/**
* OpenAL cross platform audio library
* Copyright (C) 2013 by Mike Gorchak
* This library is free software; you can redistribute it and/or
* modify it under the terms of the GNU Library General Public
* License as published by the Free Software Foundation; either
* version 2 of the License, or (at your option) any later version.
*
* This library is distributed in the hope that it will be useful,
* but WITHOUT ANY WARRANTY; without even the implied warranty of
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
* Library General Public License for more details.
*
* You should have received a copy of the GNU Library General Public
* License along with this library; if not, write to the
* Free Software Foundation, Inc.,
* 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA.
* Or go to http://www.gnu.org/copyleft/lgpl.html
*/
#include "config.h"
#include <math.h>
#include <stdlib.h>
#include "alMain.h"
#include "alFilter.h"
#include "alAuxEffectSlot.h"
#include "alError.h"
#include "alu.h"
typedef struct ALdistortionState {
DERIVE_FROM_TYPE(ALeffectState);
/* Effect gains for each channel */
ALfloat Gain[MAX_OUTPUT_CHANNELS];
/* Effect parameters */
ALfilterState lowpass;
ALfilterState bandpass;
ALfloat attenuation;
ALfloat edge_coeff;
} ALdistortionState;
static ALvoid ALdistortionState_Destruct(ALdistortionState *UNUSED(state))
{
}
static ALboolean ALdistortionState_deviceUpdate(ALdistortionState *UNUSED(state), ALCdevice *UNUSED(device))
{
return AL_TRUE;
}
static ALvoid ALdistortionState_update(ALdistortionState *state, ALCdevice *Device, const ALeffectslot *Slot)
{
ALfloat frequency = (ALfloat)Device->Frequency;
ALfloat bandwidth;
ALfloat cutoff;
ALfloat edge;
/* Store distorted signal attenuation settings */
state->attenuation = Slot->EffectProps.Distortion.Gain;
/* Store waveshaper edge settings */
edge = sinf(Slot->EffectProps.Distortion.Edge * (F_PI_2));
edge = minf(edge, 0.99f);
state->edge_coeff = 2.0f * edge / (1.0f-edge);
/* Lowpass filter */
cutoff = Slot->EffectProps.Distortion.LowpassCutoff;
/* Bandwidth value is constant in octaves */
bandwidth = (cutoff / 2.0f) / (cutoff * 0.67f);
ALfilterState_setParams(&state->lowpass, ALfilterType_LowPass, 1.0f,
cutoff / (frequency*4.0f), calc_rcpQ_from_bandwidth(cutoff / (frequency*4.0f), bandwidth)
);
/* Bandpass filter */
cutoff = Slot->EffectProps.Distortion.EQCenter;
/* Convert bandwidth in Hz to octaves */
bandwidth = Slot->EffectProps.Distortion.EQBandwidth / (cutoff * 0.67f);
ALfilterState_setParams(&state->bandpass, ALfilterType_BandPass, 1.0f,
cutoff / (frequency*4.0f), calc_rcpQ_from_bandwidth(cutoff / (frequency*4.0f), bandwidth)
);
ComputeAmbientGains(Device, Slot->Gain, state->Gain);
}
static ALvoid ALdistortionState_process(ALdistortionState *state, ALuint SamplesToDo, const ALfloat *restrict SamplesIn, ALfloat (*restrict SamplesOut)[BUFFERSIZE], ALuint NumChannels)
{
const ALfloat fc = state->edge_coeff;
ALuint base;
ALuint it;
ALuint ot;
ALuint kt;
for(base = 0;base < SamplesToDo;)
{
float oversample_buffer[64][4];
ALuint td = minu(64, SamplesToDo-base);
/* Perform 4x oversampling to avoid aliasing. */
/* Oversampling greatly improves distortion */
/* quality and allows to implement lowpass and */
/* bandpass filters using high frequencies, at */
/* which classic IIR filters became unstable. */
/* Fill oversample buffer using zero stuffing */
for(it = 0;it < td;it++)
{
oversample_buffer[it][0] = SamplesIn[it+base];
oversample_buffer[it][1] = 0.0f;
oversample_buffer[it][2] = 0.0f;
oversample_buffer[it][3] = 0.0f;
}
/* First step, do lowpass filtering of original signal, */
/* additionally perform buffer interpolation and lowpass */
/* cutoff for oversampling (which is fortunately first */
/* step of distortion). So combine three operations into */
/* the one. */
for(it = 0;it < td;it++)
{
for(ot = 0;ot < 4;ot++)
{
ALfloat smp;
smp = ALfilterState_processSingle(&state->lowpass, oversample_buffer[it][ot]);
/* Restore signal power by multiplying sample by amount of oversampling */
oversample_buffer[it][ot] = smp * 4.0f;
}
}
for(it = 0;it < td;it++)
{
/* Second step, do distortion using waveshaper function */
/* to emulate signal processing during tube overdriving. */
/* Three steps of waveshaping are intended to modify */
/* waveform without boost/clipping/attenuation process. */
for(ot = 0;ot < 4;ot++)
{
ALfloat smp = oversample_buffer[it][ot];
smp = (1.0f + fc) * smp/(1.0f + fc*fabsf(smp));
smp = (1.0f + fc) * smp/(1.0f + fc*fabsf(smp)) * -1.0f;
smp = (1.0f + fc) * smp/(1.0f + fc*fabsf(smp));
/* Third step, do bandpass filtering of distorted signal */
smp = ALfilterState_processSingle(&state->bandpass, smp);
oversample_buffer[it][ot] = smp;
}
}
for(kt = 0;kt < NumChannels;kt++)
{
/* Fourth step, final, do attenuation and perform decimation,
* store only one sample out of 4.
*/
ALfloat gain = state->Gain[kt] * state->attenuation;
if(!(fabsf(gain) > GAIN_SILENCE_THRESHOLD))
continue;
for(it = 0;it < td;it++)
SamplesOut[kt][base+it] += gain * oversample_buffer[it][0];
}
base += td;
}
}
DECLARE_DEFAULT_ALLOCATORS(ALdistortionState)
DEFINE_ALEFFECTSTATE_VTABLE(ALdistortionState);
typedef struct ALdistortionStateFactory {
DERIVE_FROM_TYPE(ALeffectStateFactory);
} ALdistortionStateFactory;
static ALeffectState *ALdistortionStateFactory_create(ALdistortionStateFactory *UNUSED(factory))
{
ALdistortionState *state;
state = ALdistortionState_New(sizeof(*state));
if(!state) return NULL;
SET_VTABLE2(ALdistortionState, ALeffectState, state);
ALfilterState_clear(&state->lowpass);
ALfilterState_clear(&state->bandpass);
return STATIC_CAST(ALeffectState, state);
}
DEFINE_ALEFFECTSTATEFACTORY_VTABLE(ALdistortionStateFactory);
ALeffectStateFactory *ALdistortionStateFactory_getFactory(void)
{
static ALdistortionStateFactory DistortionFactory = { { GET_VTABLE2(ALdistortionStateFactory, ALeffectStateFactory) } };
return STATIC_CAST(ALeffectStateFactory, &DistortionFactory);
}
void ALdistortion_setParami(ALeffect *UNUSED(effect), ALCcontext *context, ALenum UNUSED(param), ALint UNUSED(val))
{ SET_ERROR_AND_RETURN(context, AL_INVALID_ENUM); }
void ALdistortion_setParamiv(ALeffect *effect, ALCcontext *context, ALenum param, const ALint *vals)
{
ALdistortion_setParami(effect, context, param, vals[0]);
}
void ALdistortion_setParamf(ALeffect *effect, ALCcontext *context, ALenum param, ALfloat val)
{
ALeffectProps *props = &effect->Props;
switch(param)
{
case AL_DISTORTION_EDGE:
if(!(val >= AL_DISTORTION_MIN_EDGE && val <= AL_DISTORTION_MAX_EDGE))
SET_ERROR_AND_RETURN(context, AL_INVALID_VALUE);
props->Distortion.Edge = val;
break;
case AL_DISTORTION_GAIN:
if(!(val >= AL_DISTORTION_MIN_GAIN && val <= AL_DISTORTION_MAX_GAIN))
SET_ERROR_AND_RETURN(context, AL_INVALID_VALUE);
props->Distortion.Gain = val;
break;
case AL_DISTORTION_LOWPASS_CUTOFF:
if(!(val >= AL_DISTORTION_MIN_LOWPASS_CUTOFF && val <= AL_DISTORTION_MAX_LOWPASS_CUTOFF))
SET_ERROR_AND_RETURN(context, AL_INVALID_VALUE);
props->Distortion.LowpassCutoff = val;
break;
case AL_DISTORTION_EQCENTER:
if(!(val >= AL_DISTORTION_MIN_EQCENTER && val <= AL_DISTORTION_MAX_EQCENTER))
SET_ERROR_AND_RETURN(context, AL_INVALID_VALUE);
props->Distortion.EQCenter = val;
break;
case AL_DISTORTION_EQBANDWIDTH:
if(!(val >= AL_DISTORTION_MIN_EQBANDWIDTH && val <= AL_DISTORTION_MAX_EQBANDWIDTH))
SET_ERROR_AND_RETURN(context, AL_INVALID_VALUE);
props->Distortion.EQBandwidth = val;
break;
default:
SET_ERROR_AND_RETURN(context, AL_INVALID_ENUM);
}
}
void ALdistortion_setParamfv(ALeffect *effect, ALCcontext *context, ALenum param, const ALfloat *vals)
{
ALdistortion_setParamf(effect, context, param, vals[0]);
}
void ALdistortion_getParami(const ALeffect *UNUSED(effect), ALCcontext *context, ALenum UNUSED(param), ALint *UNUSED(val))
{ SET_ERROR_AND_RETURN(context, AL_INVALID_ENUM); }
void ALdistortion_getParamiv(const ALeffect *effect, ALCcontext *context, ALenum param, ALint *vals)
{
ALdistortion_getParami(effect, context, param, vals);
}
void ALdistortion_getParamf(const ALeffect *effect, ALCcontext *context, ALenum param, ALfloat *val)
{
const ALeffectProps *props = &effect->Props;
switch(param)
{
case AL_DISTORTION_EDGE:
*val = props->Distortion.Edge;
break;
case AL_DISTORTION_GAIN:
*val = props->Distortion.Gain;
break;
case AL_DISTORTION_LOWPASS_CUTOFF:
*val = props->Distortion.LowpassCutoff;
break;
case AL_DISTORTION_EQCENTER:
*val = props->Distortion.EQCenter;
break;
case AL_DISTORTION_EQBANDWIDTH:
*val = props->Distortion.EQBandwidth;
break;
default:
SET_ERROR_AND_RETURN(context, AL_INVALID_ENUM);
}
}
void ALdistortion_getParamfv(const ALeffect *effect, ALCcontext *context, ALenum param, ALfloat *vals)
{
ALdistortion_getParamf(effect, context, param, vals);
}
DEFINE_ALEFFECT_VTABLE(ALdistortion);