92 lines
3.1 KiB
C++
92 lines
3.1 KiB
C++
/*
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* Copyright (C) 2014 Jared Boone, ShareBrained Technology, Inc.
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*
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* This file is part of PortaPack.
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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, or (at your option)
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* 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; see the file COPYING. If not, write to
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* the Free Software Foundation, Inc., 51 Franklin Street,
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* Boston, MA 02110-1301, USA.
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*/
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#include "channel_decimator.hpp"
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buffer_c16_t ChannelDecimator::execute_decimation(const buffer_c8_t& buffer) {
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const buffer_c16_t work_baseband_buffer {
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work_baseband.data(),
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work_baseband.size()
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};
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const buffer_s16_t work_audio_buffer {
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(int16_t*)work_baseband.data(),
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sizeof(work_baseband) / sizeof(int16_t)
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};
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/* 3.072MHz complex<int8_t>[2048], [-128, 127]
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* -> Shift by -fs/4
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* -> 3rd order CIC: -0.1dB @ 0.028fs, -1dB @ 0.088fs, -60dB @ 0.468fs
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* -0.1dB @ 86kHz, -1dB @ 270kHz, -60dB @ 1.44MHz
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* -> gain of 256
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* -> decimation by 2
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* -> 1.544MHz complex<int16_t>[1024], [-32768, 32512] */
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auto stage_0_out = execute_stage_0(buffer, work_baseband_buffer);
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if( decimation_factor == DecimationFactor::By2 ) {
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return stage_0_out;
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}
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/* 1.536MHz complex<int16_t>[1024], [-32768, 32512]
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* -> 3rd order CIC: -0.1dB @ 0.028fs, -1dB @ 0.088fs, -60dB @ 0.468fs
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* -0.1dB @ 43kHz, -1dB @ 136kHz, -60dB @ 723kHz
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* -> gain of 1
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* -> decimation by 2
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* -> 768kHz complex<int16_t>[512], [-8192, 8128] */
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auto cic_1_out = cic_1.execute(stage_0_out, work_baseband_buffer);
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if( decimation_factor == DecimationFactor::By4 ) {
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return cic_1_out;
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}
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/* 768kHz complex<int16_t>[512], [-32768, 32512]
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* -> 3rd order CIC decimation by 2, gain of 1
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* -> 384kHz complex<int16_t>[256], [-32768, 32512] */
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auto cic_2_out = cic_2.execute(cic_1_out, work_baseband_buffer);
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if( decimation_factor == DecimationFactor::By8 ) {
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return cic_2_out;
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}
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/* 384kHz complex<int16_t>[256], [-32768, 32512]
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* -> 3rd order CIC decimation by 2, gain of 1
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* -> 192kHz complex<int16_t>[128], [-32768, 32512] */
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auto cic_3_out = cic_3.execute(cic_2_out, work_baseband_buffer);
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if( decimation_factor == DecimationFactor::By16 ) {
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return cic_3_out;
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}
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/* 192kHz complex<int16_t>[128], [-32768, 32512]
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* -> 3rd order CIC decimation by 2, gain of 1
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* -> 96kHz complex<int16_t>[64], [-32768, 32512] */
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auto cic_4_out = cic_4.execute(cic_3_out, work_baseband_buffer);
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return cic_4_out;
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}
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buffer_c16_t ChannelDecimator::execute_stage_0(
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const buffer_c8_t& buffer,
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const buffer_c16_t& work_baseband_buffer
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) {
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if( fs_over_4_downconvert ) {
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return translate.execute(buffer, work_baseband_buffer);
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} else {
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return cic_0.execute(buffer, work_baseband_buffer);
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}
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}
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