ACMDM_STREAM_CLOSE

This message requests an ACM driver to close a conversion stream that was opened with an ACMDM_STREAM_OPEN message.

Parameters

dwDriverID

Specifies a driver instance identifier. The driver returns this value in response to the ACM_Open function.

hDriver

Handle to a driver.

uMsg

Specifies this message.

lParam1

Pointer to an ACMDRVSTREAMINSTANCE structure.

lParam2

Not used.

Return Values

MMSYSERR_NOERROR indicates success. Otherwise, the driver returns one of the MMSYSERR error values declared in the Mmsystem.h header file or one of the ACMERR error values declared in the Msacm.h header file. An asynchronous driver might have to return ACMERR_BUSY if a conversion operation has not completed.

Remarks

The ACM (Waveapi.dll) sends this message by calling the ACM driver’s ACM_IOControl entry point through the DeviceIoControl function. The ACM sends this message when an application calls the acmStreamClose function.

All ACM drivers that provide stream conversions must support this message. For more information about stream conversions, see the Windows NT DDK.

If the driver supports asynchronous operations and the client has specified the ACM_STREAMOPENF_ASYNC flag, which is contained in the fdwOpen member of ACMDRVSTREAMINSTANCE, the driver sends the client an MM_ACM_CLOSE callback message. It does this by calling the PostThreadMessage function after the operation completes.