bsnes/higan/sfc/dsp/gaussian.cpp

const int16 DSP::GaussianTable[512] = {
     0,    0,    0,    0,    0,    0,    0,    0,    0,    0,    0,    0,    0,    0,    0,    0,
     1,    1,    1,    1,    1,    1,    1,    1,    1,    1,    1,    2,    2,    2,    2,    2,
     2,    2,    3,    3,    3,    3,    3,    4,    4,    4,    4,    4,    5,    5,    5,    5,
     6,    6,    6,    6,    7,    7,    7,    8,    8,    8,    9,    9,    9,   10,   10,   10,
    11,   11,   11,   12,   12,   13,   13,   14,   14,   15,   15,   15,   16,   16,   17,   17,
    18,   19,   19,   20,   20,   21,   21,   22,   23,   23,   24,   24,   25,   26,   27,   27,
    28,   29,   29,   30,   31,   32,   32,   33,   34,   35,   36,   36,   37,   38,   39,   40,
    41,   42,   43,   44,   45,   46,   47,   48,   49,   50,   51,   52,   53,   54,   55,   56,
    58,   59,   60,   61,   62,   64,   65,   66,   67,   69,   70,   71,   73,   74,   76,   77,
    78,   80,   81,   83,   84,   86,   87,   89,   90,   92,   94,   95,   97,   99,  100,  102,
   104,  106,  107,  109,  111,  113,  115,  117,  118,  120,  122,  124,  126,  128,  130,  132,
   134,  137,  139,  141,  143,  145,  147,  150,  152,  154,  156,  159,  161,  163,  166,  168,
   171,  173,  175,  178,  180,  183,  186,  188,  191,  193,  196,  199,  201,  204,  207,  210,
   212,  215,  218,  221,  224,  227,  230,  233,  236,  239,  242,  245,  248,  251,  254,  257,
   260,  263,  267,  270,  273,  276,  280,  283,  286,  290,  293,  297,  300,  304,  307,  311,
   314,  318,  321,  325,  328,  332,  336,  339,  343,  347,  351,  354,  358,  362,  366,  370,
   374,  378,  381,  385,  389,  393,  397,  401,  405,  410,  414,  418,  422,  426,  430,  434,
   439,  443,  447,  451,  456,  460,  464,  469,  473,  477,  482,  486,  491,  495,  499,  504,
   508,  513,  517,  522,  527,  531,  536,  540,  545,  550,  554,  559,  563,  568,  573,  577,
   582,  587,  592,  596,  601,  606,  611,  615,  620,  625,  630,  635,  640,  644,  649,  654,
   659,  664,  669,  674,  678,  683,  688,  693,  698,  703,  708,  713,  718,  723,  728,  732,
   737,  742,  747,  752,  757,  762,  767,  772,  777,  782,  787,  792,  797,  802,  806,  811,
   816,  821,  826,  831,  836,  841,  846,  851,  855,  860,  865,  870,  875,  880,  884,  889,
   894,  899,  904,  908,  913,  918,  923,  927,  932,  937,  941,  946,  951,  955,  960,  965,
   969,  974,  978,  983,  988,  992,  997, 1001, 1005, 1010, 1014, 1019, 1023, 1027, 1032, 1036,
  1040, 1045, 1049, 1053, 1057, 1061, 1066, 1070, 1074, 1078, 1082, 1086, 1090, 1094, 1098, 1102,
  1106, 1109, 1113, 1117, 1121, 1125, 1128, 1132, 1136, 1139, 1143, 1146, 1150, 1153, 1157, 1160,
  1164, 1167, 1170, 1174, 1177, 1180, 1183, 1186, 1190, 1193, 1196, 1199, 1202, 1205, 1207, 1210,
  1213, 1216, 1219, 1221, 1224, 1227, 1229, 1232, 1234, 1237, 1239, 1241, 1244, 1246, 1248, 1251,
  1253, 1255, 1257, 1259, 1261, 1263, 1265, 1267, 1269, 1270, 1272, 1274, 1275, 1277, 1279, 1280,
  1282, 1283, 1284, 1286, 1287, 1288, 1290, 1291, 1292, 1293, 1294, 1295, 1296, 1297, 1297, 1298,
  1299, 1300, 1300, 1301, 1302, 1302, 1303, 1303, 1303, 1304, 1304, 1304, 1304, 1304, 1305, 1305,
};

auto DSP::gaussianInterpolate(const Voice& v) -> signed {
  //make pointers into gaussian table based on fractional position between samples
  signed offset = (v.gaussianOffset >> 4) & 0xff;
  const int16* forward = GaussianTable + 255 - offset;
  const int16* reverse = GaussianTable       + offset;  //mirror left half of gaussian table

  offset = v.bufferOffset + (v.gaussianOffset >> 12);
  signed output;
  output  = (forward[  0] * v.buffer[offset + 0]) >> 11;
  output += (forward[256] * v.buffer[offset + 1]) >> 11;
  output += (reverse[256] * v.buffer[offset + 2]) >> 11;
  output  = (int16)output;
  output += (reverse[  0] * v.buffer[offset + 3]) >> 11;
  return sclamp<16>(output) & ~1;
}