mirror of
https://github.com/f4exb/sdrangel.git
synced 2024-11-15 21:01:45 -05:00
123 lines
2.9 KiB
C++
123 lines
2.9 KiB
C++
/*---------------------------------------------------------------------------*\
|
|
|
|
FILE........: gp_interleaver.c
|
|
AUTHOR......: David Rowe
|
|
DATE CREATED: April 2018
|
|
|
|
Golden Prime Interleaver. My interpretation of "On the Analysis and
|
|
Design of Good Algebraic Interleavers", Xie et al,eq (5).
|
|
|
|
See also octvae/gp_interleaver.m
|
|
|
|
\*---------------------------------------------------------------------------*/
|
|
|
|
/*
|
|
Copyright (C) 2018 David Rowe
|
|
|
|
All rights reserved.
|
|
|
|
This program is free software; you can redistribute it and/or modify
|
|
it under the terms of the GNU Lesser General Public License version 2.1, as
|
|
published by the Free Software Foundation. This program 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 General Public
|
|
License for more details.
|
|
|
|
You should have received a copy of the GNU Lesser General Public License
|
|
along with this program; if not, see <http://www.gnu.org/licenses/>.
|
|
*/
|
|
|
|
#include <assert.h>
|
|
#include <stdio.h>
|
|
#include "gp_interleaver.h"
|
|
|
|
namespace FreeDV
|
|
{
|
|
|
|
/*
|
|
Choose b for Golden Prime Interleaver. b is chosen to be the
|
|
closest integer, which is relatively prime to N, to the Golden
|
|
section of N.
|
|
|
|
Implemented with a LUT in C for convenience, Octave version
|
|
has a more complete implementation.
|
|
*/
|
|
|
|
int b_table[] = {
|
|
112,71,
|
|
224,139,
|
|
448,277,
|
|
672,419,
|
|
896,557,
|
|
1120,701,
|
|
1344,839,
|
|
1568,971,
|
|
1792,1109,
|
|
2016,1249,
|
|
2240,1399,
|
|
2464,1523,
|
|
2688,1663,
|
|
2912,1801,
|
|
3136,1949,
|
|
3360,2081,
|
|
3584,2213
|
|
};
|
|
|
|
int choose_interleaver_b(int Nbits)
|
|
{
|
|
unsigned int i;
|
|
|
|
for(i=0; i<sizeof(b_table)/(2*sizeof(int)); i+=2) {
|
|
if (b_table[i] == Nbits) {
|
|
return b_table[i+1];
|
|
}
|
|
}
|
|
|
|
/* if we get it means a Nbits we dont have in our table so choke */
|
|
|
|
fprintf(stderr, "FreeDV::choose_interleaver_b: Nbits not in table return 0 as default");
|
|
return 0;
|
|
}
|
|
|
|
|
|
void gp_interleave_comp(COMP interleaved_frame[], COMP frame[], int Nbits) {
|
|
int b = choose_interleaver_b(Nbits);
|
|
int i,j;
|
|
for (i=0; i<Nbits; i++) {
|
|
j = (b*i) % Nbits;
|
|
interleaved_frame[j] = frame[i];
|
|
}
|
|
}
|
|
|
|
void gp_deinterleave_comp(COMP frame[], COMP interleaved_frame[], int Nbits) {
|
|
int b = choose_interleaver_b(Nbits);
|
|
int i,j;
|
|
for (i=0; i<Nbits; i++) {
|
|
j = (b*i) % Nbits;
|
|
frame[i] = interleaved_frame[j];
|
|
}
|
|
}
|
|
|
|
void gp_interleave_float(float interleaved_frame[], float frame[], int Nbits) {
|
|
int b = choose_interleaver_b(Nbits);
|
|
int i,j;
|
|
|
|
for (i=0; i<Nbits; i++) {
|
|
j = (b*i) % Nbits;
|
|
interleaved_frame[j] = frame[i];
|
|
}
|
|
}
|
|
|
|
void gp_deinterleave_float(float frame[], float interleaved_frame[], int Nbits) {
|
|
int b = choose_interleaver_b(Nbits);
|
|
int i,j;
|
|
|
|
for (i=0; i<Nbits; i++) {
|
|
j = (b*i) % Nbits;
|
|
frame[i] = interleaved_frame[j];
|
|
}
|
|
}
|
|
|
|
} // FreeDV
|