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acmFilterEnum function

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 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.

Value Meaning
ACM_FILTERENUMF_DWFILTERTAGThe dwFilterTag member of the WAVEFILTER structure pointed to by the pwfltr member of the ACMFILTERDETAILS 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.

 

Return value

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

Return codeDescription
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

Minimum supported client

Windows 2000 Professional [desktop apps only]

Minimum supported server

Windows 2000 Server [desktop apps only]

Header

Msacm.h

Library

Msacm32.lib

DLL

Msacm32.dll

Unicode and ANSI names

acmFilterEnumW (Unicode) and acmFilterEnumA (ANSI)

See also

Audio Compression Manager
Audio Compression Functions

 

 

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