117 lines
3.0 KiB
C
117 lines
3.0 KiB
C
#ifndef _AL_FILTER_H_
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#define _AL_FILTER_H_
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#include "AL/al.h"
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#include "alu.h"
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#ifdef __cplusplus
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extern "C" {
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#endif
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typedef struct {
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ALfloat coeff;
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#ifndef _MSC_VER
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ALfloat history[0];
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#else
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ALfloat history[1];
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#endif
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} FILTER;
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static __inline ALfloat lpFilter4P(FILTER *iir, ALuint offset, ALfloat input)
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{
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ALfloat *history = &iir->history[offset];
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ALfloat a = iir->coeff;
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ALfloat output = input;
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output = output + (history[0]-output)*a;
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history[0] = output;
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output = output + (history[1]-output)*a;
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history[1] = output;
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output = output + (history[2]-output)*a;
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history[2] = output;
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output = output + (history[3]-output)*a;
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history[3] = output;
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return output;
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}
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static __inline ALfloat lpFilter2P(FILTER *iir, ALuint offset, ALfloat input)
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{
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ALfloat *history = &iir->history[offset];
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ALfloat a = iir->coeff;
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ALfloat output = input;
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output = output + (history[0]-output)*a;
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history[0] = output;
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output = output + (history[1]-output)*a;
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history[1] = output;
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return output;
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}
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static __inline ALfloat lpFilter1P(FILTER *iir, ALuint offset, ALfloat input)
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{
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ALfloat *history = &iir->history[offset];
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ALfloat a = iir->coeff;
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ALfloat output = input;
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output = output + (history[0]-output)*a;
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history[0] = output;
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return output;
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}
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/* Calculates the low-pass filter coefficient given the pre-scaled gain and
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* cos(w) value. Note that g should be pre-scaled (sqr(gain) for one-pole,
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* sqrt(gain) for four-pole, etc) */
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static __inline ALfloat lpCoeffCalc(ALfloat g, ALfloat cw)
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{
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ALfloat a = 0.0f;
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/* Be careful with gains < 0.01, as that causes the coefficient
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* head towards 1, which will flatten the signal */
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g = __max(g, 0.01f);
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if(g < 0.9999f) /* 1-epsilon */
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a = (1 - g*cw - aluSqrt(2*g*(1-cw) - g*g*(1 - cw*cw))) /
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(1 - g);
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return a;
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}
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typedef struct ALfilter
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{
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// Filter type (AL_FILTER_NULL, ...)
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ALenum type;
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ALfloat Gain;
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ALfloat GainHF;
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// Index to itself
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ALuint filter;
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struct ALfilter *next;
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} ALfilter;
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AL_API ALvoid AL_APIENTRY alGenFilters(ALsizei n, ALuint *filters);
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AL_API ALvoid AL_APIENTRY alDeleteFilters(ALsizei n, ALuint *filters);
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AL_API ALboolean AL_APIENTRY alIsFilter(ALuint filter);
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AL_API ALvoid AL_APIENTRY alFilteri(ALuint filter, ALenum param, ALint iValue);
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AL_API ALvoid AL_APIENTRY alFilteriv(ALuint filter, ALenum param, ALint *piValues);
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AL_API ALvoid AL_APIENTRY alFilterf(ALuint filter, ALenum param, ALfloat flValue);
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AL_API ALvoid AL_APIENTRY alFilterfv(ALuint filter, ALenum param, ALfloat *pflValues);
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AL_API ALvoid AL_APIENTRY alGetFilteri(ALuint filter, ALenum param, ALint *piValue);
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AL_API ALvoid AL_APIENTRY alGetFilteriv(ALuint filter, ALenum param, ALint *piValues);
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AL_API ALvoid AL_APIENTRY alGetFilterf(ALuint filter, ALenum param, ALfloat *pflValue);
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AL_API ALvoid AL_APIENTRY alGetFilterfv(ALuint filter, ALenum param, ALfloat *pflValues);
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ALvoid ReleaseALFilters(ALCdevice *device);
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#ifdef __cplusplus
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}
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#endif
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#endif
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