superbuild/modules/openal-soft/core/ambidefs.h

#ifndef CORE_AMBIDEFS_H
#define CORE_AMBIDEFS_H

#include <array>
#include <stddef.h>
#include <stdint.h>

using uint = unsigned int;

/* The maximum number of Ambisonics channels. For a given order (o), the size
 * needed will be (o+1)**2, thus zero-order has 1, first-order has 4, second-
 * order has 9, third-order has 16, and fourth-order has 25.
 */
constexpr uint8_t MaxAmbiOrder{3};
constexpr inline size_t AmbiChannelsFromOrder(size_t order) noexcept
{ return (order+1) * (order+1); }
constexpr size_t MaxAmbiChannels{AmbiChannelsFromOrder(MaxAmbiOrder)};

/* A bitmask of ambisonic channels for 0 to 4th order. This only specifies up
 * to 4th order, which is the highest order a 32-bit mask value can specify (a
 * 64-bit mask could handle up to 7th order).
 */
constexpr uint Ambi0OrderMask{0x00000001};
constexpr uint Ambi1OrderMask{0x0000000f};
constexpr uint Ambi2OrderMask{0x000001ff};
constexpr uint Ambi3OrderMask{0x0000ffff};
constexpr uint Ambi4OrderMask{0x01ffffff};

/* A bitmask of ambisonic channels with height information. If none of these
 * channels are used/needed, there's no height (e.g. with most surround sound
 * speaker setups). This is ACN ordering, with bit 0 being ACN 0, etc.
 */
constexpr uint AmbiPeriphonicMask{0xfe7ce4};

/* The maximum number of ambisonic channels for 2D (non-periphonic)
 * representation. This is 2 per each order above zero-order, plus 1 for zero-
 * order. Or simply, o*2 + 1.
 */
constexpr inline size_t Ambi2DChannelsFromOrder(size_t order) noexcept
{ return order*2 + 1; }
constexpr size_t MaxAmbi2DChannels{Ambi2DChannelsFromOrder(MaxAmbiOrder)};


/* NOTE: These are scale factors as applied to Ambisonics content. Decoder
 * coefficients should be divided by these values to get proper scalings.
 */
struct AmbiScale {
    static auto& FromN3D() noexcept
    {
        static constexpr const std::array<float,MaxAmbiChannels> ret{{
            1.0f, 1.0f, 1.0f, 1.0f, 1.0f, 1.0f, 1.0f, 1.0f,
            1.0f, 1.0f, 1.0f, 1.0f, 1.0f, 1.0f, 1.0f, 1.0f
        }};
        return ret;
    }
    static auto& FromSN3D() noexcept
    {
        static constexpr const std::array<float,MaxAmbiChannels> ret{{
            1.000000000f, /* ACN  0, sqrt(1) */
            1.732050808f, /* ACN  1, sqrt(3) */
            1.732050808f, /* ACN  2, sqrt(3) */
            1.732050808f, /* ACN  3, sqrt(3) */
            2.236067978f, /* ACN  4, sqrt(5) */
            2.236067978f, /* ACN  5, sqrt(5) */
            2.236067978f, /* ACN  6, sqrt(5) */
            2.236067978f, /* ACN  7, sqrt(5) */
            2.236067978f, /* ACN  8, sqrt(5) */
            2.645751311f, /* ACN  9, sqrt(7) */
            2.645751311f, /* ACN 10, sqrt(7) */
            2.645751311f, /* ACN 11, sqrt(7) */
            2.645751311f, /* ACN 12, sqrt(7) */
            2.645751311f, /* ACN 13, sqrt(7) */
            2.645751311f, /* ACN 14, sqrt(7) */
            2.645751311f, /* ACN 15, sqrt(7) */
        }};
        return ret;
    }
    static auto& FromFuMa() noexcept
    {
        static constexpr const std::array<float,MaxAmbiChannels> ret{{
            1.414213562f, /* ACN  0 (W), sqrt(2) */
            1.732050808f, /* ACN  1 (Y), sqrt(3) */
            1.732050808f, /* ACN  2 (Z), sqrt(3) */
            1.732050808f, /* ACN  3 (X), sqrt(3) */
            1.936491673f, /* ACN  4 (V), sqrt(15)/2 */
            1.936491673f, /* ACN  5 (T), sqrt(15)/2 */
            2.236067978f, /* ACN  6 (R), sqrt(5) */
            1.936491673f, /* ACN  7 (S), sqrt(15)/2 */
            1.936491673f, /* ACN  8 (U), sqrt(15)/2 */
            2.091650066f, /* ACN  9 (Q), sqrt(35/8) */
            1.972026594f, /* ACN 10 (O), sqrt(35)/3 */
            2.231093404f, /* ACN 11 (M), sqrt(224/45) */
            2.645751311f, /* ACN 12 (K), sqrt(7) */
            2.231093404f, /* ACN 13 (L), sqrt(224/45) */
            1.972026594f, /* ACN 14 (N), sqrt(35)/3 */
            2.091650066f, /* ACN 15 (P), sqrt(35/8) */
        }};
        return ret;
    }
    static auto& FromUHJ() noexcept
    {
        static constexpr const std::array<float,MaxAmbiChannels> ret{{
            1.000000000f, /* ACN  0 (W), sqrt(1) */
            1.224744871f, /* ACN  1 (Y), sqrt(3/2) */
            1.224744871f, /* ACN  2 (Z), sqrt(3/2) */
            1.224744871f, /* ACN  3 (X), sqrt(3/2) */
            /* Higher orders not relevant for UHJ. */
            1.0f, 1.0f, 1.0f, 1.0f, 1.0f, 1.0f, 1.0f, 1.0f, 1.0f, 1.0f, 1.0f, 1.0f,
        }};
        return ret;
    }

    /* Retrieves per-order HF scaling factors for "upsampling" ambisonic data. */
    static std::array<float,MaxAmbiOrder+1> GetHFOrderScales(const uint in_order,
        const uint out_order) noexcept;
};

struct AmbiIndex {
    static auto& FromFuMa() noexcept
    {
        static constexpr const std::array<uint8_t,MaxAmbiChannels> ret{{
            0,  /* W */
            3,  /* X */
            1,  /* Y */
            2,  /* Z */
            6,  /* R */
            7,  /* S */
            5,  /* T */
            8,  /* U */
            4,  /* V */
            12, /* K */
            13, /* L */
            11, /* M */
            14, /* N */
            10, /* O */
            15, /* P */
            9,  /* Q */
        }};
        return ret;
    }
    static auto& FromFuMa2D() noexcept
    {
        static constexpr const std::array<uint8_t,MaxAmbi2DChannels> ret{{
            0,  /* W */
            3,  /* X */
            1,  /* Y */
            8,  /* U */
            4,  /* V */
            15, /* P */
            9,  /* Q */
        }};
        return ret;
    }

    static auto& FromACN() noexcept
    {
        static constexpr const std::array<uint8_t,MaxAmbiChannels> ret{{
            0,  1,  2,  3,  4,  5,  6,  7,
            8,  9, 10, 11, 12, 13, 14, 15
        }};
        return ret;
    }
    static auto& FromACN2D() noexcept
    {
        static constexpr const std::array<uint8_t,MaxAmbi2DChannels> ret{{
            0, 1,3, 4,8, 9,15
        }};
        return ret;
    }

    static auto& OrderFromChannel() noexcept
    {
        static constexpr const std::array<uint8_t,MaxAmbiChannels> ret{{
            0, 1,1,1, 2,2,2,2,2, 3,3,3,3,3,3,3,
        }};
        return ret;
    }
    static auto& OrderFrom2DChannel() noexcept
    {
        static constexpr const std::array<uint8_t,MaxAmbi2DChannels> ret{{
            0, 1,1, 2,2, 3,3,
        }};
        return ret;
    }
};

#endif /* CORE_AMBIDEFS_H */