acmStreamConvertCallback callback function

The acmStreamConvertCallback function specifies an application-provided callback function to be used when the acmStreamOpen function specifies the CALLBACK_FUNCTION flag. The acmStreamConvertCallback name is a placeholder for an application-defined function name.


void CALLBACK acmStreamConvertCallback(
   UINT       uMsg,
   DWORD      dwInstance,
   LPARAM     lParam1,
   LPARAM     lParam2


  • has
    Handle to the ACM conversion stream associated with the callback function.

  • uMsg
    ACM conversion stream message. The following values are defined.

    Value Meaning
    MM_ACM_CLOSE ACM has successfully closed the conversion stream identified by has. The handle specified by has is no longer valid after receiving this message.
    MM_ACM_DONE ACM has successfully converted the buffer identified by lParam1 (which is a pointer to the ACMSTREAMHEADER structure) for the stream handle identified by has.
    MM_ACM_OPEN ACM has successfully opened the conversion stream identified by has.


  • dwInstance
    User-instance data given as the dwInstance parameter of the acmStreamOpen function.

  • lParam1
    Message parameter.

  • lParam2
    Message parameter.

Return value

This function does not return a value.


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


Minimum supported client

Windows 2000 Professional [desktop apps only]

Minimum supported server

Windows 2000 Server [desktop apps only]



See also

Audio Compression Manager

Audio Compression Functions