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