150 lines
4.1 KiB
C
150 lines
4.1 KiB
C
/*
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* Siren Encoder/Decoder library
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*
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* @author: Youness Alaoui <kakaroto@kakaroto.homelinux.net>
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*
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* This library is free software; you can redistribute it and/or
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* modify it under the terms of the GNU Library General Public
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* License as published by the Free Software Foundation; either
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* version 2 of the License, or (at your option) any later version.
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*
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* This library is distributed in the hope that it will be useful,
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* but WITHOUT ANY WARRANTY; without even the implied warranty of
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* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
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* Library General Public License for more details.
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*
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* You should have received a copy of the GNU Library General Public
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* License along with this library; if not, write to the
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* Free Software Foundation, Inc., 51 Franklin St, Fifth Floor,
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* Boston, MA 02110-1301, USA.
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*/
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#include "siren7.h"
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static int rmlt_initialized = 0;
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static float rmlt_window_640[640];
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static float rmlt_window_320[320];
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#define PI_2 1.57079632679489661923
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void
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siren_rmlt_init (void)
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{
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int i = 0;
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float angle;
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for (i = 0; i < 640; i++) {
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angle = (float) (((i + 0.5) * PI_2) / 640);
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rmlt_window_640[i] = (float) sin (angle);
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}
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for (i = 0; i < 320; i++) {
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angle = (float) (((i + 0.5) * PI_2) / 320);
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rmlt_window_320[i] = (float) sin (angle);
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}
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rmlt_initialized = 1;
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}
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int
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siren_rmlt_encode_samples (float *samples, float *old_samples, int dct_length,
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float *rmlt_coefs)
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{
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int half_dct_length = dct_length / 2;
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float *old_ptr = old_samples + half_dct_length;
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float *coef_high = rmlt_coefs + half_dct_length;
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float *coef_low = rmlt_coefs + half_dct_length;
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float *samples_low = samples;
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float *samples_high = samples + dct_length;
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float *window_low = NULL;
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float *window_high = NULL;
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int i = 0;
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if (rmlt_initialized == 0)
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siren_rmlt_init ();
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if (dct_length == 320)
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window_low = rmlt_window_320;
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else if (dct_length == 640)
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window_low = rmlt_window_640;
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else
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return 4;
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window_high = window_low + dct_length;
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for (i = 0; i < half_dct_length; i++) {
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*--coef_low = *--old_ptr;
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*coef_high++ =
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(*samples_low * *--window_high) - (*--samples_high * *window_low);
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*old_ptr =
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(*samples_high * *window_high) + (*samples_low++ * *window_low++);
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}
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siren_dct4 (rmlt_coefs, rmlt_coefs, dct_length);
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return 0;
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}
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int
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siren_rmlt_decode_samples (float *coefs, float *old_coefs, int dct_length,
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float *samples)
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{
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int half_dct_length = dct_length / 2;
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float *old_low = old_coefs;
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float *old_high = old_coefs + half_dct_length;
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float *samples_low = samples;
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float *samples_high = samples + dct_length;
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float *samples_middle_low = samples + half_dct_length;
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float *samples_middle_high = samples + half_dct_length;
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float *window_low = NULL;
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float *window_high = NULL;
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float *window_middle_low = NULL;
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float *window_middle_high = NULL;
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float sample_low_val;
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float sample_high_val;
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float sample_middle_low_val;
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float sample_middle_high_val;
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int i = 0;
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if (rmlt_initialized == 0)
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siren_rmlt_init ();
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if (dct_length == 320)
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window_low = rmlt_window_320;
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else if (dct_length == 640)
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window_low = rmlt_window_640;
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else
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return 4;
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window_high = window_low + dct_length;
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window_middle_low = window_low + half_dct_length;
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window_middle_high = window_low + half_dct_length;
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siren_dct4 (coefs, samples, dct_length);
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for (i = 0; i < half_dct_length; i += 2) {
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sample_low_val = *samples_low;
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sample_high_val = *--samples_high;
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sample_middle_low_val = *--samples_middle_low;
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sample_middle_high_val = *samples_middle_high;
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*samples_low++ =
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(*old_low * *--window_high) + (sample_middle_low_val * *window_low);
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*samples_high =
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(sample_middle_low_val * *window_high) - (*old_low * *window_low++);
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*samples_middle_high++ =
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(sample_low_val * *window_middle_high) -
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(*--old_high * *--window_middle_low);
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*samples_middle_low =
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(*old_high * *window_middle_high++) +
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(sample_low_val * *window_middle_low);
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*old_low++ = sample_middle_high_val;
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*old_high = sample_high_val;
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}
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return 0;
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}
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