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/*
* Siren Encoder/Decoder library
*
* @author: Youness Alaoui <kakaroto@kakaroto.homelinux.net>
*
* This library is free software; you can redistribute it and/or
* modify it under the terms of the GNU Library General Public
* License as published by the Free Software Foundation; either
* version 2 of the License, or (at your option) any later version.
*
* This library is distributed in the hope that it will be useful,
* but WITHOUT ANY WARRANTY; without even the implied warranty of
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
* Library General Public License for more details.
*
* You should have received a copy of the GNU Library General Public
* License along with this library; if not, write to the
* Free Software Foundation, Inc., 59 Temple Place - Suite 330,
* Boston, MA 02111-1307, USA.
*/
#include "siren7.h"
static int rmlt_initialized = 0;
static float rmlt_window_640[640];
static float rmlt_window_320[320];
#define PI_2 1.57079632679489661923
void siren_rmlt_init() {
int i = 0;
float angle;
for (i = 0; i < 640; i++) {
angle = (float) (((i + 0.5) * PI_2) / 640);
rmlt_window_640[i] = (float) sin(angle);
}
for (i = 0; i < 320; i++) {
angle = (float) (((i + 0.5) * PI_2) / 320);
rmlt_window_320[i] = (float) sin(angle);
}
rmlt_initialized = 1;
}
int siren_rmlt_encode_samples(float *samples, float *old_samples, int dct_length, float *rmlt_coefs) {
int half_dct_length = dct_length / 2;
float *old_ptr = old_samples + half_dct_length;
float *coef_high = rmlt_coefs + half_dct_length;
float *coef_low = rmlt_coefs + half_dct_length;
float *samples_low = samples;
float *samples_high = samples + dct_length;
float *window_low = NULL;
float *window_high = NULL;
int i = 0;
if (rmlt_initialized == 0)
siren_rmlt_init();
if (dct_length == 320)
window_low = rmlt_window_320;
else if (dct_length == 640)
window_low = rmlt_window_640;
else
return 4;
window_high = window_low + dct_length;
for (i = 0; i < half_dct_length; i++) {
*--coef_low = *--old_ptr;
*coef_high++ = (*samples_low * *--window_high) - (*--samples_high * *window_low);
*old_ptr = (*samples_high * *window_high) + (*samples_low++ * *window_low++);
}
siren_dct4(rmlt_coefs, rmlt_coefs, dct_length);
return 0;
}
int siren_rmlt_decode_samples(float *coefs, float *old_coefs, int dct_length, float *samples) {
int half_dct_length = dct_length / 2;
float *old_low = old_coefs;
float *old_high = old_coefs + half_dct_length;
float *samples_low = samples ;
float *samples_high = samples + dct_length;
float *samples_middle_low = samples + half_dct_length;
float *samples_middle_high = samples + half_dct_length;
float *window_low = NULL;
float *window_high = NULL;
float *window_middle_low = NULL;
float *window_middle_high = NULL;
float sample_low_val;
float sample_high_val;
float sample_middle_low_val;
float sample_middle_high_val;
int i = 0;
if (rmlt_initialized == 0)
siren_rmlt_init();
if (dct_length == 320)
window_low = rmlt_window_320;
else if (dct_length == 640)
window_low = rmlt_window_640;
else
return 4;
window_high = window_low + dct_length;
window_middle_low = window_low + half_dct_length;
window_middle_high = window_low + half_dct_length;
siren_dct4(coefs, samples, dct_length);
for (i = 0; i < half_dct_length; i+=2) {
sample_low_val = *samples_low;
sample_high_val = *--samples_high;
sample_middle_low_val = *--samples_middle_low;
sample_middle_high_val = *samples_middle_high;
*samples_low++ = (*old_low * *--window_high) + (sample_middle_low_val * *window_low);
*samples_high = (sample_middle_low_val * *window_high) - (*old_low * *window_low++);
*samples_middle_high++ = (sample_low_val * *window_middle_high) - (*--old_high * *--window_middle_low);
*samples_middle_low = (*old_high * *window_middle_high++) + (sample_low_val * *window_middle_low);
*old_low++ = sample_middle_high_val;
*old_high = sample_high_val;
}
return 0;
}
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