ACMDM_STREAM_RESET

lParam1 = (LPARAM) pacmDSI  // address of ACMDRVSTREAMINSTANCE
lParam2 = reserved          // ignore

Sent to an Audio Compression Manager (ACM) driver to reset a previously opened asynchronous conversion stream. This message is typically sent to an ACM driver in response to a call to the acmStreamReset function.

Return MMSYSERR_NOERROR if the operation is successful or an error value otherwise. The following errors are possible:

ACMERR_NOTPOSSIBLE

The ACMDRVSTREAMSIZE structure and query type specified information that cannot be satisfied by the driver.

lParam1: Address of the ACMDRVSTREAMINSTANCE structure for the asynchronous conversion stream that is to be reset.
lParam2: Reserved. Should be ignored.

An asynchronous ACM driver must support this message. If the driver is converting data, it should stop immediately and mark all pending stream headers as done by clearing the ACMSTREAMHEADER_STATUSF_INQUEUE bit in the fdwStatus member of the ACMDRVSTREAMHEADER structure for each buffer. The driver should set the cbSrcLengthUsed and cbDstLengthUsed members of the structure appropriately. The driver should then notify the client by using DriverCallback to send an MM_ACM_DONE message for each buffer.

Note that the following parameters for the ACMDM_STREAM_RESET message will be validated before calling the driver:

The lParam1 parameter will contain a valid pointer to an ACMDRVSTREAMINSTANCE structure, with the same information as the corresponding ACMDM_STREAM_OPEN message.
A driver will never be called to reset an asynchronous conversion stream unless the driver sets the ACMDRIVERDETAILS_SUPPORTF_ASYNC flag in the fdwSupport member of the ACMDRIVERDETAILS structure that is returned by the driver during the ACMDM_DRIVER_DETAILS message.
A driver will never be called to reset a conversion stream that was not opened for asynchronous conversions.

The driver does not need to check for these conditions.