Fix for slow Vista Network Transfer while playing Music

Martin Brinkmann
Aug 29, 2007
Updated • Jul 29, 2013
Windows, Windows Vista

Reports have been flooding the web that the network transfer speed of Windows Vista drops to a low level whenever you start to play music on the system.

If you are running into the issue you are probably not considering that audio may have the effect on the performance of your network transfers as it seems highly unlikely that the two would clash on the system.

It is very likely that you start to investigate other possible causes first. Eventually, you may come to this page after you have searched the Internet for a solution, and that is when you find out that audio is in fact the cause of the issue.

More precisely, it is a new service that Microsoft calls Multimedia Class Scheduler service or short MMCSS.

Mark Russinovich described the technical process on his blog explaining that 'when a multimedia application begins playback, the multimedia APIs it uses call the MMCSS service to boost the priority of the playback thread into the mealtime range' which basically means that every other thread - including network transfers - see a performance drop because of this.

The following method has worked for most users who have experienced slowdowns in network traffic in Vista while music was playing on the system.

  • Don't play music while transferring files. This is pretty obvious but probably not the best solution for most users, especially if you like to listen to music or audio while you are working on your system.
  • Remove the MMCSS dependency of Windows Audio in the registry. To do that navigate to the key HKEY_LOCAL_MACHINE \SYSTEM \CurrentControlSet \Services \Audiosrv, right-click the DependOnService string and remove MMCSS from it.

Update: Microsoft has fixed the issue in newer versions of Windows Vista and newer versions of the operating system. You should not run into this issue anymore when you play audio on your system, provided that you have installed the latest Windows Vista service pack that the company has published.


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