OpenAL32/Include/bs2b.h

   1 /*-
   2  * Copyright (c) 2005 Boris Mikhaylov
   3  *
   4  * Permission is hereby granted, free of charge, to any person obtaining
   5  * a copy of this software and associated documentation files (the
   6  * "Software"), to deal in the Software without restriction, including
   7  * without limitation the rights to use, copy, modify, merge, publish,
   8  * distribute, sublicense, and/or sell copies of the Software, and to
   9  * permit persons to whom the Software is furnished to do so, subject to
  10  * the following conditions:
  11  *
  12  * The above copyright notice and this permission notice shall be
  13  * included in all copies or substantial portions of the Software.
  14  *
  15  * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND,
  16  * EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF
  17  * MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT.
  18  * IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY
  19  * CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT,
  20  * TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE
  21  * SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
  22  */
  23
  24 #ifndef BS2B_H
  25 #define BS2B_H
  26
  27 /* Number of crossfeed levels */
  28 #define BS2B_CLEVELS           3
  29
  30 /* Normal crossfeed levels */
  31 #define BS2B_HIGH_CLEVEL       3
  32 #define BS2B_MIDDLE_CLEVEL     2
  33 #define BS2B_LOW_CLEVEL        1
  34
  35 /* Easy crossfeed levels */
  36 #define BS2B_HIGH_ECLEVEL      BS2B_HIGH_CLEVEL    + BS2B_CLEVELS
  37 #define BS2B_MIDDLE_ECLEVEL    BS2B_MIDDLE_CLEVEL  + BS2B_CLEVELS
  38 #define BS2B_LOW_ECLEVEL       BS2B_LOW_CLEVEL     + BS2B_CLEVELS
  39
  40 /* Default crossfeed levels */
  41 #define BS2B_DEFAULT_CLEVEL    BS2B_HIGH_ECLEVEL
  42 /* Default sample rate (Hz) */
  43 #define BS2B_DEFAULT_SRATE     44100
  44
  45 #ifdef __cplusplus
  46 extern "C" {
  47 #endif /* __cplusplus */
  48
  49 struct bs2b {
  50     int level;  /* Crossfeed level */
  51     int srate;   /* Sample rate (Hz) */
  52
  53     /* Lowpass IIR filter coefficients */
  54     float a0_lo;
  55     float b1_lo;
  56
  57     /* Highboost IIR filter coefficients */
  58     float a0_hi;
  59     float a1_hi;
  60     float b1_hi;
  61
  62     /* Buffer of last filtered sample.
  63      * [0] - first channel, [1] - second channel
  64      */
  65     struct t_last_sample {
  66         float asis[2];
  67         float lo[2];
  68         float hi[2];
  69     } last_sample;
  70 };
  71
  72 /* Clear buffers and set new coefficients with new crossfeed level value.
  73  * level - crossfeed level of *LEVEL values.
  74  */
  75 void bs2b_set_level(struct bs2b *bs2b, int level);
  76
  77 /* Return current crossfeed level value */
  78 int bs2b_get_level(struct bs2b *bs2b);
  79
  80 /* Clear buffers and set new coefficients with new sample rate value.
  81  * srate - sample rate by Hz.
  82  */
  83 void bs2b_set_srate(struct bs2b *bs2b, int srate);
  84
  85 /* Return current sample rate value */
  86 int bs2b_get_srate(struct bs2b *bs2b);
  87
  88 /* Clear buffer */
  89 void bs2b_clear(struct bs2b *bs2b);
  90
  91 /* Crossfeeds one stereo sample that are pointed by sample.
  92  * [0] - first channel, [1] - second channel.
  93  * Returns crossfided sample by sample pointer.
  94  */
  95 inline void bs2b_cross_feed(struct bs2b *bs2b, float *restrict sample)
  96 {
  97 /* Single pole IIR filter.
  98  * O[n] = a0*I[n] + a1*I[n-1] + b1*O[n-1]
  99  */
 100
 101 /* Lowpass filter */
 102 #define lo_filter(in, out_1) (bs2b->a0_lo*(in) + bs2b->b1_lo*(out_1))
 103
 104 /* Highboost filter */
 105 #define hi_filter(in, in_1, out_1) (bs2b->a0_hi*(in) + bs2b->a1_hi*(in_1) + bs2b->b1_hi*(out_1))
 106
 107     /* Lowpass filter */
 108     bs2b->last_sample.lo[0] = lo_filter(sample[0], bs2b->last_sample.lo[0]);
 109     bs2b->last_sample.lo[1] = lo_filter(sample[1], bs2b->last_sample.lo[1]);
 110
 111     /* Highboost filter */
 112     bs2b->last_sample.hi[0] = hi_filter(sample[0], bs2b->last_sample.asis[0], bs2b->last_sample.hi[0]);
 113     bs2b->last_sample.hi[1] = hi_filter(sample[1], bs2b->last_sample.asis[1], bs2b->last_sample.hi[1]);
 114     bs2b->last_sample.asis[0] = sample[0];
 115     bs2b->last_sample.asis[1] = sample[1];
 116
 117     /* Crossfeed */
 118     sample[0] = bs2b->last_sample.hi[0] + bs2b->last_sample.lo[1];
 119     sample[1] = bs2b->last_sample.hi[1] + bs2b->last_sample.lo[0];
 120 #undef hi_filter
 121 #undef lo_filter
 122 } /* bs2b_cross_feed */
 123
 124 #ifdef __cplusplus
 125 }    /* extern "C" */
 126 #endif /* __cplusplus */
 127
 128 #endif /* BS2B_H */