108 lines
3.9 KiB
C
108 lines
3.9 KiB
C
#ifndef _AL_FILTER_H_
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#define _AL_FILTER_H_
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#include "alMain.h"
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#ifdef __cplusplus
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extern "C" {
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#endif
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#define LOWPASSFREQREF (5000.0f)
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#define HIGHPASSFREQREF (250.0f)
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/* Filters implementation is based on the "Cookbook formulae for audio *
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* EQ biquad filter coefficients" by Robert Bristow-Johnson *
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* http://www.musicdsp.org/files/Audio-EQ-Cookbook.txt */
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typedef enum ALfilterType {
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/** EFX-style low-pass filter, specifying a gain and reference frequency. */
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ALfilterType_HighShelf,
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/** EFX-style high-pass filter, specifying a gain and reference frequency. */
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ALfilterType_LowShelf,
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/** Peaking filter, specifying a gain, reference frequency, and bandwidth. */
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ALfilterType_Peaking,
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/** Low-pass cut-off filter, specifying a cut-off frequency and bandwidth. */
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ALfilterType_LowPass,
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/** High-pass cut-off filter, specifying a cut-off frequency and bandwidth. */
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ALfilterType_HighPass,
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/** Band-pass filter, specifying a center frequency and bandwidth. */
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ALfilterType_BandPass,
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} ALfilterType;
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typedef struct ALfilterState {
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ALfloat x[2]; /* History of two last input samples */
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ALfloat y[2]; /* History of two last output samples */
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ALfloat a[3]; /* Transfer function coefficients "a" */
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ALfloat b[3]; /* Transfer function coefficients "b" */
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} ALfilterState;
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void ALfilterState_clear(ALfilterState *filter);
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void ALfilterState_setParams(ALfilterState *filter, ALfilterType type, ALfloat gain, ALfloat freq_mult, ALfloat bandwidth);
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inline ALfloat ALfilterState_processSingle(ALfilterState *filter, ALfloat sample)
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{
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ALfloat outsmp;
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outsmp = filter->b[0] * sample +
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filter->b[1] * filter->x[0] +
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filter->b[2] * filter->x[1] -
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filter->a[1] * filter->y[0] -
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filter->a[2] * filter->y[1];
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filter->x[1] = filter->x[0];
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filter->x[0] = sample;
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filter->y[1] = filter->y[0];
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filter->y[0] = outsmp;
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return outsmp;
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}
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typedef struct ALfilter {
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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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ALfloat HFReference;
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ALfloat GainLF;
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ALfloat LFReference;
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void (*SetParami)(struct ALfilter *filter, ALCcontext *context, ALenum param, ALint val);
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void (*SetParamiv)(struct ALfilter *filter, ALCcontext *context, ALenum param, const ALint *vals);
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void (*SetParamf)(struct ALfilter *filter, ALCcontext *context, ALenum param, ALfloat val);
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void (*SetParamfv)(struct ALfilter *filter, ALCcontext *context, ALenum param, const ALfloat *vals);
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void (*GetParami)(struct ALfilter *filter, ALCcontext *context, ALenum param, ALint *val);
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void (*GetParamiv)(struct ALfilter *filter, ALCcontext *context, ALenum param, ALint *vals);
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void (*GetParamf)(struct ALfilter *filter, ALCcontext *context, ALenum param, ALfloat *val);
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void (*GetParamfv)(struct ALfilter *filter, ALCcontext *context, ALenum param, ALfloat *vals);
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/* Self ID */
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ALuint id;
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} ALfilter;
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#define ALfilter_SetParami(x, c, p, v) ((x)->SetParami((x),(c),(p),(v)))
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#define ALfilter_SetParamiv(x, c, p, v) ((x)->SetParamiv((x),(c),(p),(v)))
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#define ALfilter_SetParamf(x, c, p, v) ((x)->SetParamf((x),(c),(p),(v)))
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#define ALfilter_SetParamfv(x, c, p, v) ((x)->SetParamfv((x),(c),(p),(v)))
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#define ALfilter_GetParami(x, c, p, v) ((x)->GetParami((x),(c),(p),(v)))
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#define ALfilter_GetParamiv(x, c, p, v) ((x)->GetParamiv((x),(c),(p),(v)))
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#define ALfilter_GetParamf(x, c, p, v) ((x)->GetParamf((x),(c),(p),(v)))
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#define ALfilter_GetParamfv(x, c, p, v) ((x)->GetParamfv((x),(c),(p),(v)))
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inline struct ALfilter *LookupFilter(ALCdevice *device, ALuint id)
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{ return (struct ALfilter*)LookupUIntMapKey(&device->FilterMap, id); }
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inline struct ALfilter *RemoveFilter(ALCdevice *device, ALuint id)
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{ return (struct ALfilter*)RemoveUIntMapKey(&device->FilterMap, id); }
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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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