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Parse alternate frequency list, methods A and B
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@argilo
argilo committed Nov 3, 2024
1 parent 23a83b0 commit 3f18324
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Showing 2 changed files with 123 additions and 58 deletions.
177 changes: 120 additions & 57 deletions lib/parser_impl.cc
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Original file line number Diff line number Diff line change
Expand Up @@ -24,6 +24,7 @@
#include <gnuradio/io_signature.h>
#include <math.h>
#include <boost/locale.hpp>
#include <algorithm>
#include <cstring>
#include <iomanip>
#include <limits>
Expand Down Expand Up @@ -57,6 +58,7 @@ void parser_impl::reset() {

radiotext_segment_flags = 0;
program_service_name_segment_flags = 0;
af_pairs.clear();

radiotext_AB_flag = 0;
traffic_program = false;
Expand Down Expand Up @@ -150,36 +152,12 @@ void parser_impl::decode_type0(unsigned int *group, bool B) {
flagstring[4] = artificial_head ? '1' : '0';
flagstring[5] = compressed ? '1' : '0';
flagstring[6] = dynamic_pty ? '1' : '0';
static std::string af_string;

if(!B) { // type 0A
af_code_1 = int(group[2] >> 8) & 0xff;
af_code_2 = int(group[2]) & 0xff;
af_1 = decode_af(af_code_1);
af_2 = decode_af(af_code_2);

std::stringstream af_stringstream;
af_stringstream << std::fixed << std::setprecision(2);

if(af_1) {
if(af_1 > 80e3) {
af_stringstream << (af_1/1e3) << "MHz";
} else if((af_1<2e3)&&(af_1>100)) {
af_stringstream << int(af_1) << "kHz";
}
}
if(af_1 && af_2) {
af_stringstream << ", ";
}
if(af_2) {
if(af_2 > 80e3) {
af_stringstream << (af_2/1e3) << "MHz";
} else if((af_2<2e3)&&(af_2>100)) {
af_stringstream << int(af_2) << "kHz";
}
}
if(af_1 || af_2) {
af_string = af_stringstream.str();
// Check whether this is a new pair of AF codes
if (std::find(af_pairs.begin(), af_pairs.end(), group[2]) == af_pairs.end()) {
af_pairs.push_back(group[2]);
decode_af_pairs();
}
}

Expand All @@ -188,44 +166,129 @@ void parser_impl::decode_type0(unsigned int *group, bool B) {
<< '-' << (traffic_announcement ? "TA" : " ")
<< '-' << (music_speech ? "Music" : "Speech")
<< '-' << (mono_stereo ? "STEREO" : "MONO")
<< " - AF:" << af_string << std::endl;
<< std::endl;

send_message(3, flagstring);
send_message(6, af_string);
}

double parser_impl::decode_af(unsigned int af_code) {
static unsigned int number_of_freqs = 0;
static bool vhf_or_lfmf = 0; // 0 = vhf, 1 = lf/mf
double alt_frequency = 0; // in kHz

if((af_code == 0) || // not to be used
( af_code == 205) || // filler code
((af_code >= 206) && (af_code <= 223)) || // not assigned
( af_code == 224) || // No AF exists
( af_code >= 251)) { // not assigned
number_of_freqs = 0;
alt_frequency = 0;
void parser_impl::decode_af_pairs() {
// Search for the first row, which indicates the number of frequencies
int first_row = -1;
int number_of_freqs = -1;
int freqs_seen = 0;
std::vector<int> freqs;

for (int i = 0; i < af_pairs.size(); i++) {
unsigned int af_1 = (af_pairs[i] >> 8);

if ((af_1 >= 224) && (af_1 <= 249)) {
first_row = i;
number_of_freqs = af_1 - 224;
break;
}
}
if((af_code >= 225) && (af_code <= 249)) { // VHF frequencies follow
number_of_freqs = af_code - 224;
alt_frequency = 0;
vhf_or_lfmf = 1;

if (number_of_freqs == 0) {
return;
}
if(af_code == 250) { // an LF/MF frequency follows
number_of_freqs = 1;
alt_frequency = 0;
vhf_or_lfmf = 0;

if (first_row >= 0) {
unsigned int special_af = 0;
for (int i = first_row; i < first_row + af_pairs.size(); i++) {
unsigned int af_1 = (af_pairs[i % af_pairs.size()] >> 8);
unsigned int af_2 = (af_pairs[i % af_pairs.size()] & 0xff);

if (i == first_row) {
int freq = decode_af(af_2, false);
if (freq >= 0) {
freqs.push_back(freq);
freqs_seen++;
special_af = af_2;
}
} else if (af_1 == 250) {
// One LF/MF frequency follows
int freq = decode_af(af_2, true);
if (freq >= 0) {
freqs.push_back(freq);
freqs_seen++;
}
} else {
if ((af_1 == special_af) || (af_2 == special_af)) {
// AF method B
bool regional = (af_2 < af_1);

unsigned int new_af = (af_1 == special_af) ? af_2 : af_1;
int freq = decode_af(new_af, false);
if (freq >= 0) {
freqs.push_back(regional ? -freq : freq); // Negative indicates regional frequency
freqs_seen += 2;
}
} else {
int freq = decode_af(af_1, false);
if (freq >= 0) {
freqs.push_back(freq);
freqs_seen++;
}
freq = decode_af(af_2, false);
if (freq >= 0) {
freqs.push_back(freq);
freqs_seen++;
}
}
}
}

// Check whether we have the whole frequency list
if (freqs_seen == number_of_freqs) {
std::stringstream af_stringstream;
af_stringstream << std::fixed << std::setprecision(1);

bool first = true;
for (int freq : freqs) {
bool regional = false;
if (freq < 0) {
freq = -freq;
regional = true;
}

if (first) {
first = false;
} else {
af_stringstream << ", ";
}

if (freq > 10000) {
af_stringstream << (freq / 1000.0) << " MHz";
} else {
af_stringstream << freq << " kHz";
}

if (regional) {
af_stringstream << " (regional)";
}
}

send_message(6, af_stringstream.str());
lout << "AF: " << af_stringstream.str() << std::endl;
}
}

if((af_code > 0) && (af_code < 205) && vhf_or_lfmf)
alt_frequency = 100.0 * (af_code + 875); // VHF (87.6-107.9MHz)
else if((af_code > 0) && (af_code < 16) && !vhf_or_lfmf)
alt_frequency = 153.0 + (af_code - 1) * 9; // LF (153-279kHz)
else if((af_code > 15) && (af_code < 136) && !vhf_or_lfmf)
alt_frequency = 531.0 + (af_code - 16) * 9 + 531; // MF (531-1602kHz)
}

int parser_impl::decode_af(unsigned int af_code, bool lf_mf) {
if (lf_mf) {
if ((af_code >= 1) && (af_code <= 15)) {
return 153 + (af_code - 1) * 9; // LF (153-279kHz)
} else if ((af_code >= 16) && (af_code < 135)) {
return 531 + (af_code - 16) * 9; // MF (531-1602kHz)
}
} else {
if ((af_code >= 1) && (af_code <= 204)) {
return 87600 + (af_code - 1) * 100; // VHF (87.6-107.9MHz)
}
}

return alt_frequency;
return -1; // Invalid input
}

void parser_impl::decode_type1(unsigned int *group, bool B){
Expand Down
4 changes: 3 additions & 1 deletion lib/parser_impl.h
View file
Original file line number Diff line number Diff line change
Expand Up @@ -34,7 +34,8 @@ class parser_impl : public parser
void reset();
void send_message(long, std::string);
void parse(pmt::pmt_t pdu);
double decode_af(unsigned int);
void decode_af_pairs();
int decode_af(unsigned int af_code, bool lf_mf);
void decode_optional_content(int, unsigned long int *);

void decode_type0( unsigned int* group, bool B);
Expand Down Expand Up @@ -64,6 +65,7 @@ class parser_impl : public parser
char program_service_name[8];
unsigned int program_service_name_segment_flags;
bool radiotext_AB_flag;
std::vector<unsigned int> af_pairs;
bool traffic_program;
bool traffic_announcement;
bool music_speech;
Expand Down

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