[linux-audio-dev] Paper on dynamic range compression

[Dan Mills]

--- Steve Harris <S.W.Harris at ecs.soton.ac.uk> wrote:
 
> These are aliasing artifacts in the sidechain
> though, right? So they will
> show up as modulations in the output, rather than
> directly audible
> aliasing.

The last thing almost all software compressors do is
something of the form output = gain * sample; 

If either gain or sample contain aliasing, or if the
sum of their bandwidths would cause aliasing then
there will be aliasing present at the output. 

To an extent what happens earlier is in the sidechain
is less important as long as the last condition can be
met at the 'gain cell'.

Audio_bw + Gain_bw must be < 0.5 * SR at the gain
control multiplier. 

To address Erics point, in a slow 'gain riding'
compressor your point is valid, but this fails for
things like fast limiters or even for something like
an emulation of an SSL Mix bus comp, which has some
seriously fast attacks available. 

Further, it is not the instruments fundamental that is
the problem, as energy in the harmonics  will also get
aliased quite happily (And the aliasing products are
non harmonically related). 

I am going to code it up, we will see what happens
when we have something measurable (and listenable). 


Regards, Dan.

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