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freeswitch/libs/spandsp/src/v17tx.c

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/*
* SpanDSP - a series of DSP components for telephony
*
* v17tx.c - ITU V.17 modem transmit part
*
* Written by Steve Underwood <steveu@coppice.org>
*
* Copyright (C) 2004 Steve Underwood
*
* 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 Lesser 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, write to the Free Software
* Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.
*
* $Id: v17tx.c,v 1.72 2009/04/12 04:20:01 steveu Exp $
*/
/*! \file */
#if defined(HAVE_CONFIG_H)
#include "config.h"
#endif
#include <stdio.h>
#include <inttypes.h>
#include <stdlib.h>
#include <string.h>
#if defined(HAVE_TGMATH_H)
#include <tgmath.h>
#endif
#if defined(HAVE_MATH_H)
#include <math.h>
#endif
#include "floating_fudge.h"
#include "spandsp/telephony.h"
#include "spandsp/fast_convert.h"
#include "spandsp/logging.h"
#include "spandsp/complex.h"
#include "spandsp/vector_float.h"
#include "spandsp/complex_vector_float.h"
#include "spandsp/async.h"
#include "spandsp/dds.h"
#include "spandsp/power_meter.h"
#include "spandsp/v17tx.h"
#include "spandsp/private/logging.h"
#include "spandsp/private/v17tx.h"
#if defined(SPANDSP_USE_FIXED_POINT)
#define SPANDSP_USE_FIXED_POINTx
#endif
#include "v17tx_constellation_maps.h"
#if defined(SPANDSP_USE_FIXED_POINT)
#include "v17tx_fixed_rrc.h"
#else
#include "v17tx_floating_rrc.h"
#endif
/*! The nominal frequency of the carrier, in Hertz */
#define CARRIER_NOMINAL_FREQ 1800.0f
/* Segments of the training sequence */
/*! The start of the optional TEP, that may preceed the actual training, in symbols */
#define V17_TRAINING_SEG_TEP_A 0
/*! The mid point of the optional TEP, that may preceed the actual training, in symbols */
#define V17_TRAINING_SEG_TEP_B (V17_TRAINING_SEG_TEP_A + 480)
/*! The start of training segment 1, in symbols */
#define V17_TRAINING_SEG_1 (V17_TRAINING_SEG_TEP_B + 48)
/*! The start of training segment 2, in symbols */
#define V17_TRAINING_SEG_2 (V17_TRAINING_SEG_1 + 256)
/*! The start of training segment 3, in symbols */
#define V17_TRAINING_SEG_3 (V17_TRAINING_SEG_2 + 2976)
/*! The start of training segment 4, in symbols */
#define V17_TRAINING_SEG_4 (V17_TRAINING_SEG_3 + 64)
/*! The start of training segment 4 in short training mode, in symbols */
#define V17_TRAINING_SHORT_SEG_4 (V17_TRAINING_SEG_2 + 38)
/*! The end of the training, in symbols */
#define V17_TRAINING_END (V17_TRAINING_SEG_4 + 48)
#define V17_TRAINING_SHUTDOWN_A (V17_TRAINING_END + 32)
/*! The end of the shutdown sequence, in symbols */
#define V17_TRAINING_SHUTDOWN_END (V17_TRAINING_SHUTDOWN_A + 48)
/*! The 16 bit pattern used in the bridge section of the training sequence */
#define V17_BRIDGE_WORD 0x8880
static __inline__ int scramble(v17_tx_state_t *s, int in_bit)
{
int out_bit;
out_bit = (in_bit ^ (s->scramble_reg >> 17) ^ (s->scramble_reg >> 22)) & 1;
s->scramble_reg = (s->scramble_reg << 1) | out_bit;
return out_bit;
}
/*- End of function --------------------------------------------------------*/
#if defined(SPANDSP_USE_FIXED_POINT)
static __inline__ complexi16_t training_get(v17_tx_state_t *s)
#else
static __inline__ complexf_t training_get(v17_tx_state_t *s)
#endif
{
static const int cdba_to_abcd[4] =
{
2, 3, 1, 0
};
static const int dibit_to_step[4] =
{
1, 0, 2, 3
};
#if defined(SPANDSP_USE_FIXED_POINT)
static const complexi16_t zero = {0, 0};
#else
static const complexf_t zero = {0.0f, 0.0f};
#endif
int bits;
int shift;
if (++s->training_step <= V17_TRAINING_SEG_3)
{
if (s->training_step <= V17_TRAINING_SEG_2)
{
if (s->training_step <= V17_TRAINING_SEG_TEP_B)
{
/* Optional segment: Unmodulated carrier (talker echo protection) */
return v17_abcd_constellation[0];
}
if (s->training_step <= V17_TRAINING_SEG_1)
{
/* Optional segment: silence (talker echo protection) */
return zero;
}
/* Segment 1: ABAB... */
return v17_abcd_constellation[(s->training_step & 1) ^ 1];
}
/* Segment 2: CDBA... */
/* Apply the scrambler */
bits = scramble(s, 1);
bits = (bits << 1) | scramble(s, 1);
s->constellation_state = cdba_to_abcd[bits];
if (s->short_train && s->training_step == V17_TRAINING_SHORT_SEG_4)
{
/* Go straight to the ones test. */
s->training_step = V17_TRAINING_SEG_4;
}
return v17_abcd_constellation[s->constellation_state];
}
/* Segment 3: Bridge... */
shift = ((s->training_step - V17_TRAINING_SEG_3 - 1) & 0x7) << 1;
//span_log(&s->logging, SPAN_LOG_FLOW, "Seg 3 shift %d\n", shift);
bits = scramble(s, V17_BRIDGE_WORD >> shift);
bits = (bits << 1) | scramble(s, V17_BRIDGE_WORD >> (shift + 1));
s->constellation_state = (s->constellation_state + dibit_to_step[bits]) & 3;
return v17_abcd_constellation[s->constellation_state];
}
/*- End of function --------------------------------------------------------*/
static __inline__ int diff_and_convolutional_encode(v17_tx_state_t *s, int q)
{
static const int diff_code[16] =
{
0, 1, 2, 3, 1, 2, 3, 0, 2, 3, 0, 1, 3, 0, 1, 2
};
int y1;
int y2;
int this1;
int this2;
/* Differentially encode */
s->diff = diff_code[((q & 0x03) << 2) | s->diff];
/* Convolutionally encode the redundant bit */
y2 = s->diff >> 1;
y1 = s->diff;
this2 = y2 ^ y1 ^ (s->convolution >> 2) ^ ((y2 ^ (s->convolution >> 1)) & s->convolution);
this1 = y2 ^ (s->convolution >> 1) ^ (y1 & s->convolution);
s->convolution = ((s->convolution & 1) << 2) | ((this2 & 1) << 1) | (this1 & 1);
return ((q << 1) & 0x78) | (s->diff << 1) | ((s->convolution >> 2) & 1);
}
/*- End of function --------------------------------------------------------*/
static int fake_get_bit(void *user_data)
{
return 1;
}
/*- End of function --------------------------------------------------------*/
#if defined(SPANDSP_USE_FIXED_POINT)
static __inline__ complexi16_t getbaud(v17_tx_state_t *s)
#else
static __inline__ complexf_t getbaud(v17_tx_state_t *s)
#endif
{
int i;
int bit;
int bits;
if (s->in_training)
{
if (s->training_step <= V17_TRAINING_END)
{
/* Send the training sequence */
if (s->training_step < V17_TRAINING_SEG_4)
return training_get(s);
/* The last step in training is to send some 1's */
if (++s->training_step > V17_TRAINING_END)
{
/* Training finished - commence normal operation. */
s->current_get_bit = s->get_bit;
s->in_training = FALSE;
}
}
else
{
if (++s->training_step > V17_TRAINING_SHUTDOWN_A)
{
/* The shutdown sequence is 32 bauds of all 1's, then 48 bauds
of silence */
#if defined(SPANDSP_USE_FIXED_POINT)
return complex_seti16(0, 0);
#else
return complex_setf(0.0f, 0.0f);
#endif
}
if (s->training_step == V17_TRAINING_SHUTDOWN_END)
{
if (s->status_handler)
s->status_handler(s->status_user_data, SIG_STATUS_SHUTDOWN_COMPLETE);
}
}
}
bits = 0;
for (i = 0; i < s->bits_per_symbol; i++)
{
if ((bit = s->current_get_bit(s->get_bit_user_data)) == SIG_STATUS_END_OF_DATA)
{
/* End of real data. Switch to the fake get_bit routine, until we
have shut down completely. */
if (s->status_handler)
s->status_handler(s->status_user_data, SIG_STATUS_END_OF_DATA);
s->current_get_bit = fake_get_bit;
s->in_training = TRUE;
bit = 1;
}
bits |= (scramble(s, bit) << i);
}
return s->constellation[diff_and_convolutional_encode(s, bits)];
}
/*- End of function --------------------------------------------------------*/
SPAN_DECLARE(int) v17_tx(v17_tx_state_t *s, int16_t amp[], int len)
{
#if defined(SPANDSP_USE_FIXED_POINT)
complexi_t x;
complexi_t z;
#else
complexf_t x;
complexf_t z;
#endif
int i;
int sample;
if (s->training_step >= V17_TRAINING_SHUTDOWN_END)
{
/* Once we have sent the shutdown sequence, we stop sending completely. */
return 0;
}
for (sample = 0; sample < len; sample++)
{
if ((s->baud_phase += 3) >= 10)
{
s->baud_phase -= 10;
s->rrc_filter[s->rrc_filter_step] =
s->rrc_filter[s->rrc_filter_step + V17_TX_FILTER_STEPS] = getbaud(s);
if (++s->rrc_filter_step >= V17_TX_FILTER_STEPS)
s->rrc_filter_step = 0;
}
/* Root raised cosine pulse shaping at baseband */
#if defined(SPANDSP_USE_FIXED_POINT)
x = complex_seti(0, 0);
for (i = 0; i < V17_TX_FILTER_STEPS; i++)
{
x.re += (int32_t) tx_pulseshaper[TX_PULSESHAPER_COEFF_SETS - 1 - s->baud_phase][i]*(int32_t) s->rrc_filter[i + s->rrc_filter_step].re;
x.im += (int32_t) tx_pulseshaper[TX_PULSESHAPER_COEFF_SETS - 1 - s->baud_phase][i]*(int32_t) s->rrc_filter[i + s->rrc_filter_step].im;
}
/* Now create and modulate the carrier */
x.re >>= 4;
x.im >>= 4;
z = dds_complexi(&(s->carrier_phase), s->carrier_phase_rate);
/* Don't bother saturating. We should never clip. */
i = (x.re*z.re - x.im*z.im) >> 15;
amp[sample] = (int16_t) ((i*s->gain) >> 15);
#else
x = complex_setf(0.0f, 0.0f);
for (i = 0; i < V17_TX_FILTER_STEPS; i++)
{
x.re += tx_pulseshaper[TX_PULSESHAPER_COEFF_SETS - 1 - s->baud_phase][i]*s->rrc_filter[i + s->rrc_filter_step].re;
x.im += tx_pulseshaper[TX_PULSESHAPER_COEFF_SETS - 1 - s->baud_phase][i]*s->rrc_filter[i + s->rrc_filter_step].im;
}
/* Now create and modulate the carrier */
z = dds_complexf(&(s->carrier_phase), s->carrier_phase_rate);
/* Don't bother saturating. We should never clip. */
amp[sample] = (int16_t) lfastrintf((x.re*z.re - x.im*z.im)*s->gain);
#endif
}
return sample;
}
/*- End of function --------------------------------------------------------*/
SPAN_DECLARE(void) v17_tx_power(v17_tx_state_t *s, float power)
{
/* The constellation design seems to keep the average power the same, regardless
of which bit rate is in use. */
#if defined(SPANDSP_USE_FIXED_POINT)
s->gain = 0.223f*powf(10.0f, (power - DBM0_MAX_POWER)/20.0f)*16.0f*(32767.0f/30672.52f)*32768.0f/TX_PULSESHAPER_GAIN;
#else
s->gain = 0.223f*powf(10.0f, (power - DBM0_MAX_POWER)/20.0f)*32768.0f/TX_PULSESHAPER_GAIN;
#endif
}
/*- End of function --------------------------------------------------------*/
SPAN_DECLARE(void) v17_tx_set_get_bit(v17_tx_state_t *s, get_bit_func_t get_bit, void *user_data)
{
if (s->get_bit == s->current_get_bit)
s->current_get_bit = get_bit;
s->get_bit = get_bit;
s->get_bit_user_data = user_data;
}
/*- End of function --------------------------------------------------------*/
SPAN_DECLARE(void) v17_tx_set_modem_status_handler(v17_tx_state_t *s, modem_tx_status_func_t handler, void *user_data)
{
s->status_handler = handler;
s->status_user_data = user_data;
}
/*- End of function --------------------------------------------------------*/
SPAN_DECLARE(logging_state_t *) v17_tx_get_logging_state(v17_tx_state_t *s)
{
return &s->logging;
}
/*- End of function --------------------------------------------------------*/
SPAN_DECLARE(int) v17_tx_restart(v17_tx_state_t *s, int bit_rate, int tep, int short_train)
{
switch (bit_rate)
{
case 14400:
s->bits_per_symbol = 6;
s->constellation = v17_14400_constellation;
break;
case 12000:
s->bits_per_symbol = 5;
s->constellation = v17_12000_constellation;
break;
case 9600:
s->bits_per_symbol = 4;
s->constellation = v17_9600_constellation;
break;
case 7200:
s->bits_per_symbol = 3;
s->constellation = v17_7200_constellation;
break;
default:
return -1;
}
/* NB: some modems seem to use 3 instead of 1 for long training */
s->diff = (short_train) ? 0 : 1;
s->bit_rate = bit_rate;
#if defined(SPANDSP_USE_FIXED_POINT)
memset(s->rrc_filter, 0, sizeof(s->rrc_filter));
#else
cvec_zerof(s->rrc_filter, sizeof(s->rrc_filter)/sizeof(s->rrc_filter[0]));
#endif
s->rrc_filter_step = 0;
s->convolution = 0;
s->scramble_reg = 0x2ECDD5;
s->in_training = TRUE;
s->short_train = short_train;
s->training_step = (tep) ? V17_TRAINING_SEG_TEP_A : V17_TRAINING_SEG_1;
s->carrier_phase = 0;
s->baud_phase = 0;
s->constellation_state = 0;
s->current_get_bit = fake_get_bit;
return 0;
}
/*- End of function --------------------------------------------------------*/
SPAN_DECLARE(v17_tx_state_t *) v17_tx_init(v17_tx_state_t *s, int bit_rate, int tep, get_bit_func_t get_bit, void *user_data)
{
if (s == NULL)
{
if ((s = (v17_tx_state_t *) malloc(sizeof(*s))) == NULL)
return NULL;
}
memset(s, 0, sizeof(*s));
span_log_init(&s->logging, SPAN_LOG_NONE, NULL);
span_log_set_protocol(&s->logging, "V.17 TX");
s->get_bit = get_bit;
s->get_bit_user_data = user_data;
s->carrier_phase_rate = dds_phase_ratef(CARRIER_NOMINAL_FREQ);
v17_tx_power(s, -14.0f);
v17_tx_restart(s, bit_rate, tep, FALSE);
return s;
}
/*- End of function --------------------------------------------------------*/
SPAN_DECLARE(int) v17_tx_release(v17_tx_state_t *s)
{
return 0;
}
/*- End of function --------------------------------------------------------*/
SPAN_DECLARE(int) v17_tx_free(v17_tx_state_t *s)
{
free(s);
return 0;
}
/*- End of function --------------------------------------------------------*/
/*- End of file ------------------------------------------------------------*/
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