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added CRC check of payload

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This commit is contained in:
Ahmet Inan 2021-06-10 09:33:26 +02:00
commit cc3e9cc10f
3 changed files with 36 additions and 16 deletions
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8
README.md
View file

@ -3,7 +3,13 @@
Quick start:
Encode file ```uncoded.dat``` with ```64800``` bits to ```encoded.wav``` [WAV](https://en.wikipedia.org/wiki/WAV) audio file with 8000 Hz sample rate, 16 bits and only 1 (real) channel:
Create file ```uncoded.dat``` with ```64768``` bits of random data:
```
dd if=/dev/urandom of=uncoded.dat bs=1 count=8096
```
Encode file ```uncoded.dat``` to ```encoded.wav``` [WAV](https://en.wikipedia.org/wiki/WAV) audio file with 8000 Hz sample rate, 16 bits and only 1 (real) channel:
```
./encode encoded.wav 8000 16 1 uncoded.dat

23
decode.cc
View file

@ -174,7 +174,8 @@ struct Decoder
DSP::Resampler<value, filter_len, 3> resample;
DSP::BipBuffer<cmplx, buffer_len> input_hist;
SchmidlCox<value, cmplx, search_pos, symbol_len/2, guard_len> correlator;
CODE::CRC<uint16_t> crc;
CODE::CRC<uint16_t> crc0;
CODE::CRC<uint32_t> crc1;
CODE::OrderedStatisticsDecoder<255, 71, 4> osddec;
int8_t genmat[255*71];
cmplx head[symbol_len], tail[symbol_len];
@ -232,7 +233,7 @@ struct Decoder
return sum / (count * symbol_len/2);
}
Decoder(uint8_t *out, DSP::ReadPCM<value> *pcm, int skip_count) :
pcm(pcm), resample(rate, (rate * 19) / 40, 2), correlator(mls0_seq()), crc(0xA8F4)
pcm(pcm), resample(rate, (rate * 19) / 40, 2), correlator(mls0_seq()), crc0(0xA8F4), crc1(0xD419CC15)
{
CODE::BoseChaudhuriHocquenghemGenerator<255, 71>::matrix(genmat, true, {
0b100011101, 0b101110111, 0b111110011, 0b101101001,
@ -287,9 +288,9 @@ struct Decoder
uint16_t cs = 0;
for (int i = 0; i < 16; ++i)
cs |= (uint16_t)CODE::get_be_bit(data, i+55) << i;
crc.reset();
if (crc(md<<9) != cs) {
std::cerr << "CRC error." << std::endl;
crc0.reset();
if (crc0(md<<9) != cs) {
std::cerr << "header CRC error." << std::endl;
return;
}
if ((md&255) != 2) {
@ -339,6 +340,11 @@ struct Decoder
}
}
}
crc1.reset();
for (int i = 0; i < data_bits / 8; ++i)
crc1(out[i]);
if (crc1())
std::cerr << "payload CRC error." << std::endl;
}
};
@ -366,8 +372,8 @@ int main(int argc, char **argv)
if (argc > 3)
skip_count = std::atoi(argv[3]);
const int length = 64800 / 8;
uint8_t *output_data = new uint8_t[length];
const int code_len = 64800 / 8;
uint8_t *output_data = new uint8_t[code_len];
switch (input_file.rate()) {
case 8000:
@ -392,7 +398,8 @@ int main(int argc, char **argv)
std::cerr << "Couldn't open file \"" << output_name << "\" for writing." << std::endl;
return 1;
}
for (int i = 0; i < length; ++i)
const int data_len = code_len - 32 / 8;
for (int i = 0; i < data_len; ++i)
output_file.put(output_data[i]);
delete []output_data;
return 0;

21
encode.cc
View file

@ -36,7 +36,8 @@ struct Encoder
static const int mls2_poly = 0b100101010001;
DSP::WritePCM<value> *pcm;
DSP::FastFourierTransform<symbol_len, cmplx, 1> bwd;
CODE::CRC<uint16_t> crc;
CODE::CRC<uint16_t> crc0;
CODE::CRC<uint32_t> crc1;
CODE::BoseChaudhuriHocquenghemEncoder<255, 71> bchenc;
cmplx fdom[symbol_len];
cmplx tdom[symbol_len];
@ -109,8 +110,8 @@ struct Encoder
uint8_t data[9] = { 0 }, parity[23] = { 0 };
for (int i = 0; i < 55; ++i)
CODE::set_be_bit(data, i, (md>>i)&1);
crc.reset();
uint16_t cs = crc(md << 9);
crc0.reset();
uint16_t cs = crc0(md << 9);
for (int i = 0; i < 16; ++i)
CODE::set_be_bit(data, i+55, (cs>>i)&1);
bchenc(data, parity);
@ -130,7 +131,7 @@ struct Encoder
symbol();
}
Encoder(DSP::WritePCM<value> *pcm, uint8_t *inp, int freq_off, uint64_t call_sign) :
pcm(pcm), crc(0xA8F4), bchenc({
pcm(pcm), crc0(0xA8F4), crc1(0xD419CC15), bchenc({
0b100011101, 0b101110111, 0b111110011, 0b101101001,
0b110111101, 0b111100111, 0b100101011, 0b111010111,
0b000010011, 0b101100101, 0b110001011, 0b101100011,
@ -146,6 +147,11 @@ struct Encoder
schmidl_cox();
meta_data((call_sign << 8) | 2);
pilot_block();
crc1.reset();
for (int i = 0; i < (data_bits-32)/8; ++i)
crc1(inp[i]);
for (int i = 0; i < 4; ++i)
inp[(data_bits-32)/8+i] = (crc1() >> (8*i)) & 255;
for (int j = 0; j < data_rows; ++j) {
for (int i = 0; i < data_cols; ++i) {
value tmp[Mod::BITS];
@ -225,9 +231,10 @@ int main(int argc, char **argv)
std::cerr << "Couldn't open file \"" << input_name << "\" for reading." << std::endl;
return 1;
}
const int length = 64800 / 8;
uint8_t *input_data = new uint8_t[length];
for (int i = 0; i < length; ++i)
const int code_len = 64800 / 8;
const int data_len = code_len - 32 / 8;
uint8_t *input_data = new uint8_t[code_len];
for (int i = 0; i < data_len; ++i)
input_data[i] = input_file.get();
DSP::WriteWAV<value> output_file(output_name, output_rate, output_bits, output_chan);