acmFilterEnum function (msacm.h)

Article
08/16/2022

The acmFilterEnum function enumerates waveform-audio filters available for a given filter tag from an ACM driver. This function continues enumerating until there are no more suitable filters for the filter tag or the callback function returns FALSE.

Syntax

MMRESULT ACMAPI acmFilterEnum(
  HACMDRIVER         had,
  LPACMFILTERDETAILS pafd,
  ACMFILTERENUMCB    fnCallback,
  DWORD_PTR          dwInstance,
  DWORD              fdwEnum
);

Parameters

had

Handle to the ACM driver to query for waveform-audio filter details. If this parameter is NULL, the ACM uses the details from the first suitable ACM driver.

pafd

Pointer to the ACMFILTERDETAILS structure that contains the filter details when it is passed to the function specified by fnCallback. When your application calls acmFilterEnum, the cbStruct, pwfltr, and cbwfltr members of this structure must be initialized. The dwFilterTag member must also be initialized to either WAVE_FILTER_UNKNOWN or a valid filter tag.

fnCallback

Procedure-instance address of the application-defined callback function.

dwInstance

A 32-bit (DWORD), 64-bit (DWORD_PTR) application-defined value that is passed to the callback function along with ACM filter details.

fdwEnum

Flags for enumerating the filters for a given filter tag. The following values are defined.

[ACMFILTERDETAILS](./nf-msacm-acmfilterdetails.md) structure is valid. The enumerator will enumerate only a filter that conforms to this attribute. The dwFilterTag member of the ACMFILTERDETAILS structure must be equal to the dwFilterTag member of the WAVEFILTER structure.

Value	Meaning
ACM_FILTERENUMF_DWFILTERTAG

Return value

Returns zero if successful or an error otherwise. Possible error values include the following.

Return code	Description
ACMERR_NOTPOSSIBLE	The details for the filter cannot be returned.
MMSYSERR_INVALFLAG	At least one flag is invalid.
MMSYSERR_INVALHANDLE	The specified handle is invalid.
MMSYSERR_INVALPARAM	At least one parameter is invalid.

Remarks

The acmFilterEnum function will return MMSYSERR_NOERROR (zero) if no suitable ACM drivers are installed. Moreover, the callback function will not be called.

The following functions should not be called from within the callback function: acmDriverAdd, acmDriverRemove, and acmDriverPriority.

Requirements

Requirement	Value
Minimum supported client	Windows 2000 Professional [desktop apps only]
Minimum supported server	Windows 2000 Server [desktop apps only]
Target Platform	Windows
Header	msacm.h
Library	Msacm32.lib
DLL	Msacm32.dll