ACMDM_STREAM

ACMDM_STREAM_SIZE

See also ACMDM_STREAM_CLOSE, ACMDM_STREAM_CONVERT, ACMDM_STREAM_OPEN, ACMDM_STREAM_PREPARE, ACMDM_STREAM_RESET, ACMDM_STREAM_UNPREPARE, ACMDRVOPENDESC, ACMDRVSTREAMHEADER, ACMDRVSTREAMINSTANCE, ACMDRVSTREAMSIZE

lParam1 = (LPARAM) pacmDSI  // see below
lParam2 = (LPARAM) pacmDSS  // see below

Sent to an Audio Compression Manager (ACM) driver to query recommended buffer conversion sizes for a conversion stream. This message is usually sent to an ACM driver in response to an acmStreamSize call.

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

MMSYSERR_NOTENABLED	The driver failed to load or initialize.
ACMERR_NOTPOSSIBLE	The ACMDRVSTREAMSIZE structure and query type specified information that cannot be satisfied by the driver.
MMSYSERR_NOTSUPPORTED	The driver does not support the requested query type. A driver must always support the ACM_STREAMSIZEF_SOURCE and ACM_STREAMSIZEF_DESTINATION query types.

lParam1

Address of the ACMDRVSTREAMINSTANCE structure for the conversion stream that the conversion size request is for.

lParam2

Address of the ACMDRVSTREAMSIZE structure that defines the conversion stream size query attributes.

An ACM driver must support this message if it supports the ACMDM_STREAM_OPEN message. Note that the following parameters for the ACMDM_STREAM_SIZE 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.
The lParam2 parameter will contain a valid pointer to an ACMDRVSTREAMSIZE structure with the proper members initialized for the requested query operation. This structure will be at least the size of the base ACMDRVSTREAMSIZE structure.
The cbStruct member of the ACMDRVSTREAMSIZE structure will be set to at least the size, in bytes, of the base ACMDRVSTREAMSIZE structure.
The cbSrcLength will be nonzero if the ACM_STREAMSIZEF_SOURCE flag is specified.
The cbDstLength will be nonzero if the ACM_STREAMSIZEF_DESTINATION flag is specified.
No invalid flag combinations will be specified in the fdwSize member.

The driver does not need to check for these conditions.