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https://github.com/f4exb/sdrangel.git
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124 lines
4.1 KiB
C++
124 lines
4.1 KiB
C++
//////////////////////////////////////////////////////////////////////////////////////////////////////////////
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// Copyright (C) 2021 Edouard Griffiths, F4EXB //
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// //
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// This program is free software; you can redistribute it and/or modify //
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// it under the terms of the GNU General Public License as published by //
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// the Free Software Foundation as version 3 of the License, or //
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// (at your option) any later version. //
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// //
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// This program is distributed in the hope that it will be useful, //
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// but WITHOUT ANY WARRANTY; without even the implied warranty of //
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// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the //
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// GNU General Public License V3 for more details. //
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// //
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// You should have received a copy of the GNU General Public License //
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// along with this program. If not, see <http://www.gnu.org/licenses/>. //
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//////////////////////////////////////////////////////////////////////////////////////////////////////////////
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#include <algorithm>
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#include <QMutexLocker>
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#include "dcsdetector.h"
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DCSDetector::DCSDetector() :
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m_bitIndex(0.0),
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m_sampleRate(48000),
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m_eqSamples(nullptr),
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m_high(0.0f),
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m_low(0.0f),
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m_mid(0.0f),
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m_prevSample(0.0f),
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m_dcsWord(0)
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{
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setBitrate(134.3);
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setEqWindow(23);
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}
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bool DCSDetector::analyze(Real *sample, unsigned int& dcsCode)
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{
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QMutexLocker mlock(&m_mutex);
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bool codeAvailable = false;
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if (!m_eqSamples) {
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return false;
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}
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// Equalizer
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m_eqSamples[m_eqIndex++] = *sample;
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if (m_eqIndex == m_eqSize)
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{
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m_high = *std::max_element(m_eqSamples, m_eqSamples + m_eqSize);
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m_low = *std::min_element(m_eqSamples, m_eqSamples + m_eqSize);
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m_mid = (m_high + m_low) / 2.0f;
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// qDebug("DCSDetector::analyze: %f %f %f", m_low, m_mid, m_high);
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m_eqIndex = 0;
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}
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// Edge detection
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if (((m_prevSample < m_mid) && (*sample >= m_mid)) || ((m_prevSample > m_mid) && (*sample <= m_mid))) {
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m_bitIndex = 0.0;
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}
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// Symbol detection
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m_prevSample = *sample;
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float fprev = m_bitIndex;
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m_bitIndex += m_bitsPerSample;
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if ((fprev < 0.5f) && (m_bitIndex >= 0.5f)) // mid point detection
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{
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unsigned int bit = *sample > m_mid ? 1 : 0; // always work in positive mode
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m_dcsWord = (bit << 23) + (m_dcsWord >> 1);
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if (((m_dcsWord >> 9) & 0x07) == 4) // magic signature
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{
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codeAvailable = m_golay2312.decodeParityFirst(&m_dcsWord);
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if (codeAvailable) {
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dcsCode = m_dcsWord & 0x1FF;
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}
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}
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}
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if (m_bitIndex > 1.0f) {
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m_bitIndex -= 1.0f;
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}
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return codeAvailable;
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}
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void DCSDetector::setBitrate(float bitrate)
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{
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m_bitrate = bitrate;
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m_bitsPerSample = m_bitrate / m_sampleRate;
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m_samplesPerBit = m_sampleRate / m_bitrate;
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}
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void DCSDetector::setSampleRate(int sampleRate)
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{
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m_sampleRate = sampleRate;
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m_bitsPerSample = m_bitrate / m_sampleRate;
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m_samplesPerBit = m_sampleRate / m_bitrate;
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}
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void DCSDetector::setEqWindow(int nbBits)
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{
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QMutexLocker mlock(&m_mutex);
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m_eqBits = nbBits;
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m_eqSize = (int) m_samplesPerBit * m_eqBits;
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if (m_eqSamples) {
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delete[] m_eqSamples;
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}
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m_eqSamples = new float[m_eqSize];
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m_eqIndex = 0;
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}
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DCSDetector::~DCSDetector()
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{
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if (m_eqSamples) {
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delete[] m_eqSamples;
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}
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}
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