acmDriverAddW function

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.


  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 Value

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

Return code Description
At least one flag is invalid.
At least one parameter is invalid.
The system is unable to allocate resources.


Minimum supported client Windows 2000 Professional [desktop apps only]
Minimum supported server Windows 2000 Server [desktop apps only]
Target Platform Windows
Header msacm.h
Library Msacm32.lib
DLL Msacm32.dll

See Also

Audio Compression Functions

Audio Compression Manager