alpha_p3.h

// Copyright 2020-2022 Jon Ville

#pragma once

#include "../simd_granodi_math/simd_granodi_math.h"

namespace jon_dsp {

using namespace simd_granodi;

// For scaling attack / release times to be the same as many compressors /
// expanders, equal to 1/2.2
// Use on the time, NOT the alpha
static constexpr double conventional_time_scale_ = 0.45454545454545453;

// Utility function for exponential smoothing filters (single pole lowpass
// filters calc from time)
// Gives an alpha of 0.0 for true instant attack / release if time_ms = 0.0
template <typename VecType>
inline VecType sg_vectorcall(exp_smoothing_alpha_p3)(const float sample_rate,
    const VecType time_ms)
{
    typedef typename VecType::elem_t elem_t;
    VecType denom = time_ms * (elem_t{sample_rate} * elem_t{0.001});
    auto dgtz = denom > 0.0;
    denom = dgtz.choose(denom, 1.0);
    VecType result = exp_p3(-1.0 / denom);
    return dgtz.choose_else_zero(result);
}

} // namespace jon_dsp