buildroot/package/spandsp/0002-Changes-to-address-V.17-fixed-point-issue.patch

From 239bf2f6a80bbfb6ef92418ceb5402d1fb256a2b Mon Sep 17 00:00:00 2001
From: Steve Underwood <steveu@coppice.org>
Date: Fri, 18 Aug 2023 01:24:21 +0100
Subject: [PATCH] Changes to address V.17 fixed point issue.

Upstream: https://github.com/freeswitch/spandsp/commit/239bf2f6a80bbfb6ef92418ceb5402d1fb256a2b

Signed-off-by: Bernd Kuhls <bernd@kuhls.net>
---
 src/spandsp/private/v17rx.h |  2 +-
 src/v17rx.c                 | 30 +++++++++++++++++++-----------
 2 files changed, 20 insertions(+), 12 deletions(-)

diff --git a/src/spandsp/private/v17rx.h b/src/spandsp/private/v17rx.h
index 8ea7a9fe..8613b5a5 100644
--- a/src/spandsp/private/v17rx.h
+++ b/src/spandsp/private/v17rx.h
@@ -97,7 +97,7 @@ struct v17_rx_state_s
 
     /*! \brief A measure of how much mismatch there is between the real constellation,
         and the decoded symbol positions. */
-    int32_t training_error;
+    int64_t training_error;
 
     /*! \brief The proportional part of the carrier tracking filter. */
     int32_t carrier_track_p;
diff --git a/src/v17rx.c b/src/v17rx.c
index a823dad2..295d26a9 100644
--- a/src/v17rx.c
+++ b/src/v17rx.c
@@ -64,6 +64,10 @@
 #include "spandsp/dds.h"
 #include "spandsp/complex_filters.h"
 
+#if defined(SPANDSP_USE_FIXED_POINT)
+#define SPANDSP_USE_FIXED_POINTx
+#endif
+
 #include "spandsp/v29rx.h"
 #include "spandsp/v17tx.h"
 #include "spandsp/v17rx.h"
@@ -389,7 +393,7 @@ static __inline__ void put_bit(v17_rx_state_t *s, int bit)
 /*- End of function --------------------------------------------------------*/
 
 #if defined(SPANDSP_USE_FIXED_POINTx)
-static __inline__ uint32_t dist_sq(const complexi16_t *x, const complexi16_t *y)
+static __inline__ uint32_t dist_sq(const complexi32_t *x, const complexi32_t *y)
 {
     return (int32_t) (x->re - y->re)*(x->re - y->re) + (int32_t) (x->im - y->im)*(x->im - y->im);
 }
@@ -954,11 +958,12 @@ static void process_half_baud(v17_rx_state_t *s, const complexf_t *sample)
         else if (s->training_count >= V17_TRAINING_SEG_2_LEN)
         {
 #if defined(SPANDSP_USE_FIXED_POINTx)
-            span_log(&s->logging, SPAN_LOG_FLOW, "Long training error %d\n", s->training_error);
+            span_log(&s->logging, SPAN_LOG_FLOW, "Long training error %ld\n", s->training_error);
+            if (s->training_error < (int64_t) FP_SCALE(20.0f)*FP_SCALE(1.414f)*constellation_spacing[s->space_map])
 #else
             span_log(&s->logging, SPAN_LOG_FLOW, "Long training error %f\n", s->training_error);
-#endif
             if (s->training_error < FP_SCALE(20.0f)*FP_SCALE(1.414f)*constellation_spacing[s->space_map])
+#endif
             {
                 s->training_error = FP_SCALE(0.0f);
                 s->training_count = 0;
@@ -1055,19 +1060,20 @@ static void process_half_baud(v17_rx_state_t *s, const complexf_t *sample)
         /*endif*/
         if (++s->training_count >= V17_TRAINING_SHORT_SEG_2_LEN)
         {
+            /* TODO: This was increased by a factor of 10 after studying real world failures.
+                     However, it is not clear why this is an improvement, If something gives
+                     a huge training error, surely it shouldn't decode too well? */
 #if defined(SPANDSP_USE_FIXED_POINTx)
             span_log(&s->logging, SPAN_LOG_FLOW, "Short training error %d\n", s->training_error);
             s->carrier_track_i = 100;
             s->carrier_track_p = 500000;
+            if (s->training_error < (int64_t) (V17_TRAINING_SHORT_SEG_2_LEN - 8)*FP_SCALE(4.0f)*FP_SCALE(1.0f)*constellation_spacing[s->space_map])
 #else
             span_log(&s->logging, SPAN_LOG_FLOW, "Short training error %f\n", s->training_error);
             s->carrier_track_i = 100.0f;
             s->carrier_track_p = 500000.0f;
-#endif
-            /* TODO: This was increased by a factor of 10 after studying real world failures.
-                     However, it is not clear why this is an improvement, If something gives
-                     a huge training error, surely it shouldn't decode too well? */
             if (s->training_error < (V17_TRAINING_SHORT_SEG_2_LEN - 8)*FP_SCALE(4.0f)*FP_SCALE(1.0f)*constellation_spacing[s->space_map])
+#endif
             {
                 s->training_count = 0;
                 if (s->bits_per_symbol == 2)
@@ -1136,11 +1142,13 @@ static void process_half_baud(v17_rx_state_t *s, const complexf_t *sample)
 #endif
         if (++s->training_count >= V17_TRAINING_SEG_4_LEN)
         {
-            if (s->training_error < V17_TRAINING_SEG_4_LEN*FP_SCALE(1.0f)*FP_SCALE(1.0f)*constellation_spacing[s->space_map])
-            {
 #if defined(SPANDSP_USE_FIXED_POINTx)
-                span_log(&s->logging, SPAN_LOG_FLOW, "Training succeeded at %dbps (constellation mismatch %d)\n", s->bit_rate, s->training_error);
+            if (s->training_error < (int64_t) V17_TRAINING_SEG_4_LEN*FP_SCALE(1.0f)*FP_SCALE(1.0f)*constellation_spacing[s->space_map])
+            {
+                span_log(&s->logging, SPAN_LOG_FLOW, "Training succeeded at %dbps (constellation mismatch %ld)\n", s->bit_rate, s->training_error);
 #else
+            if (s->training_error < V17_TRAINING_SEG_4_LEN*FP_SCALE(1.0f)*FP_SCALE(1.0f)*constellation_spacing[s->space_map])
+            {
                 span_log(&s->logging, SPAN_LOG_FLOW, "Training succeeded at %dbps (constellation mismatch %f)\n", s->bit_rate, s->training_error);
 #endif
                 /* We are up and running */
@@ -1157,7 +1165,7 @@ static void process_half_baud(v17_rx_state_t *s, const complexf_t *sample)
             {
                 /* Training has failed. Park this modem. */
 #if defined(SPANDSP_USE_FIXED_POINTx)
-                span_log(&s->logging, SPAN_LOG_FLOW, "Training failed (constellation mismatch %d)\n", s->training_error);
+                span_log(&s->logging, SPAN_LOG_FLOW, "Training failed (constellation mismatch %ld)\n", s->training_error);
 #else
                 span_log(&s->logging, SPAN_LOG_FLOW, "Training failed (constellation mismatch %f)\n", s->training_error);
 #endif