Multimedia Class Scheduler (MMCSS) Service Defaults in Windows 7

Enables relative prioritization of work based on system-wide task priorities. This is intended mainly for multimedia applications. If this service is stopped, individual tasks resort to their default priority.

Default Settings

Startup type:Automatic
Display name:Multimedia Class Scheduler
Service name:MMCSS
Service type:share
Error control:normal
Object:LocalSystem
Path:%SystemRoot%\system32\svchost.exe -k netsvcs
File:%SystemRoot%\system32\mmcss.dll
Registry key:HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Services\MMCSS
Privileges:
  • SeIncreaseBasePriorityPrivilege
  • SeImpersonatePrivilege

Default Behavior

Multimedia Class Scheduler is a Win32 service. In Windows 7 it is starting automatically on the operating system startup. Then the Multimedia Class Scheduler service is running as LocalSystem in a shared process of svchost.exe. Other system components, such as drivers and services, may run in the same process. If Multimedia Class Scheduler fails to start, Windows 7 attempts to write the failure details into Event Log. Then Windows 7 startup should proceed and the user should be notified that the MMCSS service is not running because of the error.

Dependencies

If Multimedia Class Scheduler is stopped, the Windows Audio service fails to start and initialize.

Restore Default Startup Configuration for Multimedia Class Scheduler

1. Select your Windows 7 edition and service pack, and then click Download.

2. Save the Win7_MMCSS_Service_Startup.cmd file to a local storage device.

3. Run the saved file as an administrator.

4. Restart the computer.

The MMCSS service is using the mmcss.dll file that is located in the %WinDir%\system32 folder. If the file is changed, damaged or deleted, you can restore its original version from Windows 7 installation media.