ACMDM_FILTER

ACMDM_FILTER_DETAILS

ACMDM_FILTER_DETAILS
lParam1 = (LPARAM) pacmFD          // see below
lParam2 = (LPARAM) fFilterDetails  // see below

Sent to an Audio Compression Manager (ACM) driver to request details about a filter for a specific filter tag. This message is usually sent to an ACM driver in response to an acmFilterDetails or acmFilterEnum call.

Returns MMSYSERR_NOERROR if successful or an error value otherwise. The following errors are possible:

ACMERR_NOTPOSSIBLE	The ACMFILTERDETAILS structure and query operation specify information that is not understood by the driver.
MMSYSERR_NOTENABLED	The driver failed to load or initialize.
MMSYSERR_NOTSUPPORTED	The driver does not support filter operations or the specified query operation.

lParam1

Address of the ACMFILTERDETAILS structure that should be filled in with the filter details for the specified filter tag. The cbStruct member of the ACMFILTERDETAILS structure will contain the desired size, in bytes, of the details that the driver should return for the filter.

lParam2

Flags for getting the filter details for the specified filter tag. This parameter is identical to the fdwDetails parameter passed to acmFilterDetails.

ACM_FILTERDETAILSF_FILTER	Indicates that a WAVEFILTER structure pointed to by pwfltr of the ACMFILTERDETAILS structure was given and the remaining details should be returned. The dwFilterTag member of the ACMFILTERDETAILS will be initialized to the same filter tag as the pwfltr member specifies. This query type can be used to get a string description of an arbitrary filter structure.
ACM_FILTERDETAILSF_INDEX	Indicates that a filter index for the filter tag was given in the dwFilterIndex member of the ACMFILTERDETAILS structure. The filter details must be returned in the structure specified by lParam1. The index ranges from zero to one less than the cStandardFilters member returned in the ACMFILTERTAGDETAILS structure for a filter tag.

An ACM driver that supports filter operations must support this message. If a driver does not support filters, this message should not be handled (MMSYSERR_NOTSUPPORTED must be returned). Note that the following parameters for the ACMDM_FILTER_DETAILS message will be validated before calling the driver:

The lParam1 parameter will contain a valid pointer to an ACMFILTERDETAILS structure with the proper members initialized for the requested query operation. This structure will be at least the size of the base ACMFILTERDETAILS structure.
The cbStruct member of the ACMFILTERDETAILS structure will be set to at least the size in bytes of the base ACMFILTERDETAILS structure.
The pwfltr member of the ACMFILTERDETAILS structure will be a valid pointer to a WAVEFILTER structure that is at least the size, in bytes, specified in the cbwfltr member of the ACMFILTERDETAILS structure.
No invalid flag combinations will be specified in lParam2.

The driver does not need to check for these conditions.

To enable the driver to successfully query for the filter of the specified filter tag, the cbStruct member of the ACMFILTERDETAILS structure should be set to the actual size, in bytes, of the details being returned. This size cannot exceed the requested size. Note that the smallest possible size is the size of the base ACMFILTERDETAILS structure.