The MMCSS (not sure why the extra letters) is a service in Vista (SP1+), 7, Server 2008, and Server 2008R2, which places priority on video and audio data. Here are some good tweaks. Click here for a VBS script, called MCSO, which does everything below automatically.

So we go here in the registry:

HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Windows NT\CurrentVersion\Multimedia\SystemProfile

open the item named “NetworkThrottlingIndex”, and change it to “FFFFFFFF” (that’s eight F’s) hex. We can do the same for “SystemResponsiveness”.

Then drill further down to here:

HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Windows NT\CurrentVersion\Multimedia\SystemProfile\Tasks

and you’ll see a list of folders. Each folder is a “multimedia profile” according to one reference. Each can contain the following:

Affinity        dword:00000000
Background Only        False
BackgroundPriority        dword:00000001
Clock Rate       dword:00002710
GPU Priority        dword:00000001
Priority       dword:00000001
Scheduling Category       High
SFIO Priority       High

I kept the “Window Manager” set at the default, and set the rest to the above. According to one reference it is possible to create custom multimedia profiles and use some applications’ capabilities to assign them, I have not tried this yet.

According to one reference, the above changes only activate at reboot. However, I have found that if you restart MMCSS and then Audiosrv, the same results obtain.

Addendum. Have just recently looked into Windows 10 in this. It appears to be a driver, not a service, in 10. Will be investigating further. Not sure about Audiosrv either.