alc/effects/distortion.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 <cmath>
  24 #include <cstdlib>
  25
  26 #include <cmath>
  27
  28 #include "al/auxeffectslot.h"
  29 #include "alcmain.h"
  30 #include "alcontext.h"
  31 #include "alu.h"
  32 #include "filters/biquad.h"
  33
  34
  35 namespace {
  36
  37 struct DistortionState final : public EffectState {
  38     /* Effect gains for each channel */
  39     ALfloat mGain[MAX_OUTPUT_CHANNELS]{};
  40
  41     /* Effect parameters */
  42     BiquadFilter mLowpass;
  43     BiquadFilter mBandpass;
  44     ALfloat mAttenuation{};
  45     ALfloat mEdgeCoeff{};
  46
  47     ALfloat mBuffer[2][BUFFERSIZE]{};
  48
  49
  50     ALboolean deviceUpdate(const ALCdevice *device) override;
  51     void update(const ALCcontext *context, const ALeffectslot *slot, const EffectProps *props, const EffectTarget target) override;
  52     void process(const size_t samplesToDo, const al::span<const FloatBufferLine> samplesIn, const al::span<FloatBufferLine> samplesOut) override;
  53
  54     DEF_NEWDEL(DistortionState)
  55 };
  56
  57 ALboolean DistortionState::deviceUpdate(const ALCdevice*)
  58 {
  59     mLowpass.clear();
  60     mBandpass.clear();
  61     return AL_TRUE;
  62 }
  63
  64 void DistortionState::update(const ALCcontext *context, const ALeffectslot *slot, const EffectProps *props, const EffectTarget target)
  65 {
  66     const ALCdevice *device{context->mDevice.get()};
  67
  68     /* Store waveshaper edge settings. */
  69     const ALfloat edge{
  70         minf(std::sin(al::MathDefs<float>::Pi()*0.5f * props->Distortion.Edge), 0.99f)};
  71     mEdgeCoeff = 2.0f * edge / (1.0f-edge);
  72
  73     ALfloat cutoff{props->Distortion.LowpassCutoff};
  74     /* Bandwidth value is constant in octaves. */
  75     ALfloat bandwidth{(cutoff / 2.0f) / (cutoff * 0.67f)};
  76     /* Multiply sampling frequency by the amount of oversampling done during
  77      * processing.
  78      */
  79     auto frequency = static_cast<ALfloat>(device->Frequency);
  80     mLowpass.setParams(BiquadType::LowPass, 1.0f, cutoff / (frequency*4.0f),
  81         mLowpass.rcpQFromBandwidth(cutoff / (frequency*4.0f), bandwidth));
  82
  83     cutoff = props->Distortion.EQCenter;
  84     /* Convert bandwidth in Hz to octaves. */
  85     bandwidth = props->Distortion.EQBandwidth / (cutoff * 0.67f);
  86     mBandpass.setParams(BiquadType::BandPass, 1.0f, cutoff / (frequency*4.0f),
  87         mBandpass.rcpQFromBandwidth(cutoff / (frequency*4.0f), bandwidth));
  88
  89     ALfloat coeffs[MAX_AMBI_CHANNELS];
  90     CalcDirectionCoeffs({0.0f, 0.0f, -1.0f}, 0.0f, coeffs);
  91
  92     mOutTarget = target.Main->Buffer;
  93     ComputePanGains(target.Main, coeffs, slot->Params.Gain*props->Distortion.Gain, mGain);
  94 }
  95
  96 void DistortionState::process(const size_t samplesToDo, const al::span<const FloatBufferLine> samplesIn, const al::span<FloatBufferLine> samplesOut)
  97 {
  98     const ALfloat fc{mEdgeCoeff};
  99     for(size_t base{0u};base < samplesToDo;)
 100     {
 101         /* Perform 4x oversampling to avoid aliasing. Oversampling greatly
 102          * improves distortion quality and allows to implement lowpass and
 103          * bandpass filters using high frequencies, at which classic IIR
 104          * filters became unstable.
 105          */
 106         size_t todo{minz(BUFFERSIZE, (samplesToDo-base) * 4)};
 107
 108         /* Fill oversample buffer using zero stuffing. Multiply the sample by
 109          * the amount of oversampling to maintain the signal's power.
 110          */
 111         for(size_t i{0u};i < todo;i++)
 112             mBuffer[0][i] = !(i&3) ? samplesIn[0][(i>>2)+base] * 4.0f : 0.0f;
 113
 114         /* First step, do lowpass filtering of original signal. Additionally
 115          * perform buffer interpolation and lowpass cutoff for oversampling
 116          * (which is fortunately first step of distortion). So combine three
 117          * operations into the one.
 118          */
 119         mLowpass.process(mBuffer[1], mBuffer[0], todo);
 120
 121         /* Second step, do distortion using waveshaper function to emulate
 122          * signal processing during tube overdriving. Three steps of
 123          * waveshaping are intended to modify waveform without boost/clipping/
 124          * attenuation process.
 125          */
 126         for(size_t i{0u};i < todo;i++)
 127         {
 128             ALfloat smp{mBuffer[1][i]};
 129
 130             smp = (1.0f + fc) * smp/(1.0f + fc*fabsf(smp));
 131             smp = (1.0f + fc) * smp/(1.0f + fc*fabsf(smp)) * -1.0f;
 132             smp = (1.0f + fc) * smp/(1.0f + fc*fabsf(smp));
 133
 134             mBuffer[0][i] = smp;
 135         }
 136
 137         /* Third step, do bandpass filtering of distorted signal. */
 138         mBandpass.process(mBuffer[1], mBuffer[0], todo);
 139
 140         todo >>= 2;
 141         const ALfloat *outgains{mGain};
 142         for(FloatBufferLine &output : samplesOut)
 143         {
 144             /* Fourth step, final, do attenuation and perform decimation,
 145              * storing only one sample out of four.
 146              */
 147             const ALfloat gain{*(outgains++)};
 148             if(!(std::fabs(gain) > GAIN_SILENCE_THRESHOLD))
 149                 continue;
 150
 151             for(size_t i{0u};i < todo;i++)
 152                 output[base+i] += gain * mBuffer[1][i*4];
 153         }
 154
 155         base += todo;
 156     }
 157 }
 158
 159
 160 void Distortion_setParami(EffectProps*, ALCcontext *context, ALenum param, ALint)
 161 { context->setError(AL_INVALID_ENUM, "Invalid distortion integer property 0x%04x", param); }
 162 void Distortion_setParamiv(EffectProps*, ALCcontext *context, ALenum param, const ALint*)
 163 { context->setError(AL_INVALID_ENUM, "Invalid distortion integer-vector property 0x%04x", param); }
 164 void Distortion_setParamf(EffectProps *props, ALCcontext *context, ALenum param, ALfloat val)
 165 {
 166     switch(param)
 167     {
 168         case AL_DISTORTION_EDGE:
 169             if(!(val >= AL_DISTORTION_MIN_EDGE && val <= AL_DISTORTION_MAX_EDGE))
 170                 SETERR_RETURN(context, AL_INVALID_VALUE,, "Distortion edge out of range");
 171             props->Distortion.Edge = val;
 172             break;
 173
 174         case AL_DISTORTION_GAIN:
 175             if(!(val >= AL_DISTORTION_MIN_GAIN && val <= AL_DISTORTION_MAX_GAIN))
 176                 SETERR_RETURN(context, AL_INVALID_VALUE,, "Distortion gain out of range");
 177             props->Distortion.Gain = val;
 178             break;
 179
 180         case AL_DISTORTION_LOWPASS_CUTOFF:
 181             if(!(val >= AL_DISTORTION_MIN_LOWPASS_CUTOFF && val <= AL_DISTORTION_MAX_LOWPASS_CUTOFF))
 182                 SETERR_RETURN(context, AL_INVALID_VALUE,, "Distortion low-pass cutoff out of range");
 183             props->Distortion.LowpassCutoff = val;
 184             break;
 185
 186         case AL_DISTORTION_EQCENTER:
 187             if(!(val >= AL_DISTORTION_MIN_EQCENTER && val <= AL_DISTORTION_MAX_EQCENTER))
 188                 SETERR_RETURN(context, AL_INVALID_VALUE,, "Distortion EQ center out of range");
 189             props->Distortion.EQCenter = val;
 190             break;
 191
 192         case AL_DISTORTION_EQBANDWIDTH:
 193             if(!(val >= AL_DISTORTION_MIN_EQBANDWIDTH && val <= AL_DISTORTION_MAX_EQBANDWIDTH))
 194                 SETERR_RETURN(context, AL_INVALID_VALUE,, "Distortion EQ bandwidth out of range");
 195             props->Distortion.EQBandwidth = val;
 196             break;
 197
 198         default:
 199             context->setError(AL_INVALID_ENUM, "Invalid distortion float property 0x%04x", param);
 200     }
 201 }
 202 void Distortion_setParamfv(EffectProps *props, ALCcontext *context, ALenum param, const ALfloat *vals)
 203 { Distortion_setParamf(props, context, param, vals[0]); }
 204
 205 void Distortion_getParami(const EffectProps*, ALCcontext *context, ALenum param, ALint*)
 206 { context->setError(AL_INVALID_ENUM, "Invalid distortion integer property 0x%04x", param); }
 207 void Distortion_getParamiv(const EffectProps*, ALCcontext *context, ALenum param, ALint*)
 208 { context->setError(AL_INVALID_ENUM, "Invalid distortion integer-vector property 0x%04x", param); }
 209 void Distortion_getParamf(const EffectProps *props, ALCcontext *context, ALenum param, ALfloat *val)
 210 {
 211     switch(param)
 212     {
 213         case AL_DISTORTION_EDGE:
 214             *val = props->Distortion.Edge;
 215             break;
 216
 217         case AL_DISTORTION_GAIN:
 218             *val = props->Distortion.Gain;
 219             break;
 220
 221         case AL_DISTORTION_LOWPASS_CUTOFF:
 222             *val = props->Distortion.LowpassCutoff;
 223             break;
 224
 225         case AL_DISTORTION_EQCENTER:
 226             *val = props->Distortion.EQCenter;
 227             break;
 228
 229         case AL_DISTORTION_EQBANDWIDTH:
 230             *val = props->Distortion.EQBandwidth;
 231             break;
 232
 233         default:
 234             context->setError(AL_INVALID_ENUM, "Invalid distortion float property 0x%04x", param);
 235     }
 236 }
 237 void Distortion_getParamfv(const EffectProps *props, ALCcontext *context, ALenum param, ALfloat *vals)
 238 { Distortion_getParamf(props, context, param, vals); }
 239
 240 DEFINE_ALEFFECT_VTABLE(Distortion);
 241
 242
 243 struct DistortionStateFactory final : public EffectStateFactory {
 244     EffectState *create() override { return new DistortionState{}; }
 245     EffectProps getDefaultProps() const noexcept override;
 246     const EffectVtable *getEffectVtable() const noexcept override { return &Distortion_vtable; }
 247 };
 248
 249 EffectProps DistortionStateFactory::getDefaultProps() const noexcept
 250 {
 251     EffectProps props{};
 252     props.Distortion.Edge = AL_DISTORTION_DEFAULT_EDGE;
 253     props.Distortion.Gain = AL_DISTORTION_DEFAULT_GAIN;
 254     props.Distortion.LowpassCutoff = AL_DISTORTION_DEFAULT_LOWPASS_CUTOFF;
 255     props.Distortion.EQCenter = AL_DISTORTION_DEFAULT_EQCENTER;
 256     props.Distortion.EQBandwidth = AL_DISTORTION_DEFAULT_EQBANDWIDTH;
 257     return props;
 258 }
 259
 260 } // namespace
 261
 262 EffectStateFactory *DistortionStateFactory_getFactory()
 263 {
 264     static DistortionStateFactory DistortionFactory{};
 265     return &DistortionFactory;
 266 }