OpenAL32/Include/alFilter.h

   1 #ifndef _AL_FILTER_H_
   2 #define _AL_FILTER_H_
   3
   4 #include "alMain.h"
   5
   6 #include "math_defs.h"
   7
   8 #ifdef __cplusplus
   9 extern "C" {
  10 #endif
  11
  12 #define LOWPASSFREQREF  (5000.0f)
  13 #define HIGHPASSFREQREF  (250.0f)
  14
  15
  16 /* Filters implementation is based on the "Cookbook formulae for audio
  17  * EQ biquad filter coefficients" by Robert Bristow-Johnson
  18  * http://www.musicdsp.org/files/Audio-EQ-Cookbook.txt
  19  */
  20 /* Implementation note: For the shelf filters, the specified gain is for the
  21  * reference frequency, which is the centerpoint of the transition band. This
  22  * better matches EFX filter design. To set the gain for the shelf itself, use
  23  * the square root of the desired linear gain (or halve the dB gain).
  24  */
  25
  26 typedef enum ALfilterType {
  27     /** EFX-style low-pass filter, specifying a gain and reference frequency. */
  28     ALfilterType_HighShelf,
  29     /** EFX-style high-pass filter, specifying a gain and reference frequency. */
  30     ALfilterType_LowShelf,
  31     /** Peaking filter, specifying a gain and reference frequency. */
  32     ALfilterType_Peaking,
  33
  34     /** Low-pass cut-off filter, specifying a cut-off frequency. */
  35     ALfilterType_LowPass,
  36     /** High-pass cut-off filter, specifying a cut-off frequency. */
  37     ALfilterType_HighPass,
  38     /** Band-pass filter, specifying a center frequency. */
  39     ALfilterType_BandPass,
  40 } ALfilterType;
  41
  42 typedef struct ALfilterState {
  43     ALfloat x[2]; /* History of two last input samples  */
  44     ALfloat y[2]; /* History of two last output samples */
  45     ALfloat a1, a2; /* Transfer function coefficients "a" (a0 is pre-applied) */
  46     ALfloat b0, b1, b2; /* Transfer function coefficients "b" */
  47
  48     void (*process)(struct ALfilterState *self, ALfloat *restrict dst, const ALfloat *restrict src, ALuint numsamples);
  49 } ALfilterState;
  50 #define ALfilterState_process(a, ...) ((a)->process((a), __VA_ARGS__))
  51
  52 /* Calculates the rcpQ (i.e. 1/Q) coefficient for shelving filters, using the
  53  * reference gain and shelf slope parameter.
  54  * 0 < gain
  55  * 0 < slope <= 1
  56  */
  57 inline ALfloat calc_rcpQ_from_slope(ALfloat gain, ALfloat slope)
  58 {
  59     return sqrtf((gain + 1.0f/gain)*(1.0f/slope - 1.0f) + 2.0f);
  60 }
  61 /* Calculates the rcpQ (i.e. 1/Q) coefficient for filters, using the frequency
  62  * multiple (i.e. ref_freq / sampling_freq) and bandwidth.
  63  * 0 < freq_mult < 0.5.
  64  */
  65 inline ALfloat calc_rcpQ_from_bandwidth(ALfloat freq_mult, ALfloat bandwidth)
  66 {
  67     ALfloat w0 = F_TAU * freq_mult;
  68     return 2.0f*sinhf(logf(2.0f)/2.0f*bandwidth*w0/sinf(w0));
  69 }
  70
  71 inline void ALfilterState_clear(ALfilterState *filter)
  72 {
  73     filter->x[0] = 0.0f;
  74     filter->x[1] = 0.0f;
  75     filter->y[0] = 0.0f;
  76     filter->y[1] = 0.0f;
  77 }
  78
  79 void ALfilterState_setParams(ALfilterState *filter, ALfilterType type, ALfloat gain, ALfloat freq_mult, ALfloat rcpQ);
  80
  81 inline ALfloat ALfilterState_processSingle(ALfilterState *filter, ALfloat sample)
  82 {
  83     ALfloat outsmp;
  84
  85     outsmp = filter->b0 * sample +
  86              filter->b1 * filter->x[0] +
  87              filter->b2 * filter->x[1] -
  88              filter->a1 * filter->y[0] -
  89              filter->a2 * filter->y[1];
  90     filter->x[1] = filter->x[0];
  91     filter->x[0] = sample;
  92     filter->y[1] = filter->y[0];
  93     filter->y[0] = outsmp;
  94
  95     return outsmp;
  96 }
  97
  98 void ALfilterState_processC(ALfilterState *filter, ALfloat *restrict dst, const ALfloat *restrict src, ALuint numsamples);
  99
 100 inline void ALfilterState_processPassthru(ALfilterState *filter, const ALfloat *src, ALuint numsamples)
 101 {
 102     if(numsamples >= 2)
 103     {
 104         filter->x[1] = src[numsamples-2];
 105         filter->x[0] = src[numsamples-1];
 106         filter->y[1] = src[numsamples-2];
 107         filter->y[0] = src[numsamples-1];
 108     }
 109     else if(numsamples == 1)
 110     {
 111         filter->x[1] = filter->x[0];
 112         filter->x[0] = src[0];
 113         filter->y[1] = filter->y[0];
 114         filter->y[0] = src[0];
 115     }
 116 }
 117
 118
 119 typedef struct ALfilter {
 120     // Filter type (AL_FILTER_NULL, ...)
 121     ALenum type;
 122
 123     ALfloat Gain;
 124     ALfloat GainHF;
 125     ALfloat HFReference;
 126     ALfloat GainLF;
 127     ALfloat LFReference;
 128
 129     void (*SetParami)(struct ALfilter *filter, ALCcontext *context, ALenum param, ALint val);
 130     void (*SetParamiv)(struct ALfilter *filter, ALCcontext *context, ALenum param, const ALint *vals);
 131     void (*SetParamf)(struct ALfilter *filter, ALCcontext *context, ALenum param, ALfloat val);
 132     void (*SetParamfv)(struct ALfilter *filter, ALCcontext *context, ALenum param, const ALfloat *vals);
 133
 134     void (*GetParami)(struct ALfilter *filter, ALCcontext *context, ALenum param, ALint *val);
 135     void (*GetParamiv)(struct ALfilter *filter, ALCcontext *context, ALenum param, ALint *vals);
 136     void (*GetParamf)(struct ALfilter *filter, ALCcontext *context, ALenum param, ALfloat *val);
 137     void (*GetParamfv)(struct ALfilter *filter, ALCcontext *context, ALenum param, ALfloat *vals);
 138
 139     /* Self ID */
 140     ALuint id;
 141 } ALfilter;
 142
 143 #define ALfilter_SetParami(x, c, p, v)  ((x)->SetParami((x),(c),(p),(v)))
 144 #define ALfilter_SetParamiv(x, c, p, v) ((x)->SetParamiv((x),(c),(p),(v)))
 145 #define ALfilter_SetParamf(x, c, p, v)  ((x)->SetParamf((x),(c),(p),(v)))
 146 #define ALfilter_SetParamfv(x, c, p, v) ((x)->SetParamfv((x),(c),(p),(v)))
 147
 148 #define ALfilter_GetParami(x, c, p, v)  ((x)->GetParami((x),(c),(p),(v)))
 149 #define ALfilter_GetParamiv(x, c, p, v) ((x)->GetParamiv((x),(c),(p),(v)))
 150 #define ALfilter_GetParamf(x, c, p, v)  ((x)->GetParamf((x),(c),(p),(v)))
 151 #define ALfilter_GetParamfv(x, c, p, v) ((x)->GetParamfv((x),(c),(p),(v)))
 152
 153 inline void LockFiltersRead(ALCdevice *device)
 154 { LockUIntMapRead(&device->FilterMap); }
 155 inline void UnlockFiltersRead(ALCdevice *device)
 156 { UnlockUIntMapRead(&device->FilterMap); }
 157 inline void LockFiltersWrite(ALCdevice *device)
 158 { LockUIntMapWrite(&device->FilterMap); }
 159 inline void UnlockFiltersWrite(ALCdevice *device)
 160 { UnlockUIntMapWrite(&device->FilterMap); }
 161
 162 inline struct ALfilter *LookupFilter(ALCdevice *device, ALuint id)
 163 { return (struct ALfilter*)LookupUIntMapKeyNoLock(&device->FilterMap, id); }
 164 inline struct ALfilter *RemoveFilter(ALCdevice *device, ALuint id)
 165 { return (struct ALfilter*)RemoveUIntMapKeyNoLock(&device->FilterMap, id); }
 166
 167 ALvoid ReleaseALFilters(ALCdevice *device);
 168
 169 #ifdef __cplusplus
 170 }
 171 #endif
 172
 173 #endif