/** * OpenAL cross platform audio library * Copyright (C) 2013 by Mike Gorchak * 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 #include #include #include #include "alcmain.h" #include "alcontext.h" #include "core/filters/biquad.h" #include "effectslot.h" #include "vecmat.h" namespace { /* The document "Effects Extension Guide.pdf" says that low and high * * frequencies are cutoff frequencies. This is not fully correct, they * * are corner frequencies for low and high shelf filters. If they were * * just cutoff frequencies, there would be no need in cutoff frequency * * gains, which are present. Documentation for "Creative Proteus X2" * * software describes 4-band equalizer functionality in a much better * * way. This equalizer seems to be a predecessor of OpenAL 4-band * * equalizer. With low and high shelf filters we are able to cutoff * * frequencies below and/or above corner frequencies using attenuation * * gains (below 1.0) and amplify all low and/or high frequencies using * * gains above 1.0. * * * * Low-shelf Low Mid Band High Mid Band High-shelf * * corner center center corner * * frequency frequency frequency frequency * * 50Hz..800Hz 200Hz..3000Hz 1000Hz..8000Hz 4000Hz..16000Hz * * * * | | | | * * | | | | * * B -----+ /--+--\ /--+--\ +----- * * O |\ | | | | | | /| * * O | \ - | - - | - / | * * S + | \ | | | | | | / | * * T | | | | | | | | | | * * ---------+---------------+------------------+---------------+-------- * * C | | | | | | | | | | * * U - | / | | | | | | \ | * * T | / - | - - | - \ | * * O |/ | | | | | | \| * * F -----+ \--+--/ \--+--/ +----- * * F | | | | * * | | | | * * * * Gains vary from 0.126 up to 7.943, which means from -18dB attenuation * * up to +18dB amplification. Band width varies from 0.01 up to 1.0 in * * octaves for two mid bands. * * * * Implementation is based on the "Cookbook formulae for audio EQ biquad * * filter coefficients" by Robert Bristow-Johnson * * http://www.musicdsp.org/files/Audio-EQ-Cookbook.txt */ struct EqualizerState final : public EffectState { struct { /* Effect parameters */ BiquadFilter filter[4]; /* Effect gains for each channel */ float CurrentGains[MAX_OUTPUT_CHANNELS]{}; float TargetGains[MAX_OUTPUT_CHANNELS]{}; } mChans[MaxAmbiChannels]; FloatBufferLine mSampleBuffer{}; void deviceUpdate(const ALCdevice *device, const Buffer &buffer) override; void update(const ALCcontext *context, const EffectSlot *slot, const EffectProps *props, const EffectTarget target) override; void process(const size_t samplesToDo, const al::span samplesIn, const al::span samplesOut) override; DEF_NEWDEL(EqualizerState) }; void EqualizerState::deviceUpdate(const ALCdevice*, const Buffer&) { for(auto &e : mChans) { std::for_each(std::begin(e.filter), std::end(e.filter), std::mem_fn(&BiquadFilter::clear)); std::fill(std::begin(e.CurrentGains), std::end(e.CurrentGains), 0.0f); } } void EqualizerState::update(const ALCcontext *context, const EffectSlot *slot, const EffectProps *props, const EffectTarget target) { const ALCdevice *device{context->mDevice.get()}; auto frequency = static_cast(device->Frequency); float gain, f0norm; /* Calculate coefficients for the each type of filter. Note that the shelf * and peaking filters' gain is for the centerpoint of the transition band, * while the effect property gains are for the shelf/peak itself. So the * property gains need their dB halved (sqrt of linear gain) for the * shelf/peak to reach the provided gain. */ gain = std::sqrt(props->Equalizer.LowGain); f0norm = props->Equalizer.LowCutoff / frequency; mChans[0].filter[0].setParamsFromSlope(BiquadType::LowShelf, f0norm, gain, 0.75f); gain = std::sqrt(props->Equalizer.Mid1Gain); f0norm = props->Equalizer.Mid1Center / frequency; mChans[0].filter[1].setParamsFromBandwidth(BiquadType::Peaking, f0norm, gain, props->Equalizer.Mid1Width); gain = std::sqrt(props->Equalizer.Mid2Gain); f0norm = props->Equalizer.Mid2Center / frequency; mChans[0].filter[2].setParamsFromBandwidth(BiquadType::Peaking, f0norm, gain, props->Equalizer.Mid2Width); gain = std::sqrt(props->Equalizer.HighGain); f0norm = props->Equalizer.HighCutoff / frequency; mChans[0].filter[3].setParamsFromSlope(BiquadType::HighShelf, f0norm, gain, 0.75f); /* Copy the filter coefficients for the other input channels. */ for(size_t i{1u};i < slot->Wet.Buffer.size();++i) { mChans[i].filter[0].copyParamsFrom(mChans[0].filter[0]); mChans[i].filter[1].copyParamsFrom(mChans[0].filter[1]); mChans[i].filter[2].copyParamsFrom(mChans[0].filter[2]); mChans[i].filter[3].copyParamsFrom(mChans[0].filter[3]); } mOutTarget = target.Main->Buffer; auto set_gains = [slot,target](auto &chan, al::span coeffs) { ComputePanGains(target.Main, coeffs.data(), slot->Gain, chan.TargetGains); }; SetAmbiPanIdentity(std::begin(mChans), slot->Wet.Buffer.size(), set_gains); } void EqualizerState::process(const size_t samplesToDo, const al::span samplesIn, const al::span samplesOut) { const al::span buffer{mSampleBuffer.data(), samplesToDo}; auto chan = std::addressof(mChans[0]); for(const auto &input : samplesIn) { const al::span inbuf{input.data(), samplesToDo}; DualBiquad{chan->filter[0], chan->filter[1]}.process(inbuf, buffer.begin()); DualBiquad{chan->filter[2], chan->filter[3]}.process(buffer, buffer.begin()); MixSamples(buffer, samplesOut, chan->CurrentGains, chan->TargetGains, samplesToDo, 0u); ++chan; } } struct EqualizerStateFactory final : public EffectStateFactory { al::intrusive_ptr create() override { return al::intrusive_ptr{new EqualizerState{}}; } }; } // namespace EffectStateFactory *EqualizerStateFactory_getFactory() { static EqualizerStateFactory EqualizerFactory{}; return &EqualizerFactory; }