portapack-mayhem/firmware/baseband/dsp_decimate.hpp

/*
 * 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.
 */

#ifndef __DSP_DECIMATE_H__
#define __DSP_DECIMATE_H__

#include <cstdint>
#include <algorithm>
#include <array>
#include <memory>

#include "dsp_types.hpp"
#include "simd.hpp"
#include "utility.hpp"

namespace dsp {
namespace decimate {

/* "Saturating" scalars used by decimators to scale either
 * 8 or 16 bit complex values into 32 bit complex values.
 * Some of the decimators accept a scale factor as part of
 * configuration, which is then passed to scale_round_and_pack. */
// c8_to_c32_sat_scalar == 2^25. 2^25 * 2^7 (signed C8 Max) == 2^32.
constexpr int32_t c8_to_c32_sat_scalar = 0x2000000;
// c16_to_c32_sat_scalar == 2^17. 2^17 * 2^15 (signed C16 Max) == 2^32.
constexpr int32_t c16_to_c32_sat_scalar = 0x20000;

class Complex8DecimateBy2CIC3 {
   public:
    buffer_c16_t execute(
        const buffer_c8_t& src,
        const buffer_c16_t& dst);

   private:
    uint32_t _i1_i0{0};
    uint32_t _q1_q0{0};
};

class TranslateByFSOver4AndDecimateBy2CIC3 {
   public:
    buffer_c16_t execute(
        const buffer_c8_t& src,
        const buffer_c16_t& dst);

   private:
    uint32_t _q1_i0{0};
    uint32_t _q0_i1{0};
};

class DecimateBy2CIC3 {
   public:
    buffer_c16_t execute(
        const buffer_c16_t& src,
        const buffer_c16_t& dst);

   private:
    uint32_t _iq0{0};
    uint32_t _iq1{0};
};

class FIR64AndDecimateBy2Real {
   public:
    static constexpr size_t taps_count = 64;

    void configure(
        const std::array<int16_t, taps_count>& taps);

    buffer_s16_t execute(
        const buffer_s16_t& src,
        const buffer_s16_t& dst);

   private:
    std::array<int16_t, taps_count + 2> z{};
    std::array<int16_t, taps_count> taps{};
};

class FIRC8xR16x24FS4Decim4 {
   public:
    static constexpr size_t taps_count = 24;
    static constexpr size_t decimation_factor = 4;

    using sample_t = complex8_t;
    using tap_t = int16_t;

    enum class Shift : bool {
        Down = true,
        Up = false
    };

    void configure(
        const std::array<tap_t, taps_count>& taps,
        const int32_t scale = c8_to_c32_sat_scalar,
        const Shift shift = Shift::Down);

    buffer_c16_t execute(
        const buffer_c8_t& src,
        const buffer_c16_t& dst);

   private:
    std::array<vec2_s16, taps_count - decimation_factor> z_{};
    std::array<tap_t, taps_count> taps_{};
    int32_t output_scale = 0;
};

class FIRC8xR16x24FS4Decim8 {
   public:
    static constexpr size_t taps_count = 24;
    static constexpr size_t decimation_factor = 8;

    using sample_t = complex8_t;
    using tap_t = int16_t;

    enum class Shift : bool {
        Down = true,
        Up = false
    };

    void configure(
        const std::array<tap_t, taps_count>& taps,
        const int32_t scale = c8_to_c32_sat_scalar,
        const Shift shift = Shift::Down);

    buffer_c16_t execute(
        const buffer_c8_t& src,
        const buffer_c16_t& dst);

   private:
    std::array<vec2_s16, taps_count - decimation_factor> z_{};
    std::array<tap_t, taps_count> taps_{};
    int32_t output_scale = 0;
};

class FIRC16xR16x16Decim2 {
   public:
    static constexpr size_t taps_count = 16;
    static constexpr size_t decimation_factor = 2;

    using sample_t = complex16_t;
    using tap_t = int16_t;

    void configure(
        const std::array<tap_t, taps_count>& taps,
        const int32_t scale = c16_to_c32_sat_scalar);

    buffer_c16_t execute(
        const buffer_c16_t& src,
        const buffer_c16_t& dst);

   private:
    std::array<vec2_s16, taps_count - decimation_factor> z_{};
    std::array<tap_t, taps_count> taps_{};
    int32_t output_scale = 0;
};

class FIRC16xR16x32Decim8 {
   public:
    static constexpr size_t taps_count = 32;
    static constexpr size_t decimation_factor = 8;

    using sample_t = complex16_t;
    using tap_t = int16_t;

    void configure(
        const std::array<tap_t, taps_count>& taps,
        const int32_t scale = c16_to_c32_sat_scalar);

    buffer_c16_t execute(
        const buffer_c16_t& src,
        const buffer_c16_t& dst);

   private:
    std::array<vec2_s16, taps_count - decimation_factor> z_{};
    std::array<tap_t, taps_count> taps_{};
    int32_t output_scale = 0;
};

class FIRAndDecimateComplex {
   public:
    using sample_t = complex16_t;
    using tap_t = complex16_t;

    using taps_t = tap_t[];

    /* NOTE! Current code makes an assumption that block of samples to be
     * processed will be a multiple of the taps_count.
     */

    template <typename T>
    void configure(
        const T& taps,
        const size_t decimation_factor) {
        configure(taps.data(), taps.size(), decimation_factor);
    }

    buffer_c16_t execute(
        const buffer_c16_t& src,
        const buffer_c16_t& dst);

   private:
    using samples_t = sample_t[];

    std::unique_ptr<samples_t> samples_{};
    std::unique_ptr<taps_t> taps_reversed_{};
    size_t taps_count_{0};
    size_t decimation_factor_{1};

    template <typename T>
    void configure(
        const T* const taps,
        const size_t taps_count,
        const size_t decimation_factor) {
        configure_common(taps_count, decimation_factor);
        std::reverse_copy(&taps[0], &taps[taps_count], &taps_reversed_[0]);
    }

    void configure_common(
        const size_t taps_count,
        const size_t decimation_factor);
};

class DecimateBy2CIC4Real {
   public:
    buffer_s16_t execute(
        const buffer_s16_t& src,
        const buffer_s16_t& dst);

   private:
    int16_t z[5]{};
    int16_t _dummy{};  // TODO: Addresses GCC bug when constructing a class that's not sizeof() % 4 == 0?
};

} /* namespace decimate */
} /* namespace dsp */

#endif /*__DSP_DECIMATE_H__*/