alc/effects/autowah.cpp

   1 /**
   2  * OpenAL cross platform audio library
   3  * Copyright (C) 2018 by Raul Herraiz.
   4  * This library is free software; you can redistribute it and/or
   5  *  modify it under the terms of the GNU Library General Public
   6  *  License as published by the Free Software Foundation; either
   7  *  version 2 of the License, or (at your option) any later version.
   8  *
   9  * This library is distributed in the hope that it will be useful,
  10  *  but WITHOUT ANY WARRANTY; without even the implied warranty of
  11  *  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
  12  *  Library General Public License for more details.
  13  *
  14  * You should have received a copy of the GNU Library General Public
  15  *  License along with this library; if not, write to the
  16  *  Free Software Foundation, Inc.,
  17  *  51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA.
  18  * Or go to http://www.gnu.org/copyleft/lgpl.html
  19  */
  20
  21 #include "config.h"
  22
  23 #include <algorithm>
  24 #include <array>
  25 #include <cmath>
  26 #include <cstdlib>
  27 #include <variant>
  28
  29 #include "alc/effects/base.h"
  30 #include "alnumbers.h"
  31 #include "alnumeric.h"
  32 #include "alspan.h"
  33 #include "core/ambidefs.h"
  34 #include "core/bufferline.h"
  35 #include "core/context.h"
  36 #include "core/device.h"
  37 #include "core/effects/base.h"
  38 #include "core/effectslot.h"
  39 #include "core/mixer.h"
  40 #include "intrusive_ptr.h"
  41
  42 struct BufferStorage;
  43
  44 namespace {
  45
  46 constexpr float GainScale{31621.0f};
  47 constexpr float MinFreq{20.0f};
  48 constexpr float MaxFreq{2500.0f};
  49 constexpr float QFactor{5.0f};
  50
  51 struct AutowahState final : public EffectState {
  52     /* Effect parameters */
  53     float mAttackRate{};
  54     float mReleaseRate{};
  55     float mResonanceGain{};
  56     float mPeakGain{};
  57     float mFreqMinNorm{};
  58     float mBandwidthNorm{};
  59     float mEnvDelay{};
  60
  61     /* Filter components derived from the envelope. */
  62     struct FilterParam {
  63         float cos_w0{};
  64         float alpha{};
  65     };
  66     std::array<FilterParam,BufferLineSize> mEnv;
  67
  68     struct ChannelData {
  69         uint mTargetChannel{InvalidChannelIndex};
  70
  71         struct FilterHistory {
  72             float z1{}, z2{};
  73         };
  74         FilterHistory mFilter;
  75
  76         /* Effect gains for each output channel */
  77         float mCurrentGain{};
  78         float mTargetGain{};
  79     };
  80     std::array<ChannelData,MaxAmbiChannels> mChans;
  81
  82     /* Effects buffers */
  83     alignas(16) FloatBufferLine mBufferOut{};
  84
  85
  86     void deviceUpdate(const DeviceBase *device, const BufferStorage *buffer) override;
  87     void update(const ContextBase *context, const EffectSlot *slot, const EffectProps *props,
  88         const EffectTarget target) override;
  89     void process(const size_t samplesToDo, const al::span<const FloatBufferLine> samplesIn,
  90         const al::span<FloatBufferLine> samplesOut) override;
  91 };
  92
  93 void AutowahState::deviceUpdate(const DeviceBase*, const BufferStorage*)
  94 {
  95     /* (Re-)initializing parameters and clear the buffers. */
  96
  97     mAttackRate    = 1.0f;
  98     mReleaseRate   = 1.0f;
  99     mResonanceGain = 10.0f;
 100     mPeakGain      = 4.5f;
 101     mFreqMinNorm   = 4.5e-4f;
 102     mBandwidthNorm = 0.05f;
 103     mEnvDelay      = 0.0f;
 104
 105     for(auto &e : mEnv)
 106     {
 107         e.cos_w0 = 0.0f;
 108         e.alpha = 0.0f;
 109     }
 110
 111     for(auto &chan : mChans)
 112     {
 113         chan.mTargetChannel = InvalidChannelIndex;
 114         chan.mFilter.z1 = 0.0f;
 115         chan.mFilter.z2 = 0.0f;
 116         chan.mCurrentGain = 0.0f;
 117     }
 118 }
 119
 120 void AutowahState::update(const ContextBase *context, const EffectSlot *slot,
 121     const EffectProps *props_, const EffectTarget target)
 122 {
 123     auto &props = std::get<AutowahProps>(*props_);
 124     const DeviceBase *device{context->mDevice};
 125     const auto frequency = static_cast<float>(device->Frequency);
 126
 127     const float ReleaseTime{std::clamp(props.ReleaseTime, 0.001f, 1.0f)};
 128
 129     mAttackRate    = std::exp(-1.0f / (props.AttackTime*frequency));
 130     mReleaseRate   = std::exp(-1.0f / (ReleaseTime*frequency));
 131     /* 0-20dB Resonance Peak gain */
 132     mResonanceGain = std::sqrt(std::log10(props.Resonance)*10.0f / 3.0f);
 133     mPeakGain      = 1.0f - std::log10(props.PeakGain / GainScale);
 134     mFreqMinNorm   = MinFreq / frequency;
 135     mBandwidthNorm = (MaxFreq-MinFreq) / frequency;
 136
 137     mOutTarget = target.Main->Buffer;
 138     auto set_channel = [this](size_t idx, uint outchan, float outgain)
 139     {
 140         mChans[idx].mTargetChannel = outchan;
 141         mChans[idx].mTargetGain = outgain;
 142     };
 143     target.Main->setAmbiMixParams(slot->Wet, slot->Gain, set_channel);
 144 }
 145
 146 void AutowahState::process(const size_t samplesToDo,
 147     const al::span<const FloatBufferLine> samplesIn, const al::span<FloatBufferLine> samplesOut)
 148 {
 149     const float attack_rate{mAttackRate};
 150     const float release_rate{mReleaseRate};
 151     const float res_gain{mResonanceGain};
 152     const float peak_gain{mPeakGain};
 153     const float freq_min{mFreqMinNorm};
 154     const float bandwidth{mBandwidthNorm};
 155
 156     float env_delay{mEnvDelay};
 157     for(size_t i{0u};i < samplesToDo;i++)
 158     {
 159         /* Envelope follower described on the book: Audio Effects, Theory,
 160          * Implementation and Application.
 161          */
 162         const float sample{peak_gain * std::fabs(samplesIn[0][i])};
 163         const float a{(sample > env_delay) ? attack_rate : release_rate};
 164         env_delay = lerpf(sample, env_delay, a);
 165
 166         /* Calculate the cos and alpha components for this sample's filter. */
 167         const float w0{std::min(bandwidth*env_delay + freq_min, 0.46f) *
 168             (al::numbers::pi_v<float>*2.0f)};
 169         mEnv[i].cos_w0 = std::cos(w0);
 170         mEnv[i].alpha = std::sin(w0)/(2.0f * QFactor);
 171     }
 172     mEnvDelay = env_delay;
 173
 174     auto chandata = mChans.begin();
 175     for(const auto &insamples : samplesIn)
 176     {
 177         const size_t outidx{chandata->mTargetChannel};
 178         if(outidx == InvalidChannelIndex)
 179         {
 180             ++chandata;
 181             continue;
 182         }
 183
 184         /* This effectively inlines BiquadFilter_setParams for a peaking
 185          * filter and BiquadFilter_processC. The alpha and cosine components
 186          * for the filter coefficients were previously calculated with the
 187          * envelope. Because the filter changes for each sample, the
 188          * coefficients are transient and don't need to be held.
 189          */
 190         float z1{chandata->mFilter.z1};
 191         float z2{chandata->mFilter.z2};
 192
 193         for(size_t i{0u};i < samplesToDo;i++)
 194         {
 195             const float alpha{mEnv[i].alpha};
 196             const float cos_w0{mEnv[i].cos_w0};
 197
 198             const std::array b{
 199                 1.0f + alpha*res_gain,
 200                 -2.0f * cos_w0,
 201                 1.0f - alpha*res_gain};
 202             const std::array a{
 203                 1.0f + alpha/res_gain,
 204                 -2.0f * cos_w0,
 205                 1.0f - alpha/res_gain};
 206
 207             const float input{insamples[i]};
 208             const float output{input*(b[0]/a[0]) + z1};
 209             z1 = input*(b[1]/a[0]) - output*(a[1]/a[0]) + z2;
 210             z2 = input*(b[2]/a[0]) - output*(a[2]/a[0]);
 211             mBufferOut[i] = output;
 212         }
 213         chandata->mFilter.z1 = z1;
 214         chandata->mFilter.z2 = z2;
 215
 216         /* Now, mix the processed sound data to the output. */
 217         MixSamples(al::span{mBufferOut}.first(samplesToDo), samplesOut[outidx],
 218             chandata->mCurrentGain, chandata->mTargetGain, samplesToDo);
 219         ++chandata;
 220     }
 221 }
 222
 223
 224 struct AutowahStateFactory final : public EffectStateFactory {
 225     al::intrusive_ptr<EffectState> create() override
 226     { return al::intrusive_ptr<EffectState>{new AutowahState{}}; }
 227 };
 228
 229 } // namespace
 230
 231 EffectStateFactory *AutowahStateFactory_getFactory()
 232 {
 233     static AutowahStateFactory AutowahFactory{};
 234     return &AutowahFactory;
 235 }