Multimedia Class Scheduler is important

[walaradu]

After using the RC, I found out that the Multimedia Class Scheduler service is important. I got rid of it and sounds became very choppy. Anytime I try listening to music, it would crackle when I'm doing anything, even surfing the web. I also found cpu usage to spike all over the place while listening to music. After I reinstalled, everything was back to normal. I just thought you should put a warning on it.

[nuhi]

Indeed.

Jamieo warned me about it as well but I didn't have any issues at first. But now while testing in virtual extensively it can crackle sometimes, very annoying.

Red warning is due.

[SnapShot]

You should never remove Multimedia Class Scheduler IMHO. It's one of the most important performance services in Vista:

Multimedia Class Scheduler Service

Users expect multimedia applications, including music and video players, to offer a seamless playback experience. However, demand for the CPU by other concurrently running applications, like antivirus, content indexing, or even the mail client, can result in unpleasant hiccups. To provide a better playback experience, Windows Vista introduces MMCSS to manage the CPU priorities of multimedia threads.

So it's used to manage the priorities od multimedia threads. Multimedia players register their threads to Multimedia Class Scheduler so it can properly schedule their execution for seamless playback of multimedia.

Edited July 9, 2007 by SnapShot

[nuhi]

Well I wonder why is it so sluggish anyway. In XP we didn't need such a boost...

Maybe when more services is removed we'll be able to remove this one and not have any problem...maaybe.

[GrofLuigi]

This smells like DRM. Maybe there will be other consequences if removed?

GL

[SnapShot]

I think that there isn't any DRM in Multimedia Class Scehduler. From all the info I have read, I can say that it's multimedia thread scheduler, it boosts the priority of registered multimedia threads depending of the type of the thread. By default on Vista there are several types of multimedia threads that application can register (other can be added later by user or automaticaly after some software isntalation). Here is the picture:

As you can see Audio threads have CPU priortiy 6. Also there is a clock rate settings which I assume is used to boost the clock speed of the CPU if Cool'n'Quite, EIST or similar frequency scaling technology is in use.

There is also Game class of threads, so this service is probably important for games. I'm sure new games will use it to register their threads and get higher priority. There is GPU Priority setting, which would be most important for games, but GPU Priority is NOT yet implemented in Vista. I hope it will get implemented in some SP, but I doubt it. MS will probalby wait for new Windows version to implement GPU Priority.

Multimedia Class Scheduler also tries to offer fair CPU service for non-multimedia threads. It boosts the multimedia threads but at the same time cares for other threads so the system remains repsonsive. By default it reservs 20% of CPU time for non-multimedia threads. But it can be changed in:

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

Someone which is not using multimedia apps can think that it's better if this service is removed, but I think that this service shouldn't be removed becuase it won't do any harm if there are no multimedia threads registered AFAIK. And you never know which application will use it to boost its performance. Maybe some professional applications like: PhotoShop, 3ds max, AutoCAD will use it to boost their performance.

Edited July 10, 2007 by SnapShot

[Bilar Crais]

Well I wonder why is it so sluggish anyway. In XP we didn't need such a boost...

Maybe when more services is removed we'll be able to remove this one and not have any problem...maaybe.

Do you suppose it's because hardware accelerated audio is no longer an option?

[nuhi]

Bilar Crais, I think that only matters in games, unless that Control Panel - Multimedia - Sounds - ... Acceleration setting was what helped in XP.

You might be on to something.

But it's really disappointing because this new audio stack should have been more responsive. Or the whole point of this new way of things is to allow easier programming and control in expense of direct hardware access...thus needing this boost. Anyway I reinstalled with this kept and it's fine now.

[Bilar Crais]

One thing I'll say about the class scheduler...I never experience audio dropouts anymore...

Under XP, with Nvidia Soundstorm audio, I experienced frequent crackles or dropouts when copying and pasting large files & other resource intensive operations. Not the case with Vista.

BTW:

For those of you using Adobe Audition or CoolEdit, the 100% CPU utilization during recording is not DRM or anything like that....it's the scroller. Turn off Auto Scrolling, and CPU use is just about nil.