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feat: refactor input source handling and add audio input service

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Nedifinita
2025-12-05 17:01:42 +08:00
parent 7772112658
commit 99bc081583
13 changed files with 838 additions and 522 deletions
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158
android/app/src/main/cpp/demod.cpp
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@@ -14,17 +14,29 @@ uint32_t bits;
uint32_t code_words[PAGERDEMOD_BATCH_WORDS];
bool code_words_bch_error[PAGERDEMOD_BATCH_WORDS];
static bool hysteresis_state = false;
static bool dsp_initialized = false;
std::string numeric_msg, alpha_msg;
int function_bits;
uint32_t address;
uint32_t alpha_bit_buffer; // Bit buffer to 7-bit chars spread across codewords
int alpha_bit_buffer_bits; // Count of bits in alpha_bit_buffer
int parity_errors; // Count of parity errors in current message
int bch_errors; // Count of BCH errors in current message
int batch_num; // Count of batches in current transmission
uint32_t alpha_bit_buffer;
int alpha_bit_buffer_bits;
int parity_errors;
int bch_errors;
int batch_num;
double magsqRaw;
void ensureDSPInitialized() {
if (dsp_initialized) return;
lowpassBaud.create(301, SAMPLE_RATE, BAUD_RATE * 5.0f);
phaseDiscri.setFMScaling(SAMPLE_RATE / (2.0f * DEVIATION));
dsp_initialized = true;
}
int pop_cnt(uint32_t cw)
{
int cnt = 0;
@@ -39,10 +51,9 @@ int pop_cnt(uint32_t cw)
uint32_t bchEncode(const uint32_t cw)
{
uint32_t bit = 0;
uint32_t localCW = cw & 0xFFFFF800; // Mask off BCH parity and even parity bits
uint32_t localCW = cw & 0xFFFFF800;
uint32_t cwE = localCW;
// Calculate BCH bits
for (bit = 1; bit <= 21; bit++)
{
if (cwE & 0x80000000)
@@ -56,38 +67,28 @@ uint32_t bchEncode(const uint32_t cw)
return localCW;
}
// Use BCH decoding to try to fix any bit errors
// Returns true if able to be decode/repair successful
// See: https://www.eevblog.com/forum/microcontrollers/practical-guides-to-bch-fec/
bool bchDecode(const uint32_t cw, uint32_t &correctedCW)
{
// Calculate syndrome
// We do this by recalculating the BCH parity bits and XORing them against the received ones
uint32_t syndrome = ((bchEncode(cw) ^ cw) >> 1) & 0x3FF;
if (syndrome == 0)
{
// Syndrome of zero indicates no repair required
correctedCW = cw;
return true;
}
// Meggitt decoder
uint32_t result = 0;
uint32_t damagedCW = cw;
// Calculate BCH bits
for (uint32_t xbit = 0; xbit < 31; xbit++)
{
// Produce the next corrected bit in the high bit of the result
result <<= 1;
if ((syndrome == 0x3B4) || // 0x3B4: Syndrome when a single error is detected in the MSB
(syndrome == 0x26E) || // 0x26E: Two adjacent errors
(syndrome == 0x359) || // 0x359: Two errors, one OK bit between
(syndrome == 0x076) || // 0x076: Two errors, two OK bits between
(syndrome == 0x255) || // 0x255: Two errors, three OK bits between
(syndrome == 0x0F0) || // 0x0F0: Two errors, four OK bits between
if ((syndrome == 0x3B4) ||
(syndrome == 0x26E) ||
(syndrome == 0x359) ||
(syndrome == 0x076) ||
(syndrome == 0x255) ||
(syndrome == 0x0F0) ||
(syndrome == 0x216) ||
(syndrome == 0x365) ||
(syndrome == 0x068) ||
@@ -114,36 +115,29 @@ bool bchDecode(const uint32_t cw, uint32_t &correctedCW)
(syndrome == 0x3B6) ||
(syndrome == 0x3B5))
{
// Syndrome matches an error in the MSB
// Correct that error and adjust the syndrome to account for it
syndrome ^= 0x3B4;
result |= (~damagedCW & 0x80000000) >> 30;
}
else
{
// No error
result |= (damagedCW & 0x80000000) >> 30;
}
damagedCW <<= 1;
// Handle syndrome shift register feedback
if (syndrome & 0x200)
{
syndrome <<= 1;
syndrome ^= 0x769; // 0x769 = POCSAG generator polynomial -- x^10 + x^9 + x^8 + x^6 + x^5 + x^3 + 1
syndrome ^= 0x769;
}
else
{
syndrome <<= 1;
}
// Mask off bits which fall off the end of the syndrome shift register
syndrome &= 0x3FF;
}
// Check if error correction was successful
if (syndrome != 0)
{
// Syndrome nonzero at end indicates uncorrectable errors
correctedCW = cw;
return false;
}
@@ -162,13 +156,11 @@ int xorBits(uint32_t word, int firstBit, int lastBit)
return x;
}
// Check for even parity
bool evenParity(uint32_t word, int firstBit, int lastBit, int parityBit)
{
return xorBits(word, firstBit, lastBit) == parityBit;
}
// Reverse order of bits
uint32_t reverse(uint32_t x)
{
x = (((x & 0xaaaaaaaa) >> 1) | ((x & 0x55555555) << 1));
@@ -178,10 +170,6 @@ uint32_t reverse(uint32_t x)
return ((x >> 16) | (x << 16));
}
// Decode a batch of codewords to addresses and messages
// Messages may be spreadout over multiple batches
// https://www.itu.int/dms_pubrec/itu-r/rec/m/R-REC-M.584-1-198607-S!!PDF-E.pdf
// https://www.itu.int/dms_pubrec/itu-r/rec/m/R-REC-M.584-2-199711-I!!PDF-E.pdf
void decodeBatch()
{
int i = 1;
@@ -190,17 +178,13 @@ void decodeBatch()
for (int word = 0; word < PAGERDEMOD_CODEWORDS_PER_FRAME; word++)
{
bool addressCodeWord = ((code_words[i] >> 31) & 1) == 0;
// Check parity bit
bool parityError = !evenParity(code_words[i], 1, 31, code_words[i] & 0x1);
if (code_words[i] == PAGERDEMOD_POCSAG_IDLECODE)
{
// Idle
}
else if (addressCodeWord)
{
// Address
function_bits = (code_words[i] >> 11) & 0x3;
int addressBits = (code_words[i] >> 13) & 0x3ffff;
address = (addressBits << 3) | frame;
@@ -213,44 +197,30 @@ void decodeBatch()
}
else
{
// Message - decode as both numeric and ASCII - not all operators use functionBits to indidcate encoding
int messageBits = (code_words[i] >> 11) & 0xfffff;
if (parityError)
{
parity_errors++;
}
if (code_words_bch_error[i])
{
bch_errors++;
}
if (parityError) parity_errors++;
if (code_words_bch_error[i]) bch_errors++;
// Numeric format
for (int j = 16; j >= 0; j -= 4)
{
uint32_t numericBits = (messageBits >> j) & 0xf;
numericBits = reverse(numericBits) >> (32 - 4);
// Spec has 0xa as 'spare', but other decoders treat is as .
const char numericChars[] = {
'0', '1', '2', '3', '4', '5', '6', '7', '8', '9', '.', 'U', ' ', '-', ')', '('};
char numericChar = numericChars[numericBits];
numeric_msg.push_back(numericChar);
}
// 7-bit ASCII alpnanumeric format
alpha_bit_buffer = (alpha_bit_buffer << 20) | messageBits;
alpha_bit_buffer_bits += 20;
while (alpha_bit_buffer_bits >= 7)
{
// Extract next 7-bit character from bit buffer
char c = (alpha_bit_buffer >> (alpha_bit_buffer_bits - 7)) & 0x7f;
// Reverse bit ordering
c = reverse(c) >> (32 - 7);
// Add to received message string (excluding, null, end of text, end ot transmission)
if (c != 0 && c != 0x3 && c != 0x4)
{
alpha_msg.push_back(c);
}
// Remove from bit buffer
alpha_bit_buffer_bits -= 7;
if (alpha_bit_buffer_bits == 0)
{
@@ -262,25 +232,16 @@ void decodeBatch()
}
}
}
// Move to next codeword
i++;
}
}
}
void processOneSample(int8_t i, int8_t q)
void processBasebandSample(double sample)
{
float fi = ((float)i) / 128.0f;
float fq = ((float)q) / 128.0f;
ensureDSPInitialized();
std::complex<float> iq(fi, fq);
float deviation;
double fmDemod = phaseDiscri.phaseDiscriminatorDelta(iq, magsqRaw, deviation);
// printf("fmDemod: %.3f\n", fmDemod);
double filt = lowpassBaud.filter(fmDemod);
double filt = lowpassBaud.filter(sample);
if (!got_SC)
{
@@ -288,54 +249,49 @@ void processOneSample(int8_t i, int8_t q)
dc_offset = preambleMovingAverage.asDouble();
}
bool data = (filt - dc_offset) >= 0.0;
// printf("filt - dc: %.3f\n", filt - dc_offset);
double sample_val = filt - dc_offset;
double threshold = 0.05;
if (sample_val > threshold)
{
hysteresis_state = true;
}
else if (sample_val < -threshold)
{
hysteresis_state = false;
}
bool data = hysteresis_state;
if (data != prev_data)
{
sync_cnt = SAMPLES_PER_SYMBOL / 2; // reset
sync_cnt = SAMPLES_PER_SYMBOL / 2;
}
else
{
sync_cnt--; // wait until next bit's midpoint
sync_cnt--;
if (sync_cnt <= 0)
{
if (bit_inverted)
{
data_bit = data;
}
else
{
data_bit = !data;
}
// printf("%d", data_bit);
if (bit_inverted) data_bit = data;
else data_bit = !data;
bits = (bits << 1) | data_bit;
bit_cnt++;
if (bit_cnt > 32)
{
bit_cnt = 32;
}
if (bit_cnt > 32) bit_cnt = 32;
if (bit_cnt == 32 && !got_SC)
{
// printf("pop count: %d\n", pop_cnt(bits ^ POCSAG_SYNCCODE));
// printf("pop count inv: %d\n", pop_cnt(bits ^ POCSAG_SYNCCODE_INV));
if (bits == POCSAG_SYNCCODE)
{
got_SC = true;
bit_inverted = false;
printf("\nSync code found\n");
}
else if (bits == POCSAG_SYNCCODE_INV)
{
got_SC = true;
bit_inverted = true;
printf("\nSync code found\n");
}
else if (pop_cnt(bits ^ POCSAG_SYNCCODE) <= 3)
{
@@ -344,9 +300,7 @@ void processOneSample(int8_t i, int8_t q)
{
got_SC = true;
bit_inverted = false;
printf("\nSync code found\n");
}
// else printf("\nSync code not found\n");
}
else if (pop_cnt(bits ^ POCSAG_SYNCCODE_INV) <= 3)
{
@@ -355,9 +309,7 @@ void processOneSample(int8_t i, int8_t q)
{
got_SC = true;
bit_inverted = true;
printf("\nSync code found\n");
}
// else printf("\nSync code not found\n");
}
if (got_SC)
@@ -394,7 +346,6 @@ void processOneSample(int8_t i, int8_t q)
if (address > 0 && !numeric_msg.empty())
{
is_message_ready = true;
printf("Addr: %d | Numeric: %s | Alpha: %s\n", address, numeric_msg.c_str(), alpha_msg.c_str());
}
else
{
@@ -408,3 +359,16 @@ void processOneSample(int8_t i, int8_t q)
prev_data = data;
}
void processOneSample(int8_t i, int8_t q)
{
float fi = ((float)i) / 128.0f;
float fq = ((float)q) / 128.0f;
std::complex<float> iq(fi, fq);
float deviation;
double fmDemod = phaseDiscri.phaseDiscriminatorDelta(iq, magsqRaw, deviation);
processBasebandSample(fmDemod);
}