Re: [ecasound] Effects

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Subject: Re: [ecasound] Effects
From: Kai Vehmanen (
Date: Sun Feb 25 2001 - 16:13:15 EET

On Fri, 23 Feb 2001, S. Massy wrote:

> You know, guys, I think he's right. To use the effects in ecasound
> you've got to have a thorough understanding of how each effect works,
> both at the sound level and at the computing level. The usual pedal
> has about four knobs with pretty clear labels and usually does not
> require understanding of how things work, twisting the knobs is all
> you have to do. Of course, it is best to know how the effect works but
> it is not mandatory. With ecasound, on the other hand, one has to know
> what he's doing and even understanding the effect is not enough at

To some degree, this is intended. With hw effect boxes you don't usually
have direct access to the fx engine. Instead you get a set of pre-defined
presets, and a set of easily understandable parameters, usually with
pre-defined range of possible (=usable) parameter values.

I've taken a different approach in ecasound. Effect params directly
reflect what happens in the algorithms. This has a couple of benefits:

(i) Adding effects is easy. I don't have to spend time finding good
    sounding parameter combinations, and I don't need to care about
    whether the effect sounds good or whether it is usable. It's
    up to the users to judge that. As I have no commercial pressure,
    I can do this. :)
(ii) Users are not limited to using parameter values I or some other
     developer think are good. In other words, it's easy to abuse
     ecasound effects. For instance, you can give negative values to
     amplify --> you can invert signals with "-ea:-100".

> times. Take the flanger effect for example:
> -etl:delay-time-msec,variance-time-samples,feedback-%,lfo-freq
> For someone who knows what a flanger effect is the delay, feedback and
> frequency parameters are obvious. However, what is
> variance-time-samples exactly? I suppose it's the difference between

Hmm, I guess the correct commercial-sounding parameter name would be

> the actual delay and the peaks in the shiftings, right? But why
> express it in samples, why not in ms? I think that would be more intuitive.

It's in samples, because it seemed that even really small variance values
are usable (<= 'one sample' is a smaller unit than 'one ms').

> Maybe if I get the time I'll give a try at producing a document with a
> short description for each parameters in some effects, the ones I
> understand anyway...

This would be great! And of course, nothing stops you from sending fixes
and additions to ecasound man pages. Contributing code is just one way in
participating in ecasound development. Documentation and distribution
issues are just as important.

>> do? (I.e. with reverb, how should the room size and various
>> percentages be altered to produce different effects?)
> BTW, the manpage says that roomsize is expressed in meters but it
> doesn't make sense, shouldn't it be square meters?

That probably should be square meters. I don't know for sure, as the
-ete reverb code comes from Stefan Fendt (author of Bacterium).

> Anyway, I suggest you take a look at the preset file coming with
> ecasound, that is:
> /usr/local/share/ecasound/effect_presets, and use the presets as basis for experimentation.

This is a very good advice! This is basicly just the thing you get with
rack effects and pedals. And here too, contributions are welcome! There's
always room for new presets.

 . ... [ audio software for linux ] /\ . 
 . [ my armchair-tunes mp3/ra/wav ]

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