hmx);
[ DllImport( "winmm.dll", CharSet=CharSet.Ansi )]
private static extern int mixerGetControlDetailsA (int hmxobj,ref
MIXERCONTROLDETAILS pmxcd , int fdwDetails);
[ DllImport( "winmm.dll", CharSet=CharSet.Ansi )]
private static extern int mixerGetDevCapsA( int uMxId, MIXERCAPS
pmxcaps, int cbmxcaps) ;
[ DllImport( "winmm.dll", CharSet=CharSet.Ansi )]
private static extern int mixerGetID (int hmxobj, int pumxID, int
fdwId );
[ DllImport( "winmm.dll", CharSet=CharSet.Ansi )]
private static extern int mixerGetLineControlsA (int hmxobj,ref
MIXERLINECONTROLS pmxlc, int fdwControls);
[ DllImport( "winmm.dll", CharSet=CharSet.Ansi )]
private static extern int mixerGetLineInfoA (int hmxobj,ref
MIXERLINE pmxl , int fdwInfo);
[ DllImport( "winmm.dll", CharSet=CharSet.Ansi )]
private static extern int mixerGetNumDevs();
[ DllImport( "winmm.dll", CharSet=CharSet.Ansi )]
private static extern int mixerMessage(int hmx , int uMsg , int
dwParam1 , int dwParam2);
[ DllImport( "winmm.dll", CharSet=CharSet.Ansi )]
private static extern int mixerOpen (out int phmx , int uMxId ,
int dwCallback , int dwInstance , int fdwOpen);
[ DllImport( "winmm.dll", CharSet=CharSet.Ansi )]
private static extern int mixerSetControlDetails(int hmxobj ,ref
MIXERCONTROLDETAILS pmxcd , int fdwDetails);
public struct MIXERCAPS{
public int wMid ; // manufacturer id
public int wPid ; // product id
public int vDriverVersion ; // version of the driver
[ MarshalAs( UnmanagedType.ByValTStr, SizeConst=MAXPNAMELEN)]
public string szPname ; // product name
public int fdwSupport ; // misc. support bits
public int cDestinations ; // count of destinations
}
public struct MIXERCONTROL{
public int cbStruct ; // size in Byte of MIXERCONTROL
public int dwControlID ; // unique control id for mixer
device
public int dwControlType ; // MIXERCONTROL_CONTROLpublic
enum _xxx
public int fdwControl ; // MIXERCONTROL_CONTROLF_xxx
public int cMultipleItems ; // if
MIXERCONTROL_CONTROLF_MULTIPLE
[ MarshalAs( UnmanagedType.ByValTStr,
SizeConst=MIXER_SHORT_NAME_CHARS )]
public string szShortName ; // short name of
[ MarshalAs( UnmanagedType.ByValTStr,
SizeConst=MIXER_LONG_NAME_CHARS )]
public string szName ; // long name of
public int lMinimum ; // Minimum value
public int lMaximum ; // Maximum value
// [ MarshalAs( UnmanagedType.ByValArray, SizeConst=10 )]
[ MarshalAs( UnmanagedType.U4, SizeConst=10 )]
public int reserved; // replaced // reserved structure space
}
public struct MIXERCONTROLDETAILS{
public int cbStruct ; // size in Byte of MIXERCONTROLDETAILS
public int dwControlID ; // control id to get/set details on
public int cChannels ; // number of channels in paDetails
array
public int item ; // hwndOwner or cMultipleItems
public int cbDetails ; // size of _one_ details_XX struct
public IntPtr paDetails ; // pointer to array of details_XX
structs
}
public struct MIXERCONTROLDETAILS_UNSIGNED{
public int dwValue ; // value of the control
}
public struct MIXERLINE{
public int cbStruct ; // size of MIXERLINE structure
public int dwDestination ; // zero based destination
index
public int dwSource ; // zero based source index (if
// source)
public int dwLineID ; // unique line id for mixer
device
public int fdwLine ; // state/information about
line
public int dwUser ; // driver specific information
public int dwComponentType ; // component public enum
line connects to
public int cChannels ; // number of channels line
supports
public int cConnections ; // number of connections
(possible)
public int cControls ;
[ MarshalAs( UnmanagedType.ByValTStr,
SizeConst=MIXER_SHORT_NAME_CHARS )] // number of controls at this
line
public string szShortName;
[ MarshalAs( UnmanagedType.ByValTStr,
SizeConst=MIXER_LONG_NAME_CHARS )]
public string szName;
public int dwType ;
public int dwDeviceID ;
public int wMid ;
public int wPid ;
public int vDriverVersion ;
[ MarshalAs( UnmanagedType.ByValTStr, SizeConst=MAXPNAMELEN)]
public string szPname ;
}
public struct MIXERLINECONTROLS{
public int cbStruct ; // size in Byte of MIXERLINECONTROLS
public int dwLineID ; // line id (from MIXERLINE.dwLineID)
// MIXER_GETLINECONTROLSF_ONEBYID or
public int dwControl ; // MIXER_GETLINECONTROLSF_ONEBYpublic
enum
public int cControls ; // count of controls pmxctrl points to
public int cbmxctrl ; // size in Byte of _one_ MIXERCONTROL
public IntPtr pamxctrl ; // pointer to first MIXERCONTROL
array
}
private static bool GetVolumeControl(int hmixer ,int componentType,
int ctrlType, out MIXERCONTROL mxc, out int vCurrentVol)
{
// This function attempts to obtain a mixer control.
// Returns True if successful.
MIXERLINECONTROLS mxlc = new MIXERLINECONTROLS();
MIXERLINE mxl = new MIXERLINE();
MIXERCONTROLDETAILS pmxcd = new MIXERCONTROLDETAILS();
MIXERCONTROLDETAILS_UNSIGNED du = new
MIXERCONTROLDETAILS_UNSIGNED();
mxc = new MIXERCONTROL();
int rc ;
bool retValue;
vCurrentVol = -1;
//mxl.szShortName = new string(' ', MIXER_SHORT_NAME_CHARS);
//mxl.szName = new string(' ', MIXER_LONG_NAME_CHARS);
mxl.cbStruct = Marshal.SizeOf(mxl);
mxl.dwComponentType = componentType ;
// Obtain a line corresponding to the component public enum
rc = mixerGetLineInfoA(hmixer,ref mxl,
MIXER_GETLINEINFOF_COMPONENTTYPE );
if(MMSYSERR_NOERROR == rc)
{
int sizeofMIXERCONTROL = 152;
//Marshal.SizeOf(typeof(MIXERCONTROL))
int ctrl = Marshal.SizeOf(typeof(MIXERCONTROL));
mxlc.pamxctrl = Marshal.AllocCoTaskMem(sizeofMIXERCONTROL) ;//new
MIXERCONTROL();
mxlc.cbStruct = Marshal.SizeOf(mxlc);
mxlc.dwLineID = mxl.dwLineID;
mxlc.dwControl = ctrlType;
mxlc.cControls = 1;
mxlc.cbmxctrl = sizeofMIXERCONTROL;
// Allocate a buffer for the control
mxc.cbStruct = sizeofMIXERCONTROL;
// Get the control
rc = mixerGetLineControlsA(hmixer,ref mxlc,
MIXER_GETLINECONTROLSF_ONEBYTYPE);
if(MMSYSERR_NOERROR == rc)
{
retValue = true;
// Copy the control into the destination structure
mxc = (MIXERCONTROL)Marshal.PtrToStructure(mxlc.pamxctrl ,typeof(MIXERCONTROL));
}
else
{
retValue = false;
}
int sizeofMIXERCONTROLDETAILS =
Marshal.SizeOf(typeof(MIXERCONTROLDETAILS));
int sizeofMIXERCONTROLDETAILS_UNSIGNED =
Marshal.SizeOf(typeof(MIXERCONTROLDETAILS_UNSIGNED ));
pmxcd.cbStruct = sizeofMIXERCONTROLDETAILS;
pmxcd.dwControlID = mxc.dwControlID;
pmxcd.paDetails =
Marshal.AllocCoTaskMem(sizeofMIXERCONTROLDETAILS_U NSIGNED) ;
pmxcd.cChannels = 1;
pmxcd.item = 0;
pmxcd.cbDetails = sizeofMIXERCONTROLDETAILS_UNSIGNED;
rc = mixerGetControlDetailsA(hmixer,ref pmxcd,
MIXER_GETCONTROLDETAILSF_VALUE);
du = (MIXERCONTROLDETAILS_UNSIGNED)Marshal.PtrToStructu re(pmxcd.paDetails,typeof(MIXERCONTROLDETAILS_UNSI GNED));
vCurrentVol = du.dwValue;
return retValue;
}
retValue = false;
return retValue;
}
private static bool SetVolumeControl(int hmixer , MIXERCONTROL mxc ,
int volume )
{
// This function sets the value for a volume control.
// Returns True if successful
bool retValue;
int rc;
MIXERCONTROLDETAILS mxcd = new MIXERCONTROLDETAILS();
MIXERCONTROLDETAILS_UNSIGNED vol = new
MIXERCONTROLDETAILS_UNSIGNED();
mxcd.item = 0;
mxcd.dwControlID = mxc.dwControlID;
mxcd.cbStruct = Marshal.SizeOf(mxcd);
mxcd.cbDetails = Marshal.SizeOf(vol);
// Allocate a buffer for the control value buffer
mxcd.cChannels = 1;
vol.dwValue = volume;
// Copy the data into the control value buffer
//mxcd.paDetails =
vol;//(MIXERCONTROL)Marshal.PtrToStructure(mxlc.pamxctrl ,typeof(MIXERCONTROL));
mxcd.paDetails = Marshal.AllocCoTaskMem(Marshal.SizeOf(typeof(MIXER CONTROLDETAILS_UNSIGNED)));
Marshal.StructureToPtr(vol, mxcd.paDetails,false);
// Set the control value
rc = mixerSetControlDetails(hmixer,ref mxcd,
MIXER_SETCONTROLDETAILSF_VALUE);
if(MMSYSERR_NOERROR == rc)
{
retValue = true;
}
else
{
retValue = false;
}
return retValue;
}
public static int GetVolume()
{
int mixer;
MIXERCONTROL volCtrl = new MIXERCONTROL();
int currentVol;
mixerOpen(out mixer,0 ,0 ,0, 0);
int type = MIXERCONTROL_CONTROLTYPE_VOLUME;
GetVolumeControl(mixer,
MIXERLINE_COMPONENTTYPE_DST_SPEAKERS,type,out volCtrl, out
currentVol);
mixerClose(mixer);
return currentVol;
}
public static void SetVolume(int vVolume)
{
int mixer;
MIXERCONTROL volCtrl = new MIXERCONTROL();
int currentVol;
mixerOpen(out mixer,0 ,0 ,0, 0);
int type = MIXERCONTROL_CONTROLTYPE_VOLUME;
GetVolumeControl(mixer,
MIXERLINE_COMPONENTTYPE_DST_SPEAKERS,type,out volCtrl, out
currentVol);
if(vVolume>volCtrl.lMaximum) vVolume = volCtrl.lMaximum;
if(vVolume<volCtrl.lMinimum) vVolume = volCtrl.lMinimum;
SetVolumeControl(mixer, volCtrl, vVolume);
GetVolumeControl(mixer,
MIXERLINE_COMPONENTTYPE_DST_SPEAKERS,type,out volCtrl, out
currentVol);
if(vVolume!=currentVol)
{
throw new Exception("Cannot Set Volume");
}
mixerClose(mixer);
}
}
