[LAU] Subject: Albums under a label recorded and/or mixed with Linux

Patrick Shirkey pshirkey at boosthardware.com
Sat Sep 25 17:07:46 UTC 2010

On Sat, September 25, 2010 7:17 am, fons at kokkinizita.net wrote:
> On Fri, Sep 24, 2010 at 09:51:07PM -0700, Patrick Shirkey wrote:
>> IIRC Fons suggested the sc4 compressor algorithm was similar to a
>> vocoder.
> I did never suggest anything of the sort concerning the sc4 compressor.
> More precisely, the * FFT-based equaliser * is not a linear filter but
> a vocoder. You just have to inspect the code to see this. The problems
> resulting from this are mitigated to a large extent by using a large
> overlap factor, at the price of much increased CPU usage. To the point
> that a real filter implementation using linear convolution would in fact
> be simpler and more efficient.

Thanks for clarifying. I recall the parametric eq was chosen because that
was recommended as the tool to use by the professionals mastering
engineers who were contributing to the development discussions.

> If this were all I'd have provided a patch years ago. But there are other
> problems with this type of filter: it provides way too much detail in the
> mid and high frequency regions. There is really no point in having any
> significant gain difference between say 4000 Hz and 4020 Hz, the only
> result would be a very bad impulse respons that destroys all transients.
> Yet the user interface makes it easy to get this sort of thing, even just
> accidentally. It's a good example of textbook DSP being applied blindly
> and without understanding the consequences.

To clarify further, are you referring to the entire ui or specifically to
the parametric eq ui which Jan designed? I think Jan would be the first to
admit that he is not a dsp expert but was instead attempting to provide a
user friendly interface for the specific plugin.

If the latter, it's trivial from a backend perspective to add a linear
filter in place of the parametric eq. After all it is just a ladspa plugin
with a custom gui. No doubt you have already released one. The much more
complex problem will be adding a frontend that allows for proper control.
However if the interface is similar to the parametric eq ui it is probably
only a weeks work or less.

Do you have an example of what the ui for a linear filter should look like
from an ui perspective?

I could look around online for example but no doubt there is a correct way
to represent it so I would rather see that first.

IIUC there is nothing to stop us from adding a linear filter as an option
for the eq section.

Patrick Shirkey
Boost Hardware Ltd.

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