[sdiy] Hardware convolution box?

[cheater00 cheater00]

Hi Frédéric,

On Mon, Feb 13, 2017 at 9:49 PM, Frédéric (Opensource)
<marzacdev at gmail.com> wrote:
> Hi cheater00,
>
> thank you for your didactic answer.
>
> I clearly understand the maths behind using an impulse response to model
> a  transfer function. It's basically converting an approximation of an
> unknown
> function into a big huge FIR or a polynomial (z domain) of an extreme high
> order (as you prefer!).
>
> I think, for many musical applications, this is a (too?) generic approach
> because
> it does not benefit from the context (what you are actually modelling).
>
> You take the example of modelling "filters".
> For audio DSP engines,  I often use IIR (or biquad) blocks in conjunction
> with
> various non-linear (well their polynomial approximation) elements.
> How big has to be the equivalent FIR to get a satisfying similar impulse
> response?
> And how do you deal with alteration of the filter parameters (still an
> example)?
> Do you make a impulse response table (with interpolation ;-)) ?
>
> Same applies for complex delays ...

I believe you're over-thinking this. A FIR filter will have its own
sound, and that's it. It will be a different sound to analog, VA,
component modelling, or FIR. Being able to change the cutoff in real
time is not a challenge. I also think that the definition of
convolution you're operating on is too low level. You're missing the
forest for the trees. Convolution basically means "do stuff in the
frequency domain" and "apply a volume and phase change based on
frequency", that's it. You don't need to think about polynomials,
FFTs, all that junk. That's too much conceptual load.

>>> Furthermore the platform could obviously support any sort of synth, be
>>> it physical modelling, string, component modelling, granular synthesis,
>>> FM, PM, VA, sampler
>
> I understand the platform as being the hardware, am I right?
>
> So what you ask is a generic box with MIDI ports, USB, audio in and out, a
> very
> beefy CPU or/and DSP, fast memory and with a well documented and accessible
> SDK for anyone to develop for?
>
> Is that alright?

Not really, no, we could just start by using dev boards, and see where
that leads us, and then we can see if we can come up with a board that
has some nice common features everyone would like to use. Some of the
DSP dev boards have really good bang for the buck and unless someone
proves to me otherwise I assume you'd be stupid to try and spin your
own boards.