[FoRK] sound/volume normalisation software

[J. Andrew Rogers]

On Dec 14, 2007, at 5:18 PM, silky wrote:
> because this is kind of hard to google for, I was hoping I can ask the
> fork collective.
>
> anyone aware of any software that "normalises" the volume produced by
> your speakers? what i mean is, if i have a movie playing a volume X,
> then I would like all other sound-generating apps (flash movies,
> whatever) to play at that same level, no matter what they think they
> should play at ... if it doesn't exist i'll consider writing it, but
> wanted to check first :) i'm not talking about mp3 normalisation, i'm
> talking about live normalisation of all sound coming out of my
> speakers.


This software (and hardware) exists in abundance, but your particular  
setup, configuration, and preferences will affect what you actually  
use.  You are looking for dynamic range compression and peak limiting  
(i.e. "compressor" and "limiter"), which algorithmically push the  
signals into a narrower amplitude range.  You can also "normalize"  
digital files, but that isn't really what you are looking for.  There  
are a dozens of software plug-ins for compressor-limiters, including  
many free ones.  Some of these are more intelligent and/or tweakable  
than others, and really good ones like Waves (waves.com) tend to cost  
money but are also better at minimizing sound coloration and getting  
good results.

It sounds trivial at first glance, but to get good mostly-transparent  
results it requires that the software (or hardware) predict future  
characteristics of the signal and dynamically implement amplitude  
leveling strategies based on those predictions (which will be wrong  
some of the time).

J. Andrew Rogers