1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
|
/**
* OpenAL cross platform audio library
* Copyright (C) 2018 by Raul Herraiz.
* This library is free software; you can redistribute it and/or
* modify it under the terms of the GNU Library General Public
* License as published by the Free Software Foundation; either
* version 2 of the License, or (at your option) any later version.
*
* This library is distributed in the hope that it will be useful,
* but WITHOUT ANY WARRANTY; without even the implied warranty of
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
* Library General Public License for more details.
*
* You should have received a copy of the GNU Library General Public
* License along with this library; if not, write to the
* Free Software Foundation, Inc.,
* 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA.
* Or go to http://www.gnu.org/copyleft/lgpl.html
*/
#include "config.h"
#include <cmath>
#include <cstdlib>
#include <algorithm>
#include "alcmain.h"
#include "alcontext.h"
#include "core/filters/biquad.h"
#include "effectslot.h"
#include "vecmat.h"
namespace {
constexpr float GainScale{31621.0f};
constexpr float MinFreq{20.0f};
constexpr float MaxFreq{2500.0f};
constexpr float QFactor{5.0f};
struct AutowahState final : public EffectState {
/* Effect parameters */
float mAttackRate;
float mReleaseRate;
float mResonanceGain;
float mPeakGain;
float mFreqMinNorm;
float mBandwidthNorm;
float mEnvDelay;
/* Filter components derived from the envelope. */
struct {
float cos_w0;
float alpha;
} mEnv[BufferLineSize];
struct {
/* Effect filters' history. */
struct {
float z1, z2;
} Filter;
/* Effect gains for each output channel */
float CurrentGains[MAX_OUTPUT_CHANNELS];
float TargetGains[MAX_OUTPUT_CHANNELS];
} mChans[MaxAmbiChannels];
/* Effects buffers */
alignas(16) float mBufferOut[BufferLineSize];
void deviceUpdate(const DeviceBase *device, const Buffer &buffer) override;
void update(const ContextBase *context, const EffectSlot *slot, const EffectProps *props,
const EffectTarget target) override;
void process(const size_t samplesToDo, const al::span<const FloatBufferLine> samplesIn,
const al::span<FloatBufferLine> samplesOut) override;
DEF_NEWDEL(AutowahState)
};
void AutowahState::deviceUpdate(const DeviceBase*, const Buffer&)
{
/* (Re-)initializing parameters and clear the buffers. */
mAttackRate = 1.0f;
mReleaseRate = 1.0f;
mResonanceGain = 10.0f;
mPeakGain = 4.5f;
mFreqMinNorm = 4.5e-4f;
mBandwidthNorm = 0.05f;
mEnvDelay = 0.0f;
for(auto &e : mEnv)
{
e.cos_w0 = 0.0f;
e.alpha = 0.0f;
}
for(auto &chan : mChans)
{
std::fill(std::begin(chan.CurrentGains), std::end(chan.CurrentGains), 0.0f);
chan.Filter.z1 = 0.0f;
chan.Filter.z2 = 0.0f;
}
}
void AutowahState::update(const ContextBase *context, const EffectSlot *slot,
const EffectProps *props, const EffectTarget target)
{
const DeviceBase *device{context->mDevice};
const auto frequency = static_cast<float>(device->Frequency);
const float ReleaseTime{clampf(props->Autowah.ReleaseTime, 0.001f, 1.0f)};
mAttackRate = std::exp(-1.0f / (props->Autowah.AttackTime*frequency));
mReleaseRate = std::exp(-1.0f / (ReleaseTime*frequency));
/* 0-20dB Resonance Peak gain */
mResonanceGain = std::sqrt(std::log10(props->Autowah.Resonance)*10.0f / 3.0f);
mPeakGain = 1.0f - std::log10(props->Autowah.PeakGain / GainScale);
mFreqMinNorm = MinFreq / frequency;
mBandwidthNorm = (MaxFreq-MinFreq) / frequency;
mOutTarget = target.Main->Buffer;
auto set_gains = [slot,target](auto &chan, al::span<const float,MaxAmbiChannels> coeffs)
{ ComputePanGains(target.Main, coeffs.data(), slot->Gain, chan.TargetGains); };
SetAmbiPanIdentity(std::begin(mChans), slot->Wet.Buffer.size(), set_gains);
}
void AutowahState::process(const size_t samplesToDo,
const al::span<const FloatBufferLine> samplesIn, const al::span<FloatBufferLine> samplesOut)
{
const float attack_rate{mAttackRate};
const float release_rate{mReleaseRate};
const float res_gain{mResonanceGain};
const float peak_gain{mPeakGain};
const float freq_min{mFreqMinNorm};
const float bandwidth{mBandwidthNorm};
float env_delay{mEnvDelay};
for(size_t i{0u};i < samplesToDo;i++)
{
float w0, sample, a;
/* Envelope follower described on the book: Audio Effects, Theory,
* Implementation and Application.
*/
sample = peak_gain * std::fabs(samplesIn[0][i]);
a = (sample > env_delay) ? attack_rate : release_rate;
env_delay = lerp(sample, env_delay, a);
/* Calculate the cos and alpha components for this sample's filter. */
w0 = minf((bandwidth*env_delay + freq_min), 0.46f) * al::MathDefs<float>::Tau();
mEnv[i].cos_w0 = std::cos(w0);
mEnv[i].alpha = std::sin(w0)/(2.0f * QFactor);
}
mEnvDelay = env_delay;
auto chandata = std::addressof(mChans[0]);
for(const auto &insamples : samplesIn)
{
/* This effectively inlines BiquadFilter_setParams for a peaking
* filter and BiquadFilter_processC. The alpha and cosine components
* for the filter coefficients were previously calculated with the
* envelope. Because the filter changes for each sample, the
* coefficients are transient and don't need to be held.
*/
float z1{chandata->Filter.z1};
float z2{chandata->Filter.z2};
for(size_t i{0u};i < samplesToDo;i++)
{
const float alpha{mEnv[i].alpha};
const float cos_w0{mEnv[i].cos_w0};
float input, output;
float a[3], b[3];
b[0] = 1.0f + alpha*res_gain;
b[1] = -2.0f * cos_w0;
b[2] = 1.0f - alpha*res_gain;
a[0] = 1.0f + alpha/res_gain;
a[1] = -2.0f * cos_w0;
a[2] = 1.0f - alpha/res_gain;
input = insamples[i];
output = input*(b[0]/a[0]) + z1;
z1 = input*(b[1]/a[0]) - output*(a[1]/a[0]) + z2;
z2 = input*(b[2]/a[0]) - output*(a[2]/a[0]);
mBufferOut[i] = output;
}
chandata->Filter.z1 = z1;
chandata->Filter.z2 = z2;
/* Now, mix the processed sound data to the output. */
MixSamples({mBufferOut, samplesToDo}, samplesOut, chandata->CurrentGains,
chandata->TargetGains, samplesToDo, 0);
++chandata;
}
}
struct AutowahStateFactory final : public EffectStateFactory {
al::intrusive_ptr<EffectState> create() override
{ return al::intrusive_ptr<EffectState>{new AutowahState{}}; }
};
} // namespace
EffectStateFactory *AutowahStateFactory_getFactory()
{
static AutowahStateFactory AutowahFactory{};
return &AutowahFactory;
}
|