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 <cstdlib>
  26 #include <functional>
  27 #include <iterator>
  28 #include <utility>
  29
  30 #include "alc/effects/base.h"
  31 #include "almalloc.h"
  32 #include "alspan.h"
  33 #include "core/ambidefs.h"
  34 #include "core/bufferline.h"
  35 #include "core/context.h"
  36 #include "core/devformat.h"
  37 #include "core/device.h"
  38 #include "core/effectslot.h"
  39 #include "core/filters/biquad.h"
  40 #include "core/mixer.h"
  41 #include "intrusive_ptr.h"
  42
  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 {
  90         /* Effect parameters */
  91         BiquadFilter filter[4];
  92
  93         /* Effect gains for each channel */
  94         float CurrentGains[MAX_OUTPUT_CHANNELS]{};
  95         float TargetGains[MAX_OUTPUT_CHANNELS]{};
  96     } mChans[MaxAmbiChannels];
  97
  98     FloatBufferLine mSampleBuffer{};
  99
 100
 101     void deviceUpdate(const DeviceBase *device, const Buffer &buffer) override;
 102     void update(const ContextBase *context, const EffectSlot *slot, const EffectProps *props,
 103         const EffectTarget target) override;
 104     void process(const size_t samplesToDo, const al::span<const FloatBufferLine> samplesIn,
 105         const al::span<FloatBufferLine> samplesOut) override;
 106
 107     DEF_NEWDEL(EqualizerState)
 108 };
 109
 110 void EqualizerState::deviceUpdate(const DeviceBase*, const Buffer&)
 111 {
 112     for(auto &e : mChans)
 113     {
 114         std::for_each(std::begin(e.filter), std::end(e.filter), std::mem_fn(&BiquadFilter::clear));
 115         std::fill(std::begin(e.CurrentGains), std::end(e.CurrentGains), 0.0f);
 116     }
 117 }
 118
 119 void EqualizerState::update(const ContextBase *context, const EffectSlot *slot,
 120     const EffectProps *props, const EffectTarget target)
 121 {
 122     const DeviceBase *device{context->mDevice};
 123     auto frequency = static_cast<float>(device->Frequency);
 124     float gain, f0norm;
 125
 126     /* Calculate coefficients for the each type of filter. Note that the shelf
 127      * and peaking filters' gain is for the centerpoint of the transition band,
 128      * while the effect property gains are for the shelf/peak itself. So the
 129      * property gains need their dB halved (sqrt of linear gain) for the
 130      * shelf/peak to reach the provided gain.
 131      */
 132     gain = std::sqrt(props->Equalizer.LowGain);
 133     f0norm = props->Equalizer.LowCutoff / frequency;
 134     mChans[0].filter[0].setParamsFromSlope(BiquadType::LowShelf, f0norm, gain, 0.75f);
 135
 136     gain = std::sqrt(props->Equalizer.Mid1Gain);
 137     f0norm = props->Equalizer.Mid1Center / frequency;
 138     mChans[0].filter[1].setParamsFromBandwidth(BiquadType::Peaking, f0norm, gain,
 139         props->Equalizer.Mid1Width);
 140
 141     gain = std::sqrt(props->Equalizer.Mid2Gain);
 142     f0norm = props->Equalizer.Mid2Center / frequency;
 143     mChans[0].filter[2].setParamsFromBandwidth(BiquadType::Peaking, f0norm, gain,
 144         props->Equalizer.Mid2Width);
 145
 146     gain = std::sqrt(props->Equalizer.HighGain);
 147     f0norm = props->Equalizer.HighCutoff / frequency;
 148     mChans[0].filter[3].setParamsFromSlope(BiquadType::HighShelf, f0norm, gain, 0.75f);
 149
 150     /* Copy the filter coefficients for the other input channels. */
 151     for(size_t i{1u};i < slot->Wet.Buffer.size();++i)
 152     {
 153         mChans[i].filter[0].copyParamsFrom(mChans[0].filter[0]);
 154         mChans[i].filter[1].copyParamsFrom(mChans[0].filter[1]);
 155         mChans[i].filter[2].copyParamsFrom(mChans[0].filter[2]);
 156         mChans[i].filter[3].copyParamsFrom(mChans[0].filter[3]);
 157     }
 158
 159     mOutTarget = target.Main->Buffer;
 160     auto set_gains = [slot,target](auto &chan, al::span<const float,MaxAmbiChannels> coeffs)
 161     { ComputePanGains(target.Main, coeffs.data(), slot->Gain, chan.TargetGains); };
 162     SetAmbiPanIdentity(std::begin(mChans), slot->Wet.Buffer.size(), set_gains);
 163 }
 164
 165 void EqualizerState::process(const size_t samplesToDo, const al::span<const FloatBufferLine> samplesIn, const al::span<FloatBufferLine> samplesOut)
 166 {
 167     const al::span<float> buffer{mSampleBuffer.data(), samplesToDo};
 168     auto chan = std::addressof(mChans[0]);
 169     for(const auto &input : samplesIn)
 170     {
 171         const al::span<const float> inbuf{input.data(), samplesToDo};
 172         DualBiquad{chan->filter[0], chan->filter[1]}.process(inbuf, buffer.begin());
 173         DualBiquad{chan->filter[2], chan->filter[3]}.process(buffer, buffer.begin());
 174
 175         MixSamples(buffer, samplesOut, chan->CurrentGains, chan->TargetGains, samplesToDo, 0u);
 176         ++chan;
 177     }
 178 }
 179
 180
 181 struct EqualizerStateFactory final : public EffectStateFactory {
 182     al::intrusive_ptr<EffectState> create() override
 183     { return al::intrusive_ptr<EffectState>{new EqualizerState{}}; }
 184 };
 185
 186 } // namespace
 187
 188 EffectStateFactory *EqualizerStateFactory_getFactory()
 189 {
 190     static EqualizerStateFactory EqualizerFactory{};
 191     return &EqualizerFactory;
 192 }