Mercurial > audio-send

     1 #ifndef _AL_FILTER_H_

     2 #define _AL_FILTER_H_

     3 

     4 #include "AL/al.h"

     5 #include "alu.h"

     6 

     7 #ifdef __cplusplus

     8 extern "C" {

     9 #endif

    10 

    11 typedef struct {

    12     ALfloat coeff;

    13 #ifndef _MSC_VER

    14     ALfloat history[0];

    15 #else

    16     ALfloat history[1];

    17 #endif

    18 } FILTER;

    19 

    20 static __inline ALfloat lpFilter2P(FILTER *iir, ALuint offset, ALfloat input)

    21 {

    22     ALfloat *history = &iir->history[offset*2];

    23     ALfloat a = iir->coeff;

    24     ALfloat output = input;

    25 

    26     output = output + (history[0]-output)*a;

    27     history[0] = output;

    28     output = output + (history[1]-output)*a;

    29     history[1] = output;

    30 

    31     return output;

    32 }

    33 static __inline ALfloat lpFilter1P(FILTER *iir, ALuint offset, ALfloat input)

    34 {

    35     ALfloat *history = &iir->history[offset];

    36     ALfloat a = iir->coeff;

    37     ALfloat output = input;

    38 

    39     output = output + (history[0]-output)*a;

    40     history[0] = output;

    41 

    42     return output;

    43 }

    44 

    45 static __inline ALfloat lpFilter2PC(const FILTER *iir, ALuint offset, ALfloat input)

    46 {

    47     const ALfloat *history = &iir->history[offset*2];

    48     ALfloat a = iir->coeff;

    49     ALfloat output = input;

    50 

    51     output = output + (history[0]-output)*a;

    52     output = output + (history[1]-output)*a;

    53 

    54     return output;

    55 }

    56 static __inline ALfloat lpFilter1PC(FILTER *iir, ALuint offset, ALfloat input)

    57 {

    58     const ALfloat *history = &iir->history[offset];

    59     ALfloat a = iir->coeff;

    60     ALfloat output = input;

    61 

    62     output = output + (history[0]-output)*a;

    63 

    64     return output;

    65 }

    66 

    67 /* Calculates the low-pass filter coefficient given the pre-scaled gain and

    68  * cos(w) value. Note that g should be pre-scaled (sqr(gain) for one-pole,

    69  * sqrt(gain) for four-pole, etc) */

    70 ALfloat lpCoeffCalc(ALfloat g, ALfloat cw);

    71 

    72 

    73 typedef struct ALfilter

    74 {

    75     // Filter type (AL_FILTER_NULL, ...)

    76     ALenum type;

    77 

    78     ALfloat Gain;

    79     ALfloat GainHF;

    80 

    81     // Index to itself

    82     ALuint filter;

    83 } ALfilter;

    84 

    85 

    86 ALvoid ReleaseALFilters(ALCdevice *device);

    87 

    88 #ifdef __cplusplus

    89 }

    90 #endif

    91 

    92 #endif
author	Robert McIntyre <rlm@mit.edu>
date	Tue, 25 Oct 2011 13:02:31 -0700
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