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#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;
}
};
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 */
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