opus1 0.3.0

Pure-Rust implementation of the Opus audio codec (RFC 6716), following libopus 1.x
Documentation 
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//! The constant tables of the analysis (libopus `src/analysis.c`), value
//! for value.

/// libopus `dct_table` (analysis.c:57-74): 8 rows of 16 cosines. Row `i`
/// turns the 16 lowest band log energies into the cepstral value `i`.
pub(super) const DCT_TABLE: [f32; 128] = [
    0.250000, 0.250000, 0.250000, 0.250000, 0.250000, 0.250000, 0.250000, 0.250000,
    0.250000, 0.250000, 0.250000, 0.250000, 0.250000, 0.250000, 0.250000, 0.250000,
    0.351851, 0.338330, 0.311806, 0.273300, 0.224292, 0.166664, 0.102631, 0.034654,
    -0.034654, -0.102631, -0.166664, -0.224292, -0.273300, -0.311806, -0.338330, -0.351851,
    0.346760, 0.293969, 0.196424, 0.068975, -0.068975, -0.196424, -0.293969, -0.346760,
    -0.346760, -0.293969, -0.196424, -0.068975, 0.068975, 0.196424, 0.293969, 0.346760,
    0.338330, 0.224292, 0.034654, -0.166664, -0.311806, -0.351851, -0.273300, -0.102631,
    0.102631, 0.273300, 0.351851, 0.311806, 0.166664, -0.034654, -0.224292, -0.338330,
    0.326641, 0.135299, -0.135299, -0.326641, -0.326641, -0.135299, 0.135299, 0.326641,
    0.326641, 0.135299, -0.135299, -0.326641, -0.326641, -0.135299, 0.135299, 0.326641,
    0.311806, 0.034654, -0.273300, -0.338330, -0.102631, 0.224292, 0.351851, 0.166664,
    -0.166664, -0.351851, -0.224292, 0.102631, 0.338330, 0.273300, -0.034654, -0.311806,
    0.293969, -0.068975, -0.346760, -0.196424, 0.196424, 0.346760, 0.068975, -0.293969,
    -0.293969, 0.068975, 0.346760, 0.196424, -0.196424, -0.346760, -0.068975, 0.293969,
    0.273300, -0.166664, -0.338330, 0.034654, 0.351851, 0.102631, -0.311806, -0.224292,
    0.224292, 0.311806, -0.102631, -0.351851, -0.034654, 0.338330, 0.166664, -0.273300,
];

/// libopus `analysis_window` (analysis.c:76-107): the first half of the
/// symmetric window of the 480 samples of one analysis block.
pub(super) const ANALYSIS_WINDOW: [f32; 240] = [
    0.000043, 0.000171, 0.000385, 0.000685, 0.001071, 0.001541, 0.002098, 0.002739,
    0.003466, 0.004278, 0.005174, 0.006156, 0.007222, 0.008373, 0.009607, 0.010926,
    0.012329, 0.013815, 0.015385, 0.017037, 0.018772, 0.020590, 0.022490, 0.024472,
    0.026535, 0.028679, 0.030904, 0.033210, 0.035595, 0.038060, 0.040604, 0.043227,
    0.045928, 0.048707, 0.051564, 0.054497, 0.057506, 0.060591, 0.063752, 0.066987,
    0.070297, 0.073680, 0.077136, 0.080665, 0.084265, 0.087937, 0.091679, 0.095492,
    0.099373, 0.103323, 0.107342, 0.111427, 0.115579, 0.119797, 0.124080, 0.128428,
    0.132839, 0.137313, 0.141849, 0.146447, 0.151105, 0.155823, 0.160600, 0.165435,
    0.170327, 0.175276, 0.180280, 0.185340, 0.190453, 0.195619, 0.200838, 0.206107,
    0.211427, 0.216797, 0.222215, 0.227680, 0.233193, 0.238751, 0.244353, 0.250000,
    0.255689, 0.261421, 0.267193, 0.273005, 0.278856, 0.284744, 0.290670, 0.296632,
    0.302628, 0.308658, 0.314721, 0.320816, 0.326941, 0.333097, 0.339280, 0.345492,
    0.351729, 0.357992, 0.364280, 0.370590, 0.376923, 0.383277, 0.389651, 0.396044,
    0.402455, 0.408882, 0.415325, 0.421783, 0.428254, 0.434737, 0.441231, 0.447736,
    0.454249, 0.460770, 0.467298, 0.473832, 0.480370, 0.486912, 0.493455, 0.500000,
    0.506545, 0.513088, 0.519630, 0.526168, 0.532702, 0.539230, 0.545751, 0.552264,
    0.558769, 0.565263, 0.571746, 0.578217, 0.584675, 0.591118, 0.597545, 0.603956,
    0.610349, 0.616723, 0.623077, 0.629410, 0.635720, 0.642008, 0.648271, 0.654508,
    0.660720, 0.666903, 0.673059, 0.679184, 0.685279, 0.691342, 0.697372, 0.703368,
    0.709330, 0.715256, 0.721144, 0.726995, 0.732807, 0.738579, 0.744311, 0.750000,
    0.755647, 0.761249, 0.766807, 0.772320, 0.777785, 0.783203, 0.788573, 0.793893,
    0.799162, 0.804381, 0.809547, 0.814660, 0.819720, 0.824724, 0.829673, 0.834565,
    0.839400, 0.844177, 0.848895, 0.853553, 0.858151, 0.862687, 0.867161, 0.871572,
    0.875920, 0.880203, 0.884421, 0.888573, 0.892658, 0.896677, 0.900627, 0.904508,
    0.908321, 0.912063, 0.915735, 0.919335, 0.922864, 0.926320, 0.929703, 0.933013,
    0.936248, 0.939409, 0.942494, 0.945503, 0.948436, 0.951293, 0.954072, 0.956773,
    0.959396, 0.961940, 0.964405, 0.966790, 0.969096, 0.971321, 0.973465, 0.975528,
    0.977510, 0.979410, 0.981228, 0.982963, 0.984615, 0.986185, 0.987671, 0.989074,
    0.990393, 0.991627, 0.992778, 0.993844, 0.994826, 0.995722, 0.996534, 0.997261,
    0.997902, 0.998459, 0.998929, 0.999315, 0.999615, 0.999829, 0.999957, 1.000000,
];

/// libopus `tbands` (analysis.c:109-111): the edges of the 18 bands of the
/// analysis, in bins of the 480-point FFT at 24 kHz (25 Hz per bin).
pub(super) const TBANDS: [usize; 19] = [
    4, 8, 12, 16, 20, 24, 28, 32, 40, 48, 56, 64, 80, 96, 112, 136, 160, 192, 240,
];

/// libopus `std_feature_bias` (analysis.c:410-413): the mean of each
/// standard deviation feature, removed before the network.
pub(super) const STD_FEATURE_BIAS: [f32; 9] = [
    5.684947, 3.475288, 1.770634, 1.599784, 3.773215, 2.163313, 1.260756, 1.116868, 1.918795,
];