linuxaudio.org

On Sat, September 25, 2010 7:17 am, fons@kokkinizita.net wrote:

quoted text
> 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

quoted text
> 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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