mirror of
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POCSAG Processor Rewrite (#1437)
* WIP Refactoring * WordExtractor building * Fix buffer sizes and squelch execute * Move impls to cpp file * Baud indicator * WIP new bit extractor * New approach for bit extraction. * Code fit and finish * Fix case on button * Cleanup * Adjust rate miss threshold * Fix count bits error calculation.
This commit is contained in:
Kyle Reed
GitHub
parent
9525738118
commit
31e8019642
13 changed files with 648 additions and 534 deletions
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@ -3,7 +3,7 @@
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* Copyright (C) 2012-2014 Elias Oenal (multimon-ng@eliasoenal.com)
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* Copyright (C) 2015 Jared Boone, ShareBrained Technology, Inc.
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* Copyright (C) 2016 Furrtek
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* Copyright (C) 2016 Kyle Reed
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* Copyright (C) 2023 Kyle Reed
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*
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* This file is part of PortaPack.
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*
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@ -34,6 +34,323 @@
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using namespace std;
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namespace {
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/* Count of bits that differ between the two values. */
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uint8_t differ_bit_count(uint32_t left, uint32_t right) {
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uint32_t diff = left ^ right;
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uint8_t count = 0;
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for (size_t i = 0; i < sizeof(diff) * 8; ++i) {
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if (((diff >> i) & 0x1) == 1)
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++count;
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}
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return count;
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}
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} // namespace
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/* AudioNormalizer ***************************************/
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void AudioNormalizer::execute_in_place(const buffer_f32_t& audio) {
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// Decay min/max every second (@24kHz).
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if (counter_ >= 24'000) {
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// 90% decay factor seems to work well.
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// This keeps large transients from wrecking the filter.
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max_ *= 0.9f;
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min_ *= 0.9f;
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counter_ = 0;
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calculate_thresholds();
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}
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counter_ += audio.count;
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for (size_t i = 0; i < audio.count; ++i) {
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auto& val = audio.p[i];
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if (val > max_) {
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max_ = val;
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calculate_thresholds();
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}
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if (val < min_) {
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min_ = val;
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calculate_thresholds();
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}
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if (val >= t_hi_)
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val = 1.0f;
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else if (val <= t_lo_)
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val = -1.0f;
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else
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val = 0.0;
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}
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}
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void AudioNormalizer::calculate_thresholds() {
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auto center = (max_ + min_) / 2.0f;
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auto range = (max_ - min_) / 2.0f;
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// 10% off center force either +/-1.0f.
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// Higher == larger dead zone.
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// Lower == more false positives.
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auto threshold = range * 0.1;
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t_hi_ = center + threshold;
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t_lo_ = center - threshold;
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}
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/* BitQueue **********************************************/
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void BitQueue::push(bool bit) {
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data_ = (data_ << 1) | (bit ? 1 : 0);
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if (count_ < max_size_) ++count_;
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}
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bool BitQueue::pop() {
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if (count_ == 0) return false;
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--count_;
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return (data_ & (1 << count_)) != 0;
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}
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void BitQueue::reset() {
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data_ = 0;
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count_ = 0;
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}
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uint8_t BitQueue::size() const {
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return count_;
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}
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uint32_t BitQueue::data() const {
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return data_;
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}
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/* BitExtractor ******************************************/
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void BitExtractor::extract_bits(const buffer_f32_t& audio) {
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// Assumes input has been normalized +/- 1.0f.
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for (size_t i = 0; i < audio.count; ++i) {
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sample_ = audio.p[i];
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++sample_index_;
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// There's a transition when both sides of the XOR are the
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// same which will result in a the overall value being 0.
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bool is_transition = ((last_sample_ < 0) ^ (sample_ >= 0)) == 0;
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if (is_transition) {
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if (handle_transition())
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bad_transitions_ = 0;
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else
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++bad_transitions_;
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// Too many bad transitions? Reset.
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if (bad_transitions_ > bad_transition_reset_threshold)
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reset();
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}
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// Time to push the next bit?
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if (sample_index_ >= next_bit_center_) {
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// Use the two most recent samples for the bit value.
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auto val = (sample_ + last_sample_) / 2.0;
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bits_.push(val < 0); // NB: '1' is negative.
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if (current_rate_)
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next_bit_center_ += current_rate_->bit_length;
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}
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last_sample_ = sample_;
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}
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}
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void BitExtractor::configure(uint32_t sample_rate) {
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sample_rate_ = sample_rate;
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min_valid_length_ = UINT16_MAX;
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// Build the baud rate info table based on the sample rate.
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for (auto& info : known_rates_) {
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info.bit_length = sample_rate / info.baud_rate;
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// Allow for 20% deviation.
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info.min_bit_length = 0.80 * info.bit_length;
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info.max_bit_length = 1.20 * info.bit_length;
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if (info.min_bit_length < min_valid_length_)
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min_valid_length_ = info.min_bit_length;
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}
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reset();
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}
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void BitExtractor::reset() {
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current_rate_ = nullptr;
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rate_misses_ = 0;
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sample_ = 0.0;
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last_sample_ = 0.0;
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next_bit_center_ = 0.0;
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sample_index_ = 0;
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last_transition_index_ = 0;
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bad_transitions_ = 0;
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}
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uint16_t BitExtractor::baud_rate() const {
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return current_rate_ ? current_rate_->baud_rate : 0;
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}
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bool BitExtractor::handle_transition() {
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auto length = sample_index_ - last_transition_index_;
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last_transition_index_ = sample_index_;
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// Length is too short, ignore this.
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if (length <= min_valid_length_) return false;
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// TODO: should the following be "bad" or "rate misses"?
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// Is length a multiple of the current rate's bit length?
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uint16_t bit_count = 0;
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if (!count_bits(length, bit_count)) return false;
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// Does the bit length correspond to a known rate?
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auto bit_length = length / static_cast<float>(bit_count);
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auto rate = get_baud_info(bit_length);
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if (!rate) return false;
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// Set current rate if it hasn't been set yet.
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if (!current_rate_)
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current_rate_ = rate;
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// Maybe current rate isn't the best rate?
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auto rate_miss = rate != current_rate_;
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if (rate_miss) {
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++rate_misses_;
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// Lots of rate misses, try another rate.
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if (rate_misses_ > rate_miss_reset_threshold) {
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current_rate_ = rate;
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rate_misses_ = 0;
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}
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} else {
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// Transition is aligned with the current rate, predict next bit.
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auto half_bit = current_rate_->bit_length / 2.0;
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next_bit_center_ = sample_index_ + half_bit;
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}
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return true;
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}
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bool BitExtractor::count_bits(uint32_t length, uint16_t& bit_count) {
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bit_count = 0;
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// No rate yet, assume one valid bit. Downstream will deal with it.
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if (!current_rate_) {
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bit_count = 1;
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return true;
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}
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// How many bits span the specified length?
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float exact_bits = length / current_rate_->bit_length;
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// < 1 bit, current rate is probably too low.
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if (exact_bits < 0.80) return false;
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// Round to the nearest # of bits and determine how
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// well the current rate fits the data.
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float round_bits = std::round(exact_bits);
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float error = std::abs(exact_bits - round_bits) / exact_bits;
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// Good transition are w/in 15% of current rate estimate.
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bit_count = round_bits;
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return error < 0.15;
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}
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const BitExtractor::BaudInfo* BitExtractor::get_baud_info(float bit_length) const {
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// NB: This assumes known_rates_ are ordered slowest first.
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for (const auto& info : known_rates_) {
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if (bit_length >= info.min_bit_length &&
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bit_length <= info.max_bit_length) {
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return &info;
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}
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}
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return nullptr;
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}
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/* CodewordExtractor *************************************/
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void CodewordExtractor::process_bits() {
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// Process all of the bits in the bits queue.
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while (bits_.size() > 0) {
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take_one_bit();
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// Wait until data_ is full.
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if (bit_count_ < data_bit_count)
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continue;
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// Wait for the sync frame.
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if (!has_sync_) {
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if (differ_bit_count(data_, sync_codeword) <= 2)
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handle_sync(/*inverted=*/false);
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else if (differ_bit_count(data_, ~sync_codeword) <= 2)
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handle_sync(/*inverted=*/true);
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continue;
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}
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save_current_codeword();
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if (word_count_ == pocsag::batch_size)
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handle_batch_complete();
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}
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}
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void CodewordExtractor::flush() {
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// Don't bother flushing if there's no pending data.
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if (word_count_ == 0) return;
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pad_idle();
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handle_batch_complete();
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}
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void CodewordExtractor::reset() {
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clear_data_bits();
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has_sync_ = false;
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inverted_ = false;
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word_count_ = 0;
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}
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void CodewordExtractor::clear_data_bits() {
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data_ = 0;
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bit_count_ = 0;
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}
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void CodewordExtractor::take_one_bit() {
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data_ = (data_ << 1) | bits_.pop();
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if (bit_count_ < data_bit_count)
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++bit_count_;
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}
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void CodewordExtractor::handle_sync(bool inverted) {
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clear_data_bits();
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has_sync_ = true;
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inverted_ = inverted;
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word_count_ = 0;
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}
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void CodewordExtractor::save_current_codeword() {
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batch_[word_count_++] = inverted_ ? ~data_ : data_;
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clear_data_bits();
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}
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void CodewordExtractor::handle_batch_complete() {
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on_batch_(*this);
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has_sync_ = false;
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word_count_ = 0;
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}
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void CodewordExtractor::pad_idle() {
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while (word_count_ < pocsag::batch_size)
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batch_[word_count_++] = idle_codeword;
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}
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/* POCSAGProcessor ***************************************/
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void POCSAGProcessor::execute(const buffer_c8_t& buffer) {
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if (!configured) return;
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@ -52,12 +369,12 @@ void POCSAGProcessor::execute(const buffer_c8_t& buffer) {
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bool has_audio = squelch.execute(audio);
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squelch_history = (squelch_history << 1) | (has_audio ? 1 : 0);
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// Has there been any signal?
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// Has there been any signal recently?
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if (squelch_history == 0) {
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// No signal for a while, flush and reset.
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if (!has_been_reset) {
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OnDataFrame(m_numCode, getRate());
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resetVals();
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// No recent signal, flush and prepare for next message.
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if (word_extractor.current() > 0) {
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flush();
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reset();
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send_stats();
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}
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@ -69,18 +386,20 @@ void POCSAGProcessor::execute(const buffer_c8_t& buffer) {
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return;
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}
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// Filter out high-frequency noise. TODO: compensate gain?
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// Filter out high-frequency noise then normalize.
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lpf.execute_in_place(audio);
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normalizer.execute_in_place(audio);
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audio_output.write(audio);
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processDemodulatedSamples(audio.p, 16);
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extractFrames();
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// Decode the messages from the audio.
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bit_extractor.extract_bits(audio);
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word_extractor.process_bits();
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// Update the status.
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samples_processed += buffer.count;
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if (samples_processed >= stat_update_threshold) {
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send_stats();
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samples_processed = 0;
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samples_processed -= stat_update_threshold;
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}
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}
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@ -104,8 +423,8 @@ void POCSAGProcessor::on_message(const Message* const message) {
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void POCSAGProcessor::configure() {
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constexpr size_t decim_0_output_fs = baseband_fs / decim_0.decimation_factor;
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constexpr size_t decim_1_output_fs = decim_0_output_fs / decim_1.decimation_factor;
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const size_t channel_filter_output_fs = decim_1_output_fs / 2;
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const size_t demod_input_fs = channel_filter_output_fs;
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constexpr size_t channel_filter_output_fs = decim_1_output_fs / 2;
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constexpr size_t demod_input_fs = channel_filter_output_fs;
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decim_0.configure(taps_11k0_decim_0.taps);
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decim_1.configure(taps_11k0_decim_1.taps);
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@ -115,384 +434,41 @@ void POCSAGProcessor::configure() {
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// Don't process the audio stream.
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audio_output.configure(false);
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// Set up the frame extraction, limits of baud.
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setFrameExtractParams(demod_input_fs, 4000, 300, 32);
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bit_extractor.configure(demod_input_fs);
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// Set ready to process data.
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configured = true;
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}
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void POCSAGProcessor::send_stats() const {
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POCSAGStatsMessage message(m_fifo.codeword, m_numCode, m_gotSync);
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shared_memory.application_queue.push(message);
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void POCSAGProcessor::flush() {
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word_extractor.flush();
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}
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int POCSAGProcessor::OnDataWord(uint32_t word, int pos) {
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packet.set(pos, word);
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return 0;
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}
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int POCSAGProcessor::OnDataFrame(int len, int baud) {
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if (len > 0) {
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packet.set_bitrate(baud);
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packet.set_flag(pocsag::PacketFlag::NORMAL);
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packet.set_timestamp(Timestamp::now());
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const POCSAGPacketMessage message(packet);
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shared_memory.application_queue.push(message);
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}
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return 0;
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}
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#define BAUD_STABLE (104)
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#define MAX_CONSEC_SAME (32)
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#define MAX_WITHOUT_SINGLE (64)
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#define MAX_BAD_TRANS (10)
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#define M_SYNC (0x7cd215d8)
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#define M_NOTSYNC (0x832dea27)
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#define M_IDLE (0x7a89c197)
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inline int bitsDiff(unsigned long left, unsigned long right) {
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unsigned long xord = left ^ right;
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int count = 0;
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for (int i = 0; i < 32; i++) {
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if ((xord & 0x01) != 0) ++count;
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xord = xord >> 1;
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}
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return (count);
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}
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void POCSAGProcessor::initFrameExtraction() {
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m_averageSymbolLen_1024 = m_maxSymSamples_1024;
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m_lastStableSymbolLen_1024 = m_minSymSamples_1024;
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m_badTransitions = 0;
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m_bitsStart = 0;
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m_bitsEnd = 0;
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m_inverted = false;
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resetVals();
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}
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void POCSAGProcessor::resetVals() {
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if (has_been_reset) return;
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// Reset the parameters
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m_goodTransitions = 0;
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m_badTransitions = 0;
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m_averageSymbolLen_1024 = m_maxSymSamples_1024;
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m_shortestGoodTrans_1024 = m_maxSymSamples_1024;
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m_valMid = 0;
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// And reset the counts
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m_lastTransPos_1024 = 0;
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m_lastBitPos_1024 = 0;
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m_lastSample = 0;
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m_sampleNo = 0;
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m_nextBitPos_1024 = m_maxSymSamples_1024;
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m_nextBitPosInt = (long)m_nextBitPos_1024;
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// Extraction
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m_fifo.numBits = 0;
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m_fifo.codeword = 0;
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m_gotSync = false;
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m_numCode = 0;
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has_been_reset = true;
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void POCSAGProcessor::reset() {
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bits.reset();
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bit_extractor.reset();
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word_extractor.reset();
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samples_processed = 0;
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}
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void POCSAGProcessor::setFrameExtractParams(long a_samplesPerSec, long a_maxBaud, long a_minBaud, long maxRunOfSameValue) {
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m_samplesPerSec = a_samplesPerSec;
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m_minSymSamples_1024 = (uint32_t)(1024.0f * (float)a_samplesPerSec / (float)a_maxBaud);
|
||||
m_maxSymSamples_1024 = (uint32_t)(1024.0f * (float)a_samplesPerSec / (float)a_minBaud);
|
||||
m_maxRunOfSameValue = maxRunOfSameValue;
|
||||
|
||||
m_shortestGoodTrans_1024 = m_maxSymSamples_1024;
|
||||
m_averageSymbolLen_1024 = m_maxSymSamples_1024;
|
||||
m_lastStableSymbolLen_1024 = m_minSymSamples_1024;
|
||||
|
||||
m_nextBitPos_1024 = m_averageSymbolLen_1024 / 2;
|
||||
m_nextBitPosInt = m_nextBitPos_1024 >> 10;
|
||||
|
||||
initFrameExtraction();
|
||||
void POCSAGProcessor::send_stats() const {
|
||||
POCSAGStatsMessage message(
|
||||
word_extractor.current(), word_extractor.count(),
|
||||
word_extractor.has_sync(), bit_extractor.baud_rate());
|
||||
shared_memory.application_queue.push(message);
|
||||
}
|
||||
|
||||
int POCSAGProcessor::processDemodulatedSamples(float* sampleBuff, int noOfSamples) {
|
||||
bool transition = false;
|
||||
uint32_t samplePos_1024 = 0;
|
||||
uint32_t len_1024 = 0;
|
||||
void POCSAGProcessor::send_packet() {
|
||||
packet.set_flag(pocsag::PacketFlag::NORMAL);
|
||||
packet.set_timestamp(Timestamp::now());
|
||||
packet.set_bitrate(bit_extractor.baud_rate());
|
||||
packet.set(word_extractor.batch());
|
||||
|
||||
has_been_reset = false;
|
||||
|
||||
// Loop through the block of data
|
||||
// ------------------------------
|
||||
for (int pos = 0; pos < noOfSamples; ++pos) {
|
||||
m_sample = sampleBuff[pos];
|
||||
m_valMid += (m_sample - m_valMid) / 1024.0f;
|
||||
|
||||
++m_sampleNo;
|
||||
|
||||
// Detect Transition
|
||||
// -----------------
|
||||
transition = !((m_lastSample < m_valMid) ^ (m_sample >= m_valMid)); // use XOR for speed
|
||||
|
||||
// If this is a transition
|
||||
// -----------------------
|
||||
if (transition) {
|
||||
// Calculate samples since last trans
|
||||
// ----------------------------------
|
||||
int32_t fractional_1024 = (int32_t)(((m_sample - m_valMid) * 1024) / (m_sample - m_lastSample));
|
||||
if (fractional_1024 < 0) {
|
||||
fractional_1024 = -fractional_1024;
|
||||
}
|
||||
|
||||
samplePos_1024 = (m_sampleNo << 10) - fractional_1024;
|
||||
len_1024 = samplePos_1024 - m_lastTransPos_1024;
|
||||
m_lastTransPos_1024 = samplePos_1024;
|
||||
|
||||
// If symbol is large enough to be valid
|
||||
// -------------------------------------
|
||||
if (len_1024 > m_minSymSamples_1024) {
|
||||
// Check for shortest good transition
|
||||
// ----------------------------------
|
||||
if ((len_1024 < m_shortestGoodTrans_1024) &&
|
||||
(m_goodTransitions < BAUD_STABLE)) // detect change of symbol size
|
||||
{
|
||||
int32_t fractionOfShortest_1024 = (len_1024 << 10) / m_shortestGoodTrans_1024;
|
||||
|
||||
// If currently at half the baud rate
|
||||
// ----------------------------------
|
||||
if ((fractionOfShortest_1024 > 410) && (fractionOfShortest_1024 < 614)) // 0.4 and 0.6
|
||||
{
|
||||
m_averageSymbolLen_1024 /= 2;
|
||||
m_shortestGoodTrans_1024 = len_1024;
|
||||
}
|
||||
// If currently at the wrong baud rate
|
||||
// -----------------------------------
|
||||
else if (fractionOfShortest_1024 < 768) // 0.75
|
||||
{
|
||||
m_averageSymbolLen_1024 = len_1024;
|
||||
m_shortestGoodTrans_1024 = len_1024;
|
||||
m_goodTransitions = 0;
|
||||
m_lastSingleBitPos_1024 = samplePos_1024 - len_1024;
|
||||
}
|
||||
}
|
||||
|
||||
// Calc the number of bits since events
|
||||
// ------------------------------------
|
||||
int32_t halfSymbol_1024 = m_averageSymbolLen_1024 / 2;
|
||||
int bitsSinceLastTrans = max((uint32_t)1, (len_1024 + halfSymbol_1024) / m_averageSymbolLen_1024);
|
||||
int bitsSinceLastSingle = (((m_sampleNo << 10) - m_lastSingleBitPos_1024) + halfSymbol_1024) / m_averageSymbolLen_1024;
|
||||
|
||||
// Check for single bit
|
||||
// --------------------
|
||||
if (bitsSinceLastTrans == 1) {
|
||||
m_lastSingleBitPos_1024 = samplePos_1024;
|
||||
}
|
||||
|
||||
// If too long since last transition
|
||||
// ---------------------------------
|
||||
if (bitsSinceLastTrans > MAX_CONSEC_SAME) {
|
||||
resetVals();
|
||||
}
|
||||
// If too long sice last single bit
|
||||
// --------------------------------
|
||||
else if (bitsSinceLastSingle > MAX_WITHOUT_SINGLE) {
|
||||
resetVals();
|
||||
} else {
|
||||
// If this is a good transition
|
||||
// ----------------------------
|
||||
int32_t offsetFromExtectedTransition_1024 = len_1024 - (bitsSinceLastTrans * m_averageSymbolLen_1024);
|
||||
if (offsetFromExtectedTransition_1024 < 0) {
|
||||
offsetFromExtectedTransition_1024 = -offsetFromExtectedTransition_1024;
|
||||
}
|
||||
if (offsetFromExtectedTransition_1024 < ((int32_t)m_averageSymbolLen_1024 / 4)) // Has to be within 1/4 of symbol to be good
|
||||
{
|
||||
++m_goodTransitions;
|
||||
uint32_t bitsCount = min((uint32_t)BAUD_STABLE, m_goodTransitions);
|
||||
|
||||
uint32_t propFromPrevious = m_averageSymbolLen_1024 * bitsCount;
|
||||
uint32_t propFromCurrent = (len_1024 / bitsSinceLastTrans);
|
||||
m_averageSymbolLen_1024 = (propFromPrevious + propFromCurrent) / (bitsCount + 1);
|
||||
m_badTransitions = 0;
|
||||
// if ( len < m_shortestGoodTrans ){m_shortestGoodTrans = len;}
|
||||
// Store the old symbol size
|
||||
if (m_goodTransitions >= BAUD_STABLE) {
|
||||
m_lastStableSymbolLen_1024 = m_averageSymbolLen_1024;
|
||||
}
|
||||
}
|
||||
}
|
||||
|
||||
// Set the point of the last bit if not yet stable
|
||||
// -----------------------------------------------
|
||||
if ((m_goodTransitions < BAUD_STABLE) || (m_badTransitions > 0)) {
|
||||
m_lastBitPos_1024 = samplePos_1024 - (m_averageSymbolLen_1024 / 2);
|
||||
}
|
||||
|
||||
// Calculate the exact positiom of the next bit
|
||||
// --------------------------------------------
|
||||
int32_t thisPlusHalfsymbol_1024 = samplePos_1024 + (m_averageSymbolLen_1024 / 2);
|
||||
int32_t lastPlusSymbol = m_lastBitPos_1024 + m_averageSymbolLen_1024;
|
||||
m_nextBitPos_1024 = lastPlusSymbol + ((thisPlusHalfsymbol_1024 - lastPlusSymbol) / 16);
|
||||
|
||||
// Check for bad pos error
|
||||
// -----------------------
|
||||
if (m_nextBitPos_1024 < samplePos_1024) m_nextBitPos_1024 += m_averageSymbolLen_1024;
|
||||
|
||||
// Calculate integer sample after next bit
|
||||
// ---------------------------------------
|
||||
m_nextBitPosInt = (m_nextBitPos_1024 >> 10) + 1;
|
||||
|
||||
} // symbol is large enough to be valid
|
||||
else {
|
||||
// Bad transition, so reset the counts
|
||||
// -----------------------------------
|
||||
++m_badTransitions;
|
||||
if (m_badTransitions > MAX_BAD_TRANS) {
|
||||
resetVals();
|
||||
}
|
||||
}
|
||||
} // end of if transition
|
||||
|
||||
// Reached the point of the next bit
|
||||
// ---------------------------------
|
||||
if (m_sampleNo >= m_nextBitPosInt) {
|
||||
// Everything is good so extract a bit
|
||||
// -----------------------------------
|
||||
if (m_goodTransitions > 20) {
|
||||
// Store value at the center of bit
|
||||
// --------------------------------
|
||||
storeBit();
|
||||
}
|
||||
// Check for long 1 or zero
|
||||
// ------------------------
|
||||
uint32_t bitsSinceLastTrans = ((m_sampleNo << 10) - m_lastTransPos_1024) / m_averageSymbolLen_1024;
|
||||
if (bitsSinceLastTrans > m_maxRunOfSameValue) {
|
||||
resetVals();
|
||||
}
|
||||
|
||||
// Store the point of the last bit
|
||||
// -------------------------------
|
||||
m_lastBitPos_1024 = m_nextBitPos_1024;
|
||||
|
||||
// Calculate the exact point of the next bit
|
||||
// -----------------------------------------
|
||||
m_nextBitPos_1024 += m_averageSymbolLen_1024;
|
||||
|
||||
// Look for the bit after the next bit pos
|
||||
// ---------------------------------------
|
||||
m_nextBitPosInt = (m_nextBitPos_1024 >> 10) + 1;
|
||||
|
||||
} // Reached the point of the next bit
|
||||
|
||||
m_lastSample = m_sample;
|
||||
|
||||
} // Loop through the block of data
|
||||
|
||||
return getNoOfBits();
|
||||
POCSAGPacketMessage message(packet);
|
||||
shared_memory.application_queue.push(message);
|
||||
}
|
||||
|
||||
void POCSAGProcessor::storeBit() {
|
||||
if (++m_bitsStart >= BIT_BUF_SIZE) {
|
||||
m_bitsStart = 0;
|
||||
}
|
||||
|
||||
// Calculate the bit value
|
||||
float sample = (m_sample + m_lastSample) / 2;
|
||||
// int32_t sample_1024 = m_sample_1024;
|
||||
bool bit = sample > m_valMid;
|
||||
|
||||
// If buffer not full
|
||||
if (m_bitsStart != m_bitsEnd) {
|
||||
// Decide on output val
|
||||
if (bit) {
|
||||
m_bits[m_bitsStart] = 0;
|
||||
} else {
|
||||
m_bits[m_bitsStart] = 1;
|
||||
}
|
||||
}
|
||||
// Throw away bits if the buffer is full
|
||||
else {
|
||||
if (--m_bitsStart <= -1) {
|
||||
m_bitsStart = BIT_BUF_SIZE - 1;
|
||||
}
|
||||
}
|
||||
}
|
||||
|
||||
int POCSAGProcessor::extractFrames() {
|
||||
int msgCnt = 0;
|
||||
// While there is unread data in the bits buffer
|
||||
//----------------------------------------------
|
||||
while (getNoOfBits() > 0) {
|
||||
m_fifo.codeword = (m_fifo.codeword << 1) + getBit();
|
||||
m_fifo.numBits++;
|
||||
|
||||
// If number of bits in fifo equals 32
|
||||
//------------------------------------
|
||||
if (m_fifo.numBits >= 32) {
|
||||
// Not got sync
|
||||
// ------------
|
||||
if (!m_gotSync) {
|
||||
if (bitsDiff(m_fifo.codeword, M_SYNC) <= 2) {
|
||||
m_inverted = false;
|
||||
m_gotSync = true;
|
||||
m_numCode = -1;
|
||||
m_fifo.numBits = 0;
|
||||
} else if (bitsDiff(m_fifo.codeword, M_NOTSYNC) <= 2) {
|
||||
m_inverted = true;
|
||||
m_gotSync = true;
|
||||
m_numCode = -1;
|
||||
m_fifo.numBits = 0;
|
||||
} else {
|
||||
// Cause it to load one more bit
|
||||
m_fifo.numBits = 31;
|
||||
}
|
||||
} // Not got sync
|
||||
else {
|
||||
// Increment the word count
|
||||
// ------------------------
|
||||
++m_numCode; // It got set to -1 when a sync was found, now count the 16 words
|
||||
uint32_t val = m_inverted ? ~m_fifo.codeword : m_fifo.codeword;
|
||||
OnDataWord(val, m_numCode);
|
||||
|
||||
// If at the end of a 16 word block
|
||||
// --------------------------------
|
||||
if (m_numCode >= 15) {
|
||||
msgCnt += OnDataFrame(m_numCode + 1, getRate());
|
||||
m_gotSync = false;
|
||||
m_numCode = -1;
|
||||
}
|
||||
m_fifo.numBits = 0;
|
||||
}
|
||||
} // If number of bits in fifo equals 32
|
||||
} // While there is unread data in the bits buffer
|
||||
return msgCnt;
|
||||
} // extractFrames
|
||||
|
||||
short POCSAGProcessor::getBit() {
|
||||
if (m_bitsEnd != m_bitsStart) {
|
||||
if (++m_bitsEnd >= BIT_BUF_SIZE) {
|
||||
m_bitsEnd = 0;
|
||||
}
|
||||
return m_bits[m_bitsEnd];
|
||||
} else {
|
||||
return -1;
|
||||
}
|
||||
}
|
||||
|
||||
int POCSAGProcessor::getNoOfBits() {
|
||||
int bits = m_bitsEnd - m_bitsStart;
|
||||
if (bits < 0) {
|
||||
bits += BIT_BUF_SIZE;
|
||||
}
|
||||
return bits;
|
||||
}
|
||||
|
||||
uint32_t POCSAGProcessor::getRate() {
|
||||
return ((m_samplesPerSec << 10) + 512) / m_lastStableSymbolLen_1024;
|
||||
}
|
||||
/* main **************************************************/
|
||||
|
||||
int main() {
|
||||
EventDispatcher event_dispatcher{std::make_unique<POCSAGProcessor>()};
|
||||
|
|
|
|||
Loading…
Add table
Add a link
Reference in a new issue