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 <cstdlib>
  26 #include <iterator>
  27 #include <utility>
  28
  29 #include "alc/effects/base.h"
  30 #include "almalloc.h"
  31 #include "alnumbers.h"
  32 #include "alnumeric.h"
  33 #include "alspan.h"
  34 #include "core/ambidefs.h"
  35 #include "core/bufferline.h"
  36 #include "core/context.h"
  37 #include "core/devformat.h"
  38 #include "core/device.h"
  39 #include "core/effectslot.h"
  40 #include "core/mixer.h"
  41 #include "intrusive_ptr.h"
  42
  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 {
  63         float cos_w0;
  64         float alpha;
  65     } mEnv[BufferLineSize];
  66
  67     struct {
  68         /* Effect filters' history. */
  69         struct {
  70             float z1, z2;
  71         } Filter;
  72
  73         /* Effect gains for each output channel */
  74         float CurrentGains[MAX_OUTPUT_CHANNELS];
  75         float TargetGains[MAX_OUTPUT_CHANNELS];
  76     } mChans[MaxAmbiChannels];
  77
  78     /* Effects buffers */
  79     alignas(16) float mBufferOut[BufferLineSize];
  80
  81
  82     void deviceUpdate(const DeviceBase *device, const Buffer &buffer) override;
  83     void update(const ContextBase *context, const EffectSlot *slot, const EffectProps *props,
  84         const EffectTarget target) override;
  85     void process(const size_t samplesToDo, const al::span<const FloatBufferLine> samplesIn,
  86         const al::span<FloatBufferLine> samplesOut) override;
  87
  88     DEF_NEWDEL(AutowahState)
  89 };
  90
  91 void AutowahState::deviceUpdate(const DeviceBase*, const Buffer&)
  92 {
  93     /* (Re-)initializing parameters and clear the buffers. */
  94
  95     mAttackRate    = 1.0f;
  96     mReleaseRate   = 1.0f;
  97     mResonanceGain = 10.0f;
  98     mPeakGain      = 4.5f;
  99     mFreqMinNorm   = 4.5e-4f;
 100     mBandwidthNorm = 0.05f;
 101     mEnvDelay      = 0.0f;
 102
 103     for(auto &e : mEnv)
 104     {
 105         e.cos_w0 = 0.0f;
 106         e.alpha = 0.0f;
 107     }
 108
 109     for(auto &chan : mChans)
 110     {
 111         std::fill(std::begin(chan.CurrentGains), std::end(chan.CurrentGains), 0.0f);
 112         chan.Filter.z1 = 0.0f;
 113         chan.Filter.z2 = 0.0f;
 114     }
 115 }
 116
 117 void AutowahState::update(const ContextBase *context, const EffectSlot *slot,
 118     const EffectProps *props, const EffectTarget target)
 119 {
 120     const DeviceBase *device{context->mDevice};
 121     const auto frequency = static_cast<float>(device->Frequency);
 122
 123     const float ReleaseTime{clampf(props->Autowah.ReleaseTime, 0.001f, 1.0f)};
 124
 125     mAttackRate    = std::exp(-1.0f / (props->Autowah.AttackTime*frequency));
 126     mReleaseRate   = std::exp(-1.0f / (ReleaseTime*frequency));
 127     /* 0-20dB Resonance Peak gain */
 128     mResonanceGain = std::sqrt(std::log10(props->Autowah.Resonance)*10.0f / 3.0f);
 129     mPeakGain      = 1.0f - std::log10(props->Autowah.PeakGain / GainScale);
 130     mFreqMinNorm   = MinFreq / frequency;
 131     mBandwidthNorm = (MaxFreq-MinFreq) / frequency;
 132
 133     mOutTarget = target.Main->Buffer;
 134     auto set_gains = [slot,target](auto &chan, al::span<const float,MaxAmbiChannels> coeffs)
 135     { ComputePanGains(target.Main, coeffs.data(), slot->Gain, chan.TargetGains); };
 136     SetAmbiPanIdentity(std::begin(mChans), slot->Wet.Buffer.size(), set_gains);
 137 }
 138
 139 void AutowahState::process(const size_t samplesToDo,
 140     const al::span<const FloatBufferLine> samplesIn, const al::span<FloatBufferLine> samplesOut)
 141 {
 142     const float attack_rate{mAttackRate};
 143     const float release_rate{mReleaseRate};
 144     const float res_gain{mResonanceGain};
 145     const float peak_gain{mPeakGain};
 146     const float freq_min{mFreqMinNorm};
 147     const float bandwidth{mBandwidthNorm};
 148
 149     float env_delay{mEnvDelay};
 150     for(size_t i{0u};i < samplesToDo;i++)
 151     {
 152         float w0, sample, a;
 153
 154         /* Envelope follower described on the book: Audio Effects, Theory,
 155          * Implementation and Application.
 156          */
 157         sample = peak_gain * std::fabs(samplesIn[0][i]);
 158         a = (sample > env_delay) ? attack_rate : release_rate;
 159         env_delay = lerp(sample, env_delay, a);
 160
 161         /* Calculate the cos and alpha components for this sample's filter. */
 162         w0 = minf((bandwidth*env_delay + freq_min), 0.46f) * (al::numbers::pi_v<float>*2.0f);
 163         mEnv[i].cos_w0 = std::cos(w0);
 164         mEnv[i].alpha = std::sin(w0)/(2.0f * QFactor);
 165     }
 166     mEnvDelay = env_delay;
 167
 168     auto chandata = std::addressof(mChans[0]);
 169     for(const auto &insamples : samplesIn)
 170     {
 171         /* This effectively inlines BiquadFilter_setParams for a peaking
 172          * filter and BiquadFilter_processC. The alpha and cosine components
 173          * for the filter coefficients were previously calculated with the
 174          * envelope. Because the filter changes for each sample, the
 175          * coefficients are transient and don't need to be held.
 176          */
 177         float z1{chandata->Filter.z1};
 178         float z2{chandata->Filter.z2};
 179
 180         for(size_t i{0u};i < samplesToDo;i++)
 181         {
 182             const float alpha{mEnv[i].alpha};
 183             const float cos_w0{mEnv[i].cos_w0};
 184             float input, output;
 185             float a[3], b[3];
 186
 187             b[0] =  1.0f + alpha*res_gain;
 188             b[1] = -2.0f * cos_w0;
 189             b[2] =  1.0f - alpha*res_gain;
 190             a[0] =  1.0f + alpha/res_gain;
 191             a[1] = -2.0f * cos_w0;
 192             a[2] =  1.0f - alpha/res_gain;
 193
 194             input = insamples[i];
 195             output = input*(b[0]/a[0]) + z1;
 196             z1 = input*(b[1]/a[0]) - output*(a[1]/a[0]) + z2;
 197             z2 = input*(b[2]/a[0]) - output*(a[2]/a[0]);
 198             mBufferOut[i] = output;
 199         }
 200         chandata->Filter.z1 = z1;
 201         chandata->Filter.z2 = z2;
 202
 203         /* Now, mix the processed sound data to the output. */
 204         MixSamples({mBufferOut, samplesToDo}, samplesOut, chandata->CurrentGains,
 205             chandata->TargetGains, samplesToDo, 0);
 206         ++chandata;
 207     }
 208 }
 209
 210
 211 struct AutowahStateFactory final : public EffectStateFactory {
 212     al::intrusive_ptr<EffectState> create() override
 213     { return al::intrusive_ptr<EffectState>{new AutowahState{}}; }
 214 };
 215
 216 } // namespace
 217
 218 EffectStateFactory *AutowahStateFactory_getFactory()
 219 {
 220     static AutowahStateFactory AutowahFactory{};
 221     return &AutowahFactory;
 222 }