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 static ALboolean ALdistortionState_deviceUpdate(ALdistortionState *state, ALCdevice *device);
  48 static ALvoid ALdistortionState_update(ALdistortionState *state, const ALCdevice *Device, const ALeffectslot *Slot, const ALeffectProps *props);
  49 static ALvoid ALdistortionState_process(ALdistortionState *state, ALsizei SamplesToDo, const ALfloat (*restrict SamplesIn)[BUFFERSIZE], ALfloat (*restrict SamplesOut)[BUFFERSIZE], ALsizei NumChannels);
  50 DECLARE_DEFAULT_ALLOCATORS(ALdistortionState)
  51
  52 DEFINE_ALEFFECTSTATE_VTABLE(ALdistortionState);
  53
  54
  55 static void ALdistortionState_Construct(ALdistortionState *state)
  56 {
  57     ALeffectState_Construct(STATIC_CAST(ALeffectState, state));
  58     SET_VTABLE2(ALdistortionState, ALeffectState, state);
  59
  60     ALfilterState_clear(&state->lowpass);
  61     ALfilterState_clear(&state->bandpass);
  62 }
  63
  64 static ALvoid ALdistortionState_Destruct(ALdistortionState *state)
  65 {
  66     ALeffectState_Destruct(STATIC_CAST(ALeffectState,state));
  67 }
  68
  69 static ALboolean ALdistortionState_deviceUpdate(ALdistortionState *UNUSED(state), ALCdevice *UNUSED(device))
  70 {
  71     return AL_TRUE;
  72 }
  73
  74 static ALvoid ALdistortionState_update(ALdistortionState *state, const ALCdevice *Device, const ALeffectslot *Slot, const ALeffectProps *props)
  75 {
  76     ALfloat frequency = (ALfloat)Device->Frequency;
  77     ALfloat bandwidth;
  78     ALfloat cutoff;
  79     ALfloat edge;
  80
  81     /* Store distorted signal attenuation settings. */
  82     state->attenuation = props->Distortion.Gain;
  83
  84     /* Store waveshaper edge settings. */
  85     edge = sinf(props->Distortion.Edge * (F_PI_2));
  86     edge = minf(edge, 0.99f);
  87     state->edge_coeff = 2.0f * edge / (1.0f-edge);
  88
  89     cutoff = props->Distortion.LowpassCutoff;
  90     /* Bandwidth value is constant in octaves. */
  91     bandwidth = (cutoff / 2.0f) / (cutoff * 0.67f);
  92     /* Multiply sampling frequency by the amount of oversampling done during
  93      * processing.
  94      */
  95     ALfilterState_setParams(&state->lowpass, ALfilterType_LowPass, 1.0f,
  96         cutoff / (frequency*4.0f), calc_rcpQ_from_bandwidth(cutoff / (frequency*4.0f), bandwidth)
  97     );
  98
  99     cutoff = props->Distortion.EQCenter;
 100     /* Convert bandwidth in Hz to octaves. */
 101     bandwidth = props->Distortion.EQBandwidth / (cutoff * 0.67f);
 102     ALfilterState_setParams(&state->bandpass, ALfilterType_BandPass, 1.0f,
 103         cutoff / (frequency*4.0f), calc_rcpQ_from_bandwidth(cutoff / (frequency*4.0f), bandwidth)
 104     );
 105
 106     ComputeAmbientGains(Device->Dry, Slot->Params.Gain, state->Gain);
 107 }
 108
 109 static ALvoid ALdistortionState_process(ALdistortionState *state, ALsizei SamplesToDo, const ALfloat (*restrict SamplesIn)[BUFFERSIZE], ALfloat (*restrict SamplesOut)[BUFFERSIZE], ALsizei NumChannels)
 110 {
 111     const ALfloat fc = state->edge_coeff;
 112     ALsizei it, kt;
 113     ALsizei base;
 114
 115     for(base = 0;base < SamplesToDo;)
 116     {
 117         float buffer[2][64 * 4];
 118         ALsizei td = mini(64, SamplesToDo-base);
 119
 120         /* Perform 4x oversampling to avoid aliasing. Oversampling greatly
 121          * improves distortion quality and allows to implement lowpass and
 122          * bandpass filters using high frequencies, at which classic IIR
 123          * filters became unstable.
 124          */
 125
 126         /* Fill oversample buffer using zero stuffing. */
 127         for(it = 0;it < td;it++)
 128         {
 129             /* Multiply the sample by the amount of oversampling to maintain
 130              * the signal's power.
 131              */
 132             buffer[0][it*4 + 0] = SamplesIn[0][it+base] * 4.0f;
 133             buffer[0][it*4 + 1] = 0.0f;
 134             buffer[0][it*4 + 2] = 0.0f;
 135             buffer[0][it*4 + 3] = 0.0f;
 136         }
 137
 138         /* First step, do lowpass filtering of original signal. Additionally
 139          * perform buffer interpolation and lowpass cutoff for oversampling
 140          * (which is fortunately first step of distortion). So combine three
 141          * operations into the one.
 142          */
 143         ALfilterState_process(&state->lowpass, buffer[1], buffer[0], td*4);
 144
 145         /* Second step, do distortion using waveshaper function to emulate
 146          * signal processing during tube overdriving. Three steps of
 147          * waveshaping are intended to modify waveform without boost/clipping/
 148          * attenuation process.
 149          */
 150         for(it = 0;it < td*4;it++)
 151         {
 152             ALfloat smp = buffer[1][it];
 153
 154             smp = (1.0f + fc) * smp/(1.0f + fc*fabsf(smp));
 155             smp = (1.0f + fc) * smp/(1.0f + fc*fabsf(smp)) * -1.0f;
 156             smp = (1.0f + fc) * smp/(1.0f + fc*fabsf(smp));
 157
 158             buffer[0][it] = smp;
 159         }
 160
 161         /* Third step, do bandpass filtering of distorted signal. */
 162         ALfilterState_process(&state->bandpass, buffer[1], buffer[0], td*4);
 163
 164         for(kt = 0;kt < NumChannels;kt++)
 165         {
 166             /* Fourth step, final, do attenuation and perform decimation,
 167              * store only one sample out of 4.
 168              */
 169             ALfloat gain = state->Gain[kt] * state->attenuation;
 170             if(!(fabsf(gain) > GAIN_SILENCE_THRESHOLD))
 171                 continue;
 172
 173             for(it = 0;it < td;it++)
 174                 SamplesOut[kt][base+it] += gain * buffer[1][it*4];
 175         }
 176
 177         base += td;
 178     }
 179 }
 180
 181
 182 typedef struct ALdistortionStateFactory {
 183     DERIVE_FROM_TYPE(ALeffectStateFactory);
 184 } ALdistortionStateFactory;
 185
 186 static ALeffectState *ALdistortionStateFactory_create(ALdistortionStateFactory *UNUSED(factory))
 187 {
 188     ALdistortionState *state;
 189
 190     NEW_OBJ0(state, ALdistortionState)();
 191     if(!state) return NULL;
 192
 193     return STATIC_CAST(ALeffectState, state);
 194 }
 195
 196 DEFINE_ALEFFECTSTATEFACTORY_VTABLE(ALdistortionStateFactory);
 197
 198
 199 ALeffectStateFactory *ALdistortionStateFactory_getFactory(void)
 200 {
 201     static ALdistortionStateFactory DistortionFactory = { { GET_VTABLE2(ALdistortionStateFactory, ALeffectStateFactory) } };
 202
 203     return STATIC_CAST(ALeffectStateFactory, &DistortionFactory);
 204 }
 205
 206
 207 void ALdistortion_setParami(ALeffect *UNUSED(effect), ALCcontext *context, ALenum UNUSED(param), ALint UNUSED(val))
 208 { SET_ERROR_AND_RETURN(context, AL_INVALID_ENUM); }
 209 void ALdistortion_setParamiv(ALeffect *effect, ALCcontext *context, ALenum param, const ALint *vals)
 210 {
 211     ALdistortion_setParami(effect, context, param, vals[0]);
 212 }
 213 void ALdistortion_setParamf(ALeffect *effect, ALCcontext *context, ALenum param, ALfloat val)
 214 {
 215     ALeffectProps *props = &effect->Props;
 216     switch(param)
 217     {
 218         case AL_DISTORTION_EDGE:
 219             if(!(val >= AL_DISTORTION_MIN_EDGE && val <= AL_DISTORTION_MAX_EDGE))
 220                 SET_ERROR_AND_RETURN(context, AL_INVALID_VALUE);
 221             props->Distortion.Edge = val;
 222             break;
 223
 224         case AL_DISTORTION_GAIN:
 225             if(!(val >= AL_DISTORTION_MIN_GAIN && val <= AL_DISTORTION_MAX_GAIN))
 226                 SET_ERROR_AND_RETURN(context, AL_INVALID_VALUE);
 227             props->Distortion.Gain = val;
 228             break;
 229
 230         case AL_DISTORTION_LOWPASS_CUTOFF:
 231             if(!(val >= AL_DISTORTION_MIN_LOWPASS_CUTOFF && val <= AL_DISTORTION_MAX_LOWPASS_CUTOFF))
 232                 SET_ERROR_AND_RETURN(context, AL_INVALID_VALUE);
 233             props->Distortion.LowpassCutoff = val;
 234             break;
 235
 236         case AL_DISTORTION_EQCENTER:
 237             if(!(val >= AL_DISTORTION_MIN_EQCENTER && val <= AL_DISTORTION_MAX_EQCENTER))
 238                 SET_ERROR_AND_RETURN(context, AL_INVALID_VALUE);
 239             props->Distortion.EQCenter = val;
 240             break;
 241
 242         case AL_DISTORTION_EQBANDWIDTH:
 243             if(!(val >= AL_DISTORTION_MIN_EQBANDWIDTH && val <= AL_DISTORTION_MAX_EQBANDWIDTH))
 244                 SET_ERROR_AND_RETURN(context, AL_INVALID_VALUE);
 245             props->Distortion.EQBandwidth = val;
 246             break;
 247
 248         default:
 249             SET_ERROR_AND_RETURN(context, AL_INVALID_ENUM);
 250     }
 251 }
 252 void ALdistortion_setParamfv(ALeffect *effect, ALCcontext *context, ALenum param, const ALfloat *vals)
 253 {
 254     ALdistortion_setParamf(effect, context, param, vals[0]);
 255 }
 256
 257 void ALdistortion_getParami(const ALeffect *UNUSED(effect), ALCcontext *context, ALenum UNUSED(param), ALint *UNUSED(val))
 258 { SET_ERROR_AND_RETURN(context, AL_INVALID_ENUM); }
 259 void ALdistortion_getParamiv(const ALeffect *effect, ALCcontext *context, ALenum param, ALint *vals)
 260 {
 261     ALdistortion_getParami(effect, context, param, vals);
 262 }
 263 void ALdistortion_getParamf(const ALeffect *effect, ALCcontext *context, ALenum param, ALfloat *val)
 264 {
 265     const ALeffectProps *props = &effect->Props;
 266     switch(param)
 267     {
 268         case AL_DISTORTION_EDGE:
 269             *val = props->Distortion.Edge;
 270             break;
 271
 272         case AL_DISTORTION_GAIN:
 273             *val = props->Distortion.Gain;
 274             break;
 275
 276         case AL_DISTORTION_LOWPASS_CUTOFF:
 277             *val = props->Distortion.LowpassCutoff;
 278             break;
 279
 280         case AL_DISTORTION_EQCENTER:
 281             *val = props->Distortion.EQCenter;
 282             break;
 283
 284         case AL_DISTORTION_EQBANDWIDTH:
 285             *val = props->Distortion.EQBandwidth;
 286             break;
 287
 288         default:
 289             SET_ERROR_AND_RETURN(context, AL_INVALID_ENUM);
 290     }
 291 }
 292 void ALdistortion_getParamfv(const ALeffect *effect, ALCcontext *context, ALenum param, ALfloat *vals)
 293 {
 294     ALdistortion_getParamf(effect, context, param, vals);
 295 }
 296
 297 DEFINE_ALEFFECT_VTABLE(ALdistortion);