I can also confirm that even for videos of much lower resolution, “Media Foundation Protected Pipeline EXE” gets starten when I open them and uses 100% CPU at the beginning and around 10-20% CPU during playback. In addition, it takes almost 45 seconds before Media Player actually starts playing the video after opening it.
Video and audio playback seems to use much more resources in Vista, and you even get freezes and gaps in the audio.
On that very same PC, in XP, everything worked much faster.