[chbot] Software filter. Fast attack, slow decay

[Synco Reynders]

attack_rate = 0.8
decay_rate = 0.1
decay_method = 1
# Full-wave rectify the input signal is probably what you actually want, so
suggest using the absolute value function.
diff = abs(in) - out
if diff > 0 then:
    out = out + diff * attack_rate
else:
    if decay_method:
        out = out * (1 - decay_rate)     # for constant decay
    else:
        out = out + diff * decay_rate    # for proportional decay



On Sun, 19 Jun 2022 at 16:35, Robin Gilks <gb7ipd at gmail.com> wrote:

> Here's another question for you all!!
>
> I'm trying to implement "something like" a VU Meter in software (in an
> embedded system so it has to be small & fast).
> The hardware equivalent to a diode running into an RC filter
>
>           |\ |             R
>    in ----|  |----------vvvvvv--------- out
>           |/ |                    |
>                                  ___
>                                  ___  C
>                                   |
>                                   |
>  common ----------------------------------------
>
> My first port of call for filters is an IIR but that does not have the
> fast attack I'm after, especially if I want the long tail.
>
> Does anyone have any magic that doesn't disappear into a morass of DFTs
> and FFTs and 3 page equations summing integrals from 0 to infinity ;)
>
> Cheers - hopefully see you tomorrow.
>
> --
> Robin Gilks
>
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-- 
Synco Reynders
  m: +64 21 1825332
  e: synco.reynders at gmail.com
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