82 lines
2.1 KiB
C++
82 lines
2.1 KiB
C++
// Copyright (c) Charles J. Cliffe
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// SPDX-License-Identifier: GPL-2.0+
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#include "ModemUSB.h"
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ModemUSB::ModemUSB() : ModemAnalog() {
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// half band filter used for side-band elimination
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// demodAM_USB = ampmodem_create(0.25, -0.25, LIQUID_AMPMODEM_USB, 1);
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#ifdef WIN32
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ssbFilt = firfilt_crcf_create_kaiser(23, 0.25, 90.0, 0.01f);
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#else
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ssbFilt = iirfilt_crcf_create_lowpass(6, 0.25);
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#endif
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ssbShift = nco_crcf_create(LIQUID_NCO);
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nco_crcf_set_frequency(ssbShift, (2.0f * M_PI) * 0.25f);
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c2rFilt = firhilbf_create(5, 90.0);
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useSignalOutput(true);
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}
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ModemBase *ModemUSB::factory() {
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return new ModemUSB;
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}
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std::string ModemUSB::getName() {
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return "USB";
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}
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ModemUSB::~ModemUSB() {
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#ifdef WIN32
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firfilt_crcf_destroy(ssbFilt);
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#else
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iirfilt_crcf_destroy(ssbFilt);
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#endif
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nco_crcf_destroy(ssbShift);
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firhilbf_destroy(c2rFilt);
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// ampmodem_destroy(demodAM_USB);
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}
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int ModemUSB::checkSampleRate(long long sampleRate, int /* audioSampleRate */) {
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if (sampleRate < MIN_BANDWIDTH) {
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return MIN_BANDWIDTH;
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}
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if (sampleRate % 2 == 0) {
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return sampleRate;
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}
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return sampleRate+1;
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}
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int ModemUSB::getDefaultSampleRate() {
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return 5400;
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}
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void ModemUSB::demodulate(ModemKit *kit, ModemIQData *input, AudioThreadInput *audioOut) {
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ModemKitAnalog *akit = (ModemKitAnalog *)kit;
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initOutputBuffers(akit,input);
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if (!bufSize) {
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input->decRefCount();
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return;
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}
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liquid_float_complex x, y;
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for (size_t i = 0; i < bufSize; i++) { // Reject lower band
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nco_crcf_step(ssbShift);
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nco_crcf_mix_down(ssbShift, input->data[i], &x);
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#ifdef WIN32
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firfilt_crcf_push(ssbFilt, x);
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firfilt_crcf_execute(ssbFilt, &y);
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#else
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iirfilt_crcf_execute(ssbFilt, x, &y);
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#endif
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nco_crcf_mix_up(ssbShift, y, &x);
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// Liquid-DSP AMPModem SSB drifts with strong signals near baseband (like a carrier?)
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// ampmodem_demodulate(demodAM_USB, y, &demodOutputData[i]);
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firhilbf_c2r_execute(c2rFilt, x, &demodOutputData[i]);
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}
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buildAudioOutput(akit, audioOut, true);
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}
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