mirror of
https://github.com/QB64Official/qb64.git
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139 lines
3.2 KiB
C
139 lines
3.2 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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ALfp coeff;
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#ifndef _MSC_VER
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ALfp history[0];
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#else
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ALfp history[1];
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#endif
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} FILTER;
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static __inline ALfp lpFilter4P(FILTER *iir, ALuint offset, ALfp input)
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{
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ALfp *history = &iir->history[offset];
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ALfp a = iir->coeff;
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ALfp output = input;
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output = output + ALfpMult((history[0]-output),a);
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history[0] = output;
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output = output + ALfpMult((history[1]-output),a);
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history[1] = output;
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output = output + ALfpMult((history[2]-output),a);
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history[2] = output;
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output = output + ALfpMult((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 ALfp lpFilter2P(FILTER *iir, ALuint offset, ALfp input)
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{
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ALfp *history = &iir->history[offset];
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ALfp a = iir->coeff;
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ALfp output = input;
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output = output + ALfpMult((history[0]-output),a);
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history[0] = output;
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output = output + ALfpMult((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 ALfp lpFilter1P(FILTER *iir, ALuint offset, ALfp input)
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{
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ALfp *history = &iir->history[offset];
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ALfp a = iir->coeff;
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ALfp output = input;
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output = output + ALfpMult((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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static __inline ALfp lpFilter4PC(const FILTER *iir, ALuint offset, ALfp input)
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{
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const ALfp *history = &iir->history[offset];
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ALfp a = iir->coeff;
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ALfp output = input;
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output = output + ALfpMult((history[0]-output),a);
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output = output + ALfpMult((history[1]-output),a);
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output = output + ALfpMult((history[2]-output),a);
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output = output + ALfpMult((history[3]-output),a);
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return output;
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}
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static __inline ALfp lpFilter2PC(const FILTER *iir, ALuint offset, ALfp input)
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{
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const ALfp *history = &iir->history[offset];
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ALfp a = iir->coeff;
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ALfp output = input;
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output = output + ALfpMult((history[0]-output),a);
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output = output + ALfpMult((history[1]-output),a);
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return output;
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}
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static __inline ALfp lpFilter1PC(FILTER *iir, ALuint offset, ALfp input)
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{
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const ALfp *history = &iir->history[offset];
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ALfp a = iir->coeff;
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ALfp output = input;
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output = output + ALfpMult((history[0]-output),a);
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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 ALfp lpCoeffCalc(ALfp g, ALfp cw)
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{
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ALfp a = int2ALfp(0);
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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, float2ALfp(0.01f));
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if(g < float2ALfp(0.9999f)) /* 1-epsilon */ {
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ALfp tmp; tmp = ALfpMult(ALfpMult(int2ALfp(2),g),(int2ALfp(1)-cw)) - ALfpMult(ALfpMult(g,g),(int2ALfp(1) - ALfpMult(cw,cw)));
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a = ALfpDiv((int2ALfp(1) - ALfpMult(g,cw) - aluSqrt(tmp)), (int2ALfp(1) - g));
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}
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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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ALfp Gain;
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ALfp GainHF;
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// Index to itself
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ALuint filter;
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} ALfilter;
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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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