Developer Forum

My CreateCaptureBuffer fails with E_INVALIDARG. Before I add AEC to the
DSCBUFFERDESC, it worked fine.
I am using windowsXP and DirectX 9.0 SDK.

Here's my code.

// Create the capture buffer
DSCBUFFERDESC dscbd;
ZeroMemory( &dscbd, sizeof(dscbd) );
dscbd.dwSize = sizeof(dscbd);
dscbd.dwBufferBytes = m_dwCaptureBufferSize;
dscbd.lpwfxFormat = pwfxInput; // Set the format during creatation
DSCEFFECTDESC ds_effects[2];
ZeroMemory(&ds_effects, sizeof(DSCEFFECTDESC)*2);

ds_effects[0].dwSize = sizeof(DSCEFFECTDESC);
ds_effects[0].dwFlags = DSCFX_LOCSOFTWARE;
ds_effects[0].guidDSCFXClass = GUID_DSCFX_CLASS_AEC;
ds_effects[0].guidDSCFXInstance = GUID_DSCFX_SYSTEM_AEC;
ds_effects[1].dwSize = sizeof(DSCEFFECTDESC);
ds_effects[1].dwFlags = DSCFX_LOCSOFTWARE;
ds_effects[1].guidDSCFXClass = GUID_DSCFX_CLASS_NS;
ds_effects[1].guidDSCFXInstance = GUID_DSCFX_SYSTEM_NS;
dscbd.dwFlags = DSBCAPS_CTRLFX;
dscbd.dwFXCount = 2;
dscbd.lpDSCFXDesc = ds_effects ;//NULL; //;// ;

if( FAILED( hr = m_pDSCapture8->CreateCaptureBuffer( &dscbd,
&m_pDSBCapture,
NULL ) ) )
return DXTRACE_ERR_MSGBOX( TEXT("CreateCaptureBuffer"), hr );

Currently, I think it is because I am using the DirectSoundCaptureCreate8
function instead of the DirectSoundFullDuplexCreate8.
As I know the AEC algorithm identifies the echo sound by comparing of the
rendering sound and that's why DirectSoundFullDuplexCreate8.
But my application has two or more sound outputs and all the outputs could
make echo sound (it is a voice conference system via network). I don't know
whether I can put multiful sound sources into one renderer without sound
mixer.

Any good solutions?

Thank you.

I've only seen AEC work with a full-duplex buffer.


I would do the mixing myself. It's quite simple to do for basic mixing,
just a matter of adding sample values together one-for-one, and accounting
for short integer overflow.