1 | //lowp.c: |
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2 | |
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3 | /* |
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4 | * Copyright (C) Philipp 'ph3-der-loewe' Schafft - August 2008 |
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5 | * |
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6 | * This file is part of libroardsp a part of RoarAudio, |
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7 | * a cross-platform sound system for both, home and professional use. |
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8 | * See README for details. |
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9 | * |
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10 | * This file is free software; you can redistribute it and/or modify |
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11 | * it under the terms of the GNU General Public License version 3 |
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12 | * as published by the Free Software Foundation. |
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13 | * |
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14 | * libroardsp is distributed in the hope that it will be useful, |
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15 | * but WITHOUT ANY WARRANTY; without even the implied warranty of |
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16 | * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the |
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17 | * GNU General Public License for more details. |
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18 | * |
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19 | * You should have received a copy of the GNU General Public License |
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20 | * along with this software; see the file COPYING. If not, write to |
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21 | * the Free Software Foundation, 675 Mass Ave, Cambridge, MA 02139, USA. |
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22 | * |
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23 | */ |
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24 | |
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25 | #include "libroardsp.h" |
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26 | |
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27 | int roardsp_lowp_init (struct roardsp_filter * filter, struct roar_stream * stream, int id) { |
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28 | struct roardsp_lowp * self = malloc(sizeof(struct roardsp_lowp)); |
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29 | float freq = filter->rate/2; |
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30 | |
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31 | ROAR_DBG("roardsp_lowp_init(*): self=%p", self); |
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32 | |
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33 | if ( self == NULL ) |
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34 | return -1; |
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35 | |
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36 | memset(self, 0, sizeof(struct roardsp_lowp)); |
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37 | |
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38 | filter->inst = (void*) self; |
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39 | |
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40 | roardsp_lowp_ctl(filter, ROARDSP_FCTL_FREQ, &freq); |
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41 | |
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42 | return 0; |
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43 | } |
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44 | |
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45 | int roardsp_lowp_uninit(struct roardsp_filter * filter) { |
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46 | |
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47 | free(filter->inst); |
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48 | return 0; |
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49 | } |
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50 | |
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51 | int roardsp_lowp_calc16 (struct roardsp_filter * filter, void * data, size_t samples) { |
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52 | struct roardsp_lowp * self = (struct roardsp_lowp *) filter->inst; |
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53 | int16_t * samp = (int16_t *) data; |
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54 | register int32_t s; |
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55 | int i, c; |
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56 | int channels = filter->channels; |
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57 | |
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58 | if ( channels > ROAR_MAX_CHANNELS ) |
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59 | return -1; |
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60 | |
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61 | samples /= channels; |
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62 | |
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63 | ROAR_DBG("roardsp_lowp_calc16(*): filtering %i frames of %i channels...", samples, channels); |
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64 | |
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65 | // * output[N] = input[N] * A + output[N-1] * B |
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66 | |
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67 | for (i = 0; i < samples; i++) { |
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68 | for (c = 0; c < channels; c++) { |
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69 | s = samp[i*channels + c] * self->a + self->old[c] * self->b; |
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70 | |
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71 | s /= 65536; |
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72 | |
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73 | samp[i*channels + c] = s; |
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74 | self->old[ c] = s; |
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75 | } |
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76 | } |
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77 | |
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78 | return 0; |
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79 | } |
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80 | |
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81 | int roardsp_lowp_ctl (struct roardsp_filter * filter, int cmd, void * data) { |
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82 | struct roardsp_lowp * self = (struct roardsp_lowp *) filter->inst; |
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83 | float lp; |
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84 | float oldfreq; |
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85 | float newfreq; |
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86 | |
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87 | if ( cmd != ROARDSP_FCTL_FREQ ) |
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88 | return -1; |
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89 | |
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90 | newfreq = *(float*)data; |
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91 | |
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92 | lp = exp(-2 * M_PI * newfreq / filter->rate) * 65536; |
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93 | |
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94 | self->b = lp; |
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95 | self->a = 65536 - lp; |
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96 | |
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97 | oldfreq = self->freq / 1000; |
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98 | self->freq = newfreq * 1000; |
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99 | |
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100 | *(float*)data = oldfreq; |
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101 | |
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102 | ROAR_DBG("roardsp_lowp_ctl(*): oldfreq=%f, newfreq=%f", oldfreq, newfreq); |
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103 | |
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104 | return 0; |
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105 | } |
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106 | |
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107 | //ll |
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