linuxaudio.org

On Wed, Oct 18, 2006 at 06:50:39PM +1000, Erik de Castro Lopo wrote:

quoted text
> 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.

Yes but my point is that the resulting aliasing sounds worse than the

harmonic distortion.
> Most instruments with fast transients usually *already* have a high

quoted text
> levels of higher harmonics (and inharmonics) that die away far more

> quickly than the lower harmonics.

True, but those are removed by the anti-aliasing filters in

the ADCs. The problem here is harmonics generated _inside_ the digital

domain. Once they're generated it's too late to filter them out, as

the aliasing has already occurred.
> > The 3rd harmonic alone potentially increases the signal bandwidth by

quoted text
> > 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?????

A lead guitarist will often deliberately play a harmonic `squeal'

in a lead solo (particularly in rock and metal). As a guitarist myself,

I fairly frequently generate fundamentals of around 4 kHz. Deliberate

use of higher frequencies than that might not be very common, but

the equipment should at least deal with it gracefully.
The fact remains that a lot of high end professional users consider many

of the free software plugins to be "nearly unusable" (see Ben Loftis'

earlier post in this thread). This isn't intended as a criticism of the

developers, just an acknowledgement that perhaps more attention needs to be

paid to some fairly subtle aspects of design that have not been

considered important up to now, if these high end users are to take

Linux audio more seriously.
John