alc/effects/equalizer.cpp

   1 /**
   2  * OpenAL cross platform audio library
   3  * Copyright (C) 2013 by Mike Gorchak
   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 <functional>
  28 #include <variant>
  29
  30 #include "alc/effects/base.h"
  31 #include "alspan.h"
  32 #include "core/ambidefs.h"
  33 #include "core/bufferline.h"
  34 #include "core/context.h"
  35 #include "core/device.h"
  36 #include "core/effects/base.h"
  37 #include "core/effectslot.h"
  38 #include "core/filters/biquad.h"
  39 #include "core/mixer.h"
  40 #include "intrusive_ptr.h"
  41
  42 struct BufferStorage;
  43
  44 namespace {
  45
  46 /*  The document  "Effects Extension Guide.pdf"  says that low and high  *
  47  *  frequencies are cutoff frequencies. This is not fully correct, they  *
  48  *  are corner frequencies for low and high shelf filters. If they were  *
  49  *  just cutoff frequencies, there would be no need in cutoff frequency  *
  50  *  gains, which are present.  Documentation for  "Creative Proteus X2"  *
  51  *  software describes  4-band equalizer functionality in a much better  *
  52  *  way.  This equalizer seems  to be a predecessor  of  OpenAL  4-band  *
  53  *  equalizer.  With low and high  shelf filters  we are able to cutoff  *
  54  *  frequencies below and/or above corner frequencies using attenuation  *
  55  *  gains (below 1.0) and amplify all low and/or high frequencies using  *
  56  *  gains above 1.0.                                                     *
  57  *                                                                       *
  58  *     Low-shelf       Low Mid Band      High Mid Band     High-shelf    *
  59  *      corner            center             center          corner      *
  60  *     frequency        frequency          frequency       frequency     *
  61  *    50Hz..800Hz     200Hz..3000Hz      1000Hz..8000Hz  4000Hz..16000Hz *
  62  *                                                                       *
  63  *          |               |                  |               |         *
  64  *          |               |                  |               |         *
  65  *   B -----+            /--+--\            /--+--\            +-----    *
  66  *   O      |\          |   |   |          |   |   |          /|         *
  67  *   O      | \        -    |    -        -    |    -        / |         *
  68  *   S +    |  \      |     |     |      |     |     |      /  |         *
  69  *   T      |   |    |      |      |    |      |      |    |   |         *
  70  * ---------+---------------+------------------+---------------+-------- *
  71  *   C      |   |    |      |      |    |      |      |    |   |         *
  72  *   U -    |  /      |     |     |      |     |     |      \  |         *
  73  *   T      | /        -    |    -        -    |    -        \ |         *
  74  *   O      |/          |   |   |          |   |   |          \|         *
  75  *   F -----+            \--+--/            \--+--/            +-----    *
  76  *   F      |               |                  |               |         *
  77  *          |               |                  |               |         *
  78  *                                                                       *
  79  * Gains vary from 0.126 up to 7.943, which means from -18dB attenuation *
  80  * up to +18dB amplification. Band width varies from 0.01 up to 1.0 in   *
  81  * octaves for two mid bands.                                            *
  82  *                                                                       *
  83  * Implementation is based on the "Cookbook formulae for audio EQ biquad *
  84  * filter coefficients" by Robert Bristow-Johnson                        *
  85  * http://www.musicdsp.org/files/Audio-EQ-Cookbook.txt                   */
  86
  87
  88 struct EqualizerState final : public EffectState {
  89     struct OutParams {
  90         uint mTargetChannel{InvalidChannelIndex};
  91
  92         /* Effect parameters */
  93         std::array<BiquadFilter,4> mFilter;
  94
  95         /* Effect gains for each channel */
  96         float mCurrentGain{};
  97         float mTargetGain{};
  98     };
  99     std::array<OutParams,MaxAmbiChannels> mChans;
 100
 101     alignas(16) FloatBufferLine mSampleBuffer{};
 102
 103
 104     void deviceUpdate(const DeviceBase *device, const BufferStorage *buffer) override;
 105     void update(const ContextBase *context, const EffectSlot *slot, const EffectProps *props,
 106         const EffectTarget target) override;
 107     void process(const size_t samplesToDo, const al::span<const FloatBufferLine> samplesIn,
 108         const al::span<FloatBufferLine> samplesOut) override;
 109 };
 110
 111 void EqualizerState::deviceUpdate(const DeviceBase*, const BufferStorage*)
 112 {
 113     for(auto &e : mChans)
 114     {
 115         e.mTargetChannel = InvalidChannelIndex;
 116         std::for_each(e.mFilter.begin(), e.mFilter.end(), std::mem_fn(&BiquadFilter::clear));
 117         e.mCurrentGain = 0.0f;
 118     }
 119 }
 120
 121 void EqualizerState::update(const ContextBase *context, const EffectSlot *slot,
 122     const EffectProps *props_, const EffectTarget target)
 123 {
 124     auto &props = std::get<EqualizerProps>(*props_);
 125     const DeviceBase *device{context->mDevice};
 126     auto frequency = static_cast<float>(device->Frequency);
 127
 128     /* Calculate coefficients for the each type of filter. Note that the shelf
 129      * and peaking filters' gain is for the centerpoint of the transition band,
 130      * while the effect property gains are for the shelf/peak itself. So the
 131      * property gains need their dB halved (sqrt of linear gain) for the
 132      * shelf/peak to reach the provided gain.
 133      */
 134     float gain{std::sqrt(props.LowGain)};
 135     float f0norm{props.LowCutoff / frequency};
 136     mChans[0].mFilter[0].setParamsFromSlope(BiquadType::LowShelf, f0norm, gain, 0.75f);
 137
 138     gain = std::sqrt(props.Mid1Gain);
 139     f0norm = props.Mid1Center / frequency;
 140     mChans[0].mFilter[1].setParamsFromBandwidth(BiquadType::Peaking, f0norm, gain,
 141         props.Mid1Width);
 142
 143     gain = std::sqrt(props.Mid2Gain);
 144     f0norm = props.Mid2Center / frequency;
 145     mChans[0].mFilter[2].setParamsFromBandwidth(BiquadType::Peaking, f0norm, gain,
 146         props.Mid2Width);
 147
 148     gain = std::sqrt(props.HighGain);
 149     f0norm = props.HighCutoff / frequency;
 150     mChans[0].mFilter[3].setParamsFromSlope(BiquadType::HighShelf, f0norm, gain, 0.75f);
 151
 152     /* Copy the filter coefficients for the other input channels. */
 153     for(size_t i{1u};i < slot->Wet.Buffer.size();++i)
 154     {
 155         mChans[i].mFilter[0].copyParamsFrom(mChans[0].mFilter[0]);
 156         mChans[i].mFilter[1].copyParamsFrom(mChans[0].mFilter[1]);
 157         mChans[i].mFilter[2].copyParamsFrom(mChans[0].mFilter[2]);
 158         mChans[i].mFilter[3].copyParamsFrom(mChans[0].mFilter[3]);
 159     }
 160
 161     mOutTarget = target.Main->Buffer;
 162     auto set_channel = [this](size_t idx, uint outchan, float outgain)
 163     {
 164         mChans[idx].mTargetChannel = outchan;
 165         mChans[idx].mTargetGain = outgain;
 166     };
 167     target.Main->setAmbiMixParams(slot->Wet, slot->Gain, set_channel);
 168 }
 169
 170 void EqualizerState::process(const size_t samplesToDo, const al::span<const FloatBufferLine> samplesIn, const al::span<FloatBufferLine> samplesOut)
 171 {
 172     const auto buffer = al::span{mSampleBuffer}.first(samplesToDo);
 173     auto chan = mChans.begin();
 174     for(const auto &input : samplesIn)
 175     {
 176         if(const size_t outidx{chan->mTargetChannel}; outidx != InvalidChannelIndex)
 177         {
 178             const auto inbuf = al::span{input}.first(samplesToDo);
 179             DualBiquad{chan->mFilter[0], chan->mFilter[1]}.process(inbuf, buffer);
 180             DualBiquad{chan->mFilter[2], chan->mFilter[3]}.process(buffer, buffer);
 181
 182             MixSamples(buffer, samplesOut[outidx], chan->mCurrentGain, chan->mTargetGain,
 183                 samplesToDo);
 184         }
 185         ++chan;
 186     }
 187 }
 188
 189
 190 struct EqualizerStateFactory final : public EffectStateFactory {
 191     al::intrusive_ptr<EffectState> create() override
 192     { return al::intrusive_ptr<EffectState>{new EqualizerState{}}; }
 193 };
 194
 195 } // namespace
 196
 197 EffectStateFactory *EqualizerStateFactory_getFactory()
 198 {
 199     static EqualizerStateFactory EqualizerFactory{};
 200     return &EqualizerFactory;
 201 }