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added support for base37 encoded call sign

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This commit is contained in:
Ahmet Inan 2025-07-18 15:16:36 +02:00
commit 53acfab11c
3 changed files with 45 additions and 12 deletions
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2
Makefile vendored
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@ -15,7 +15,7 @@ CXX = clang++ -stdlib=libc++ -march=native
all: encode decode
test: encode decode
$(QEMU) ./encode audio.wav 48000 16 1 1500 5 /dev/urandom
$(QEMU) ./encode audio.wav 48000 16 1 1500 ANONYMOUS 48 /dev/urandom
$(QEMU) ./decode audio.wav /dev/null
encode: encode.cc common.hh

17
decode.cc
View file

@ -80,6 +80,11 @@ struct Decoder : Common
}
return 0;
}
static void base37_decoder(char *str, int64_t val, int len)
{
for (int i = len-1; i >= 0; --i, val /= 37)
str[i] = " 0123456789ABCDEFGHIJKLMNOPQRSTUVWXYZ"[val%37];
}
const cmplx *mls0_seq()
{
CODE::MLS seq0(mls0_poly, mls0_seed);
@ -393,11 +398,17 @@ struct Decoder : Common
std::cerr << "preamble decoding error." << std::endl;
break;
}
if (meta_info > 255) {
std::cerr << "unsupported operation mode: " << meta_info << std::endl;
int64_t call = meta_info >> 8;
if (call == 0 || call >= 129961739795077L) {
std::cerr << "call sign unsupported." << std::endl;
break;
}
if (!setup(meta_info))
char call_sign[10];
base37_decoder(call_sign, call, 9);
call_sign[9] = 0;
std::cerr << "call sign: " << call_sign << std::endl;
int mode = meta_info & 255;
if (!setup(mode))
break;
k = 0;
for (int i = 0; i < symbol_pos+symbol_len+extended_len; ++i)

38
encode.cc
View file

@ -277,14 +277,14 @@ struct Encoder : public Common
for (int i = guard_len / 4 + guard_len / 2; i < guard_len; ++i)
weight[i] = 1;
}
Encoder(DSP::WritePCM<value> *pcm, const char *const *input_names, int input_count, int freq_off, int oper_mode) : pcm(pcm)
Encoder(DSP::WritePCM<value> *pcm, const char *const *input_names, int input_count, int freq_off, int64_t call_sign, int oper_mode) : pcm(pcm)
{
if (!setup(oper_mode))
return;
int offset = (freq_off * symbol_len) / rate;
tone_off = offset - tone_count / 2;
guard_interval_weights();
meta_data(oper_mode);
meta_data((call_sign << 8) | oper_mode);
leading_noise();
for (int input_index = 0; input_index < input_count; ++input_index) {
const char *input_name = input_names[input_index];
@ -342,10 +342,27 @@ struct Encoder : public Common
}
};
int64_t base37_encoder(const char *str)
{
int64_t acc = 0;
for (char c = *str++; c; c = *str++) {
acc *= 37;
if (c >= '0' && c <= '9')
acc += c - '0' + 1;
else if (c >= 'a' && c <= 'z')
acc += c - 'a' + 11;
else if (c >= 'A' && c <= 'Z')
acc += c - 'A' + 11;
else if (c != ' ')
return -1;
}
return acc;
}
int main(int argc, char **argv)
{
if (argc < 8) {
std::cerr << "usage: " << argv[0] << " OUTPUT RATE BITS CHANNELS OFFSET MODE INPUT.." << std::endl;
if (argc < 9) {
std::cerr << "usage: " << argv[0] << " OUTPUT RATE BITS CHANNELS OFFSET CALLSIGN MODE INPUT.." << std::endl;
return 1;
}
@ -361,8 +378,13 @@ int main(int argc, char **argv)
std::cerr << "Frequency offset must be divisible by 300." << std::endl;
return 1;
}
int input_count = argc - 7;
int oper_mode = std::atoi(argv[6]);
int64_t call_sign = base37_encoder(argv[6]);
if (call_sign <= 0 || call_sign >= 129961739795077L) {
std::cerr << "Unsupported call sign." << std::endl;
return 1;
}
int input_count = argc - 8;
int oper_mode = std::atoi(argv[7]);
if (oper_mode < 0 || oper_mode > 255) {
std::cerr << "Unsupported operation mode." << std::endl;
return 1;
@ -379,10 +401,10 @@ int main(int argc, char **argv)
output_file.silence(output_rate);
switch (output_rate) {
case 44100:
delete new Encoder<value, cmplx, 44100>(&output_file, argv+7, input_count, freq_off, oper_mode);
delete new Encoder<value, cmplx, 44100>(&output_file, argv + 8, input_count, freq_off, call_sign, oper_mode);
break;
case 48000:
delete new Encoder<value, cmplx, 48000>(&output_file, argv+7, input_count, freq_off, oper_mode);
delete new Encoder<value, cmplx, 48000>(&output_file, argv + 8, input_count, freq_off, call_sign, oper_mode);
break;
default:
std::cerr << "Unsupported sample rate." << std::endl;