kopia lustrzana https://github.com/mobilinkd/NucleoTNC
71 wiersze
1.4 KiB
C++
71 wiersze
1.4 KiB
C++
// Copyright 2020 Mobilinkd LLC.
|
|
|
|
#pragma once
|
|
|
|
#include "IirFilter.hpp"
|
|
|
|
#include <array>
|
|
#include <algorithm>
|
|
#include <numeric>
|
|
|
|
namespace mobilinkd
|
|
{
|
|
|
|
template <typename FloatType, size_t N>
|
|
struct SymbolEvm
|
|
{
|
|
using filter_type = tnc::IirFilter<N>;
|
|
using symbol_t = int;
|
|
using result_type = std::tuple<symbol_t, FloatType>;
|
|
|
|
filter_type filter_;
|
|
FloatType evm_ = 0.0;
|
|
|
|
SymbolEvm(const std::array<FloatType, N>& b, const std::array<FloatType, N>& a)
|
|
: filter_(b, a)
|
|
{}
|
|
|
|
FloatType evm() const { return evm_; }
|
|
|
|
/**
|
|
* Decode a normalized sample into a symbol. Symbols
|
|
* are decoded into +3, +1, -1, -3. If an erasure limit
|
|
* is set, symbols outside this limit are 'erased' and
|
|
* returned as 0.
|
|
*/
|
|
result_type operator()(FloatType sample)
|
|
{
|
|
symbol_t symbol;
|
|
FloatType evm;
|
|
|
|
sample = std::min(3.0f, std::max(-3.0f, sample));
|
|
|
|
if (sample > 2)
|
|
{
|
|
symbol = 3;
|
|
evm = (sample - 3) * 0.333333f;
|
|
}
|
|
else if (sample > 0)
|
|
{
|
|
symbol = 1;
|
|
evm = sample - 1;
|
|
}
|
|
else if (sample >= -2)
|
|
{
|
|
symbol = -1;
|
|
evm = sample + 1;
|
|
}
|
|
else
|
|
{
|
|
symbol = -3;
|
|
evm = (sample + 3) * 0.333333f;
|
|
}
|
|
|
|
evm_ = filter_(evm);
|
|
|
|
return std::make_tuple(symbol, evm);
|
|
}
|
|
};
|
|
|
|
} // mobilinkd
|