acmFormatEnum

Article
12/10/2007

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

MMRESULT acmFormatEnum(
  HACMDRIVER         had,        
  LPACMFORMATDETAILS pafd,       
  ACMFORMATENUMCB    fnCallback, 
  DWORD_PTR          dwInstance, 
  DWORD              fdwEnum     
);

Parameters

had

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

pafd

Pointer to an ACMFORMATDETAILS structure to contain the format details passed to the fnCallback function. This structure must have the cbStruct, pwfx, and cbwfx members of the ACMFORMATDETAILS structure initialized. The dwFormatTag member must also be initialized to either WAVE_FORMAT_UNKNOWN or a valid format tag.

fnCallback

Procedure instance address of the application-defined callback function.

dwInstance

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

fdwEnum

Flags for enumerating the formats for a given format tag. The following values are defined.

Value	Meaning
ACM_FORMATENUMF_CONVERT	The WAVEFORMATEX structure pointed to by the pwfx member of the ACMFORMATDETAILS structure is valid. The enumerator will only enumerate destination formats that can be converted from the given pwfx format.
ACM_FORMATENUMF_HARDWARE	The enumerator should only enumerate formats that are supported as native input or output formats on one or more of the installed waveform-audio devices. This flag provides a way for an application to choose only formats native to an installed waveform-audio device. This flag must be used with one or both of the ACM_FORMATENUMF_INPUT and ACM_FORMATENUMF_OUTPUT flags. Specifying both ACM_FORMATENUMF_INPUT and ACM_FORMATENUMF_OUTPUT will enumerate only formats that can be opened for input or output. This is true regardless of whether this flag is specified.
ACM_FORMATENUMF_INPUT	Enumerator should enumerate only formats that are supported for input (recording).
ACM_FORMATENUMF_NCHANNELS	The nChannels member of the WAVEFORMATEX structure pointed to by the pwfx member of the ACMFORMATDETAILS structure is valid. The enumerator will enumerate only a format that conforms to this attribute.
ACM_FORMATENUMF_NSAMPLESPERSEC	The nSamplesPerSec member of the WAVEFORMATEX structure pointed to by the pwfx member of the ACMFORMATDETAILS structure is valid. The enumerator will enumerate only a format that conforms to this attribute.
ACM_FORMATENUMF_OUTPUT	Enumerator should enumerate only formats that are supported for output (playback).
ACM_FORMATENUMF_SUGGEST	The WAVEFORMATEX structure pointed to by the pwfx member of the ACMFORMATDETAILS structure is valid. The enumerator will enumerate all suggested destination formats for the given pwfx format. This mechanism can be used instead of the acmFormatSuggest function to allow an application to choose the best suggested format for conversion. The dwFormatIndex member will always be set to zero on return.
ACM_FORMATENUMF_WBITSPERSAMPLE	The wBitsPerSample member of the WAVEFORMATEX structure pointed to by the pwfx member of the ACMFORMATDETAILS structure is valid. The enumerator will enumerate only a format that conforms to this attribute.
ACM_FORMATENUMF_WFORMATTAG	The wFormatTag member of the WAVEFORMATEX structure pointed to by the pwfx member of the ACMFORMATDETAILS structure is valid. The enumerator will enumerate only a format that conforms to this attribute. The dwFormatTag member of the ACMFORMATDETAILS structure must be equal to the wFormatTag member.

Return Values

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

Value	Description
ACMERR_NOTPOSSIBLE	The details for the format 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

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

Requirements

**  Windows NT/2000/XP:** Included in Windows NT 3.1 and later.
**  Windows 95/98/Me:** Included in Windows 95 and later.
**  Header:** Declared in Msacm.h.
**  Library:** Use Msacm32.lib.
**  Unicode:** Implemented as Unicode and ANSI versions on Windows NT/2000/XP.

acmFormatEnum

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