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 b0, b1, b2; /* Transfer function coefficients "b" */
  46     ALfloat a1, a2; /* Transfer function coefficients "a" (a0 is pre-applied) */
  47 } ALfilterState;
  48 /* Currently only a C-based filter process method is implemented. */
  49 #define ALfilterState_process ALfilterState_processC
  50
  51 /* Calculates the rcpQ (i.e. 1/Q) coefficient for shelving filters, using the
  52  * reference gain and shelf slope parameter.
  53  * 0 < gain
  54  * 0 < slope <= 1
  55  */
  56 inline ALfloat calc_rcpQ_from_slope(ALfloat gain, ALfloat slope)
  57 {
  58     return sqrtf((gain + 1.0f/gain)*(1.0f/slope - 1.0f) + 2.0f);
  59 }
  60 /* Calculates the rcpQ (i.e. 1/Q) coefficient for filters, using the frequency
  61  * multiple (i.e. ref_freq / sampling_freq) and bandwidth.
  62  * 0 < freq_mult < 0.5.
  63  */
  64 inline ALfloat calc_rcpQ_from_bandwidth(ALfloat freq_mult, ALfloat bandwidth)
  65 {
  66     ALfloat w0 = F_TAU * freq_mult;
  67     return 2.0f*sinhf(logf(2.0f)/2.0f*bandwidth*w0/sinf(w0));
  68 }
  69
  70 inline void ALfilterState_clear(ALfilterState *filter)
  71 {
  72     filter->x[0] = 0.0f;
  73     filter->x[1] = 0.0f;
  74     filter->y[0] = 0.0f;
  75     filter->y[1] = 0.0f;
  76 }
  77
  78 void ALfilterState_setParams(ALfilterState *filter, ALfilterType type, ALfloat gain, ALfloat freq_mult, ALfloat rcpQ);
  79
  80 void ALfilterState_processC(ALfilterState *filter, ALfloat *restrict dst, const ALfloat *restrict src, ALsizei numsamples);
  81
  82 inline void ALfilterState_processPassthru(ALfilterState *filter, const ALfloat *restrict src, ALsizei numsamples)
  83 {
  84     if(numsamples >= 2)
  85     {
  86         filter->x[1] = src[numsamples-2];
  87         filter->x[0] = src[numsamples-1];
  88         filter->y[1] = src[numsamples-2];
  89         filter->y[0] = src[numsamples-1];
  90     }
  91     else if(numsamples == 1)
  92     {
  93         filter->x[1] = filter->x[0];
  94         filter->x[0] = src[0];
  95         filter->y[1] = filter->y[0];
  96         filter->y[0] = src[0];
  97     }
  98 }
  99
 100
 101 typedef struct ALfilter {
 102     // Filter type (AL_FILTER_NULL, ...)
 103     ALenum type;
 104
 105     ALfloat Gain;
 106     ALfloat GainHF;
 107     ALfloat HFReference;
 108     ALfloat GainLF;
 109     ALfloat LFReference;
 110
 111     void (*SetParami)(struct ALfilter *filter, ALCcontext *context, ALenum param, ALint val);
 112     void (*SetParamiv)(struct ALfilter *filter, ALCcontext *context, ALenum param, const ALint *vals);
 113     void (*SetParamf)(struct ALfilter *filter, ALCcontext *context, ALenum param, ALfloat val);
 114     void (*SetParamfv)(struct ALfilter *filter, ALCcontext *context, ALenum param, const ALfloat *vals);
 115
 116     void (*GetParami)(struct ALfilter *filter, ALCcontext *context, ALenum param, ALint *val);
 117     void (*GetParamiv)(struct ALfilter *filter, ALCcontext *context, ALenum param, ALint *vals);
 118     void (*GetParamf)(struct ALfilter *filter, ALCcontext *context, ALenum param, ALfloat *val);
 119     void (*GetParamfv)(struct ALfilter *filter, ALCcontext *context, ALenum param, ALfloat *vals);
 120
 121     /* Self ID */
 122     ALuint id;
 123 } ALfilter;
 124
 125 #define ALfilter_SetParami(x, c, p, v)  ((x)->SetParami((x),(c),(p),(v)))
 126 #define ALfilter_SetParamiv(x, c, p, v) ((x)->SetParamiv((x),(c),(p),(v)))
 127 #define ALfilter_SetParamf(x, c, p, v)  ((x)->SetParamf((x),(c),(p),(v)))
 128 #define ALfilter_SetParamfv(x, c, p, v) ((x)->SetParamfv((x),(c),(p),(v)))
 129
 130 #define ALfilter_GetParami(x, c, p, v)  ((x)->GetParami((x),(c),(p),(v)))
 131 #define ALfilter_GetParamiv(x, c, p, v) ((x)->GetParamiv((x),(c),(p),(v)))
 132 #define ALfilter_GetParamf(x, c, p, v)  ((x)->GetParamf((x),(c),(p),(v)))
 133 #define ALfilter_GetParamfv(x, c, p, v) ((x)->GetParamfv((x),(c),(p),(v)))
 134
 135 inline void LockFiltersRead(ALCdevice *device)
 136 { LockUIntMapRead(&device->FilterMap); }
 137 inline void UnlockFiltersRead(ALCdevice *device)
 138 { UnlockUIntMapRead(&device->FilterMap); }
 139 inline void LockFiltersWrite(ALCdevice *device)
 140 { LockUIntMapWrite(&device->FilterMap); }
 141 inline void UnlockFiltersWrite(ALCdevice *device)
 142 { UnlockUIntMapWrite(&device->FilterMap); }
 143
 144 inline struct ALfilter *LookupFilter(ALCdevice *device, ALuint id)
 145 { return (struct ALfilter*)LookupUIntMapKeyNoLock(&device->FilterMap, id); }
 146 inline struct ALfilter *RemoveFilter(ALCdevice *device, ALuint id)
 147 { return (struct ALfilter*)RemoveUIntMapKeyNoLock(&device->FilterMap, id); }
 148
 149 ALvoid ReleaseALFilters(ALCdevice *device);
 150
 151 #ifdef __cplusplus
 152 }
 153 #endif
 154
 155 #endif