[K.B.]

This must seem like the dumbest of dumb questions, but right now it would be a godsend to Canon 5D Mk II users:

One shortcoming of these HDSLR cameras is their lack of high quality audio recording. Ironically, the audio recording hardware isn't terribly bad, and the final audio recorded is actually uncompressed.

The monkey wrench is that these HDSLR cameras record the audio with automatic gain control (AGC) always on. AGC is a method of compressing and/or limiting audio input levels so they do not overload the camera's audio preamps. Think of it as an automatic volume knob for incoming sound.

This is normally a good thing as it safeguards the camera's internal audio hardware from inexperienced users that may override the preamps with signal that is too hot. However, an AGC system that cannot be turned off is a curse in any professional environment. It creates a noticeably higher noise floor that can be very annoying.

Surely, someone somewhere must have dreamed up a way of anticipating and fixing this in post - some clever way of reverse-attenuating the sound...
(And yes, I know, "Don't call me Shirley!" )

Some pics of a full HDSLR rig: http://hddslr-hire.com/