shallow zip-file copy from codec2 e9d726bf20

1 files changed, 166 insertions, 0 deletions

diff --git a/src/deframer.c b/src/deframer.c
new file mode 100644
index 0000000..013e069
--- /dev/null
+++ b/src/deframer.c
@@ -0,0 +1,166 @@
+/*---------------------------------------------------------------------------*\
+
+  FILE........: deframer.c
+  AUTHOR......: David Rowe
+  DATE CREATED: July 2020
+
+  Command line deframer, obtains UW sync, then extracts frame of data bits.
+
+\*---------------------------------------------------------------------------*/
+
+/*
+  Copyright (C) 2020 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 <stdlib.h>
+#include <string.h>
+#include "fsk.h"
+
+unsigned int toInt(char c)
+{
+  if (c >= '0' && c <= '9') return      c - '0';
+  if (c >= 'A' && c <= 'F') return 10 + c - 'A';
+  if (c >= 'a' && c <= 'f') return 10 + c - 'a';
+  return -1;
+}
+
+int main(int argc,char *argv[]){
+    FILE *fin, *fout;
+    
+    if (argc < 5) {
+        fprintf(stderr,"usage: %s InOneFloatPerLLR OutOneFloatPerLLR frameSizeBits HexUW [--hard]\n",argv[0]);
+        fprintf(stderr,"    --hard  Treat input and output files as OneBitPerByte hard decisions\n");
+                exit(1);
+    }
+
+    if (strcmp(argv[1],"-") == 0) {
+        fin = stdin;
+    } else {
+        if ((fin = fopen(argv[1],"rb")) == NULL) {
+            fprintf(stderr,"Couldn't open input file: %s\n", argv[1]);
+            exit(1);
+        }
+    }
+    
+    if (strcmp(argv[2],"-") == 0) {
+        fout = stdout;
+    } else {
+        if ((fout = fopen(argv[2],"wb")) == NULL) {
+            fprintf(stderr,"Couldn't open output file: %s\n", argv[2]);
+            exit(1);
+        }
+    }
+
+    /* extract UW array from hex on command line */
+    
+    size_t framesize = atoi(argv[3]);
+    char *uw_hex = argv[4];
+    uint8_t uw[4*strlen(uw_hex)];
+    int uwsize = 0;
+    for(int c=0; c<strlen(uw_hex); c++)
+        for(int i=0; i<4; i++)
+            uw[uwsize++] = (toInt(uw_hex[c]) >> (3-i)) & 0x1; /* MSB first */
+    assert(uwsize == 4*strlen(uw_hex));
+
+    fprintf(stderr, "uw_hex: %s uwsize: %d\n", uw_hex, uwsize);
+    for(int i=0; i<uwsize; i++)
+        fprintf(stderr,"%d ", uw[i]);
+    fprintf(stderr,"\n");
+
+    /* set up for LLRs or hard decision inputs */
+    
+    size_t framedsize = framesize+uwsize;
+    int oneBitPerByte = 0;
+    int nelement = sizeof(float);
+    if (argc == 6) {
+        oneBitPerByte = 1;
+        nelement = sizeof(uint8_t);
+    }
+    uint8_t *inbuf = malloc(2*nelement*framedsize);  assert(inbuf != NULL);
+    memset(inbuf, 0, 2*nelement*framedsize);
+    
+    /* main loop */
+
+    uint8_t twoframes[2*framedsize]; memset(twoframes, 0, 2*framedsize);
+    int state = 0; int thresh1 = 0.1*uwsize; int thresh2 = 0.4*uwsize; int baduw = 0;
+    fprintf(stderr, "thresh1: %d thresh2: %d\n", thresh1, thresh2);
+    int best_location, errors;
+    while(fread(&inbuf[nelement*framedsize], nelement, framedsize, fin) == framedsize) {
+
+        /* We need to maintain a two frame buffer of hard decision data for UW sync */
+        
+        if (oneBitPerByte) {
+            memcpy(&twoframes[framedsize], inbuf, framedsize);
+        } else {
+            /* convert bit LLRs to hard decisions */
+            for(int i=0; i<framedsize; i++) {
+                float *pllr = (float*)&inbuf[nelement*(framedsize+i)];
+                if (*pllr < 0)
+                    twoframes[framedsize+i] = 1;
+                else
+                    twoframes[framedsize+i] = 0;
+                //fprintf(stderr, "%d %f %d\n", i, *pllr, twoframes[framedsize+i]);
+            }
+        }
+        
+        int next_state = state;
+        switch(state) {
+        case 0:
+            /* out of sync - look for UW */
+            best_location = 0;
+            int best_errors = uwsize;
+            for(int i=0; i<framesize; i++) {
+                errors = 0;
+                for(int u=0; u<uwsize; u++)
+                    errors += twoframes[i+u] ^ uw[u];
+                //fprintf(stderr, "%d %d %d\n", i, errors, best_errors);
+                if (errors < best_errors) { best_errors = errors; best_location = i; }
+            }
+            if (best_errors <= thresh1) {
+                fprintf(stderr, "found UW!\n"); next_state = 1; baduw = 0;
+            }
+            break;
+        case 1:
+            /* in sync - check UW still OK */
+            errors = 0;
+            for(int u=0; u<uwsize; u++)
+                errors += twoframes[best_location+u] ^ uw[u];
+            if (errors >= thresh2) {
+                baduw++;
+                if (baduw == 3) {
+                    fprintf(stderr, "lost UW!\n"); next_state = 0;
+                }
+            }
+            else baduw = 0;
+            break;
+        }
+        state = next_state;
+        
+        if (state == 1) {
+            fwrite(&inbuf[(best_location+uwsize)*nelement], nelement, framesize, fout);
+        }
+        memmove(twoframes, &twoframes[framedsize], framedsize);
+        memmove(inbuf, &inbuf[nelement*framedsize], nelement*framedsize);
+    }
+
+    free(inbuf);
+    fclose(fin);
+    fclose(fout);
+
+    return 0;
+}