portapack-mayhem/firmware/baseband/proc_wfm_audio.cpp

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/*
* Copyright (C) 2014 Jared Boone, ShareBrained Technology, Inc.
*
* This file is part of PortaPack.
*
* This program is free software; you can redistribute it and/or modify
* it under the terms of the GNU General Public License as published by
* the Free Software Foundation; either version 2, or (at your option)
* any later version.
*
* This program is distributed in the hope that it will be useful,
* but WITHOUT ANY WARRANTY; without even the implied warranty of
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
* GNU General Public License for more details.
*
* You should have received a copy of the GNU General Public License
* along with this program; see the file COPYING. If not, write to
* the Free Software Foundation, Inc., 51 Franklin Street,
* Boston, MA 02110-1301, USA.
*/
#include "proc_wfm_audio.hpp"
#include <cstdint>
void WidebandFMAudio::execute(const buffer_c8_t& buffer) {
if( !configured ) {
return;
}
std::array<complex16_t, 512> dst;
const buffer_c16_t dst_buffer {
dst.data(),
dst.size()
};
const auto decim_0_out = decim_0.execute(buffer, dst_buffer);
const auto decim_1_out = decim_1.execute(decim_0_out, dst_buffer);
const auto decimator_out = decim_1_out;
const buffer_s16_t work_audio_buffer {
(int16_t*)decimator_out.p,
sizeof(*decimator_out.p) * decimator_out.count
};
auto channel = decimator_out;
// TODO: Feed channel_stats post-decimation data?
feed_channel_stats(channel);
//feed_channel_spectrum(channel);
/* 384kHz complex<int16_t>[256]
* -> FM demodulation
* -> 384kHz int16_t[256] */
/* TODO: To improve adjacent channel rejection, implement complex channel filter:
* pass < +/- 100kHz, stop > +/- 200kHz
*/
auto audio_oversampled = demod.execute(decimator_out, work_audio_buffer);
/* 384kHz int16_t[256]
* -> 4th order CIC decimation by 2, gain of 1
* -> 192kHz int16_t[128] */
auto audio_4fs = audio_dec_1.execute(audio_oversampled, work_audio_buffer);
/* 192kHz int16_t[128]
* -> 4th order CIC decimation by 2, gain of 1
* -> 96kHz int16_t[64] */
auto audio_2fs = audio_dec_2.execute(audio_4fs, work_audio_buffer);
/* 96kHz int16_t[64]
* -> FIR filter, <15kHz (0.156fs) pass, >19kHz (0.198fs) stop, gain of 1
* -> 48kHz int16_t[32] */
auto audio = audio_filter.execute(audio_2fs, work_audio_buffer);
/* -> 48kHz int16_t[32] */
audio_hpf.execute_in_place(audio);
audio_deemph.execute_in_place(audio);
fill_audio_buffer(audio);
}
void WidebandFMAudio::on_message(const Message* const message) {
switch(message->id) {
case Message::ID::WFMConfigure:
configure(*reinterpret_cast<const WFMConfigureMessage*>(message));
break;
default:
break;
}
}
void WidebandFMAudio::configure(const WFMConfigureMessage& message) {
constexpr size_t baseband_fs = 3072000;
constexpr size_t decim_0_input_fs = baseband_fs;
constexpr size_t decim_0_decimation_factor = 4;
constexpr size_t decim_0_output_fs = decim_0_input_fs / decim_0_decimation_factor;
constexpr size_t decim_1_input_fs = decim_0_output_fs;
constexpr size_t decim_1_decimation_factor = 2;
constexpr size_t decim_1_output_fs = decim_1_input_fs / decim_1_decimation_factor;
constexpr size_t demod_input_fs = decim_1_output_fs;
decim_0.configure(message.decim_0_filter.taps, 33554432);
decim_1.configure(message.decim_1_filter.taps, 131072);
demod.configure(demod_input_fs, message.deviation);
audio_filter.configure(message.audio_filter.taps);
configured = true;
}