2 * Siren Encoder/Decoder library
4 * @author: Youness Alaoui <kakaroto@kakaroto.homelinux.net>
6 * This library is free software; you can redistribute it and/or
7 * modify it under the terms of the GNU Library General Public
8 * License as published by the Free Software Foundation; either
9 * version 2 of the License, or (at your option) any later version.
11 * This library is distributed in the hope that it will be useful,
12 * but WITHOUT ANY WARRANTY; without even the implied warranty of
13 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
14 * Library General Public License for more details.
16 * You should have received a copy of the GNU Library General Public
17 * License along with this library; if not, write to the
18 * Free Software Foundation, Inc., 59 Temple Place - Suite 330,
19 * Boston, MA 02111-1307, USA.
26 static int rmlt_initialized = 0;
27 static float rmlt_window_640[640];
28 static float rmlt_window_320[320];
30 #define PI_2 1.57079632679489661923
32 void siren_rmlt_init() {
36 for (i = 0; i < 640; i++) {
37 angle = (float) (((i + 0.5) * PI_2) / 640);
38 rmlt_window_640[i] = (float) sin(angle);
40 for (i = 0; i < 320; i++) {
41 angle = (float) (((i + 0.5) * PI_2) / 320);
42 rmlt_window_320[i] = (float) sin(angle);
48 int siren_rmlt_encode_samples(float *samples, float *old_samples, int dct_length, float *rmlt_coefs) {
49 int half_dct_length = dct_length / 2;
50 float *old_ptr = old_samples + half_dct_length;
51 float *coef_high = rmlt_coefs + half_dct_length;
52 float *coef_low = rmlt_coefs + half_dct_length;
53 float *samples_low = samples;
54 float *samples_high = samples + dct_length;
55 float *window_low = NULL;
56 float *window_high = NULL;
59 if (rmlt_initialized == 0)
62 if (dct_length == 320)
63 window_low = rmlt_window_320;
64 else if (dct_length == 640)
65 window_low = rmlt_window_640;
69 window_high = window_low + dct_length;
72 for (i = 0; i < half_dct_length; i++) {
73 *--coef_low = *--old_ptr;
74 *coef_high++ = (*samples_low * *--window_high) - (*--samples_high * *window_low);
75 *old_ptr = (*samples_high * *window_high) + (*samples_low++ * *window_low++);
77 siren_dct4(rmlt_coefs, rmlt_coefs, dct_length);
84 int siren_rmlt_decode_samples(float *coefs, float *old_coefs, int dct_length, float *samples) {
85 int half_dct_length = dct_length / 2;
86 float *old_low = old_coefs;
87 float *old_high = old_coefs + half_dct_length;
88 float *samples_low = samples ;
89 float *samples_high = samples + dct_length;
90 float *samples_middle_low = samples + half_dct_length;
91 float *samples_middle_high = samples + half_dct_length;
92 float *window_low = NULL;
93 float *window_high = NULL;
94 float *window_middle_low = NULL;
95 float *window_middle_high = NULL;
97 float sample_high_val;
98 float sample_middle_low_val;
99 float sample_middle_high_val;
102 if (rmlt_initialized == 0)
105 if (dct_length == 320)
106 window_low = rmlt_window_320;
107 else if (dct_length == 640)
108 window_low = rmlt_window_640;
113 window_high = window_low + dct_length;
114 window_middle_low = window_low + half_dct_length;
115 window_middle_high = window_low + half_dct_length;
117 siren_dct4(coefs, samples, dct_length);
119 for (i = 0; i < half_dct_length; i+=2) {
120 sample_low_val = *samples_low;
121 sample_high_val = *--samples_high;
122 sample_middle_low_val = *--samples_middle_low;
123 sample_middle_high_val = *samples_middle_high;
124 *samples_low++ = (*old_low * *--window_high) + (sample_middle_low_val * *window_low);
125 *samples_high = (sample_middle_low_val * *window_high) - (*old_low * *window_low++);
126 *samples_middle_high++ = (sample_low_val * *window_middle_high) - (*--old_high * *--window_middle_low);
127 *samples_middle_low = (*old_high * *window_middle_high++) + (sample_low_val * *window_middle_low);
128 *old_low++ = sample_middle_high_val;
129 *old_high = sample_high_val;