The acmDriverAdd function adds a driver to the list of available ACM drivers. The driver type and location are dependent on the flags used to add ACM drivers. After a driver is successfully added, the driver entry function will receive ACM driver messages.

MMRESULT acmDriverAdd(
  HINSTANCE hinstModule,  
  LPARAM lParam,          
  DWORD dwPriority,       
  DWORD fdwAdd            



Pointer to the buffer that receives a handle identifying the installed driver. This handle is used to identify the driver in calls to other ACM functions.


Handle to the instance of the module whose executable or dynamic-link library (DLL) contains the driver entry function.


Driver function address or a notification window handle, depending on the fdwAdd flags.


Window message to send for notification broadcasts. This parameter is used only with the ACM_DRIVERADDF_NOTIFYHWND flag. All other flags require this member to be set to zero.


Flags for adding ACM drivers. The following values are defined.

Value Meaning
ACM_DRIVERADDF_FUNCTION The lParam parameter is a driver function address conforming to the acmDriverProc prototype. The function may reside in either an executable or DLL file.
ACM_DRIVERADDF_GLOBAL Provided for compatibility with 16-bit applications. For the Win32 API, ACM drivers added by the acmDriverAdd function can be used only by the application that added the driver. This is true whether or not ACM_DRIVERADDF_GLOBAL is specified. For more information, see Adding Drivers Within an Application.
ACM_DRIVERADDF_LOCAL The ACM automatically gives a local driver higher priority than a global driver when searching for a driver to satisfy a function call. For more information, see Adding Drivers Within an Application.
ACM_DRIVERADDF_NAME The lParam parameter is a registry value name in HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Windows NT\CurrentVersion\Drivers32. The value identifies a DLL that implements an ACM codec. Applications can use this flag if new registry entries are created after the application has already started using the ACM.
ACM_DRIVERADDF_NOTIFYHWND The lParam parameter is a handle of a notification window that receives messages when changes to global driver priorities and states are made. The window message to receive is defined by the application and must be passed in dwPriority. The wParam and lParam parameters passed with the window message are reserved for future use and should be ignored. ACM_DRIVERADDF_GLOBAL cannot be specified in conjunction with this flag. For more information about driver priorities, see the description for the acmDriverPriority function.

Return Values

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

Value Description
MMSYSERR_INVALFLAG At least one flag is invalid.
MMSYSERR_INVALPARAM At least one parameter is invalid.
MMSYSERR_NOMEM The system is unable to allocate resources.


  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.

See Also

Audio Compression Manager, Audio Compression Functions, acmDriverProc, acmDriverPriority