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1 #ifndef _AL_FILTER_H_
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2 #define _AL_FILTER_H_
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3
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4 #include "AL/al.h"
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5 #include "alu.h"
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6
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7 #ifdef __cplusplus
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8 extern "C" {
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9 #endif
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10
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11 typedef struct {
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12 ALfloat coeff;
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13 #ifndef _MSC_VER
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14 ALfloat history[0];
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15 #else
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16 ALfloat history[1];
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17 #endif
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18 } FILTER;
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19
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20 static __inline ALfloat lpFilter2P(FILTER *iir, ALuint offset, ALfloat input)
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21 {
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22 ALfloat *history = &iir->history[offset*2];
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23 ALfloat a = iir->coeff;
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24 ALfloat output = input;
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25
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26 output = output + (history[0]-output)*a;
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27 history[0] = output;
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28 output = output + (history[1]-output)*a;
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29 history[1] = output;
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30
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31 return output;
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32 }
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33 static __inline ALfloat lpFilter1P(FILTER *iir, ALuint offset, ALfloat input)
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34 {
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35 ALfloat *history = &iir->history[offset];
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36 ALfloat a = iir->coeff;
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37 ALfloat output = input;
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38
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39 output = output + (history[0]-output)*a;
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40 history[0] = output;
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41
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42 return output;
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43 }
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44
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45 static __inline ALfloat lpFilter2PC(const FILTER *iir, ALuint offset, ALfloat input)
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46 {
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47 const ALfloat *history = &iir->history[offset*2];
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48 ALfloat a = iir->coeff;
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49 ALfloat output = input;
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50
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51 output = output + (history[0]-output)*a;
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52 output = output + (history[1]-output)*a;
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53
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54 return output;
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55 }
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56 static __inline ALfloat lpFilter1PC(FILTER *iir, ALuint offset, ALfloat input)
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57 {
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58 const ALfloat *history = &iir->history[offset];
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59 ALfloat a = iir->coeff;
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60 ALfloat output = input;
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61
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62 output = output + (history[0]-output)*a;
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63
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64 return output;
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65 }
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66
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67 /* Calculates the low-pass filter coefficient given the pre-scaled gain and
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68 * cos(w) value. Note that g should be pre-scaled (sqr(gain) for one-pole,
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69 * sqrt(gain) for four-pole, etc) */
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70 ALfloat lpCoeffCalc(ALfloat g, ALfloat cw);
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71
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72
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73 typedef struct ALfilter
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74 {
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75 // Filter type (AL_FILTER_NULL, ...)
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76 ALenum type;
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77
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78 ALfloat Gain;
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79 ALfloat GainHF;
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80
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81 // Index to itself
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82 ALuint filter;
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83 } ALfilter;
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84
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85
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86 ALvoid ReleaseALFilters(ALCdevice *device);
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87
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88 #ifdef __cplusplus
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89 }
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90 #endif
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91
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92 #endif
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