From 0145d2642d38ff651690ac40cd823b663265401f Mon Sep 17 00:00:00 2001
From: drowe67 <drowe67@01035d8c-6547-0410-b346-abe4f91aad63>
Date: Tue, 19 Mar 2013 23:10:23 +0000
Subject: [PATCH] prototype more reliable sync

git-svn-id: https://svn.code.sf.net/p/freetel/code@1217 01035d8c-6547-0410-b346-abe4f91aad63
---
 codec2-dev/src/codec2_fdmdv.h   |  2 +-
 codec2-dev/src/fdmdv.c          | 14 ++++---
 codec2-dev/src/fdmdv_demod.c    | 71 ++++++++++++++-------------------
 codec2-dev/src/fdmdv_internal.h |  2 +-
 4 files changed, 41 insertions(+), 48 deletions(-)

diff --git a/codec2-dev/src/codec2_fdmdv.h b/codec2-dev/src/codec2_fdmdv.h
index e0e8abb7..1d9db7d2 100644
--- a/codec2-dev/src/codec2_fdmdv.h
+++ b/codec2-dev/src/codec2_fdmdv.h
@@ -96,7 +96,7 @@ void           CODEC2_WIN32SUPPORT fdmdv_use_old_qpsk_mapping(struct FDMDV *fdmd
 int            CODEC2_WIN32SUPPORT fdmdv_bits_per_frame(struct FDMDV *fdmdv_state);
     
 void           CODEC2_WIN32SUPPORT fdmdv_mod(struct FDMDV *fdmdv_state, COMP tx_fdm[], int tx_bits[], int *sync_bit);
-void           CODEC2_WIN32SUPPORT fdmdv_demod(struct FDMDV *fdmdv_state, int rx_bits[], int *sync_bit, COMP rx_fdm[], int *nin);
+void           CODEC2_WIN32SUPPORT fdmdv_demod(struct FDMDV *fdmdv_state, int rx_bits[], int *reliable_sync_bit, COMP rx_fdm[], int *nin);
     
 void           CODEC2_WIN32SUPPORT fdmdv_get_test_bits(struct FDMDV *fdmdv_state, int tx_bits[]);
 int            CODEC2_WIN32SUPPORT fdmdv_error_pattern_size(struct FDMDV *fdmdv_state);
diff --git a/codec2-dev/src/fdmdv.c b/codec2-dev/src/fdmdv.c
index 2ca7d7e0..b1e76fa5 100644
--- a/codec2-dev/src/fdmdv.c
+++ b/codec2-dev/src/fdmdv.c
@@ -1183,11 +1183,11 @@ void CODEC2_WIN32SUPPORT fdmdv_put_test_bits(struct FDMDV *f, int *sync, short e
 
 \*---------------------------------------------------------------------------*/
 
-int freq_state(int sync_bit, int *state, int *timer, int *sync_mem)
+int freq_state(int *reliable_sync_bit, int sync_bit, int *state, int *timer, int *sync_mem)
 {
     int next_state, sync, unique_word, i, corr;
 
-    /* look for 6 symbols (120ms) 010101 of sync sequence */
+    /* look for 6 symbols (120ms) 101010 of sync sequence */
 
     unique_word = 0;
     for(i=0; i<NSYNC_MEM-1; i++)
@@ -1198,6 +1198,7 @@ int freq_state(int sync_bit, int *state, int *timer, int *sync_mem)
         corr += sync_mem[i]*sync_uw[i];
     if (abs(corr) == NSYNC_MEM)
         unique_word = 1;
+    *reliable_sync_bit = (corr == NSYNC_MEM);
 
     /* iterate state machine */
 
@@ -1266,7 +1267,7 @@ int freq_state(int sync_bit, int *state, int *timer, int *sync_mem)
 \*---------------------------------------------------------------------------*/
 
 void CODEC2_WIN32SUPPORT fdmdv_demod(struct FDMDV *fdmdv, int rx_bits[], 
-				     int *sync_bit, COMP rx_fdm[], int *nin)
+				     int *reliable_sync_bit, COMP rx_fdm[], int *nin)
 {
     float         foff_coarse, foff_fine;
     COMP          rx_fdm_fcorr[M+M/P];
@@ -1274,7 +1275,8 @@ void CODEC2_WIN32SUPPORT fdmdv_demod(struct FDMDV *fdmdv, int rx_bits[],
     COMP          rx_filt[NC+1][P+1];
     COMP          rx_symbols[NC+1];
     float         env[NT*P];
- 
+    int           sync_bit;
+
     /* freq offset estimation and correction */
    
     foff_coarse = rx_est_freq_offset(fdmdv, rx_fdm, *nin);
@@ -1299,14 +1301,14 @@ void CODEC2_WIN32SUPPORT fdmdv_demod(struct FDMDV *fdmdv, int rx_bits[],
     if (fdmdv->rx_timing < 0)
 	*nin -= M/P;
     
-    foff_fine = qpsk_to_bits(rx_bits, sync_bit, fdmdv->Nc, fdmdv->phase_difference, fdmdv->prev_rx_symbols, rx_symbols, 
+    foff_fine = qpsk_to_bits(rx_bits, &sync_bit, fdmdv->Nc, fdmdv->phase_difference, fdmdv->prev_rx_symbols, rx_symbols, 
                              fdmdv->old_qpsk_mapping);
     memcpy(fdmdv->prev_rx_symbols, rx_symbols, sizeof(COMP)*(fdmdv->Nc+1));
     snr_update(fdmdv->sig_est, fdmdv->noise_est, fdmdv->Nc, fdmdv->phase_difference);
 
     /* freq offset estimation state machine */
 
-    fdmdv->sync = freq_state(*sync_bit, &fdmdv->fest_state, &fdmdv->timer, fdmdv->sync_mem);
+    fdmdv->sync = freq_state(reliable_sync_bit, sync_bit, &fdmdv->fest_state, &fdmdv->timer, fdmdv->sync_mem);
     fdmdv->foff  -= TRACK_COEFF*foff_fine;
 }
 
diff --git a/codec2-dev/src/fdmdv_demod.c b/codec2-dev/src/fdmdv_demod.c
index fd47050f..5783279f 100644
--- a/codec2-dev/src/fdmdv_demod.c
+++ b/codec2-dev/src/fdmdv_demod.c
@@ -58,8 +58,8 @@ int main(int argc, char *argv[])
     short         rx_fdm_scaled[FDMDV_MAX_SAMPLES_PER_FRAME];
     int           i, bit, byte, c;
     int           nin, nin_prev;
-    int           sync_bit;
-    int           state, next_state;
+    int           sync_bit, reliable_sync_bit;
+    int           sync;
     int           f;
     FILE         *foct = NULL;
     struct FDMDV_STATS stats;
@@ -136,7 +136,6 @@ int main(int argc, char *argv[])
     assert(rx_fdm_log != NULL);
 
     f = 0;
-    state = 0;
     nin = FDMDV_NOM_SAMPLES_PER_FRAME;
     rx_fdm_log_col_index = 0;
     max_frames_reached = 0;
@@ -148,7 +147,7 @@ int main(int argc, char *argv[])
             rx_fdm[i].imag = 0;
         }
 	nin_prev = nin;
-	fdmdv_demod(fdmdv, rx_bits, &sync_bit, rx_fdm, &nin);
+	fdmdv_demod(fdmdv, rx_bits, &reliable_sync_bit, rx_fdm, &nin);
 
 	/* log data for optional Octave dump */
 
@@ -179,43 +178,35 @@ int main(int argc, char *argv[])
 	    max_frames_reached = 1;
 	}
 
-	/* state machine to output codec bits only if we have a 0,1
-	   sync bit sequence */
+        if (reliable_sync_bit)
+            sync = 1;
+        //printf("sync_bit: %d reliable_sync_bit: %d sync: %d\n", sync_bit, reliable_sync_bit, sync);
 
-	next_state = state;
-	switch (state) {
-	case 0:
-	    if (sync_bit == 0) {
-		next_state = 1;
-		memcpy(codec_bits, rx_bits, bits_per_fdmdv_frame*sizeof(int));
-	    }
-	    else
-		next_state = 0;
-	    break;
-	case 1:
-	    if (sync_bit == 1) {
-		memcpy(&codec_bits[bits_per_fdmdv_frame], rx_bits, bits_per_fdmdv_frame*sizeof(int));
-
-		/* pack bits, MSB received first  */
-
-		bit = 7; byte = 0;
-		memset(packed_bits, 0, bytes_per_codec_frame);
-		for(i=0; i<bits_per_codec_frame; i++) {
-		    packed_bits[byte] |= (codec_bits[i] << bit);
-		    bit--;
-		    if (bit < 0) {
-			bit = 7;
-			byte++;
-		    }
-		}
-		assert(byte == bytes_per_codec_frame);
-
-		fwrite(packed_bits, sizeof(char), bytes_per_codec_frame, fout);
-	    }
-	    next_state = 0;
-	    break;
-	}	
-	state = next_state;
+        if (sync == 0) {
+            memcpy(codec_bits, rx_bits, bits_per_fdmdv_frame*sizeof(int));
+            sync = 1;
+        }
+        else {
+            memcpy(&codec_bits[bits_per_fdmdv_frame], rx_bits, bits_per_fdmdv_frame*sizeof(int));
+
+            /* pack bits, MSB received first  */
+
+            bit = 7; byte = 0;
+            memset(packed_bits, 0, bytes_per_codec_frame);
+            for(i=0; i<bits_per_codec_frame; i++) {
+                packed_bits[byte] |= (codec_bits[i] << bit);
+                bit--;
+                if (bit < 0) {
+                    bit = 7;
+                    byte++;
+                }
+            }
+            assert(byte == bytes_per_codec_frame);
+
+            fwrite(packed_bits, sizeof(char), bytes_per_codec_frame, fout);
+            sync = 0;
+        }
+           
 
 	/* if this is in a pipeline, we probably don't want the usual
 	   buffering to occur */
diff --git a/codec2-dev/src/fdmdv_internal.h b/codec2-dev/src/fdmdv_internal.h
index b4cf62ff..34ff7bde 100644
--- a/codec2-dev/src/fdmdv_internal.h
+++ b/codec2-dev/src/fdmdv_internal.h
@@ -169,7 +169,7 @@ float rx_est_timing(COMP  rx_symbols[], int Nc,
 		   int   nin);	 
 float qpsk_to_bits(int rx_bits[], int *sync_bit, int Nc, COMP phase_difference[], COMP prev_rx_symbols[], COMP rx_symbols[], int old_qpsk_mapping);
 void snr_update(float sig_est[], float noise_est[], int Nc, COMP phase_difference[]);
-int freq_state(int sync_bit, int *state, int *timer, int *sync_mem);
+int freq_state(int *reliable_sync_bit, int sync_bit, int *state, int *timer, int *sync_mem);
 float calc_snr(int Nc, float sig_est[], float noise_est[]);
 
 #endif
-- 
2.25.1