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73 lines
2.0 KiB
73 lines
2.0 KiB
7 years ago
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/*
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* Copyright 2013 Google Inc.
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*
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* Licensed under the Apache License, Version 2.0 (the "License");
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* you may not use this file except in compliance with the License.
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* You may obtain a copy of the License at
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*
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* http://www.apache.org/licenses/LICENSE-2.0
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*
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* Unless required by applicable law or agreed to in writing, software
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* distributed under the License is distributed on an "AS IS" BASIS,
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* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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* See the License for the specific language governing permissions and
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* limitations under the License.
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*/
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#define _USE_MATH_DEFINES
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#include <math.h>
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#include "synth.h"
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#include "exp2.h"
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#include <stdio.h>
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#ifdef _MSC_VER
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#define exp2(arg) pow(2.0, arg)
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#endif
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int32_t exp2tab[EXP2_N_SAMPLES << 1];
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void Exp2::init() {
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double inc = exp2(1.0 / EXP2_N_SAMPLES);
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double y = 1 << 30;
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for (int i = 0; i < EXP2_N_SAMPLES; i++) {
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exp2tab[(i << 1) + 1] = (int32_t)floor(y + 0.5);
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y *= inc;
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}
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for (int i = 0; i < EXP2_N_SAMPLES - 1; i++) {
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exp2tab[i << 1] = exp2tab[(i << 1) + 3] - exp2tab[(i << 1) + 1];
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}
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exp2tab[(EXP2_N_SAMPLES << 1) - 2] = (1U << 31) - exp2tab[(EXP2_N_SAMPLES << 1) - 1];
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}
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int32_t tanhtab[TANH_N_SAMPLES << 1];
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static double dtanh(double y) {
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return 1 - y * y;
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}
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void Tanh::init() {
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double step = 4.0 / TANH_N_SAMPLES;
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double y = 0;
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for (int i = 0; i < TANH_N_SAMPLES; i++) {
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tanhtab[(i << 1) + 1] = (1 << 24) * y + 0.5;
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//printf("%d\n", tanhtab[(i << 1) + 1]);
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// Use a basic 4th order Runge-Kutte to compute tanh from its
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// differential equation.
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double k1 = dtanh(y);
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double k2 = dtanh(y + 0.5 * step * k1);
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double k3 = dtanh(y + 0.5 * step * k2);
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double k4 = dtanh(y + step * k3);
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double dy = (step / 6) * (k1 + k4 + 2 * (k2 + k3));
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y += dy;
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}
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for (int i = 0; i < TANH_N_SAMPLES - 1; i++) {
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tanhtab[i << 1] = tanhtab[(i << 1) + 3] - tanhtab[(i << 1) + 1];
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}
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int32_t lasty = (1 << 24) * y + 0.5;
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tanhtab[(TANH_N_SAMPLES << 1) - 2] = lasty - tanhtab[(TANH_N_SAMPLES << 1) - 1];
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}
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