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view spandsp-0.0.3/spandsp-0.0.3/src/v27ter_tx.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 * * v27ter_tx.c - ITU V.27ter 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: v27ter_tx.c,v 1.48 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/v27ter_tx.h" #define CARRIER_NOMINAL_FREQ 1800.0f /* Segments of the training sequence */ /* V.27ter defines a long and a short sequence. FAX doesn't use the short sequence, so it is not implemented here. */ #define V27TER_TRAINING_SEG_1 0 #define V27TER_TRAINING_SEG_2 (V27TER_TRAINING_SEG_1 + 320) #define V27TER_TRAINING_SEG_3 (V27TER_TRAINING_SEG_2 + 32) #define V27TER_TRAINING_SEG_4 (V27TER_TRAINING_SEG_3 + 50) #define V27TER_TRAINING_SEG_5 (V27TER_TRAINING_SEG_4 + 1074) #define V27TER_TRAINING_END (V27TER_TRAINING_SEG_5 + 8) #define V27TER_TRAINING_SHUTDOWN_END (V27TER_TRAINING_END + 32) /* Raised root cosine pulse shaping; Beta = 0.5; 4 symbols either side of the centre. */ /* Created with mkshape -r 0.025 0.5 181 -l and then split up */ #define PULSESHAPER_2400_GAIN (19.972065748f/20.0f) #define PULSESHAPER_2400_COEFF_SETS 20 static const float pulseshaper_2400[PULSESHAPER_2400_COEFF_SETS][V27TER_TX_FILTER_STEPS] = { { 0.0050051219f, /* Filter 0 */ 0.0107180844f, -0.0150077814f, -0.0750272071f, 0.5786341413f, 0.5786341413f, -0.0750272071f, -0.0150077814f, 0.0107180844f }, { 0.0036624469f, /* Filter 1 */ 0.0131516633f, -0.0107913392f, -0.0957820135f, 0.6671466059f, 0.4891745311f, -0.0541239470f, -0.0179109014f, 0.0079099936f }, { 0.0020204744f, /* Filter 2 */ 0.0150588729f, -0.0053908083f, -0.1154114754f, 0.7528295479f, 0.4006032722f, -0.0339459430f, -0.0194500407f, 0.0048904515f }, { 0.0001596234f, /* Filter 3 */ 0.0163079778f, 0.0009858079f, -0.1328632049f, 0.8338068363f, 0.3146585634f, -0.0152415667f, -0.0196492903f, 0.0018247182f }, { -0.0018233575f, /* Filter 4 */ 0.0167957238f, 0.0080554403f, -0.1470417557f, 0.9082626683f, 0.2329352195f, 0.0013822552f, -0.0186004475f, -0.0011283792f }, { -0.0038199491f, /* Filter 5 */ 0.0164546659f, 0.0154676597f, -0.1568448230f, 0.9744947974f, 0.1568443643f, 0.0154698286f, -0.0164532877f, -0.0038242967f }, { -0.0057152767f, /* Filter 6 */ 0.0152590213f, 0.0228163087f, -0.1612020164f, 1.0309651039f, 0.0875801110f, 0.0267201501f, -0.0134037738f, -0.0061394831f }, { -0.0073941287f, /* Filter 7 */ 0.0132286539f, 0.0296547979f, -0.1591148676f, 1.0763457753f, 0.0260941722f, 0.0349842710f, -0.0096808822f, -0.0079766730f }, { -0.0087472825f, /* Filter 8 */ 0.0104308721f, 0.0355146231f, -0.1496966290f, 1.1095595051f, -0.0269209682f, 0.0402570324f, -0.0055327477f, -0.0092685626f }, { -0.0096778115f, /* Filter 9 */ 0.0069798134f, 0.0399264862f, -0.1322103702f, 1.1298123136f, -0.0710400038f, 0.0426638320f, -0.0012128224f, -0.0099797659f }, { -0.0101070340f, /* Filter 10 */ 0.0030333009f, 0.0424432507f, -0.1061038872f, 1.1366178484f, -0.1061038872f, 0.0424432507f, 0.0030333009f, -0.0101070340f }, { -0.0099797659f, /* Filter 11 */ -0.0012128224f, 0.0426638320f, -0.0710400038f, 1.1298123136f, -0.1322103702f, 0.0399264862f, 0.0069798134f, -0.0096778115f }, { -0.0092685626f, /* Filter 12 */ -0.0055327477f, 0.0402570324f, -0.0269209682f, 1.1095595051f, -0.1496966290f, 0.0355146231f, 0.0104308721f, -0.0087472825f }, { -0.0079766730f, /* Filter 13 */ -0.0096808822f, 0.0349842710f, 0.0260941722f, 1.0763457753f, -0.1591148676f, 0.0296547979f, 0.0132286539f, -0.0073941287f }, { -0.0061394831f, /* Filter 14 */ -0.0134037738f, 0.0267201501f, 0.0875801110f, 1.0309651039f, -0.1612020164f, 0.0228163087f, 0.0152590213f, -0.0057152767f }, { -0.0038242967f, /* Filter 15 */ -0.0164532877f, 0.0154698286f, 0.1568443643f, 0.9744947974f, -0.1568448230f, 0.0154676597f, 0.0164546659f, -0.0038199491f }, { -0.0011283792f, /* Filter 16 */ -0.0186004475f, 0.0013822552f, 0.2329352195f, 0.9082626683f, -0.1470417557f, 0.0080554403f, 0.0167957238f, -0.0018233575f }, { 0.0018247182f, /* Filter 17 */ -0.0196492903f, -0.0152415667f, 0.3146585634f, 0.8338068363f, -0.1328632049f, 0.0009858079f, 0.0163079778f, 0.0001596234f }, { 0.0048904515f, /* Filter 18 */ -0.0194500407f, -0.0339459430f, 0.4006032722f, 0.7528295479f, -0.1154114754f, -0.0053908083f, 0.0150588729f, 0.0020204744f }, { 0.0079099936f, /* Filter 19 */ -0.0179109014f, -0.0541239470f, 0.4891745311f, 0.6671466059f, -0.0957820135f, -0.0107913392f, 0.0131516633f, 0.0036624469f }, }; /* Raised root cosine pulse shaping; Beta = 0.5; 4 symbols either side of the centre. */ /* Created with mkshape -r 0.1 0.5 45 -l and then split up */ #define PULSESHAPER_4800_GAIN (4.9913162900f/5.0f) #define PULSESHAPER_4800_COEFF_SETS 5 static const float pulseshaper_4800[PULSESHAPER_4800_COEFF_SETS][V27TER_TX_FILTER_STEPS] = { { 0.0020173211f, /* Filter 0 */ 0.0150576434f, -0.0053888047f, -0.1154099010f, 0.7528286821f, 0.4006013374f, -0.0339462085f, -0.0194477281f, 0.0048918464f }, { -0.0057162575f, /* Filter 1 */ 0.0152563286f, 0.0228163350f, -0.1612000503f, 1.0309660372f, 0.0875788553f, 0.0267182476f, -0.0134032156f, -0.0061365979f }, { -0.0101052019f, /* Filter 2 */ 0.0030314952f, 0.0424414442f, -0.1061032862f, 1.1366196464f, -0.1061032862f, 0.0424414442f, 0.0030314952f, -0.0101052019f }, { -0.0061365979f, /* Filter 3 */ -0.0134032156f, 0.0267182476f, 0.0875788553f, 1.0309660372f, -0.1612000503f, 0.0228163350f, 0.0152563286f, -0.0057162575f }, { 0.0048918464f, /* Filter 4 */ -0.0194477281f, -0.0339462085f, 0.4006013374f, 0.7528286821f, -0.1154099010f, -0.0053888047f, 0.0150576434f, 0.0020173211f }, }; static int fake_get_bit(void *user_data) { return 1; } /*- End of function --------------------------------------------------------*/ static __inline__ int scramble(v27ter_tx_state_t *s, int in_bit) { int out_bit; /* This scrambler is really quite messy to implement. There seems to be no efficient shortcut */ out_bit = (in_bit ^ (s->scramble_reg >> 5) ^ (s->scramble_reg >> 6)) & 1; if (s->scrambler_pattern_count >= 33) { out_bit ^= 1; s->scrambler_pattern_count = 0; } else { if ((((s->scramble_reg >> 7) ^ out_bit) & ((s->scramble_reg >> 8) ^ out_bit) & ((s->scramble_reg >> 11) ^ out_bit) & 1)) s->scrambler_pattern_count = 0; else s->scrambler_pattern_count++; } s->scramble_reg = (s->scramble_reg << 1) | out_bit; return out_bit; } /*- End of function --------------------------------------------------------*/ static __inline__ int get_scrambled_bit(v27ter_tx_state_t *s) { int 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; } return scramble(s, bit); } /*- End of function --------------------------------------------------------*/ static complexf_t getbaud(v27ter_tx_state_t *s) { static const int phase_steps_4800[8] = { 1, 0, 2, 3, 6, 7, 5, 4 }; static const int phase_steps_2400[4] = { 0, 2, 6, 4 }; static const complexf_t constellation[8] = { { 1.414f, 0.0f}, /* 0deg */ { 1.0f, 1.0f}, /* 45deg */ { 0.0f, 1.414f}, /* 90deg */ {-1.0f, 1.0f}, /* 135deg */ {-1.414f, 0.0f}, /* 180deg */ {-1.0f, -1.0f}, /* 225deg */ { 0.0f, -1.414f}, /* 270deg */ { 1.0f, -1.0f} /* 315deg */ }; int bits; if (s->in_training) { /* Send the training sequence */ if (++s->training_step <= V27TER_TRAINING_SEG_5) { if (s->training_step <= V27TER_TRAINING_SEG_4) { if (s->training_step <= V27TER_TRAINING_SEG_2) { /* Segment 1: Unmodulated carrier (talker echo protection) */ return constellation[0]; } if (s->training_step <= V27TER_TRAINING_SEG_3) { /* Segment 2: Silence */ return complex_setf(0.0, 0.0); } /* Segment 3: Regular reversals... */ s->constellation_state = (s->constellation_state + 4) & 7; return constellation[s->constellation_state]; } /* Segment 4: Scrambled reversals... */ /* Apply the 1 + x^-6 + x^-7 scrambler. We want every third bit from the scrambler. */ bits = get_scrambled_bit(s) << 2; get_scrambled_bit(s); get_scrambled_bit(s); s->constellation_state = (s->constellation_state + bits) & 7; return constellation[s->constellation_state]; } /* 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.27ter. Just send some ones, to ensure we get the real data bits through, even with bad ISI. */ if (s->training_step == V27TER_TRAINING_END + 1) { /* End of the last segment - segment 5: All ones */ /* 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; } } /* 4800bps uses 8 phases. 2400bps uses 4 phases. */ if (s->bit_rate == 4800) { bits = get_scrambled_bit(s); bits = (bits << 1) | get_scrambled_bit(s); bits = (bits << 1) | get_scrambled_bit(s); bits = phase_steps_4800[bits]; } else { bits = get_scrambled_bit(s); bits = (bits << 1) | get_scrambled_bit(s); bits = phase_steps_2400[bits]; } s->constellation_state = (s->constellation_state + bits) & 7; return constellation[s->constellation_state]; } /*- End of function --------------------------------------------------------*/ int v27ter_tx(v27ter_tx_state_t *s, int16_t amp[], int len) { complexf_t x; complexf_t z; int i; int sample; if (s->training_step >= V27TER_TRAINING_SHUTDOWN_END) { /* Once we have sent the shutdown symbols, we stop sending completely. */ return 0; } /* The symbol rates for the two bit rates are different. This makes it difficult to merge both generation procedures into a single efficient loop. We do not bother trying. We use two independent loops, filter coefficients, etc. */ if (s->bit_rate == 4800) { for (sample = 0; sample < len; sample++) { if (++s->baud_phase >= 5) { s->baud_phase -= 5; s->rrc_filter[s->rrc_filter_step] = s->rrc_filter[s->rrc_filter_step + V27TER_TX_FILTER_STEPS] = getbaud(s); if (++s->rrc_filter_step >= V27TER_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 < V27TER_TX_FILTER_STEPS; i++) { x.re += pulseshaper_4800[4 - s->baud_phase][i]*s->rrc_filter[i + s->rrc_filter_step].re; x.im += pulseshaper_4800[4 - 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_4800); } } else { for (sample = 0; sample < len; sample++) { if ((s->baud_phase += 3) >= 20) { s->baud_phase -= 20; s->rrc_filter[s->rrc_filter_step] = s->rrc_filter[s->rrc_filter_step + V27TER_TX_FILTER_STEPS] = getbaud(s); if (++s->rrc_filter_step >= V27TER_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 < V27TER_TX_FILTER_STEPS; i++) { x.re += pulseshaper_2400[19 - s->baud_phase][i]*s->rrc_filter[i + s->rrc_filter_step].re; x.im += pulseshaper_2400[19 - 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_2400); } } return sample; } /*- End of function --------------------------------------------------------*/ void v27ter_tx_power(v27ter_tx_state_t *s, float power) { float l; l = powf(10.0f, (power - DBM0_MAX_POWER)/20.0f)*32768.0f; s->gain_2400 = l/PULSESHAPER_2400_GAIN; s->gain_4800 = l/PULSESHAPER_4800_GAIN; } /*- End of function --------------------------------------------------------*/ void v27ter_tx_set_get_bit(v27ter_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 v27ter_tx_restart(v27ter_tx_state_t *s, int rate, int tep) { if (rate != 4800 && rate != 2400) return -1; s->bit_rate = rate; cvec_zerof(s->rrc_filter, sizeof(s->rrc_filter)/sizeof(s->rrc_filter[0])); s->rrc_filter_step = 0; s->scramble_reg = 0x3C; s->scrambler_pattern_count = 0; s->in_training = TRUE; s->training_step = (tep) ? V27TER_TRAINING_SEG_1 : V27TER_TRAINING_SEG_2; s->carrier_phase = 0; s->baud_phase = 0; s->constellation_state = 0; s->current_get_bit = fake_get_bit; return 0; } /*- End of function --------------------------------------------------------*/ v27ter_tx_state_t *v27ter_tx_init(v27ter_tx_state_t *s, int rate, int tep, get_bit_func_t get_bit, void *user_data) { if (s == NULL) { if ((s = (v27ter_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); v27ter_tx_power(s, -14.0f); v27ter_tx_restart(s, rate, tep); return s; } /*- End of function --------------------------------------------------------*/ int v27ter_tx_release(v27ter_tx_state_t *s) { free(s); return 0; } /*- End of function --------------------------------------------------------*/ /*- End of file ------------------------------------------------------------*/