compressor

audio compressor
Author: Remco van der Most
License: BSD
Github: sss/dyn/compressor.axo

Inlets

bool32 AutoGain

frac32buffer input wave

frac32.positive adds gain to input audio

frac32.positive Level Threshold (with auto make-up gain)

frac32.positive attack

frac32.positive Release rate

frac32.positive ratio

frac32.positive Goal Volume

frac32.positive Open to turn Compressor into expander (glitches when both threshold and expander values are high, causing a fat, harsh distortion. Awesome for bassdrums!)

Outlets

frac32buffer out

Declaration
int32_t out1;
int32_t out2;
int32_t out3;

int32_t val;
Control Rate
int64_t attack = (1 << 27) - inlet_attack;
int64_t decay = (1 << 27) - inlet_decay;
attack = ___SMMUL(attack << 3, attack << 2);
attack = ___SMMUL(attack << 3, attack << 2);
decay = ___SMMUL(decay << 3, decay << 2);
decay = ___SMMUL(decay << 3, decay << 2);
int64_t arate;
int64_t drate;
arate = (1 << 27) - attack;
drate = (1 << 27) - decay;
Audio Rate
int32_t in;
in = ___SMMUL(inlet_in << 3, ((1 << 26) + (inlet_gainAdd)) << 3);

int sabs;
sabs = (in >= 0) ? in : -in;

if (sabs > val)
  val = ___SMMLA(val - sabs, (-1 << 26) + (arate >> 1), val);
else
  val = ___SMMLA(val - sabs, (-1 << 26) + (drate >> 1), val);
out1 = val;

int32_t thresa = (inlet_threshold >= (1 << 18)) ? inlet_threshold : (1 << 18);
Float_t f;
f.f = (thresa);
int32_t r1 = ((f.parts.exponent & 0x7F) - 18) << 24;
int32_t r2 = logt[f.parts.mantissa >> 15] << 10;
int32_t thresh = r1 + r2;
int32_t thresb;
thresb = ___SMMUL(out1 << 2, inlet_expander << 3) +
         ___SMMUL(thresa << 3, ((1 << 27) - inlet_expander) << 2);

f.f = (thresb > out1)
          ? (thresb)
          : ___SMMUL((out1 - thresb) << 3, inlet_ratio << 2) + thresb;
r1 = ((f.parts.exponent & 0x7F) - 18) << 24;
r2 = logt[f.parts.mantissa >> 15] << 10;
int32_t audioIn = r1 + r2;

int32_t slog = (thresh - audioIn);

f.f = (1 << 27);
r1 = ((f.parts.exponent & 0x7F) - 18) << 24;
r2 = logt[f.parts.mantissa >> 15] << 10;
int32_t normal = r1 + r2;

int32_t normat = (normal - thresh);

int8_t s = (slog >> 24) + 12;
uint8_t ei = slog >> 16;
int32_t audioOut;
if (s >= 0)
  audioOut = (expt[ei] << s);
else
  audioOut = (expt[ei] >> (-s));

s = (normat >> 24) + 6;
ei = normat >> 16;
int32_t norman;
if (s >= 0)
  norman = (expt[ei] << s);
else
  norman = (expt[ei] >> (-s));

int32_t outa = ___SMMUL(audioOut << 2, in << 3);
int32_t outb = (outa >> 3) * (norman >> 18);
if (inlet_AutoGain > 0) {
  outlet_out = ___SMMUL(outb << 3, inlet_goal << 2);
}

else {
  outlet_out = ___SMMUL(outa << 3, inlet_goal << 2);
}

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