   IDirectSound3DBuffer8 vs IDirectSoundBuffer8
  Hi,I would like to set the frequency (at which the audio samples are played) of an IDirectSound3DBuffer8 object, which parameter of the interface could do the job ?I know that IDirectSoundBuffer8 have the SetFrequency and GetFrequency methods to do that.ThanksFathya   
  zfathya,The IDirectSoundBuffer8 interface and the IDirectSound3DBuffer8 are two interfaces  exposed by the same object.  They are just two different ways of interacting with it.  What this means is that you can use the two in conjunction to manipulate the quality AND location of a sound.In practice this means you can get an IDirectSoundBuffer8 interface.  And then use the COM QueryInterface function to get access to the IDirectSound3DBuffer8 interface for that object.  Here's the code:// Use this to create an IDirectSoundBuffer// Make sure the DSBUFFERDESC struct contains DSBCAPS_CTRL3D enabledHRESULT CreateSoundBuffer(  LPCDSBUFFERDESC pcDSBufferDesc, LPDIRECTSOUNDBUFFER * ppDSBuffer, LPUNKNOWN pUnkOuter );// Once you've got the sound buffer, use QueryInterface to get the IDirectSoundBuffer8 InterfaceppDSBuffer->QueryInterface( IID_IDirectSoundBuffer8, (void**)&pSoundBuffer );// Now you can use the pSoundBuffer to set frequency, etc...// But you can also use it to get the 3d sound interfacepSoundBuffer->QueryInterface( IID_IDirectSound3DBuffer, (void**)pSoundBuffer3D );Now you can use the two interfaces, pSoundBuffer and pSoundBuffer3D to set the positions, frequency, pan, position, etc...in combination.Hope this helps, mate!  Good luck!   