The acmDriverEnumCallback function specifies a callback function used with the acmDriverEnum function. The acmDriverEnumCallback name is a placeholder for an application-defined function name.

  HACMDRIVERID hadid,     
  DWORD_PTR    dwInstance,
  DWORD        fdwSupport 



Handle to an ACM driver identifier.


Application-defined value specified in acmDriverEnum.


Driver-support flags specific to the driver specified by hadid. These flags are identical to the fdwSupport flags of the ACMDRIVERDETAILS structure. This parameter can be a combination of the following values.

Value Meaning
ACMDRIVERDETAILS_SUPPORTF_ASYNC Driver supports asynchronous conversions.
ACMDRIVERDETAILS_SUPPORTF_CODEC Driver supports conversion between two different format tags. For example, if a driver supports compression from WAVE_FORMAT_PCM to WAVE_FORMAT_ADPCM, this flag is set.
ACMDRIVERDETAILS_SUPPORTF_CONVERTER Driver supports conversion between two different formats of the same format tag. For example, if a driver supports resampling of WAVE_FORMAT_PCM, this flag is set.
ACMDRIVERDETAILS_SUPPORTF_DISABLED Driver has been disabled. An application must specify the ACM_DRIVERENUMF_DISABLED flag with acmDriverEnum to include disabled drivers in the enumeration.
ACMDRIVERDETAILS_SUPPORTF_FILTER 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.

Return Values

The callback function must return TRUE to continue enumeration or FALSE to stop enumeration.


The acmDriverEnum function will return MMSYSERR_NOERROR (zero) if no 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.


  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.

See Also

Audio Compression Manager, Audio Compression Functions, ACMDRIVERDETAILS, acmDriverEnum, acmDriverAdd, acmDriverRemove, and acmDriverPriority