kopia lustrzana https://github.com/f4exb/sdrangel
294 wiersze
6.9 KiB
C
294 wiersze
6.9 KiB
C
/* descramble.h */
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// Functions for processing the radio-header:
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// descramble
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// deinterleave
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// FECdecoder
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// (C) 2011 Jonathan Naylor G4KLX
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/*
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* This program is free software; you can redistribute it and/or modify
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* it under the terms of the GNU General Public License as published by
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* the Free Software Foundation; version 2 of the License.
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*
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* This program 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
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* GNU General Public License for more details.
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*/
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// This code was originally written by JOnathan Naylor, G4KLX, as part
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// of the "pcrepeatercontroller" project
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// More info:
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// http://groups.yahoo.com/group/pcrepeatercontroller
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// Changes:
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// Convert C++ to C
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// Version 20111106: initial release
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#include <stdio.h>
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#include <string.h>
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// function traceBack
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int traceBack (int * out, int * m_pathMemory0, int * m_pathMemory1, int * m_pathMemory2, int * m_pathMemory3) {
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enum FEC_STATE { S0, S1, S2, S3 } state;
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int loop;
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int length=0;
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state=S0;
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for (loop=329; loop >= 0; loop--, length++) {
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switch (state) {
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case S0: // if state S0
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if (m_pathMemory0[loop]) {
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state = S2; // lower path
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} else {
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state = S0; // upper path
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}; // end else - if
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out[loop]=0;
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break;
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case S1: // if state S1
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if (m_pathMemory1[loop]) {
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state = S2; // lower path
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} else {
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state = S0; // upper path
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}; // end else - if
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out[loop]=1;
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break;
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case S2: // if state S2
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if (m_pathMemory2[loop]) {
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state = S3; // lower path
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} else {
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state = S1; // upper path
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}; // end else - if
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out[loop]=0;
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break;
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case S3: // if state S3
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if (m_pathMemory3[loop]) {
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state = S3; // lower path
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} else {
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state = S1; // upper path
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}; // end else - if
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out[loop]=1;
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break;
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}; // end switch
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}; // end for
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return(length);
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}; // end function
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// function viterbiDecode
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void viterbiDecode (int n, int *data, int *m_pathMemory0, int *m_pathMemory1, int *m_pathMemory2, int *m_pathMemory3, int *m_pathMetric) {
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int tempMetric[4];
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int metric[8];
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int loop;
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int m1;
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int m2;
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metric[0]=(data[1]^0)+(data[0]^0);
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metric[1]=(data[1]^1)+(data[0]^1);
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metric[2]=(data[1]^1)+(data[0]^0);
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metric[3]=(data[1]^0)+(data[0]^1);
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metric[4]=(data[1]^1)+(data[0]^1);
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metric[5]=(data[1]^0)+(data[0]^0);
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metric[6]=(data[1]^0)+(data[0]^1);
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metric[7]=(data[1]^1)+(data[0]^0);
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// Pres. state = S0, Prev. state = S0 & S2
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m1=metric[0]+m_pathMetric[0];
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m2=metric[4]+m_pathMetric[2];
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if (m1<m2) {
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m_pathMemory0[n]=0;
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tempMetric[0]=m1;
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} else {
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m_pathMemory0[n]=1;
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tempMetric[0]=m2;
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}; // end else - if
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// Pres. state = S1, Prev. state = S0 & S2
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m1=metric[1]+m_pathMetric[0];
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m2=metric[5]+m_pathMetric[2];
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if (m1<m2) {
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m_pathMemory1[n]=0;
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tempMetric[1]=m1;
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} else {
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m_pathMemory1[n]=1;
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tempMetric[1]=m2;
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}; // end else - if
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// Pres. state = S2, Prev. state = S2 & S3
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m1=metric[2]+m_pathMetric[1];
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m2=metric[6]+m_pathMetric[3];
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if (m1<m2) {
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m_pathMemory2[n]=0;
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tempMetric[2]=m1;
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} else {
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m_pathMemory2[n]=1;
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tempMetric[2]=m2;
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}
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// Pres. state = S3, Prev. state = S1 & S3
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m1=metric[3]+m_pathMetric[1];
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m2=metric[7]+m_pathMetric[3];
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if (m1 < m2) {
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m_pathMemory3[n]=0;
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tempMetric[3]=m1;
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} else {
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m_pathMemory3[n]=1;
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tempMetric[3]=m2;
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}; // end else - if
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for (loop=0;loop<4;loop++) {
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m_pathMetric[loop]=tempMetric[loop];
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}; // end for
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}; // end function ViterbiDecode
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// function FECdecoder
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// returns outlen
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int FECdecoder (int * in, int * out) {
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int outLen;
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int m_pathMemory0[330]; memset(m_pathMemory0,0,330*sizeof(int));
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int m_pathMemory1[330]; memset(m_pathMemory1,0,330*sizeof(int));
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int m_pathMemory2[330]; memset(m_pathMemory2,0,330*sizeof(int));
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int m_pathMemory3[330]; memset(m_pathMemory3,0,330*sizeof(int));
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int m_pathMetric[4];
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int loop,loop2;
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int n=0;
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for (loop=0;loop<4;loop++) {
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m_pathMetric[loop]=0;
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}; // end for
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for (loop2=0;loop2<660;loop2+=2, n++) {
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int data[2];
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if (in[loop2]) {
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data[1]=1;
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} else {
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data[1]=0;
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}; // end else - if
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if (in[loop2+1]) {
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data[0]=1;
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} else {
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data[0]=0;
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}; // end else - if
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viterbiDecode(n, data, m_pathMemory0, m_pathMemory1, m_pathMemory2, m_pathMemory3, m_pathMetric);
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}; // end for
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outLen=traceBack(out, m_pathMemory0, m_pathMemory1, m_pathMemory2, m_pathMemory3);
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// Swap endian-ness
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// code removed (done converting bits into octets), done in main program
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//for (loop=0;loop<330;loop+=8) {
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// int temp;
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// temp=out[loop];out[loop]=out[loop+7];out[loop+7]=temp;
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// temp=out[loop+1];out[loop+1]=out[loop+6];out[loop+6]=temp;
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// temp=out[loop+2];out[loop+2]=out[loop+5];out[loop+5]=temp;
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// temp=out[loop+3];out[loop+3]=out[loop+4];out[loop+4]=temp;
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//}
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return(outLen);
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}; // end function FECdecoder
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// function deinterleave
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void deinterleave (int * in, int * out) {
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int k=0;
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int loop=0;
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// function starts here
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// init vars
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k=0;
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for (loop=0;loop<660;loop++) {
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out[k]=in[loop];
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k += 24;
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if (k >= 672) {
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k -= 671;
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} else if (k >= 660) {
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k -= 647;
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}; // end elsif - if
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}; // end for
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}; // end function deinterleave
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/// function scramble
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void scramble (int * in,int * out) {
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static const int SCRAMBLER_TABLE_BITS[] = {
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0,0,0,0,1,1,1,0,1,1,1,1,0,0,1,0,1,1,0,0,1,0,0,1,0,0,0,0,0,0,1,0,
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0,0,1,0,0,1,1,0,0,0,1,0,1,1,1,0,1,0,1,1,0,1,1,0,0,0,0,0,1,1,0,0,
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1,1,0,1,0,1,0,0,1,1,1,0,0,1,1,1,1,0,1,1,0,1,0,0,0,0,1,0,1,0,1,0,
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1,1,1,1,1,0,1,0,0,1,0,1,0,0,0,1,1,0,1,1,1,0,0,0,1,1,1,1,1,1,1,0,
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0,0,0,1,1,1,0,1,1,1,1,0,0,1,0,1,1,0,0,1,0,0,1,0,0,0,0,0,0,1,0,0,
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0,1,0,0,1,1,0,0,0,1,0,1,1,1,0,1,0,1,1,0,1,1,0,0,0,0,0,1,1,0,0,1,
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1,0,1,0,1,0,0,1,1,1,0,0,1,1,1,1,0,1,1,0,1,0,0,0,0,1,0,1,0,1,0,1,
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1,1,1,1,0,1,0,0,1,0,1,0,0,0,1,1,0,1,1,1,0,0,0,1,1,1,1,1,1,1,0,0,
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0,0,1,1,1,0,1,1,1,1,0,0,1,0,1,1,0,0,1,0,0,1,0,0,0,0,0,0,1,0,0,0,
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1,0,0,1,1,0,0,0,1,0,1,1,1,0,1,0,1,1,0,1,1,0,0,0,0,0,1,1,0,0,1,1,
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0,1,0,1,0,0,1,1,1,0,0,1,1,1,1,0,1,1,0,1,0,0,0,0,1,0,1,0,1,0,1,1,
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1,1,1,0,1,0,0,1,0,1,0,0,0,1,1,0,1,1,1,0,0,0,1,1,1,1,1,1,1,0,0,0,
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0,1,1,1,0,1,1,1,1,0,0,1,0,1,1,0,0,1,0,0,1,0,0,0,0,0,0,1,0,0,0,1,
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0,0,1,1,0,0,0,1,0,1,1,1,0,1,0,1,1,0,1,1,0,0,0,0,0,1,1,0,0,1,1,0,
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1,0,1,0,0,1,1,1,0,0,1,1,1,1,0,1,1,0,1,0,0,0,0,1,0,1,0,1,0,1,1,1,
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1,1,0,1,0,0,1,0,1,0,0,0,1,1,0,1,1,1,0,0,0,1,1,1,1,1,1,1,0,0,0,0,
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1,1,1,0,1,1,1,1,0,0,1,0,1,1,0,0,1,0,0,1,0,0,0,0,0,0,1,0,0,0,1,0,
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0,1,1,0,0,0,1,0,1,1,1,0,1,0,1,1,0,1,1,0,0,0,0,0,1,1,0,0,1,1,0,1,
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0,1,0,0,1,1,1,0,0,1,1,1,1,0,1,1,0,1,0,0,0,0,1,0,1,0,1,0,1,1,1,1,
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1,0,1,0,0,1,0,1,0,0,0,1,1,0,1,1,1,0,0,0,1,1,1,1,1,1,1,0,0,0,0,1,
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1,1,0,1,1,1,1,0,0,1,0,1,1,0,0,1,0,0,1,0,0,0,0,0,0,1,0,0,0,1,0,0,
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1,1,0,0,0,1,0,1,1,1,0,1,0,1,1,0,1,1,0,0,0,0,0,1,1,0,0,1,1,0,1,0,
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1,0,0,1,1,1,0,0,1,1,1,1,0,1,1,0};
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const int SCRAMBLER_TABLE_BITS_LENGTH=720;
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int loop=0;
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int m_count=0;
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for (loop=0; loop < 660; loop++) {
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out[loop] = in[loop] ^ SCRAMBLER_TABLE_BITS[m_count++];
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if (m_count >= SCRAMBLER_TABLE_BITS_LENGTH) {
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m_count = 0U;
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}; // end if
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}; // end for
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}; // end function scramble
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