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83 lines
4.1 KiB
83 lines
4.1 KiB
/**************************************************************************//**
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* @file
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* @author Steve Lascos
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* @company Blackaddr Audio
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*
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* This file constains precomputed co-efficients for the AudioEffectAnalogDelay
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* class.
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*
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* @copyright This program is free software: you can redistribute it and/or modify
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* it under the terms of the GNU General Public License as published by
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* the Free Software Foundation, either version 3 of the License, or
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* (at your option) any later version.*
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*
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* This program is distributed in the hope that it will be useful,
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* but WITHOUT ANY WARRANTY; without even the implied warranty of
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* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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* GNU General Public License for more details.
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*
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* You should have received a copy of the GNU General Public License
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* along with this program. If not, see <http://www.gnu.org/licenses/>.
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*****************************************************************************/
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#include <cstdint>
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namespace BAEffects {
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// The number of stages in the analog-response Biquad filter
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constexpr unsigned MAX_NUM_FILTER_STAGES = 4;
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constexpr unsigned NUM_COEFFS_PER_STAGE = 5;
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// Matlab/Octave can be helpful to design a filter. Once you have the IIR filter (bz,az) coefficients
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// in the z-domain, they can be converted to second-order-sections. AudioEffectAnalogDelay is designed
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// to accept up to a maximum of an 8th order filter, broken into four, 2nd order stages.
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//
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// Second order sections can be created with:
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// [sos] = tf2sos(bz,az);
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// The results coefficents must be converted the Q31 format required by the ARM CMSIS-DSP library. This means
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// all coefficients must lie between -1.0 and +0.9999. If your (bz,az) coefficients exceed this, you must divide
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// them down by a power of 2. For example, if your largest magnitude coefficient is -3.5, you must divide by
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// 2^shift where 4=2^2 and thus shift = 2. You must then mutliply by 2^31 to get a 32-bit signed integer value
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// that represents the required Q31 coefficient.
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// BOSS DM-3 Filters
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// b(z) = 1.0e-03 * (0.0032 0.0257 0.0900 0.1800 0.2250 0.1800 0.0900 0.0257 0.0032)
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// a(z) = 1.0000 -5.7677 14.6935 -21.3811 19.1491 -10.5202 3.2584 -0.4244 -0.0067
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constexpr unsigned DM3_NUM_STAGES = 4;
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constexpr unsigned DM3_COEFF_SHIFT = 2;
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constexpr int32_t DM3[5*MAX_NUM_FILTER_STAGES] = {
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536870912, 988616936, 455608573, 834606945, -482959709,
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536870912, 1031466345, 498793368, 965834205, -467402235,
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536870912, 1105821939, 573646688, 928470657, -448083489,
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2339, 5093, 2776, 302068995, 4412722
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};
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// Blackaddr WARM Filter
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// Butterworth, 8th order, cutoff = 2000 Hz
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// Matlab/Octave command: [bz, az] = butter(8, 2000/44100/2);
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// b(z) = 1.0e-05 * (0.0086 0.0689 0.2411 0.4821 0.6027 0.4821 0.2411 0.0689 0.0086_
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// a(z) = 1.0000 -6.5399 18.8246 -31.1340 32.3473 -21.6114 9.0643 -2.1815 0.2306
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constexpr unsigned WARM_NUM_STAGES = 4;
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constexpr unsigned WARM_COEFF_SHIFT = 2;
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constexpr int32_t WARM[5*MAX_NUM_FILTER_STAGES] = {
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536870912,1060309346,523602393,976869875,-481046241,
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536870912,1073413910,536711084,891250612,-391829326,
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536870912,1087173998,550475248,835222426,-333446881,
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46,92,46,807741349,-304811072
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};
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// Blackaddr DARK Filter
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// Chebychev Type II, 8th order, stopband = 60db, cutoff = 1000 Hz
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// Matlab command: [bz, az] = cheby2(8, 60, 1000/44100/2);
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// b(z) = 0.0009 -0.0066 0.0219 -0.0423 0.0522 -0.0423 0.0219 -0.0066 0.0009
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// a(z) = 1.0000 -7.4618 24.3762 -45.5356 53.1991 -39.8032 18.6245 -4.9829 0.5836
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constexpr unsigned DARK_NUM_STAGES = 4;
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constexpr unsigned DARK_COEFF_SHIFT = 1;
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constexpr int32_t DARK[5*MAX_NUM_FILTER_STAGES] = {
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1073741824,-2124867808,1073741824,2107780229,-1043948409,
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1073741824,-2116080466,1073741824,2042553796,-979786242,
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1073741824,-2077777790,1073741824,1964779896,-904264933,
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957356,-1462833,957356,1896884898,-838694612
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};
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};
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