linuxaudio.org

On Tue, Mar 06, 2012 at 10:43:06PM +0000, James Mckernon wrote:

quoted text
> Hi all,

>

> I have a few questions about using ecasound and/or nama with slightly more

> complex, 'non-linear' chains of audio effects. By this I mainly mean

> 'forking' chains - such as highpassing a signal and applying a delay loop

> to the high-frequency components of the sound, and a distortion to the

> rest, for example.

>

> This kind of thing would generally be straightforward enough to implement

> in hardware with physical cables, but elegant implementations in DSP seem

> rarer -- at least in linux. One of the reasons I am interested in ecasound

> is that I gather from its 'examples' webpage that it handles exactly this

> kind of thing quite elegantly:

> 'Ok, let's next do some parallel processing: two chains are created and the

> input and output files are connected to them. As a result, the input signal

> is processed with two sets of effects, and then mixed back together. You

> can create as many chains this way as you want.' (

> http://www.eca.cx/ecasound/Documentation/examples.html#effects)

>

> However, I suspect that ecasound in its raw form could be somewhat unwieldy

> for the sort of work I'd like to do, so I'd like to be able to use nama

> instead. Would this sort of 'forking' signal chain be as easy to set up in

> nama as it seems to be in ecasound? Also, in nama, is it possible/easy to

> adjust and play with the effects path (and effect parameters) on the fly,

> without interrupting playback?

Hi,
With Ecasound, you can change effect parameters without

interrupting playback. 
Adding and removing effects can create a pop, which Nama

hides by briefly muting the track.
Changing effect parameters can also change effect latency,

which would create a pop. Nama doesn't protect you in that

case.
The first example of signal processing you give is easy to

do, presuming you've spend a little time to learn the Nama

or Ecasound ways of doing it!
> Relatedly, another thing I'd like to be able to do is a delay effect, with

quoted text
> effect(s) (i.e. filters or certain kinds of distortion, followed by a gain

> reduction) applied 'inside' the delay loop, such that the effect is

> recursively, cumulatively applied to the looped material. Might sound like

> a strange requirement, I know, but it's actually a fairly central effect to

> the kind of music I'd like to make (dub reggae). Unfortunately, this is

> difficult to achieve easily in Linux. 

You may have to roll your own.
> Since no delay plugin that I know of

quoted text
> includes the kind of internal effects that I want, the only way to achieve

> this is with some kind of 'circular' DSP chain, which most programs don't

> allow. Does anyone know if this kind of 'circular' DSP chain might be

> achievable in any way in ecasound - for example, by feeding a track's

> output back to itself?

I haven't seen an example with Ecasound. 
Regards,
--

Joel Roth

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