mirror of https://github.com/g4klx/MMDVM.git
65 lines
1.9 KiB
C++
65 lines
1.9 KiB
C++
/*
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* Copyright (C) 2020 by Jonathan Naylor G4KLX
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* Copyright (C) 2020 by Geoffrey Merck F4FXL - KC3FRA
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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; either version 2 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 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, write to the Free Software
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* Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.
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*/
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#include "Config.h"
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#include "FMDownsampler.h"
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CFMDownsampler::CFMDownsampler(uint16_t length) :
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m_ringBuffer(length),//length might need tweaking
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m_samplePack(0U),
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m_samplePackPointer(0U),
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m_packIndex(0U),
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m_downSampleIndex(0U)
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{
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m_samplePackPointer = &m_samplePack;
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}
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void CFMDownsampler::addSample(q15_t sample)
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{
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//only take one of three samples
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if(m_downSampleIndex == 0U) {
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switch(m_packIndex){
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case 0:
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m_samplePack = uint32_t(sample) << 12;
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break;
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case 1:{
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m_samplePack |= uint32_t(sample);
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//we did not use MSB; skip it
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m_ringBuffer.put(m_samplePackPointer[1U]);
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m_ringBuffer.put(m_samplePackPointer[2U]);
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m_ringBuffer.put(m_samplePackPointer[3U]);
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m_samplePack = 0;//reset the sample pack
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}
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break;
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default:
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//should never happen
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break;
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}
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m_packIndex++;
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if(m_packIndex >= 2U)//did we pack to samples ?
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m_packIndex = 0U;
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}
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m_downSampleIndex++;
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if(m_downSampleIndex >= 3U)
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m_downSampleIndex = 0U;
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} |