alc/ambidefs.h

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