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192 lines
8.4 KiB
192 lines
8.4 KiB
/**
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* OpenAL cross platform audio library
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* Copyright (C) 2013 by Mike Gorchak
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* This library is free software; you can redistribute it and/or
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* modify it under the terms of the GNU Library General Public
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* License as published by the Free Software Foundation; either
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* version 2 of the License, or (at your option) any later version.
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*
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* This library is distributed in the hope that it will be useful,
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* but WITHOUT ANY WARRANTY; without even the implied warranty of
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* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
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* Library General Public License for more details.
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*
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* You should have received a copy of the GNU Library General Public
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* License along with this library; if not, write to the
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* Free Software Foundation, Inc.,
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* 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA.
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* Or go to http://www.gnu.org/copyleft/lgpl.html
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*/
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#include "config.h"
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#include <algorithm>
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#include <array>
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#include <cstdlib>
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#include <functional>
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#include <iterator>
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#include <utility>
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#include "alc/effects/base.h"
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#include "almalloc.h"
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#include "alspan.h"
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#include "core/ambidefs.h"
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#include "core/bufferline.h"
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#include "core/context.h"
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#include "core/devformat.h"
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#include "core/device.h"
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#include "core/effectslot.h"
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#include "core/filters/biquad.h"
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#include "core/mixer.h"
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#include "intrusive_ptr.h"
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namespace {
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/* The document "Effects Extension Guide.pdf" says that low and high *
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* frequencies are cutoff frequencies. This is not fully correct, they *
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* are corner frequencies for low and high shelf filters. If they were *
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* just cutoff frequencies, there would be no need in cutoff frequency *
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* gains, which are present. Documentation for "Creative Proteus X2" *
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* software describes 4-band equalizer functionality in a much better *
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* way. This equalizer seems to be a predecessor of OpenAL 4-band *
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* equalizer. With low and high shelf filters we are able to cutoff *
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* frequencies below and/or above corner frequencies using attenuation *
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* gains (below 1.0) and amplify all low and/or high frequencies using *
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* gains above 1.0. *
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* *
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* Low-shelf Low Mid Band High Mid Band High-shelf *
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* corner center center corner *
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* frequency frequency frequency frequency *
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* 50Hz..800Hz 200Hz..3000Hz 1000Hz..8000Hz 4000Hz..16000Hz *
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* *
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* | | | | *
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* | | | | *
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* B -----+ /--+--\ /--+--\ +----- *
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* O |\ | | | | | | /| *
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* O | \ - | - - | - / | *
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* S + | \ | | | | | | / | *
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* T | | | | | | | | | | *
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* ---------+---------------+------------------+---------------+-------- *
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* C | | | | | | | | | | *
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* U - | / | | | | | | \ | *
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* T | / - | - - | - \ | *
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* O |/ | | | | | | \| *
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* F -----+ \--+--/ \--+--/ +----- *
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* F | | | | *
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* | | | | *
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* *
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* Gains vary from 0.126 up to 7.943, which means from -18dB attenuation *
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* up to +18dB amplification. Band width varies from 0.01 up to 1.0 in *
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* octaves for two mid bands. *
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* *
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* Implementation is based on the "Cookbook formulae for audio EQ biquad *
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* filter coefficients" by Robert Bristow-Johnson *
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* http://www.musicdsp.org/files/Audio-EQ-Cookbook.txt */
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struct EqualizerState final : public EffectState {
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struct {
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/* Effect parameters */
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BiquadFilter filter[4];
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/* Effect gains for each channel */
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float CurrentGains[MAX_OUTPUT_CHANNELS]{};
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float TargetGains[MAX_OUTPUT_CHANNELS]{};
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} mChans[MaxAmbiChannels];
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FloatBufferLine mSampleBuffer{};
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void deviceUpdate(const DeviceBase *device, const Buffer &buffer) override;
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void update(const ContextBase *context, const EffectSlot *slot, const EffectProps *props,
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const EffectTarget target) override;
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void process(const size_t samplesToDo, const al::span<const FloatBufferLine> samplesIn,
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const al::span<FloatBufferLine> samplesOut) override;
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DEF_NEWDEL(EqualizerState)
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};
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void EqualizerState::deviceUpdate(const DeviceBase*, const Buffer&)
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{
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for(auto &e : mChans)
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{
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std::for_each(std::begin(e.filter), std::end(e.filter), std::mem_fn(&BiquadFilter::clear));
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std::fill(std::begin(e.CurrentGains), std::end(e.CurrentGains), 0.0f);
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}
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}
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void EqualizerState::update(const ContextBase *context, const EffectSlot *slot,
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const EffectProps *props, const EffectTarget target)
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{
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const DeviceBase *device{context->mDevice};
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auto frequency = static_cast<float>(device->Frequency);
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float gain, f0norm;
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/* Calculate coefficients for the each type of filter. Note that the shelf
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* and peaking filters' gain is for the centerpoint of the transition band,
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* while the effect property gains are for the shelf/peak itself. So the
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* property gains need their dB halved (sqrt of linear gain) for the
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* shelf/peak to reach the provided gain.
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*/
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gain = std::sqrt(props->Equalizer.LowGain);
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f0norm = props->Equalizer.LowCutoff / frequency;
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mChans[0].filter[0].setParamsFromSlope(BiquadType::LowShelf, f0norm, gain, 0.75f);
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gain = std::sqrt(props->Equalizer.Mid1Gain);
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f0norm = props->Equalizer.Mid1Center / frequency;
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mChans[0].filter[1].setParamsFromBandwidth(BiquadType::Peaking, f0norm, gain,
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props->Equalizer.Mid1Width);
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gain = std::sqrt(props->Equalizer.Mid2Gain);
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f0norm = props->Equalizer.Mid2Center / frequency;
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mChans[0].filter[2].setParamsFromBandwidth(BiquadType::Peaking, f0norm, gain,
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props->Equalizer.Mid2Width);
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gain = std::sqrt(props->Equalizer.HighGain);
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f0norm = props->Equalizer.HighCutoff / frequency;
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mChans[0].filter[3].setParamsFromSlope(BiquadType::HighShelf, f0norm, gain, 0.75f);
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/* Copy the filter coefficients for the other input channels. */
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for(size_t i{1u};i < slot->Wet.Buffer.size();++i)
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{
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mChans[i].filter[0].copyParamsFrom(mChans[0].filter[0]);
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mChans[i].filter[1].copyParamsFrom(mChans[0].filter[1]);
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mChans[i].filter[2].copyParamsFrom(mChans[0].filter[2]);
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mChans[i].filter[3].copyParamsFrom(mChans[0].filter[3]);
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}
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mOutTarget = target.Main->Buffer;
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auto set_gains = [slot,target](auto &chan, al::span<const float,MaxAmbiChannels> coeffs)
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{ ComputePanGains(target.Main, coeffs.data(), slot->Gain, chan.TargetGains); };
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SetAmbiPanIdentity(std::begin(mChans), slot->Wet.Buffer.size(), set_gains);
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}
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void EqualizerState::process(const size_t samplesToDo, const al::span<const FloatBufferLine> samplesIn, const al::span<FloatBufferLine> samplesOut)
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{
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const al::span<float> buffer{mSampleBuffer.data(), samplesToDo};
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auto chan = std::addressof(mChans[0]);
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for(const auto &input : samplesIn)
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{
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const al::span<const float> inbuf{input.data(), samplesToDo};
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DualBiquad{chan->filter[0], chan->filter[1]}.process(inbuf, buffer.begin());
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DualBiquad{chan->filter[2], chan->filter[3]}.process(buffer, buffer.begin());
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MixSamples(buffer, samplesOut, chan->CurrentGains, chan->TargetGains, samplesToDo, 0u);
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++chan;
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}
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}
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struct EqualizerStateFactory final : public EffectStateFactory {
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al::intrusive_ptr<EffectState> create() override
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{ return al::intrusive_ptr<EffectState>{new EqualizerState{}}; }
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};
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} // namespace
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EffectStateFactory *EqualizerStateFactory_getFactory()
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{
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static EqualizerStateFactory EqualizerFactory{};
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return &EqualizerFactory;
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}
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