How do I use mciSendCommand to change sound output-device.

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C#

Hi,

I am working on a c# application that is supposed to play several soundfiles over different output devices.

After much searching I stumbled over the winmm.dll-API. However, I have trouble to propperly set the output-device befor I play a sound.

Here is my code so far:

//open file
MCI_OPEN_PARMS open = new MCI_OPEN_PARMS();

open.wDeviceID = 0;//no reaction
open.lpstrDeviceType = Marshal.StringToHGlobalAnsi("waveaudio");
open.lpstrElementName = Marshal.StringToHGlobalAnsi(@"test.wav");

IntPtr ptr = Marshal.AllocHGlobal(Marshal.SizeOf(typeof(MCI_OPEN_PARMS)));
Marshal.StructureToPtr(open, ptr, false);

uint err = mciSendCommand(0,
    MCI_OPEN,
   MCI_WAIT | MCI_OPEN_TYPE | MCI_OPEN_ELEMENT,
    ptr);

if (0 != err) ThrowException(err);



open = (MCI_OPEN_PARMS)Marshal.PtrToStructure(ptr, typeof(MCI_OPEN_PARMS));

uint devID = open.wDeviceID;

//play file
MCI_PLAY_PARMS play = new MCI_PLAY_PARMS();

play.dwCallback = IntPtr.Zero;
play.dwFrom = 0;
play.dwTo = 0;

IntPtr ptr2 = Marshal.AllocHGlobal(Marshal.SizeOf(typeof(MCI_PLAY_PARMS)));
Marshal.StructureToPtr(play, ptr2, false);

err = mciSendCommand(devID,
     MCI_PLAY,
     MCI_NOTIFY, ptr2);

if (0 != err) ThrowException(err);

All the neccesary constants and structures are in the class-definition.

The second line (open.wDeviceID = 0;) should be the one to set the output-device, but no matter what I enter, the sound comes always out of the default-output.

I also used the winmm.dl functions waveOutGetNumDevs and waveOutGetDevCaps to list the avaliable output devices. It schows me, that I have speakers and an external USB-Soundcard, like expected.

Help would be much apreciated.

Best Regards, Marc