AuroraOpenALSoft/Alc/alcModulator.c

/**
 * OpenAL cross platform audio library
 * Copyright (C) 2009 by Chris Robinson.
 * 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., 59 Temple Place - Suite 330,
 *  Boston, MA  02111-1307, 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 ALmodulatorState {
    // Must be first in all effects!
    ALeffectState state;

    enum {
        SINUSOID,
        SAWTOOTH,
        SQUARE
    } Waveform;

    ALuint index;
    ALuint step;

    ALfloat Gain[MAXCHANNELS];

    FILTER iirFilter;
    ALfloat history[1];
} ALmodulatorState;

#define WAVEFORM_FRACBITS  16
#define WAVEFORM_FRACMASK  ((1<<WAVEFORM_FRACBITS)-1)

static __inline ALfloat sin_func(ALuint index)
{
    return sin(index / (double)(1<<WAVEFORM_FRACBITS) * M_PI * 2.0f);
}

static __inline ALfloat saw_func(ALuint index)
{
    return index*2.0f/(1<<WAVEFORM_FRACBITS) - 1.0f;
}

static __inline ALfloat square_func(ALuint index)
{
    return ((index>>(WAVEFORM_FRACBITS-1))&1) ? -1.0f : 1.0f;
}


static __inline ALfloat hpFilter1P(FILTER *iir, ALuint offset, ALfloat input)
{
    ALfloat *history = &iir->history[offset];
    ALfloat a = iir->coeff;
    ALfloat output = input;

    output = output + (history[0]-output)*a;
    history[0] = output;

    return input - output;
}


static ALvoid ModulatorDestroy(ALeffectState *effect)
{
    ALmodulatorState *state = (ALmodulatorState*)effect;
    free(state);
}

static ALboolean ModulatorDeviceUpdate(ALeffectState *effect, ALCdevice *Device)
{
    ALmodulatorState *state = (ALmodulatorState*)effect;
    ALuint index;

    for(index = 0;index < MAXCHANNELS;index++)
        state->Gain[index] = 0.0f;
    for(index = 0;index < Device->NumChan;index++)
    {
        Channel chan = Device->Speaker2Chan[index];
        state->Gain[chan] = 1.0f;
    }

    return AL_TRUE;
}

static ALvoid ModulatorUpdate(ALeffectState *effect, ALCcontext *Context, const ALeffect *Effect)
{
    ALmodulatorState *state = (ALmodulatorState*)effect;
    ALfloat cw, a = 0.0f;

    if(Effect->Params.Modulator.Waveform == AL_RING_MODULATOR_SINUSOID)
        state->Waveform = SINUSOID;
    else if(Effect->Params.Modulator.Waveform == AL_RING_MODULATOR_SAWTOOTH)
        state->Waveform = SAWTOOTH;
    else if(Effect->Params.Modulator.Waveform == AL_RING_MODULATOR_SQUARE)
        state->Waveform = SQUARE;

    state->step = Effect->Params.Modulator.Frequency*(1<<WAVEFORM_FRACBITS) /
                  Context->Device->Frequency;
    if(!state->step)
        state->step = 1;

    cw = cos(2.0*M_PI * Effect->Params.Modulator.HighPassCutoff /
                        Context->Device->Frequency);
    a = (2.0f-cw) - aluSqrt(aluPow(2.0f-cw, 2.0f) - 1.0f);
    state->iirFilter.coeff = a;
}

static ALvoid ModulatorProcess(ALeffectState *effect, const ALeffectslot *Slot, ALuint SamplesToDo, const ALfloat *SamplesIn, ALfloat (*SamplesOut)[MAXCHANNELS])
{
    ALmodulatorState *state = (ALmodulatorState*)effect;
    const ALfloat gain = Slot->Gain;
    const ALuint step = state->step;
    ALuint index = state->index;
    ALfloat samp;
    ALuint i;

    switch(state->Waveform)
    {
    case SINUSOID:
        for(i = 0;i < SamplesToDo;i++)
        {
#define FILTER_OUT(func) do {                                                 \
    samp = SamplesIn[i];                                                      \
                                                                              \
    index += step;                                                            \
    index &= WAVEFORM_FRACMASK;                                               \
    samp *= func(index);                                                      \
                                                                              \
    samp = hpFilter1P(&state->iirFilter, 0, samp);                            \
                                                                              \
    /* Apply slot gain */                                                     \
    samp *= gain;                                                             \
                                                                              \
    SamplesOut[i][FRONT_LEFT]   += state->Gain[FRONT_LEFT]   * samp;          \
    SamplesOut[i][FRONT_RIGHT]  += state->Gain[FRONT_RIGHT]  * samp;          \
    SamplesOut[i][FRONT_CENTER] += state->Gain[FRONT_CENTER] * samp;          \
    SamplesOut[i][SIDE_LEFT]    += state->Gain[SIDE_LEFT]    * samp;          \
    SamplesOut[i][SIDE_RIGHT]   += state->Gain[SIDE_RIGHT]   * samp;          \
    SamplesOut[i][BACK_LEFT]    += state->Gain[BACK_LEFT]    * samp;          \
    SamplesOut[i][BACK_RIGHT]   += state->Gain[BACK_RIGHT]   * samp;          \
    SamplesOut[i][BACK_CENTER]  += state->Gain[BACK_CENTER]  * samp;          \
} while(0)
            FILTER_OUT(sin_func);
        }
        break;

    case SAWTOOTH:
        for(i = 0;i < SamplesToDo;i++)
        {
            FILTER_OUT(saw_func);
        }
        break;

    case SQUARE:
        for(i = 0;i < SamplesToDo;i++)
        {
            FILTER_OUT(square_func);
#undef FILTER_OUT
        }
        break;
    }
    state->index = index;
}

ALeffectState *ModulatorCreate(void)
{
    ALmodulatorState *state;

    state = malloc(sizeof(*state));
    if(!state)
        return NULL;

    state->state.Destroy = ModulatorDestroy;
    state->state.DeviceUpdate = ModulatorDeviceUpdate;
    state->state.Update = ModulatorUpdate;
    state->state.Process = ModulatorProcess;

    state->index = 0.0f;
    state->step = 1.0f;

    state->iirFilter.coeff = 0.0f;
    state->iirFilter.history[0] = 0.0f;

    return &state->state;
}