linuxaudio.org

On Sat, September 25, 2010 10:48 am, fons@kokkinizita.net wrote:

quoted text
> On Sat, Sep 25, 2010 at 10:07:46AM -0700, Patrick Shirkey wrote:

>

>> 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.

>

> The confusion continues :-)

>

> AFAIK Jamin does not have a parametric EQ. It uses an FFT-based

> method with a graphical interface that makes it look either like

> a combination of 'freehand' frequency response and parametric,

> or as a 30-band 'graphic EQ'. But it's the same algorithm in all

> cases, and it's not a plugin.

>

> If works by taking the FFT of the input, multiplying in the

> frequency domain by some precomputed values, and transforming

> back using an IFFT. This modifies the frequency response of

> course, but it is *not* a linear filter and produces side

> effects (modulation). Jamin minimises this by 1) windowing,

> which amounts to crossfading between processed blocks of

> samples, and 2) processing much more overlapping blocks than

> the minimum required to do crossfading (which would be 2).

>

> The proper way to implement a filter of this type (with a FR

> defined at all multiples of Fsamp / 1024) would be by using

> linear convolution rather than cyclic. But as said, this is

> not the right kind of filter anyway.

>

Just to clarify again, are you saying here that convolution will produce a

cleaner result than fft?
Or that the implementation of the fft algorithm in jamin is not the most

efficient method of doing the transform?
--

Patrick Shirkey

Boost Hardware Ltd.
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