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use a shorter guard interval

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got rid of 8k and 16k sample rates. we can resample if needed.
This commit is contained in:
Ahmet Inan 2025-07-16 12:00:49 +02:00
commit 1dbc86c66f
2 changed files with 8 additions and 20 deletions
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12
decode.cc
View file

@ -37,9 +37,9 @@ struct Decoder : Common
typedef int16_t code_type;
typedef SIMD<code_type, 32> mesg_type;
typedef DSP::Const<value> Const;
static const int guard_len = rate / 100;
static const int symbol_len = guard_len * 16;
static const int filter_len = (((21 * rate) / 8000) & ~3) | 1;
static const int guard_len = rate / 300;
static const int symbol_len = guard_len * 40;
static const int filter_len = 129;
static const int extended_len = symbol_len + guard_len;
static const int buffer_len = 5 * extended_len;
static const int search_pos = extended_len;
@ -423,12 +423,6 @@ int main(int argc, char **argv)
std::cerr << std::fixed << std::setprecision(1);
int output_count = argc - 2;
switch (input_file.rate()) {
case 8000:
delete new Decoder<value, cmplx, 8000>(&input_file, argv+2, output_count);
break;
case 16000:
delete new Decoder<value, cmplx, 16000>(&input_file, argv+2, output_count);
break;
case 44100:
delete new Decoder<value, cmplx, 44100>(&input_file, argv+2, output_count);
break;

16
encode.cc
View file

@ -28,8 +28,8 @@ template <typename value, typename cmplx, int rate>
struct Encoder : public Common
{
typedef int8_t code_type;
static const int guard_len = rate / 100;
static const int symbol_len = guard_len * 16;
static const int guard_len = rate / 300;
static const int symbol_len = guard_len * 40;
DSP::WritePCM<value> *pcm;
DSP::FastFourierTransform<symbol_len, cmplx, -1> fwd;
DSP::FastFourierTransform<symbol_len, cmplx, 1> bwd;
@ -316,8 +316,8 @@ int main(int argc, char **argv)
int output_chan = std::atoi(argv[4]);
int freq_off = std::atoi(argv[5]);
if (freq_off % 100) {
std::cerr << "Frequency offset must be divisible by 100." << std::endl;
if (freq_off % 300) {
std::cerr << "Frequency offset must be divisible by 300." << std::endl;
return 1;
}
int input_count = argc - 7;
@ -326,7 +326,7 @@ int main(int argc, char **argv)
std::cerr << "Unsupported operation mode." << std::endl;
return 1;
}
int band_width = 2000;
int band_width = 2400;
if ((output_chan == 1 && freq_off < band_width / 2) || freq_off < band_width / 2 - output_rate / 2 || freq_off > output_rate / 2 - band_width / 2) {
std::cerr << "Unsupported frequency offset." << std::endl;
return 1;
@ -337,12 +337,6 @@ int main(int argc, char **argv)
DSP::WriteWAV<value> output_file(output_name, output_rate, output_bits, output_chan);
output_file.silence(output_rate);
switch (output_rate) {
case 8000:
delete new Encoder<value, cmplx, 8000>(&output_file, argv+7, input_count, freq_off, oper_mode);
break;
case 16000:
delete new Encoder<value, cmplx, 16000>(&output_file, argv+7, input_count, freq_off, oper_mode);
break;
case 44100:
delete new Encoder<value, cmplx, 44100>(&output_file, argv+7, input_count, freq_off, oper_mode);
break;