Playing music on Vista caps network throughput

Interesting. If you have music open in a media player, your maximum network throughput drops, even if the music is paused. Close the music player, speed goes back up. It seems not to be hardware as some people are dual booting into XP and not seeing this.

on xp the network speed was between 30-50%
on vista it was stuck at just over 5%

so I followed all the advice about disabling autotuning etc, tried setting all the differerent lan driver settings, played with the tcp window size, latest drivers etc ....
none of it made a bit of difference, I was still stuck on 5% usage

until.... I stopped playing music...
doesn't matter what I play back music with, if it's playing or paused the lan speed seems to be locked at the 5%
stopping playback or quitting the player lets the file copy go to the 30-50% instantly

It seems to be a feature:

Apparenty Vista natively boosts multimedia priority in the kernel, which could explain a lot about the drop in network throughput.

http://www.microsoft.com/technet/tec...2/VistaKernel/

I'm probably waiting for SP1 before I upgrade to Vista.

[UPDATE] The slowdown explained:

Many people have correctly surmised that the degradation in network performance during multimedia playback is directly connected with mechanisms employed by the Multimedia Class Scheduler Service (MMCSS), a feature new to Windows Vista that I covered in my three-part TechNet Magazine article series on Windows Vista kernel changes. Multimedia playback requires a constant rate of media streaming, and playback will glitch or sputter if its requirements aren’t met. The MMCSS service runs in the generic service hosting process Svchost.exe, where it automatically prioritizes the playback of video and audio in order to prevent other tasks from interfering with the CPU usage of the playback software: