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// HamFax -- an application for sending and receiving amateur radio facsimiles
// Copyright (C) 2001 Christof Schmitt, DH1CS <cschmitt@users.sourceforge.net>
//
// This program is free software; you can redistribute it and/or
// modify it under the terms of the GNU General Public License
// as published by the Free Software Foundation; either version 2
// of the License, or (at your option) any later version.
//
// 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., 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA.
#include "FaxDemodulator.hpp"
#include <math.h>
// Narrow, middle and wide fir low pass filter from ACfax
static const double lpf[3][17]={
{ -7,-18,-15, 11, 56,116,177,223,240,223,177,116, 56, 11,-15,-18, -7},
{ 0,-18,-38,-39, 0, 83,191,284,320,284,191, 83, 0,-39,-38,-18, 0},
{ 6, 20, 7,-42,-74,-12,159,353,440,353,159,-12,-74,-42, 7, 20, 6}
};
FaxDemodulator::FaxDemodulator(QObject* parent)
: QObject(parent),
carrier(0), rate(0), deviation(0), fm(true), filter(1)
{
sine=new double[sine_size];
for(int i=0; i<sine_size; i++) {
sine[i]=sin(2.0*M_PI*i/sine_size);
}
ifir=new double[fir_size](0);
ifir_end=ifir+fir_size;
qfir=new double[fir_size](0);
qfir_end=qfir+fir_size;
asine=new double[asine_size];
for(int i=0; i<asine_size; i++) {
asine[i]=asin(2.0*i/asine_size-1.0)/2.0/M_PI;
}
init();
};
FaxDemodulator::~FaxDemodulator(void)
{
delete[] ifir;
delete[] qfir;
delete[] sine;
}
void FaxDemodulator::init(void)
{
sin_phase=sine;
cos_phase=sine+sine_size/4;
icurrent=ifir;
qcurrent=qfir;
ifirold=qfirold=0;
}
void FaxDemodulator::setCarrier(int carrier)
{
this->carrier=carrier;
}
void FaxDemodulator::setSampleRate(int sampleRate)
{
rate=sampleRate;
}
void FaxDemodulator::setDeviation(int dev)
{
deviation=dev;
}
void FaxDemodulator::setFM(bool fm)
{
this->fm=fm;
}
void FaxDemodulator::newSamples(short* audio, int n)
{
int demod[n];
for(int i=0; i<n; i++) {
*icurrent=audio[i]* *cos_phase;
*qcurrent=audio[i]* *sin_phase;
double ifirout=0;
double qfirout=0;
double* pi=icurrent;
double* pq=qcurrent;
for(int k=0; k<fir_size; k++) {
ifirout+= *pi * lpf[filter][k];
qfirout+= *pq * lpf[filter][k];
if(++pi>=ifir_end) {
pi=ifir;
}
if(++pq>=qfir_end) {
pq=qfir;
}
}
if(fm) {
double abs=sqrt(qfirout*qfirout+ifirout*ifirout);
ifirout/=abs;
qfirout/=abs;
if(abs>10000) {
double y=qfirold*ifirout-ifirold*qfirout;
y=(y+1.0)/2.0*asine_size;
double x=static_cast<double>(rate)/deviation;
x*=asine[static_cast<int>(y)];
if(x<-1.0) {
x=-1.0;
} else if(x>1.0) {
x=1.0;
}
demod[i]=static_cast<int>((x/2.0+0.5)*255.0);
} else {
demod[i]=0;
}
} else {
ifirout/=96000;
qfirout/=96000;
demod[i]=static_cast<int>
(sqrt(ifirout*ifirout+qfirout*qfirout));
}
ifirold=ifirout;
qfirold=qfirout;
if(++icurrent>=ifir_end) {
icurrent=ifir;
}
if(++qcurrent>=qfir_end) {
qcurrent=qfir;
}
if((sin_phase+=sine_size*carrier/rate) >= sine+sine_size) {
sin_phase-=sine_size;
}
if((cos_phase+=sine_size*carrier/rate) >= sine+sine_size) {
cos_phase-=sine_size;
}
}
emit data(demod,n);
}
void FaxDemodulator::setFilter(int n)
{
filter=n;
}
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