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#ifndef _AL_FILTER_H_
#define _AL_FILTER_H_
#include "AL/al.h"
#include "alu.h"
#ifdef __cplusplus
extern "C" {
#endif
typedef struct {
ALfloat coeff;
#ifndef _MSC_VER
ALfloat history[0];
#else
ALfloat history[1];
#endif
} FILTER;
static __inline ALfloat lpFilter4P(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;
output = output + (history[1]-output)*a;
history[1] = output;
output = output + (history[2]-output)*a;
history[2] = output;
output = output + (history[3]-output)*a;
history[3] = output;
return output;
}
static __inline ALfloat lpFilter2P(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;
output = output + (history[1]-output)*a;
history[1] = output;
return output;
}
#define AL_FILTER_TYPE 0x8001
#define AL_FILTER_NULL 0x0000
#define AL_FILTER_LOWPASS 0x0001
#define AL_FILTER_HIGHPASS 0x0002
#define AL_FILTER_BANDPASS 0x0003
#define AL_LOWPASS_GAIN 0x0001
#define AL_LOWPASS_GAINHF 0x0002
typedef struct ALfilter
{
// Filter type (AL_FILTER_NULL, ...)
ALenum type;
ALfloat Gain;
ALfloat GainHF;
// Index to itself
ALuint filter;
struct ALfilter *next;
} ALfilter;
ALvoid AL_APIENTRY alGenFilters(ALsizei n, ALuint *filters);
ALvoid AL_APIENTRY alDeleteFilters(ALsizei n, ALuint *filters);
ALboolean AL_APIENTRY alIsFilter(ALuint filter);
ALvoid AL_APIENTRY alFilteri(ALuint filter, ALenum param, ALint iValue);
ALvoid AL_APIENTRY alFilteriv(ALuint filter, ALenum param, ALint *piValues);
ALvoid AL_APIENTRY alFilterf(ALuint filter, ALenum param, ALfloat flValue);
ALvoid AL_APIENTRY alFilterfv(ALuint filter, ALenum param, ALfloat *pflValues);
ALvoid AL_APIENTRY alGetFilteri(ALuint filter, ALenum param, ALint *piValue);
ALvoid AL_APIENTRY alGetFilteriv(ALuint filter, ALenum param, ALint *piValues);
ALvoid AL_APIENTRY alGetFilterf(ALuint filter, ALenum param, ALfloat *pflValue);
ALvoid AL_APIENTRY alGetFilterfv(ALuint filter, ALenum param, ALfloat *pflValues);
ALvoid ReleaseALFilters(ALCdevice *device);
#ifdef __cplusplus
}
#endif
#endif
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