Alc/effects/distortion.c

   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 <math.h>
  24 #include <stdlib.h>
  25
  26 #include "alMain.h"
  27 #include "alFilter.h"
  28 #include "alAuxEffectSlot.h"
  29 #include "alError.h"
  30 #include "alu.h"
  31
  32
  33 typedef struct ALdistortionState {
  34     DERIVE_FROM_TYPE(ALeffectState);
  35
  36     /* Effect gains for each channel */
  37     ALfloat Gain[MAX_OUTPUT_CHANNELS];
  38
  39     /* Effect parameters */
  40     ALfilterState lowpass;
  41     ALfilterState bandpass;
  42     ALfloat attenuation;
  43     ALfloat edge_coeff;
  44 } ALdistortionState;
  45
  46 static ALvoid ALdistortionState_Destruct(ALdistortionState *state)
  47 {
  48     ALeffectState_Destruct(STATIC_CAST(ALeffectState,state));
  49 }
  50
  51 static ALboolean ALdistortionState_deviceUpdate(ALdistortionState *UNUSED(state), ALCdevice *UNUSED(device))
  52 {
  53     return AL_TRUE;
  54 }
  55
  56 static ALvoid ALdistortionState_update(ALdistortionState *state, const ALCdevice *Device, const ALeffectslot *Slot, const ALeffectProps *props)
  57 {
  58     ALfloat frequency = (ALfloat)Device->Frequency;
  59     ALfloat bandwidth;
  60     ALfloat cutoff;
  61     ALfloat edge;
  62
  63     /* Store distorted signal attenuation settings */
  64     state->attenuation = props->Distortion.Gain;
  65
  66     /* Store waveshaper edge settings */
  67     edge = sinf(props->Distortion.Edge * (F_PI_2));
  68     edge = minf(edge, 0.99f);
  69     state->edge_coeff = 2.0f * edge / (1.0f-edge);
  70
  71     /* Lowpass filter */
  72     cutoff = props->Distortion.LowpassCutoff;
  73     /* Bandwidth value is constant in octaves */
  74     bandwidth = (cutoff / 2.0f) / (cutoff * 0.67f);
  75     ALfilterState_setParams(&state->lowpass, ALfilterType_LowPass, 1.0f,
  76         cutoff / (frequency*4.0f), calc_rcpQ_from_bandwidth(cutoff / (frequency*4.0f), bandwidth)
  77     );
  78
  79     /* Bandpass filter */
  80     cutoff = props->Distortion.EQCenter;
  81     /* Convert bandwidth in Hz to octaves */
  82     bandwidth = props->Distortion.EQBandwidth / (cutoff * 0.67f);
  83     ALfilterState_setParams(&state->bandpass, ALfilterType_BandPass, 1.0f,
  84         cutoff / (frequency*4.0f), calc_rcpQ_from_bandwidth(cutoff / (frequency*4.0f), bandwidth)
  85     );
  86
  87     ComputeAmbientGains(Device->Dry, Slot->Params.Gain, state->Gain);
  88 }
  89
  90 static ALvoid ALdistortionState_process(ALdistortionState *state, ALuint SamplesToDo, const ALfloat (*restrict SamplesIn)[BUFFERSIZE], ALfloat (*restrict SamplesOut)[BUFFERSIZE], ALuint NumChannels)
  91 {
  92     const ALfloat fc = state->edge_coeff;
  93     ALuint base;
  94     ALuint it;
  95     ALuint ot;
  96     ALuint kt;
  97
  98     for(base = 0;base < SamplesToDo;)
  99     {
 100         float buffer[2][64 * 4];
 101         ALuint td = minu(64, SamplesToDo-base);
 102
 103         /* Perform 4x oversampling to avoid aliasing.   */
 104         /* Oversampling greatly improves distortion     */
 105         /* quality and allows to implement lowpass and  */
 106         /* bandpass filters using high frequencies, at  */
 107         /* which classic IIR filters became unstable.   */
 108
 109         /* Fill oversample buffer using zero stuffing */
 110         for(it = 0;it < td;it++)
 111         {
 112             buffer[0][it*4 + 0] = SamplesIn[0][it+base];
 113             buffer[0][it*4 + 1] = 0.0f;
 114             buffer[0][it*4 + 2] = 0.0f;
 115             buffer[0][it*4 + 3] = 0.0f;
 116         }
 117
 118         /* First step, do lowpass filtering of original signal,  */
 119         /* additionally perform buffer interpolation and lowpass */
 120         /* cutoff for oversampling (which is fortunately first   */
 121         /* step of distortion). So combine three operations into */
 122         /* the one.                                              */
 123         ALfilterState_process(&state->lowpass, buffer[1], buffer[0], td*4);
 124
 125         /* Second step, do distortion using waveshaper function  */
 126         /* to emulate signal processing during tube overdriving. */
 127         /* Three steps of waveshaping are intended to modify     */
 128         /* waveform without boost/clipping/attenuation process.  */
 129         for(it = 0;it < td;it++)
 130         {
 131             for(ot = 0;ot < 4;ot++)
 132             {
 133                 /* Restore signal power by multiplying sample by amount of oversampling */
 134                 ALfloat smp = buffer[1][it*4 + ot] * 4.0f;
 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[1][it*4 + ot] = smp;
 141             }
 142         }
 143
 144         /* Third step, do bandpass filtering of distorted signal */
 145         ALfilterState_process(&state->bandpass, buffer[0], buffer[1], td*4);
 146
 147         for(kt = 0;kt < NumChannels;kt++)
 148         {
 149             /* Fourth step, final, do attenuation and perform decimation,
 150              * store only one sample out of 4.
 151              */
 152             ALfloat gain = state->Gain[kt] * state->attenuation;
 153             if(!(fabsf(gain) > GAIN_SILENCE_THRESHOLD))
 154                 continue;
 155
 156             for(it = 0;it < td;it++)
 157                 SamplesOut[kt][base+it] += gain * buffer[0][it*4];
 158         }
 159
 160         base += td;
 161     }
 162 }
 163
 164 DECLARE_DEFAULT_ALLOCATORS(ALdistortionState)
 165
 166 DEFINE_ALEFFECTSTATE_VTABLE(ALdistortionState);
 167
 168
 169 typedef struct ALdistortionStateFactory {
 170     DERIVE_FROM_TYPE(ALeffectStateFactory);
 171 } ALdistortionStateFactory;
 172
 173 static ALeffectState *ALdistortionStateFactory_create(ALdistortionStateFactory *UNUSED(factory))
 174 {
 175     ALdistortionState *state;
 176
 177     state = ALdistortionState_New(sizeof(*state));
 178     if(!state) return NULL;
 179     SET_VTABLE2(ALdistortionState, ALeffectState, state);
 180
 181     ALfilterState_clear(&state->lowpass);
 182     ALfilterState_clear(&state->bandpass);
 183
 184     return STATIC_CAST(ALeffectState, state);
 185 }
 186
 187 DEFINE_ALEFFECTSTATEFACTORY_VTABLE(ALdistortionStateFactory);
 188
 189
 190 ALeffectStateFactory *ALdistortionStateFactory_getFactory(void)
 191 {
 192     static ALdistortionStateFactory DistortionFactory = { { GET_VTABLE2(ALdistortionStateFactory, ALeffectStateFactory) } };
 193
 194     return STATIC_CAST(ALeffectStateFactory, &DistortionFactory);
 195 }
 196
 197
 198 void ALdistortion_setParami(ALeffect *UNUSED(effect), ALCcontext *context, ALenum UNUSED(param), ALint UNUSED(val))
 199 { SET_ERROR_AND_RETURN(context, AL_INVALID_ENUM); }
 200 void ALdistortion_setParamiv(ALeffect *effect, ALCcontext *context, ALenum param, const ALint *vals)
 201 {
 202     ALdistortion_setParami(effect, context, param, vals[0]);
 203 }
 204 void ALdistortion_setParamf(ALeffect *effect, ALCcontext *context, ALenum param, ALfloat val)
 205 {
 206     ALeffectProps *props = &effect->Props;
 207     switch(param)
 208     {
 209         case AL_DISTORTION_EDGE:
 210             if(!(val >= AL_DISTORTION_MIN_EDGE && val <= AL_DISTORTION_MAX_EDGE))
 211                 SET_ERROR_AND_RETURN(context, AL_INVALID_VALUE);
 212             props->Distortion.Edge = val;
 213             break;
 214
 215         case AL_DISTORTION_GAIN:
 216             if(!(val >= AL_DISTORTION_MIN_GAIN && val <= AL_DISTORTION_MAX_GAIN))
 217                 SET_ERROR_AND_RETURN(context, AL_INVALID_VALUE);
 218             props->Distortion.Gain = val;
 219             break;
 220
 221         case AL_DISTORTION_LOWPASS_CUTOFF:
 222             if(!(val >= AL_DISTORTION_MIN_LOWPASS_CUTOFF && val <= AL_DISTORTION_MAX_LOWPASS_CUTOFF))
 223                 SET_ERROR_AND_RETURN(context, AL_INVALID_VALUE);
 224             props->Distortion.LowpassCutoff = val;
 225             break;
 226
 227         case AL_DISTORTION_EQCENTER:
 228             if(!(val >= AL_DISTORTION_MIN_EQCENTER && val <= AL_DISTORTION_MAX_EQCENTER))
 229                 SET_ERROR_AND_RETURN(context, AL_INVALID_VALUE);
 230             props->Distortion.EQCenter = val;
 231             break;
 232
 233         case AL_DISTORTION_EQBANDWIDTH:
 234             if(!(val >= AL_DISTORTION_MIN_EQBANDWIDTH && val <= AL_DISTORTION_MAX_EQBANDWIDTH))
 235                 SET_ERROR_AND_RETURN(context, AL_INVALID_VALUE);
 236             props->Distortion.EQBandwidth = val;
 237             break;
 238
 239         default:
 240             SET_ERROR_AND_RETURN(context, AL_INVALID_ENUM);
 241     }
 242 }
 243 void ALdistortion_setParamfv(ALeffect *effect, ALCcontext *context, ALenum param, const ALfloat *vals)
 244 {
 245     ALdistortion_setParamf(effect, context, param, vals[0]);
 246 }
 247
 248 void ALdistortion_getParami(const ALeffect *UNUSED(effect), ALCcontext *context, ALenum UNUSED(param), ALint *UNUSED(val))
 249 { SET_ERROR_AND_RETURN(context, AL_INVALID_ENUM); }
 250 void ALdistortion_getParamiv(const ALeffect *effect, ALCcontext *context, ALenum param, ALint *vals)
 251 {
 252     ALdistortion_getParami(effect, context, param, vals);
 253 }
 254 void ALdistortion_getParamf(const ALeffect *effect, ALCcontext *context, ALenum param, ALfloat *val)
 255 {
 256     const ALeffectProps *props = &effect->Props;
 257     switch(param)
 258     {
 259         case AL_DISTORTION_EDGE:
 260             *val = props->Distortion.Edge;
 261             break;
 262
 263         case AL_DISTORTION_GAIN:
 264             *val = props->Distortion.Gain;
 265             break;
 266
 267         case AL_DISTORTION_LOWPASS_CUTOFF:
 268             *val = props->Distortion.LowpassCutoff;
 269             break;
 270
 271         case AL_DISTORTION_EQCENTER:
 272             *val = props->Distortion.EQCenter;
 273             break;
 274
 275         case AL_DISTORTION_EQBANDWIDTH:
 276             *val = props->Distortion.EQBandwidth;
 277             break;
 278
 279         default:
 280             SET_ERROR_AND_RETURN(context, AL_INVALID_ENUM);
 281     }
 282 }
 283 void ALdistortion_getParamfv(const ALeffect *effect, ALCcontext *context, ALenum param, ALfloat *vals)
 284 {
 285     ALdistortion_getParamf(effect, context, param, vals);
 286 }
 287
 288 DEFINE_ALEFFECT_VTABLE(ALdistortion);