alc/ambidefs.h

   1 #ifndef AMBIDEFS_H
   2 #define AMBIDEFS_H
   3
   4 #include <array>
   5 #include <cstdint>
   6
   7 /* The maximum number of Ambisonics channels. For a given order (o), the size
   8  * needed will be (o+1)**2, thus zero-order has 1, first-order has 4, second-
   9  * order has 9, third-order has 16, and fourth-order has 25.
  10  */
  11 #define MAX_AMBI_ORDER 3
  12 constexpr inline size_t AmbiChannelsFromOrder(size_t order) noexcept
  13 { return (order+1) * (order+1); }
  14 #define MAX_AMBI_CHANNELS AmbiChannelsFromOrder(MAX_AMBI_ORDER)
  15
  16 /* A bitmask of ambisonic channels for 0 to 4th order. This only specifies up
  17  * to 4th order, which is the highest order a 32-bit mask value can specify (a
  18  * 64-bit mask could handle up to 7th order).
  19  */
  20 #define AMBI_0ORDER_MASK 0x00000001
  21 #define AMBI_1ORDER_MASK 0x0000000f
  22 #define AMBI_2ORDER_MASK 0x000001ff
  23 #define AMBI_3ORDER_MASK 0x0000ffff
  24 #define AMBI_4ORDER_MASK 0x01ffffff
  25
  26 /* A bitmask of ambisonic channels with height information. If none of these
  27  * channels are used/needed, there's no height (e.g. with most surround sound
  28  * speaker setups). This is ACN ordering, with bit 0 being ACN 0, etc.
  29  */
  30 #define AMBI_PERIPHONIC_MASK (0xfe7ce4)
  31
  32 /* The maximum number of ambisonic channels for 2D (non-periphonic)
  33  * representation. This is 2 per each order above zero-order, plus 1 for zero-
  34  * order. Or simply, o*2 + 1.
  35  */
  36 constexpr inline size_t Ambi2DChannelsFromOrder(size_t order) noexcept
  37 { return order*2 + 1; }
  38 #define MAX_AMBI2D_CHANNELS Ambi2DChannelsFromOrder(MAX_AMBI_ORDER)
  39
  40
  41 /* NOTE: These are scale factors as applied to Ambisonics content. Decoder
  42  * coefficients should be divided by these values to get proper scalings.
  43  */
  44 struct AmbiScale {
  45     static constexpr std::array<float,MAX_AMBI_CHANNELS> FromN3D{{
  46         1.0f, 1.0f, 1.0f, 1.0f, 1.0f, 1.0f, 1.0f, 1.0f,
  47         1.0f, 1.0f, 1.0f, 1.0f, 1.0f, 1.0f, 1.0f, 1.0f
  48     }};
  49     static constexpr std::array<float,MAX_AMBI_CHANNELS> FromSN3D{{
  50         1.000000000f, /* ACN  0, sqrt(1) */
  51         1.732050808f, /* ACN  1, sqrt(3) */
  52         1.732050808f, /* ACN  2, sqrt(3) */
  53         1.732050808f, /* ACN  3, sqrt(3) */
  54         2.236067978f, /* ACN  4, sqrt(5) */
  55         2.236067978f, /* ACN  5, sqrt(5) */
  56         2.236067978f, /* ACN  6, sqrt(5) */
  57         2.236067978f, /* ACN  7, sqrt(5) */
  58         2.236067978f, /* ACN  8, sqrt(5) */
  59         2.645751311f, /* ACN  9, sqrt(7) */
  60         2.645751311f, /* ACN 10, sqrt(7) */
  61         2.645751311f, /* ACN 11, sqrt(7) */
  62         2.645751311f, /* ACN 12, sqrt(7) */
  63         2.645751311f, /* ACN 13, sqrt(7) */
  64         2.645751311f, /* ACN 14, sqrt(7) */
  65         2.645751311f, /* ACN 15, sqrt(7) */
  66     }};
  67     static constexpr std::array<float,MAX_AMBI_CHANNELS> FromFuMa{{
  68         1.414213562f, /* ACN  0 (W), sqrt(2) */
  69         1.732050808f, /* ACN  1 (Y), sqrt(3) */
  70         1.732050808f, /* ACN  2 (Z), sqrt(3) */
  71         1.732050808f, /* ACN  3 (X), sqrt(3) */
  72         1.936491673f, /* ACN  4 (V), sqrt(15)/2 */
  73         1.936491673f, /* ACN  5 (T), sqrt(15)/2 */
  74         2.236067978f, /* ACN  6 (R), sqrt(5) */
  75         1.936491673f, /* ACN  7 (S), sqrt(15)/2 */
  76         1.936491673f, /* ACN  8 (U), sqrt(15)/2 */
  77         2.091650066f, /* ACN  9 (Q), sqrt(35/8) */
  78         1.972026594f, /* ACN 10 (O), sqrt(35)/3 */
  79         2.231093404f, /* ACN 11 (M), sqrt(224/45) */
  80         2.645751311f, /* ACN 12 (K), sqrt(7) */
  81         2.231093404f, /* ACN 13 (L), sqrt(224/45) */
  82         1.972026594f, /* ACN 14 (N), sqrt(35)/3 */
  83         2.091650066f, /* ACN 15 (P), sqrt(35/8) */
  84     }};
  85 };
  86
  87 struct AmbiIndex {
  88     static constexpr std::array<uint8_t,MAX_AMBI_CHANNELS> FromFuMa{{
  89         0,  /* W */
  90         3,  /* X */
  91         1,  /* Y */
  92         2,  /* Z */
  93         6,  /* R */
  94         7,  /* S */
  95         5,  /* T */
  96         8,  /* U */
  97         4,  /* V */
  98         12, /* K */
  99         13, /* L */
 100         11, /* M */
 101         14, /* N */
 102         10, /* O */
 103         15, /* P */
 104         9,  /* Q */
 105     }};
 106     static constexpr std::array<uint8_t,MAX_AMBI_CHANNELS> FromACN{{
 107         0,  1,  2,  3,  4,  5,  6,  7,
 108         8,  9, 10, 11, 12, 13, 14, 15
 109     }};
 110
 111     static constexpr std::array<uint8_t,MAX_AMBI2D_CHANNELS> From2D{{
 112         0, 1,3, 4,8, 9,15
 113     }};
 114     static constexpr std::array<uint8_t,MAX_AMBI_CHANNELS> From3D{{
 115         0,  1,  2,  3,  4,  5,  6,  7,
 116         8,  9, 10, 11, 12, 13, 14, 15
 117     }};
 118 };
 119
 120 #endif /* AMBIDEFS_H */