159 lines
4.0 KiB
C
159 lines
4.0 KiB
C
/* $Id$
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******************************************************************************
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Fax program for ISDN.
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V.29 modulator.
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Copyright (C) 1998 Morten Rolland [Morten.Rolland@asker.mail.telia.com]
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Permission is hereby granted, free of charge, to any person obtaining a
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copy of this software and associated documentation files (the "Software"),
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to deal in the Software without restriction, including without limitation
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the rights to use, copy, modify, merge, publish, distribute, sublicense,
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and/or sell copies of the Software, and to permit persons to whom the
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Software is furnished to do so, subject to the following conditions:
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The above copyright notice and this permission notice shall be included in
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all copies or substantial portions of the Software.
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THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
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IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
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FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL
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THE AUTHOR(S) BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER
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IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN
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CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
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******************************************************************************
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*/
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/* modulator-V29.c
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*
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* Modulate a bitstream into 9600 bit/s according to V.29
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*
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* (C) 1998 Morten Rolland
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*/
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/* Bugs: Can only do 9600 */
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#include <stdio.h>
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#include <stdarg.h>
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#include <ifax/ifax.h>
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/* Samplerate and samples/symbol is closely related here */
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#define SAMPLERATE 9600
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#define SAMPLESPERSYMBOL 4
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/* Carrier frequency */
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#define CARRIERFREQ 1700
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/* This is the delta-phase for the carrier */
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#define SAMPLEPHASEINC ((0x10000*CARRIERFREQ)/SAMPLERATE)
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#define MAXBUFFERING 128
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typedef struct {
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unsigned int prev_phase;
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unsigned short w;
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signed short buffer[MAXBUFFERING+2*SAMPLESPERSYMBOL];
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/* unsigned char watingbits; (For use when symbol != 4 bits
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int waitingbits_count; */
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} modulator_V29_private;
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unsigned char bits2phase[] = { 1,0,2,3,6,7,5,4 };
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/* Free the private data
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*/
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void modulator_V29_destroy(ifax_modp self)
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{
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free(self->private);
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return;
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}
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int modulator_V29_command(ifax_modp self,int cmd,va_list cmds)
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{
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return 0;
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}
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void modulate_symbol(unsigned char bits, signed short *dst,
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unsigned int *prev_phase, unsigned short *w)
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{
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unsigned int p;
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signed short wave, amp;
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signed int sample;
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int t;
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p = (*prev_phase + bits2phase[bits>>1]) & 0x7;
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*prev_phase = p;
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fprintf(stderr,"%d\n",p*45);
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if ( p & 1 ) {
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/* 45 + 90*n */
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if ( bits & 1 ) {
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amp = 27798;
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} else {
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amp = 9266;
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}
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} else {
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/* 0 + 90*n */
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if ( bits & 1 ) {
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amp = 32760;
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} else {
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amp = 19656;
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}
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}
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p *= 0x2000;
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for ( t=0; t < SAMPLESPERSYMBOL; t++ ) {
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wave = intsin(*w + p);
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sample = wave * amp;
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sample /= 0x10000;
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printf("%d\n",sample);
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*dst++ = sample;
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*w += SAMPLEPHASEINC;
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}
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}
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int modulator_V29_handle(ifax_modp self, void *data, size_t length)
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{
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modulator_V29_private *priv=(modulator_V29_private *)self->private;
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size_t chunk, remaining=length;
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signed short *bp = priv->buffer;
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unsigned char *dp = data;
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int t;
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while ( remaining > 0 ) {
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chunk = remaining;
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if ( chunk > MAXBUFFERING )
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chunk = MAXBUFFERING;
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for ( t=0; t < chunk; t++ ) {
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modulate_symbol(dp[t]&0xf,bp,&priv->prev_phase,&priv->w);
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bp += SAMPLESPERSYMBOL;
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modulate_symbol(dp[t]>>4,bp,&priv->prev_phase,&priv->w);
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bp += SAMPLESPERSYMBOL;
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}
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/* ifax_handle_input(self->sendto,priv->buffer,chunk); */
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remaining -= chunk;
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}
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return length;
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}
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int modulator_V29_construct(ifax_modp self,va_list args)
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{
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modulator_V29_private *priv;
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if (NULL==(priv=self->private=malloc(sizeof(modulator_V29_private))))
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return 1;
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self->destroy = modulator_V29_destroy;
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self->handle_input = modulator_V29_handle;
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self->command = modulator_V29_command;
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priv->w = 0;
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priv->prev_phase = 0;
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return 0;
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}
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