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

[Erik de Castro Lopo]

John Rigg wrote:

> Soft clipping always sounds better than hard clipping, and there are
> analog compressors that behave like this. Unfortunately even a soft
> clipper generates significant harmonic distortion, largely 3rd and 5th.

But this should only be happening on transients and the clipping
should stop as soon as the attack portion of the compression
process kicks in.

Most instruments with fast transients usually *already* have a high
levels of higher harmonics (and inharmonics) that die away far more 
quickly than the lower harmonics.

> The 3rd harmonic alone potentially increases the signal bandwidth by
> three times

Ok, lets say we're sampling at 44.1kHz, which makes the highest
3rd harmonic we can represent is 22.0/3 kHz which is about 7kHz.
Do you really listen to many instruments where the fundamental
is at 7kHz?????

> and aliasing will occur if the sample frequency isn't
> high enough to accommodate all harmonics

These higher harmonics will be transitory. As soon as the attack
portion of the compressor's action is over they're gone. In 
addition, any aliasing that does occur will be almost indistinguishable
from the inharmonics frequencies already in transient part of the 
sound.

I say again, nearly all instruments with very fast transients have
a high number of inharmonics frequencuies that die off almost 
immediately. For instance, think of instruments like acoustic guitars
and pianos.

Its very easy to get carried away with trying to reach some sort
of audio perfection. Things like upsampling in order to apply 
compression is over-engineering.

Erik
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+-----------------------------------------------------------+
  Erik de Castro Lopo
+-----------------------------------------------------------+
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