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Saahil Doshi correctly points out that the dB level got messed up again.
This is an bad decision that has bit me before: the standard cookbook
biquad functions take the value 'A' as the gain argument, but for
historical reasons my helpers pass in the voltage gain, which is A
squared, and then do
float A = sqrtf(gain);
so then when using the peaking functions and not remembering this
gotcha, the math ends up being off by a power of two.
What's an order of magnitude among friends?
I probably should just fix the biquad filter interfaces to be more
standard, but let's once again fix the understandably confused use
instead.
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
* 'fix/parametric-eq-gain' of https://github.com/Legit-Ox/GuitarPedal:
parametric_eq: fix gain math, pot only delivered ~half the requested dB
46 lines
1.8 KiB
C
46 lines
1.8 KiB
C
// NAME: Parametric EQ [PEQ]
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// PRIORITY: 120
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// POT: "LS Freq" FREQUENCY(20.0 400.0) = 100.0 Hz
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// POT: "LS Gain" LINEAR(-20.0 20.0) = 0.0 dB
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// POT: "P1 Freq" FREQUENCY(50.0 1000.0) = 250.0 Hz
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// POT: "P1 Gain" LINEAR(-20.0 20.0) = 0.0 dB
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// POT: "P2 Freq" FREQUENCY(100.0 4000.0) = 1000.0 Hz
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// POT: "P2 Gain" LINEAR(-20.0 20.0) = 0.0 dB
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// POT: "P3 Freq" FREQUENCY(400.0 10000.0) = 4000.0 Hz
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// POT: "P3 Gain" LINEAR(-20.0 20.0) = 0.0 dB
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// POT: "HS Freq" FREQUENCY(1000.0 20000.0) = 8000.0 Hz
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// POT: "HS Gain" LINEAR(-20.0 20.0) = 0.0 dB
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#define EFF_ENABLE_STEPS ((int)SAMPLES_PER_SEC/10)
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struct {
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struct biquad_coeff coeff[5];
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struct biquad_state state[5];
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} peq;
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// Fixed Q for the 5-band EQ
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static const float PEQ_Q = 1.0f;
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static void parametric_eq_init(unsigned char pot[10])
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{
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struct biquad_coeff *c = peq.coeff;
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_biquad_loshelf(c+0, fastsincos(parametric_eq_pot0(pot[0]) / SAMPLES_PER_SEC), PEQ_Q, db_to_level(parametric_eq_pot1(pot[1])));
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_biquad_peaking(c+1, fastsincos(parametric_eq_pot2(pot[2]) / SAMPLES_PER_SEC), PEQ_Q, db_to_level(parametric_eq_pot3(pot[3])));
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_biquad_peaking(c+2, fastsincos(parametric_eq_pot4(pot[4]) / SAMPLES_PER_SEC), PEQ_Q, db_to_level(parametric_eq_pot5(pot[5])));
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_biquad_peaking(c+3, fastsincos(parametric_eq_pot6(pot[6]) / SAMPLES_PER_SEC), PEQ_Q, db_to_level(parametric_eq_pot7(pot[7])));
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_biquad_hishelf(c+4, fastsincos(parametric_eq_pot8(pot[8]) / SAMPLES_PER_SEC), PEQ_Q, db_to_level(parametric_eq_pot9(pot[9])));
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}
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static float parametric_eq_step(float in)
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{
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const struct biquad_coeff *c = peq.coeff;
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struct biquad_state *s = peq.state;
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float val = _biquad_step(c+0, s+0, in);
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val = _biquad_peaking_step(c+1, s+1, val);
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val = _biquad_peaking_step(c+2, s+2, val);
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val = _biquad_peaking_step(c+3, s+3, val);
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return _biquad_step(c+4, s+4, val);
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}
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