Mercurial > hg > audiostuff
view spandsp-0.0.3/spandsp-0.0.3/src/v29tx.c @ 5:f762bf195c4b
import spandsp-0.0.3
author | Peter Meerwald <pmeerw@cosy.sbg.ac.at> |
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date | Fri, 25 Jun 2010 16:00:21 +0200 |
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/* * SpanDSP - a series of DSP components for telephony * * v29tx.c - ITU V.29 modem transmit part * * Written by Steve Underwood <steveu@coppice.org> * * Copyright (C) 2003 Steve Underwood * * All rights reserved. * * This program is free software; you can redistribute it and/or modify * it under the terms of the GNU General Public License version 2, 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 General Public License * along with this program; if not, write to the Free Software * Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA. * * $Id: v29tx.c,v 1.58 2006/11/28 16:59:57 steveu Exp $ */ /*! \file */ #ifdef 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 "spandsp/telephony.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/v29tx.h" #define CARRIER_NOMINAL_FREQ 1700.0f /* Segments of the training sequence */ #define V29_TRAINING_SEG_TEP 0 #define V29_TRAINING_SEG_1 (V29_TRAINING_SEG_TEP + 480) #define V29_TRAINING_SEG_2 (V29_TRAINING_SEG_1 + 48) #define V29_TRAINING_SEG_3 (V29_TRAINING_SEG_2 + 128) #define V29_TRAINING_SEG_4 (V29_TRAINING_SEG_3 + 384) #define V29_TRAINING_END (V29_TRAINING_SEG_4 + 48) #define V29_TRAINING_SHUTDOWN_END (V29_TRAINING_END + 32) /* Raised root cosine pulse shaping; Beta = 0.25; 4 symbols either side of the centre. */ /* Created with mkshape -r 0.05 0.25 91 -l and then split up */ #define PULSESHAPER_GAIN (9.9888356312f/10.0f) #define PULSESHAPER_COEFF_SETS 10 static const float pulseshaper[PULSESHAPER_COEFF_SETS][V29_TX_FILTER_STEPS] = { { -0.0029426223f, /* Filter 0 */ -0.0183060118f, 0.0653192857f, -0.1703207714f, 0.6218069936f, 0.6218069936f, -0.1703207714f, 0.0653192857f, -0.0183060118f }, { 0.0031876922f, /* Filter 1 */ -0.0300884145f, 0.0832744718f, -0.1974255221f, 0.7664229820f, 0.4670580725f, -0.1291107519f, 0.0424189243f, -0.0059810465f }, { 0.0097229236f, /* Filter 2 */ -0.0394811291f, 0.0931039664f, -0.2043906784f, 0.8910868760f, 0.3122713836f, -0.0802880559f, 0.0179050490f, 0.0052057308f }, { 0.0156117223f, /* Filter 3 */ -0.0447125347f, 0.0922040267f, -0.1862939416f, 0.9870942864f, 0.1669790517f, -0.0301581072f, -0.0051358510f, 0.0139350286f }, { 0.0197702545f, /* Filter 4 */ -0.0443470335f, 0.0789538534f, -0.1399184160f, 1.0476130256f, 0.0393903028f, 0.0157339854f, -0.0241879599f, 0.0193774571f }, { 0.0212455717f, /* Filter 5 */ -0.0375307894f, 0.0530516472f, -0.0642195521f, 1.0682849922f, -0.0642195521f, 0.0530516472f, -0.0375307894f, 0.0212455717f }, { 0.0193774571f, /* Filter 6 */ -0.0241879599f, 0.0157339854f, 0.0393903028f, 1.0476130256f, -0.1399184160f, 0.0789538534f, -0.0443470335f, 0.0197702545f }, { 0.0139350286f, /* Filter 7 */ -0.0051358510f, -0.0301581072f, 0.1669790517f, 0.9870942864f, -0.1862939416f, 0.0922040267f, -0.0447125347f, 0.0156117223f }, { 0.0052057308f, /* Filter 8 */ 0.0179050490f, -0.0802880559f, 0.3122713836f, 0.8910868760f, -0.2043906784f, 0.0931039664f, -0.0394811291f, 0.0097229236f }, { -0.0059810465f, /* Filter 9 */ 0.0424189243f, -0.1291107519f, 0.4670580725f, 0.7664229820f, -0.1974255221f, 0.0832744718f, -0.0300884145f, 0.0031876922f }, }; static int fake_get_bit(void *user_data) { return 1; } /*- End of function --------------------------------------------------------*/ static __inline__ int get_scrambled_bit(v29_tx_state_t *s) { int bit; int out_bit; if ((bit = s->current_get_bit(s->user_data)) == PUTBIT_END_OF_DATA) { /* End of real data. Switch to the fake get_bit routine, until we have shut down completely. */ s->current_get_bit = fake_get_bit; s->in_training = TRUE; bit = 1; } out_bit = (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 --------------------------------------------------------*/ static __inline__ complexf_t getbaud(v29_tx_state_t *s) { static const int phase_steps_9600[8] = { 1, 0, 2, 3, 6, 7, 5, 4 }; static const int phase_steps_4800[4] = { 0, 2, 6, 4 }; static const complexf_t constellation[16] = { { 3.0, 0.0}, /* 0deg low */ { 1.0, 1.0}, /* 45deg low */ { 0.0, 3.0}, /* 90deg low */ {-1.0, 1.0}, /* 135deg low */ {-3.0, 0.0}, /* 180deg low */ {-1.0, -1.0}, /* 225deg low */ { 0.0, -3.0}, /* 270deg low */ { 1.0, -1.0}, /* 315deg low */ { 5.0, 0.0}, /* 0deg high */ { 3.0, 3.0}, /* 45deg high */ { 0.0, 5.0}, /* 90deg high */ {-3.0, 3.0}, /* 135deg high */ {-5.0, 0.0}, /* 180deg high */ {-3.0, -3.0}, /* 225deg high */ { 0.0, -5.0}, /* 270deg high */ { 3.0, -3.0} /* 315deg high */ }; static const complexf_t abab[6] = { { 3.0, -3.0}, /* 315deg high 9600 */ {-3.0, 0.0}, /* 180deg low */ { 1.0, -1.0}, /* 315deg low 7200 */ {-3.0, 0.0}, /* 180deg low */ { 0.0, -3.0}, /* 270deg low 4800 */ {-3.0, 0.0} /* 180deg low */ }; static const complexf_t cdcd[6] = { { 3.0, 0.0}, /* 0deg low 9600 */ {-3.0, 3.0}, /* 135deg high */ { 3.0, 0.0}, /* 0deg low 7200 */ {-1.0, 1.0}, /* 135deg low */ { 3.0, 0.0}, /* 0deg low 4800 */ { 0.0, 3.0} /* 90deg low */ }; int bits; int amp; int bit; if (s->in_training) { /* Send the training sequence */ if (++s->training_step <= V29_TRAINING_SEG_4) { if (s->training_step <= V29_TRAINING_SEG_3) { if (s->training_step <= V29_TRAINING_SEG_1) { /* Optional segment: Unmodulated carrier (talker echo protection) */ return constellation[0]; } if (s->training_step <= V29_TRAINING_SEG_2) { /* Segment 1: silence */ return complex_setf(0.0f, 0.0f); } /* Segment 2: ABAB... */ return abab[(s->training_step & 1) + s->training_offset]; } /* Segment 3: CDCD... */ /* Apply the 1 + x^-6 + x^-7 training scrambler */ bit = s->training_scramble_reg & 1; s->training_scramble_reg >>= 1; s->training_scramble_reg |= (((bit ^ s->training_scramble_reg) & 1) << 6); return cdcd[bit + s->training_offset]; } /* We should be in the block of test ones, or shutdown ones, if we get here. */ /* There is no graceful shutdown procedure defined for V.29. Just send some ones, to ensure we get the real data bits through, even with bad ISI. */ if (s->training_step == V29_TRAINING_END + 1) { /* Switch from the fake get_bit routine, to the user supplied real one, and we are up and running. */ s->current_get_bit = s->get_bit; s->in_training = FALSE; } } /* 9600bps uses the full constellation. 7200bps uses only the first half of the full constellation. 4800bps uses the smaller constellation. */ amp = 0; /* We only use an amplitude bit at 9600bps */ if (s->bit_rate == 9600 && get_scrambled_bit(s)) amp = 8; /*endif*/ bits = get_scrambled_bit(s); bits = (bits << 1) | get_scrambled_bit(s); if (s->bit_rate == 4800) { bits = phase_steps_4800[bits]; } else { bits = (bits << 1) | get_scrambled_bit(s); bits = phase_steps_9600[bits]; } s->constellation_state = (s->constellation_state + bits) & 7; return constellation[amp | s->constellation_state]; } /*- End of function --------------------------------------------------------*/ int v29_tx(v29_tx_state_t *s, int16_t amp[], int len) { complexf_t x; complexf_t z; int i; int sample; if (s->training_step >= V29_TRAINING_SHUTDOWN_END) { /* Once we have sent the shutdown symbols, 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 + V29_TX_FILTER_STEPS] = getbaud(s); if (++s->rrc_filter_step >= V29_TX_FILTER_STEPS) s->rrc_filter_step = 0; } /* Root raised cosine pulse shaping at baseband */ x.re = 0.0f; x.im = 0.0f; for (i = 0; i < V29_TX_FILTER_STEPS; i++) { x.re += pulseshaper[9 - s->baud_phase][i]*s->rrc_filter[i + s->rrc_filter_step].re; x.im += pulseshaper[9 - 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) lrintf((x.re*z.re - x.im*z.im)*s->gain); } return sample; } /*- End of function --------------------------------------------------------*/ static void set_working_gain(v29_tx_state_t *s) { switch (s->bit_rate) { case 9600: s->gain = 0.387f*s->base_gain; break; case 7200: s->gain = 0.605f*s->base_gain; break; case 4800: s->gain = 0.470f*s->base_gain; break; default: break; } } /*- End of function --------------------------------------------------------*/ void v29_tx_power(v29_tx_state_t *s, float power) { /* The constellation does not maintain constant average power as we change bit rates. We need to scale the gain we get here by a bit rate specific scaling factor each time we restart the modem. */ s->base_gain = powf(10.0f, (power - DBM0_MAX_POWER)/20.0f)*32768.0f/PULSESHAPER_GAIN; set_working_gain(s); } /*- End of function --------------------------------------------------------*/ void v29_tx_set_get_bit(v29_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->user_data = user_data; } /*- End of function --------------------------------------------------------*/ int v29_tx_restart(v29_tx_state_t *s, int rate, int tep) { span_log(&s->logging, SPAN_LOG_FLOW, "Restarting V.29\n"); s->bit_rate = rate; set_working_gain(s); switch (s->bit_rate) { case 9600: s->training_offset = 0; break; case 7200: s->training_offset = 2; break; case 4800: s->training_offset = 4; break; default: return -1; } cvec_zerof(s->rrc_filter, sizeof(s->rrc_filter)/sizeof(s->rrc_filter[0])); s->rrc_filter_step = 0; s->scramble_reg = 0; s->training_scramble_reg = 0x2A; s->in_training = TRUE; s->training_step = (tep) ? V29_TRAINING_SEG_TEP : V29_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 --------------------------------------------------------*/ v29_tx_state_t *v29_tx_init(v29_tx_state_t *s, int rate, int tep, get_bit_func_t get_bit, void *user_data) { if (s == NULL) { if ((s = (v29_tx_state_t *) malloc(sizeof(*s))) == NULL) return NULL; } memset(s, 0, sizeof(*s)); s->get_bit = get_bit; s->user_data = user_data; s->carrier_phase_rate = dds_phase_ratef(CARRIER_NOMINAL_FREQ); v29_tx_power(s, -14.0f); v29_tx_restart(s, rate, tep); return s; } /*- End of function --------------------------------------------------------*/ int v29_tx_release(v29_tx_state_t *s) { free(s); return 0; } /*- End of function --------------------------------------------------------*/ /*- End of file ------------------------------------------------------------*/