// floor1.mbt
//
// Vorbis floor1 setup 解析与 decode 预计算。
///|
/// floor1 的配置与预计算数据。
pub struct Floor1 {
partitions : Int
partition_class_list : Array[Int]
class_dimensions : Array[Int]
class_subclasses : Array[Int]
class_masterbooks : Array[Int]
subclass_books : Array[Array[Int]]
multiplier : Int
rangebits : Int
x_list : Array[Int]
sorted_order : Array[Int]
neighbors : Array[Array[Int]]
}
///|
/// 绝对值。
fn iabs(x : Int) -> Int {
if x < 0 {
-x
} else {
x
}
}
///|
/// 线性插值预测：在 (x0,y0)-(x1,y1) 线段上取 x 处的 y。
fn predict_point(x : Int, x0 : Int, x1 : Int, y0 : Int, y1 : Int) -> Int {
let dy = y1 - y0
let adx = x1 - x0
let err = iabs(dy) * (x - x0)
let off = err / adx
if dy < 0 {
y0 - off
} else {
y0 + off
}
}
///|
/// 按 x_list 的值对索引 [0..n) 做升序稳定排序（插入排序，n 很小）。
fn sort_indices(x_list : Array[Int]) -> Array[Int] {
let n = x_list.length()
let indices : Array[Int] = []
for i in 0..= 0 && x_list[indices[j]] > key_x {
indices[j + 1] = indices[j]
j -= 1
}
indices[j + 1] = key
}
indices
}
///|
/// 求 key point `n` 在 x_list 中的左右最近邻居索引（比它小/大的最近者）。
fn neighbors_of(x_list : Array[Int], n : Int) -> Array[Int] {
let mut low = -1
let mut high = 65536
let mut low_idx = 0
let mut high_idx = 0
for i in 0.. low && x_list[i] < x_list[n] {
low = x_list[i]
low_idx = i
}
if x_list[i] < high && x_list[i] > x_list[n] {
high = x_list[i]
high_idx = i
}
}
[low_idx, high_idx]
}
///|
/// 从 `br` 的当前位置解析一个 floor1 配置，并预计算 sorted_order 与 neighbors。
pub fn Floor1::parse(br : BitReader) -> Result[Floor1, String] {
let partitions = br.read_bits(5)
let partition_class_list : Array[Int] = []
let mut max_class = -1
for _ in 0.. max_class {
max_class = c
}
}
let class_dimensions : Array[Int] = []
let class_subclasses : Array[Int] = []
let class_masterbooks : Array[Int] = []
let subclass_books : Array[Array[Int]] = []
for _ in 0..<(max_class + 1) {
let dim = br.read_bits(3) + 1
class_dimensions.push(dim)
let subclasses = br.read_bits(2)
class_subclasses.push(subclasses)
let masterbook = if subclasses != 0 { br.read_bits(8) } else { -1 }
class_masterbooks.push(masterbook)
let books : Array[Int] = []
for _ in 0..<(1 << subclasses) {
books.push(br.read_bits(8) - 1)
}
subclass_books.push(books)
}
let multiplier = br.read_bits(2) + 1
let rangebits = br.read_bits(4)
let x_list : Array[Int] = [0, 1 << rangebits]
for i in 0.. Result[Array[Int], String] {
let range_list = [256, 128, 86, 64]
let range = range_list[self.multiplier - 1]
let amp_bits = ilog(range) - 1
let final_y : Array[Int] = []
final_y.push(br.read_bits(amp_bits))
final_y.push(br.read_bits(amp_bits))
for j in 0.. 0 {
let masterbook = self.class_masterbooks[pclass]
match codebooks[masterbook].decode_scalar(br) {
Ok(v) => cval = v
Err(e) => return Err(e)
}
}
for _ in 0..> cbits
if book >= 0 {
match codebooks[book].decode_scalar(br) {
Ok(v) => final_y.push(v)
Err(e) => return Err(e)
}
} else {
final_y.push(0)
}
}
}
// 用邻居插值校正各关键点
for j in 2..= room {
if highroom > lowroom {
final_y[j] = val - lowroom + pred
} else {
final_y[j] = pred - val + highroom - 1
}
} else if (val & 1) != 0 {
final_y[j] = pred - ((val + 1) >> 1)
} else {
final_y[j] = pred + (val >> 1)
}
} else {
final_y[j] = pred
}
}
Ok(final_y)
}
///|
/// dB 值到线性幅度的转换表（Vorbis 规范规定，256 项）。
let inverse_db_table : Array[Float] = [
1.0649863e-07, 1.1341951e-07, 1.2079015e-07, 1.2863978e-07, 1.3699951e-07, 1.4590251e-07,
1.5538408e-07, 1.6548181e-07, 1.7623575e-07, 1.8768855e-07, 1.9988561e-07, 2.1287530e-07,
2.2670913e-07, 2.4144197e-07, 2.5713223e-07, 2.7384213e-07, 2.9163793e-07, 3.1059021e-07,
3.3077411e-07, 3.5226968e-07, 3.7516214e-07, 3.9954229e-07, 4.2550680e-07, 4.5315863e-07,
4.8260743e-07, 5.1396998e-07, 5.4737065e-07, 5.8294187e-07, 6.2082472e-07, 6.6116941e-07,
7.0413592e-07, 7.4989464e-07, 7.9862701e-07, 8.5052630e-07, 9.0579828e-07, 9.6466216e-07,
1.0273513e-06, 1.0941144e-06, 1.1652161e-06, 1.2409384e-06, 1.3215816e-06, 1.4074654e-06,
1.4989305e-06, 1.5963394e-06, 1.7000785e-06, 1.8105592e-06, 1.9282195e-06, 2.0535261e-06,
2.1869758e-06, 2.3290978e-06, 2.4804557e-06, 2.6416497e-06, 2.8133190e-06, 2.9961443e-06,
3.1908506e-06, 3.3982101e-06, 3.6190449e-06, 3.8542308e-06, 4.1047004e-06, 4.3714470e-06,
4.6555282e-06, 4.9580707e-06, 5.2802740e-06, 5.6234160e-06, 5.9888572e-06, 6.3780469e-06,
6.7925283e-06, 7.2339451e-06, 7.7040476e-06, 8.2047000e-06, 8.7378876e-06, 9.3057248e-06,
9.9104632e-06, 1.0554501e-05, 1.1240392e-05, 1.1970856e-05, 1.2748789e-05, 1.3577278e-05,
1.4459606e-05, 1.5399272e-05, 1.6400004e-05, 1.7465768e-05, 1.8600792e-05, 1.9809576e-05,
2.1096914e-05, 2.2467911e-05, 2.3928002e-05, 2.5482978e-05, 2.7139006e-05, 2.8902651e-05,
3.0780908e-05, 3.2781225e-05, 3.4911534e-05, 3.7180282e-05, 3.9596466e-05, 4.2169667e-05,
4.4910090e-05, 4.7828601e-05, 5.0936773e-05, 5.4246931e-05, 5.7772202e-05, 6.1526565e-05,
6.5524908e-05, 6.9783085e-05, 7.4317983e-05, 7.9147585e-05, 8.4291040e-05, 8.9768747e-05,
9.5602426e-05, 0.00010181521, 0.00010843174, 0.00011547824, 0.00012298267, 0.00013097477,
0.00013948625, 0.00014855085, 0.00015820453, 0.00016848555, 0.00017943469, 0.00019109536,
0.00020351382, 0.00021673929, 0.00023082423, 0.00024582449, 0.00026179955, 0.00027881276,
0.00029693158, 0.00031622787, 0.00033677814, 0.00035866388, 0.00038197188, 0.00040679456,
0.00043323036, 0.00046138411, 0.00049136745, 0.00052329927, 0.00055730621, 0.00059352311,
0.00063209358, 0.00067317058, 0.00071691700, 0.00076350630, 0.00081312324, 0.00086596457,
0.00092223983, 0.00098217216, 0.0010459992, 0.0011139742, 0.0011863665, 0.0012634633,
0.0013455702, 0.0014330129, 0.0015261382, 0.0016253153, 0.0017309374, 0.0018434235,
0.0019632195, 0.0020908006, 0.0022266726, 0.0023713743, 0.0025254795, 0.0026895994,
0.0028643847, 0.0030505286, 0.0032487691, 0.0034598925, 0.0036847358, 0.0039241906,
0.0041792066, 0.0044507950, 0.0047400328, 0.0050480668, 0.0053761186, 0.0057254891,
0.0060975636, 0.0064938176, 0.0069158225, 0.0073652516, 0.0078438871, 0.0083536271,
0.0088964928, 0.009474637, 0.010090352, 0.010746080, 0.011444421, 0.012188144,
0.012980198, 0.013823725, 0.014722068, 0.015678791, 0.016697687, 0.017782797, 0.018938423,
0.020169149, 0.021479854, 0.022875735, 0.024362330, 0.025945531, 0.027631618, 0.029427276,
0.031339626, 0.033376252, 0.035545228, 0.037855157, 0.040315199, 0.042935108, 0.045725273,
0.048696758, 0.051861348, 0.055231591, 0.058820850, 0.062643361, 0.066714279, 0.071049749,
0.075666962, 0.080584227, 0.085821044, 0.091398179, 0.097337747, 0.10366330, 0.11039993,
0.11757434, 0.12521498, 0.13335215, 0.14201813, 0.15124727, 0.16107617, 0.17154380,
0.18269168, 0.19456402, 0.20720788, 0.22067342, 0.23501402, 0.25028656, 0.26655159,
0.28387361, 0.30232132, 0.32196786, 0.34289114, 0.36517414, 0.38890521, 0.41417847,
0.44109412, 0.46975890, 0.50028648, 0.53279791, 0.56742212, 0.60429640, 0.64356699,
0.68538959, 0.72993007, 0.77736504, 0.82788260, 0.88168307, 0.9389798, 1.0,
]
///|
/// Bresenham 线性插值，把 [x0,y0] 到 [x1,y1] 的线段累乘到 output 上（Y 经 inverse_db_table 转换）。
fn draw_line(
output : Array[Float],
x0 : Int,
y0 : Int,
x1 : Int,
y1 : Int,
n : Int,
) -> Unit {
let dy = y1 - y0
let adx = x1 - x0
let ady = iabs(dy)
let base = dy / adx
let sy = if dy < 0 { base - 1 } else { base + 1 }
let ady2 = ady - iabs(base) * adx
let x1c = if x1 > n { n } else { x1 }
let mut x = x0
let mut y = y0
let mut err = 0
if x < x1c {
output[x] = output[x] * inverse_db_table[y & 255]
x += 1
while x < x1c {
err += ady2
if err >= adx {
err -= adx
y += sy
} else {
y += base
}
output[x] = output[x] * inverse_db_table[y & 255]
x += 1
}
}
}
///|
/// floor1 第二阶段：把 finalY 关键点插值成完整 floor 曲线（长度 n2）。
pub fn Floor1::synthesize(
self : Floor1,
final_y : Array[Int],
n2 : Int,
) -> Array[Float] {
let output : Array[Float] = []
for _ in 0..= 0 {
let hy = final_y[j] * self.multiplier
let hx = self.x_list[j]
if lx != hx {
draw_line(output, lx, ly, hx, hy, n2)
}
lx = hx
ly = hy
}
}
if lx < n2 {
let mut j = lx
while j < n2 {
output[j] = output[j] * inverse_db_table[ly & 255]
j += 1
}
}
output
}