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The ACMFILTERDETAILS structure details a waveform-audio filter for a specific filter tag for an ACM driver.

typedef struct {

DWORD cbStruct;

DWORD dwFilterIndex;

DWORD dwFilterTag;

DWORD fdwSupport;


DWORD cbwfltr;





Size, in bytes, of the ACMFILTERDETAILS structure. This member must be initialized before calling the acmFilterDetails or acmFilterEnum functions. The size specified in this member must be large enough to contain the base ACMFILTERDETAILS structure. When the acmFilterDetails function returns, this member contains the actual size of the information returned. The returned information will never exceed the requested size.


Index of the filter about which details will be retrieved. The index ranges from zero to one less than the number of standard filters supported by an ACM driver for a filter tag. The number of standard filters supported by a driver for a filter tag is contained in the cStandardFilters member of the ACMFILTERTAGDETAILS structure. The dwFilterIndex member is used only when querying standard filter details about a driver by index; otherwise, this member should be zero. Also, this member will be set to zero by the ACM when an application queries for details on a filter; in other words, this member is used only for input and is never returned by the ACM or an ACM driver.


Waveform-audio filter tag that the ACMFILTERDETAILS structure describes. This member is used as an input for the ACM_FILTERDETAILSF_INDEX query flag. For the ACM_FILTERDETAILSF_FORMAT query flag, this member must be initialized to the same filter tag as the pwfltr member specifies. If the acmFilterDetails function is successful, this member is always returned. This member should be set to WAVE_FILTER_UNKNOWN for all other query flags.


Driver-support flags specific to the specified filter. These flags are identical to the fdwSupport flags of the ACMDRIVERDETAILS structure, but they are specific to the filter that is being queried. This member can be a combination of the following values and identifies which operations the driver supports for the filter tag:


Driver supports asynchronous conversions.


Driver supports conversion between two different format tags while using the specified filter. For example, if a driver supports compression from WAVE_FORMAT_PCM to WAVE_FORMAT_ADPCM with the specified filter, this flag is set.


Driver supports conversion between two different formats of the same format tag while using the specified filter. For example, if a driver supports resampling of WAVE_FORMAT_PCM with the specified filter, this flag is set.


Driver supports a filter (modification of the data without changing any of the format attributes). For example, if a driver supports volume or echo operations on WAVE_FORMAT_PCM, this flag is set.


Driver supports hardware input, output, or both with the specified filter through a waveform-audio device. An application should use the acmMetrics function with the ACM_METRIC_HARDWARE_WAVE_INPUT and ACM_METRIC_HARDWARE_WAVE_OUTPUT metric indexes to retrieve the waveform-audio device identifiers associated with the supporting ACM driver.


Address of a WAVEFILTER structure that will receive the filter details. This structure requires no initialization by the application unless the ACM_FILTERDETAILSF_FILTER flag is specified with the acmFilterDetails function. In this case, the dwFilterTag member of the WAVEFILTER structure must be equal to the dwFilterTag member of the ACMFILTERDETAILS structure.


Size, in bytes, available for pwfltr to receive the filter details. The acmMetrics and acmFilterTagDetails functions can be used to determine the maximum size required for any filter available for the specified driver (or for all installed ACM drivers).


String that describes the filter for the dwFilterTag type. If the acmFilterDetails function is successful, this string is always returned.

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