alcModulator.c

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#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_FRACONE   (1<<WAVEFORM_FRACBITS)
#define WAVEFORM_FRACMASK  (WAVEFORM_FRACONE-1)

static __inline ALfloat Sin(ALuint index)
{
    return sinf(index * (F_PI*2.0f / WAVEFORM_FRACONE));
}

static __inline ALfloat Saw(ALuint index)
{
    return index*(2.0f/WAVEFORM_FRACONE) - 1.0f;
}

static __inline ALfloat Square(ALuint index)
{
    return ((index>>(WAVEFORM_FRACBITS-1))&1)*2.0f - 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;
}


#define DECL_TEMPLATE(func)                                                   \
static void Process##func(ALmodulatorState *state, ALuint SamplesToDo,        \
  const ALfloat *RESTRICT SamplesIn,                                          \
  ALfloat (*RESTRICT SamplesOut)[BUFFERSIZE])                                 \
{                                                                             \
    const ALuint step = state->step;                                          \
    ALuint index = state->index;                                              \
    ALfloat samp;                                                             \
    ALuint i, k;                                                              \
                                                                              \
    for(i = 0;i < SamplesToDo;i++)                                            \
    {                                                                         \
        samp = SamplesIn[i];                                                  \
                                                                              \
        index += step;                                                        \
        index &= WAVEFORM_FRACMASK;                                           \
        samp *= func(index);                                                  \
                                                                              \
        samp = hpFilter1P(&state->iirFilter, 0, samp);                        \
                                                                              \
        for(k = 0;k < MaxChannels;k++)                                        \
            SamplesOut[k][i] += state->Gain[k] * samp;                        \
    }                                                                         \
    state->index = index;                                                     \
}

DECL_TEMPLATE(Sin)
DECL_TEMPLATE(Saw)
DECL_TEMPLATE(Square)

#undef DECL_TEMPLATE


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

static ALboolean ModulatorDeviceUpdate(ALeffectState *effect, ALCdevice *Device)
{
    return AL_TRUE;
    (void)effect;
    (void)Device;
}

static ALvoid ModulatorUpdate(ALeffectState *effect, ALCdevice *Device, const ALeffectslot *Slot)
{
    ALmodulatorState *state = (ALmodulatorState*)effect;
    ALfloat gain, cw, a = 0.0f;
    ALuint index;

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

    state->step = fastf2u(Slot->effect.Modulator.Frequency*WAVEFORM_FRACONE /
                          Device->Frequency);
    if(state->step == 0) state->step = 1;

    cw = cosf(F_PI*2.0f * Slot->effect.Modulator.HighPassCutoff /
                          Device->Frequency);
    a = (2.0f-cw) - sqrtf(powf(2.0f-cw, 2.0f) - 1.0f);
    state->iirFilter.coeff = a;

    gain = sqrtf(1.0f/Device->NumChan);
    gain *= Slot->Gain;
    for(index = 0;index < MaxChannels;index++)
        state->Gain[index] = 0.0f;
    for(index = 0;index < Device->NumChan;index++)
    {
        enum Channel chan = Device->Speaker2Chan[index];
        state->Gain[chan] = gain;
    }
}

static ALvoid ModulatorProcess(ALeffectState *effect, ALuint SamplesToDo, const ALfloat *RESTRICT SamplesIn, ALfloat (*RESTRICT SamplesOut)[BUFFERSIZE])
{
    ALmodulatorState *state = (ALmodulatorState*)effect;

    switch(state->Waveform)
    {
        case SINUSOID:
            ProcessSin(state, SamplesToDo, SamplesIn, SamplesOut);
            break;

        case SAWTOOTH:
            ProcessSaw(state, SamplesToDo, SamplesIn, SamplesOut);
            break;

        case SQUARE:
            ProcessSquare(state, SamplesToDo, SamplesIn, SamplesOut);
            break;
    }
}

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;
    state->step = 1;

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

    return &state->state;
}