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V.29 and V.17 now use the Godard TED module, and their internal Godar…
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…d TED code has been removed.o
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coppice-git committed Mar 28, 2024
1 parent 39cd63d commit 933d40d
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Showing 10 changed files with 42 additions and 284 deletions.
2 changes: 2 additions & 0 deletions src/fax.c
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Expand Up @@ -73,6 +73,7 @@
#include "spandsp/fsk.h"
#include "spandsp/modem_connect_tones.h"
#include "spandsp/v8.h"
#include "spandsp/godard.h"
#include "spandsp/v29tx.h"
#include "spandsp/v29rx.h"
#include "spandsp/v27ter_tx.h"
Expand Down Expand Up @@ -111,6 +112,7 @@
#include "spandsp/private/fsk.h"
#include "spandsp/private/modem_connect_tones.h"
#include "spandsp/private/v8.h"
#include "spandsp/private/godard.h"
#if defined(SPANDSP_SUPPORT_V34)
#include "spandsp/private/bitstream.h"
#include "spandsp/private/v34.h"
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2 changes: 2 additions & 0 deletions src/fax_modems.c
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Expand Up @@ -69,6 +69,7 @@
#include "spandsp/hdlc.h"
#include "spandsp/silence_gen.h"
#include "spandsp/fsk.h"
#include "spandsp/godard.h"
#include "spandsp/v29tx.h"
#include "spandsp/v29rx.h"
#include "spandsp/v27ter_tx.h"
Expand All @@ -88,6 +89,7 @@
#include "spandsp/private/power_meter.h"
#include "spandsp/private/modem_echo.h"
#include "spandsp/private/fsk.h"
#include "spandsp/private/godard.h"
#if defined(SPANDSP_SUPPORT_V34)
#include "spandsp/private/v34.h"
#endif
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10 changes: 5 additions & 5 deletions src/make_modem_godard_descriptor.c
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@@ -1,10 +1,10 @@
/*
* SpanDSP - a series of DSP components for telephony
*
* make_modem_godard_coefficients.c - Create coefficient sets for Godard
* symbol sync. filters as a pair of
* fixed and floating point descriptor
* structures for spandsp.
* make_modem_godard_descriptor.c - Create coefficient sets for Godard
* symbol sync. filters as a pair of
* fixed and floating point descriptor
* structures for spandsp.
*
* Written by Steve Underwood <steveu@coppice.org>
*
Expand Down Expand Up @@ -154,7 +154,7 @@ int main(int argc, char **argv)
printf(" FILE MAY BE OVERWRITTEN DURING FUTURE BUILDS OF THE SOFTWARE */\n");
printf("\n");
printf("\n");
printf("static const godard_timing_sync_descriptor_t godard_desc =\n");
printf("static const godard_ted_descriptor_t godard_desc =\n");
printf("{\n");
printf(" /* %.1f samples/second , %.1fHz carrier, %.1f baud, %.3f alpha */\n",
sample_rate,
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24 changes: 2 additions & 22 deletions src/spandsp/private/v17rx.h
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Expand Up @@ -86,15 +86,6 @@ struct v17_rx_state_s
/*! \brief The equalizer signal buffer. */
complexi16_t eq_buf[V17_EQUALIZER_LEN];

/*! Low band edge filter for symbol sync. */
int32_t symbol_sync_low[2];
/*! High band edge filter for symbol sync. */
int32_t symbol_sync_high[2];
/*! DC filter for symbol sync. */
int32_t symbol_sync_dc_filter[2];
/*! Baud phase for symbol sync. */
int32_t baud_phase;

/*! \brief A measure of how much mismatch there is between the real constellation,
and the decoded symbol positions. */
int64_t training_error;
Expand Down Expand Up @@ -123,15 +114,6 @@ struct v17_rx_state_s
/*! \brief The equalizer signal buffer. */
complexf_t eq_buf[V17_EQUALIZER_LEN];

/*! Low band edge filter for symbol sync. */
float symbol_sync_low[2];
/*! High band edge filter for symbol sync. */
float symbol_sync_high[2];
/*! DC filter for symbol sync. */
float symbol_sync_dc_filter[2];
/*! Baud phase for symbol sync. */
float baud_phase;

/*! \brief A measure of how much mismatch there is between the real constellation,
and the decoded symbol positions. */
float training_error;
Expand All @@ -146,6 +128,8 @@ struct v17_rx_state_s
/*! \brief A pointer to the current constellation. */
const complexf_t *constellation;
#endif
godard_ted_state_t godard;

/*! \brief Current offset into the RRC pulse shaping filter buffer. */
int rrc_filter_step;

Expand Down Expand Up @@ -197,10 +181,6 @@ struct v17_rx_state_s
/*! \brief The current half of the baud. */
int baud_half;

/*! \brief The total symbol timing correction since the carrier came up.
This is only for performance analysis purposes. */
int total_baud_timing_correction;

/*! \brief The previous symbol phase angles for the coarse carrier aquisition step. */
int32_t last_angles[2];
/*! \brief History list of phase angle differences for the coarse carrier aquisition step. */
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24 changes: 2 additions & 22 deletions src/spandsp/private/v29rx.h
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Expand Up @@ -76,15 +76,6 @@ struct v29_rx_state_s
/*! \brief The equalizer signal buffer. */
complexi16_t eq_buf[V29_EQUALIZER_LEN];

/*! Low band edge filter for symbol sync. */
int32_t symbol_sync_low[2];
/*! High band edge filter for symbol sync. */
int32_t symbol_sync_high[2];
/*! DC filter for symbol sync. */
int32_t symbol_sync_dc_filter[2];
/*! Baud phase for symbol sync. */
int32_t baud_phase;

/*! \brief A measure of how much mismatch there is between the real constellation,
and the decoded symbol positions. */
int32_t training_error;
Expand All @@ -110,15 +101,6 @@ struct v29_rx_state_s
/*! \brief The equalizer signal buffer. */
complexf_t eq_buf[V29_EQUALIZER_LEN];

/*! Low band edge filter for symbol sync. */
float symbol_sync_low[2];
/*! High band edge filter for symbol sync. */
float symbol_sync_high[2];
/*! DC filter for symbol sync. */
float symbol_sync_dc_filter[2];
/*! Baud phase for symbol sync. */
float baud_phase;

/*! \brief A measure of how much mismatch there is between the real constellation,
and the decoded symbol positions. */
float training_error;
Expand All @@ -130,6 +112,8 @@ struct v29_rx_state_s
/*! \brief The root raised cosine (RRC) pulse shaping filter buffer. */
float rrc_filter[V29_RX_FILTER_STEPS];
#endif
godard_ted_state_t godard;

/*! \brief Current offset into the RRC pulse shaping filter buffer. */
int rrc_filter_step;

Expand Down Expand Up @@ -180,10 +164,6 @@ struct v29_rx_state_s
/*! \brief The current half of the baud. */
int baud_half;

/*! \brief The total symbol timing correction since the carrier came up.
This is only for performance analysis purposes. */
int total_baud_timing_correction;

/*! \brief The previous symbol phase angles for the coarse carrier aquisition step. */
int32_t last_angles[2];
/*! \brief History list of phase angle differences for the coarse carrier aquisition step. */
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2 changes: 2 additions & 0 deletions src/t31.c
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Expand Up @@ -75,6 +75,7 @@
#include "spandsp/super_tone_rx.h"
#include "spandsp/fsk.h"
#include "spandsp/modem_connect_tones.h"
#include "spandsp/godard.h"
#include "spandsp/v8.h"
#include "spandsp/v29tx.h"
#include "spandsp/v29rx.h"
Expand Down Expand Up @@ -106,6 +107,7 @@
#include "spandsp/private/fsk.h"
#include "spandsp/private/modem_connect_tones.h"
#include "spandsp/private/v8.h"
#include "spandsp/private/godard.h"
#if defined(SPANDSP_SUPPORT_V34)
#include "spandsp/private/v34.h"
#endif
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2 changes: 2 additions & 0 deletions src/t38_gateway.c
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Expand Up @@ -72,6 +72,7 @@
#include "spandsp/ssl_fax.h"
#include "spandsp/silence_gen.h"
#include "spandsp/fsk.h"
#include "spandsp/godard.h"
#include "spandsp/v29tx.h"
#include "spandsp/v29rx.h"
#include "spandsp/v27ter_tx.h"
Expand Down Expand Up @@ -109,6 +110,7 @@
#include "spandsp/private/silence_gen.h"
#include "spandsp/private/power_meter.h"
#include "spandsp/private/fsk.h"
#include "spandsp/private/godard.h"
#if defined(SPANDSP_SUPPORT_V34)
#include "spandsp/private/bitstream.h"
#include "spandsp/private/v34.h"
Expand Down
119 changes: 8 additions & 111 deletions src/v17rx.c
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Expand Up @@ -68,12 +68,14 @@
#define SPANDSP_USE_FIXED_POINTx
#endif

#include "spandsp/godard.h"
#include "spandsp/v29rx.h"
#include "spandsp/v17tx.h"
#include "spandsp/v17rx.h"

#include "spandsp/private/logging.h"
#include "spandsp/private/power_meter.h"
#include "spandsp/private/godard.h"
#include "spandsp/private/v17rx.h"

#if defined(SPANDSP_USE_FIXED_POINTx)
Expand Down Expand Up @@ -101,6 +103,7 @@
#include "v17_v32bis_rx_rrc.h"
#include "v17_v32bis_tx_constellation_maps.h"
#include "v17_v32bis_rx_constellation_maps.h"
#include "v17_v32bis_rx_godard.h"

/*! The nominal frequency of the carrier, in Hertz */
#define CARRIER_NOMINAL_FREQ 1800.0f
Expand Down Expand Up @@ -128,23 +131,6 @@
/*! The 16 bit pattern used in the bridge section of the training sequence */
#define V17_BRIDGE_WORD 0x8880

/* Coefficients for the band edge symbol timing synchroniser (alpha = 0.99) */
/* low_edge = 2.0f*M_PI*(CARRIER_NOMINAL_FREQ - BAUD_RATE/2.0f)/SAMPLE_RATE; */
/* high_edge = 2.0f*M_PI*(CARRIER_NOMINAL_FREQ + BAUD_RATE/2.0f)/SAMPLE_RATE; */
#define SIN_LOW_BAND_EDGE 0.453990499f
#define COS_LOW_BAND_EDGE 0.891006542f
#define SIN_HIGH_BAND_EDGE 0.707106781f
#define COS_HIGH_BAND_EDGE -0.707106781f
#define ALPHA 0.99f

#define SYNC_LOW_BAND_EDGE_COEFF_0 FP_SYNC_SCALE(2.0f*ALPHA*COS_LOW_BAND_EDGE)
#define SYNC_LOW_BAND_EDGE_COEFF_1 FP_SYNC_SCALE(-ALPHA*ALPHA)
#define SYNC_LOW_BAND_EDGE_COEFF_2 FP_SYNC_SCALE(-ALPHA*SIN_LOW_BAND_EDGE)
#define SYNC_HIGH_BAND_EDGE_COEFF_0 FP_SYNC_SCALE(2.0f*ALPHA*COS_HIGH_BAND_EDGE)
#define SYNC_HIGH_BAND_EDGE_COEFF_1 FP_SYNC_SCALE(-ALPHA*ALPHA)
#define SYNC_HIGH_BAND_EDGE_COEFF_2 FP_SYNC_SCALE(-ALPHA*SIN_HIGH_BAND_EDGE)
#define SYNC_MIXED_EDGES_COEFF_3 FP_SYNC_SCALE(-ALPHA*ALPHA*(SIN_HIGH_BAND_EDGE*COS_LOW_BAND_EDGE - SIN_LOW_BAND_EDGE*COS_HIGH_BAND_EDGE))

enum
{
TRAINING_STAGE_NORMAL_OPERATION = 0,
Expand Down Expand Up @@ -182,7 +168,7 @@ SPAN_DECLARE(float) v17_rx_carrier_frequency(v17_rx_state_t *s)

SPAN_DECLARE(float) v17_rx_symbol_timing_correction(v17_rx_state_t *s)
{
return (float) s->total_baud_timing_correction/((float) RX_PULSESHAPER_COEFF_SETS*10.0f/3.0f);
return (float) godard_ted_correction(&s->godard)/((float) RX_PULSESHAPER_COEFF_SETS*10.0f/3.0f);
}
/*- End of function --------------------------------------------------------*/

Expand Down Expand Up @@ -603,65 +589,6 @@ static int decode_baud(v17_rx_state_t *s, complexf_t *z)
}
/*- End of function --------------------------------------------------------*/

static __inline__ void symbol_sync(v17_rx_state_t *s)
{
int i;
#if defined(SPANDSP_USE_FIXED_POINTx)
int32_t v;
int32_t p;
#else
float v;
float p;
#endif

/* This routine adapts the position of the half baud samples entering the equalizer. */

/* This symbol sync scheme is based on the technique first described by Dominique Godard in
Passband Timing Recovery in an All-Digital Modem Receiver
IEEE TRANSACTIONS ON COMMUNICATIONS, VOL. COM-26, NO. 5, MAY 1978 */

/* This is slightly rearranged from figure 3b of the Godard paper, as this saves a couple of
maths operations */
#if defined(SPANDSP_USE_FIXED_POINTx)
/* TODO: The scalings used here need more thorough evaluation, to see if overflows are possible. */
/* Cross correlate */
v = (((s->symbol_sync_low[1] >> (FP_SYNC_SHIFT_FACTOR/2))*(s->symbol_sync_high[0] >> (FP_SYNC_SHIFT_FACTOR/2))) >> 14)*SYNC_LOW_BAND_EDGE_COEFF_2
- (((s->symbol_sync_low[0] >> (FP_SYNC_SHIFT_FACTOR/2))*(s->symbol_sync_high[1] >> (FP_SYNC_SHIFT_FACTOR/2))) >> 14)*SYNC_HIGH_BAND_EDGE_COEFF_2
+ (((s->symbol_sync_low[1] >> (FP_SYNC_SHIFT_FACTOR/2))*(s->symbol_sync_high[1] >> (FP_SYNC_SHIFT_FACTOR/2))) >> 14)*SYNC_MIXED_EDGES_COEFF_3;
/* Filter away any DC component */
p = v - s->symbol_sync_dc_filter[1];
s->symbol_sync_dc_filter[1] = s->symbol_sync_dc_filter[0];
s->symbol_sync_dc_filter[0] = v;
/* A little integration will now filter away much of the HF noise */
s->baud_phase -= p;
v = labs(s->baud_phase);
#else
/* Cross correlate */
v = s->symbol_sync_low[1]*s->symbol_sync_high[0]*SYNC_LOW_BAND_EDGE_COEFF_2
- s->symbol_sync_low[0]*s->symbol_sync_high[1]*SYNC_HIGH_BAND_EDGE_COEFF_2
+ s->symbol_sync_low[1]*s->symbol_sync_high[1]*SYNC_MIXED_EDGES_COEFF_3;
/* Filter away any DC component */
p = v - s->symbol_sync_dc_filter[1];
s->symbol_sync_dc_filter[1] = s->symbol_sync_dc_filter[0];
s->symbol_sync_dc_filter[0] = v;
/* A little integration will now filter away much of the HF noise */
s->baud_phase -= p;
v = fabsf(s->baud_phase);
#endif
if (v > FP_SYNC_SCALE_32(100.0f))
{
i = (v > FP_SYNC_SCALE_32(1000.0f)) ? 15 : 1;
if (s->baud_phase < FP_SYNC_SCALE_32(0.0f))
i = -i;
/*endif*/
//printf("v = %10.5f %5d - %f %f %d\n", v, i, p, s->baud_phase, s->total_baud_timing_correction);
s->eq_put_step += i;
s->total_baud_timing_correction += i;
}
/*endif*/
}
/*- End of function --------------------------------------------------------*/

#if defined(SPANDSP_USE_FIXED_POINTx)
static void process_half_baud(v17_rx_state_t *s, const complexi16_t *sample)
#else
Expand Down Expand Up @@ -714,7 +641,7 @@ static void process_half_baud(v17_rx_state_t *s, const complexf_t *sample)
/*endif*/

/* Symbol timing synchronisation */
symbol_sync(s);
s->eq_put_step += godard_ted_per_baud(&s->godard);

z = equalizer_get(s);

Expand Down Expand Up @@ -1330,32 +1257,11 @@ SPAN_DECLARE(int) v17_rx(v17_rx_state_t *s, const int16_t amp[], int len)
#if defined(SPANDSP_USE_FIXED_POINTx)
v = vec_circular_dot_prodi16(s->rrc_filter, rx_pulseshaper_re[step], V17_RX_FILTER_STEPS, s->rrc_filter_step) >> 15;
sample.re = (v*s->agc_scaling) >> 10;
/* Symbol timing synchronisation band edge filters */
/* Low Nyquist band edge filter */
v = ((s->symbol_sync_low[0]*SYNC_LOW_BAND_EDGE_COEFF_0) >> FP_SYNC_SHIFT_FACTOR)
+ ((s->symbol_sync_low[1]*SYNC_LOW_BAND_EDGE_COEFF_1) >> FP_SYNC_SHIFT_FACTOR)
+ sample.re;
s->symbol_sync_low[1] = s->symbol_sync_low[0];
s->symbol_sync_low[0] = v;
/* High Nyquist band edge filter */
v = ((s->symbol_sync_high[0]*SYNC_HIGH_BAND_EDGE_COEFF_0) >> FP_SYNC_SHIFT_FACTOR)
+ ((s->symbol_sync_high[1]*SYNC_HIGH_BAND_EDGE_COEFF_1) >> FP_SYNC_SHIFT_FACTOR)
+ sample.re;
s->symbol_sync_high[1] = s->symbol_sync_high[0];
s->symbol_sync_high[0] = v;
#else
v = vec_circular_dot_prodf(s->rrc_filter, rx_pulseshaper_re[step], V17_RX_FILTER_STEPS, s->rrc_filter_step);
sample.re = v*s->agc_scaling;
/* Symbol timing synchronisation band edge filters */
/* Low Nyquist band edge filter */
v = s->symbol_sync_low[0]*SYNC_LOW_BAND_EDGE_COEFF_0 + s->symbol_sync_low[1]*SYNC_LOW_BAND_EDGE_COEFF_1 + sample.re;
s->symbol_sync_low[1] = s->symbol_sync_low[0];
s->symbol_sync_low[0] = v;
/* High Nyquist band edge filter */
v = s->symbol_sync_high[0]*SYNC_HIGH_BAND_EDGE_COEFF_0 + s->symbol_sync_high[1]*SYNC_HIGH_BAND_EDGE_COEFF_1 + sample.re;
s->symbol_sync_high[1] = s->symbol_sync_high[0];
s->symbol_sync_high[0] = v;
#endif
godard_ted_rx(&s->godard, sample.re);
/* Put things into the equalization buffer at T/2 rate. The symbol synchronisation
will fiddle the step to align this with the symbols. */
if (s->eq_put_step <= 0)
Expand Down Expand Up @@ -1569,18 +1475,9 @@ SPAN_DECLARE(int) v17_rx_restart(v17_rx_state_t *s, int bit_rate, int short_trai
span_log(&s->logging, SPAN_LOG_FLOW, "Gains %f %f\n", (float) s->agc_scaling_save, (float) s->agc_scaling);
span_log(&s->logging, SPAN_LOG_FLOW, "Phase rates %f %f\n", dds_frequencyf(s->carrier_phase_rate), dds_frequencyf(s->carrier_phase_rate_save));

/* Initialise the working data for symbol timing synchronisation */
for (i = 0; i < 2; i++)
{
s->symbol_sync_low[i] = FP_SCALE(0.0f);
s->symbol_sync_high[i] = FP_SCALE(0.0f);
s->symbol_sync_dc_filter[i] = FP_SCALE(0.0f);
}
/*endfor*/
s->baud_phase = FP_SCALE(0.0f);
s->baud_half = 0;
godard_ted_init(&s->godard, &godard_desc);

s->total_baud_timing_correction = 0;
s->baud_half = 0;

return 0;
}
Expand Down
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