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opusenc: build the PVQ V table once for encode_pulses

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encode_pulses rebuilt the full V(n, k) table with saturating u64 adds for
every coded band and summed the prefixes through a closure. Build the table
once (n <= 176, k <= 128, saturated at u32::MAX, 91 KB) and sum the prefixes
over a contiguous row slice. Shapes outside that range, which the band
layout never produces, fall back to a local table. The unused scratch Vec
is gone from BandEnc.

The bitstream is unchanged; a test keeps the old per-call encoder and
compares the coded bytes on random codewords over the whole (n, k) range.

Co-Authored-By: Claude Sonnet 5.5 <noreply@anthropic.com>
This commit is contained in:
vangel76
2026-10-25 12:01:39 +01:00
co-authored by Claude Sonnet 5.5
parent 991904888a
commit e3593d608a
1 changed files with 117 additions and 22 deletions
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crates/opusenc/src/bands.rs
+117 -22
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@@ -146,25 +146,45 @@ pub fn pvq_search(x: &[f32], k: usize, y: &mut [i32]) {
}
}
/// Encodes the PVQ codeword `y` (`sum |y| = k`) as the index the RFC 6716 §4.3.4.2 decoder maps
/// back to `y`.
pub fn encode_pulses(y: &[i32], k: usize, enc: &mut RangeEncoder, v: &mut Vec<u64>) {
let n = y.len();
let w = k + 1;
v.clear();
v.resize((n + 1) * w, 0);
/// Largest band width and pulse count the encoder codes (176 coefficients, `get_pulses(40)` = 128).
const PVQ_MAX_N: usize = 176;
const PVQ_MAX_K: usize = 128;
/// Row-major `V(n, k)` for `n <= max_n`, `k <= max_k` with row stride `max_k + 1`, saturated at
/// `u32::MAX` (a codebook that large is never coded, see `rate::fits_in32`).
fn build_pvq_table(max_n: usize, max_k: usize) -> Vec<u32> {
let w = max_k + 1;
let mut v = vec![0u32; (max_n + 1) * w];
v[0] = 1;
for nn in 1..=n {
for nn in 1..=max_n {
v[nn * w] = 1;
for kk in 1..=k {
let a = v[(nn - 1) * w + kk];
let b = v[nn * w + kk - 1];
let c = v[(nn - 1) * w + kk - 1];
v[nn * w + kk] = a.saturating_add(b).saturating_add(c);
for kk in 1..=max_k {
let sum = v[(nn - 1) * w + kk] as u64 + v[nn * w + kk - 1] as u64 + v[(nn - 1) * w + kk - 1] as u64;
v[nn * w + kk] = sum.min(u32::MAX as u64) as u32;
}
}
let total = v[n * w + k];
let vv = |nn: usize, kx: usize| v[nn * w + kx];
v
}
fn pvq_table() -> &'static [u32] {
static TABLE: std::sync::OnceLock<Vec<u32>> = std::sync::OnceLock::new();
TABLE.get_or_init(|| build_pvq_table(PVQ_MAX_N, PVQ_MAX_K))
}
/// Encodes the PVQ codeword `y` (`sum |y| = k`) as the index the RFC 6716 §4.3.4.2 decoder maps
/// back to `y`.
pub fn encode_pulses(y: &[i32], k: usize, enc: &mut RangeEncoder) {
let n = y.len();
// Shapes outside the coded range (never produced by the band layout) get a local table.
let local;
let (v, w) = if n <= PVQ_MAX_N && k <= PVQ_MAX_K {
(pvq_table(), PVQ_MAX_K + 1)
} else {
local = build_pvq_table(n, k);
(&local[..], k + 1)
};
let row = |nn: usize| &v[nn * w..(nn + 1) * w];
let total = row(n)[k] as u64;
let mut index = 0u64;
let mut kk = k;
for j in 0..n {
@@ -173,10 +193,11 @@ pub fn encode_pulses(y: &[i32], k: usize, enc: &mut RangeEncoder, v: &mut Vec<u6
}
let rem = n - j;
let t = y[j].unsigned_abs() as usize;
let below = row(rem - 1);
// Codewords with |y_j| = t start at sum_{m < kk - t} V(rem-1, m) within their sign half.
let mut base: u64 = (0..kk - t).map(|m| vv(rem - 1, m)).sum();
let mut base: u64 = below[..kk - t].iter().map(|&x| x as u64).sum();
if y[j] < 0 {
base += (vv(rem - 1, kk) + vv(rem, kk)) / 2;
base += (below[kk] as u64 + row(rem)[kk] as u64) / 2;
}
index += base;
kk -= t;
@@ -193,7 +214,6 @@ pub struct BandEnc<'m, 'e> {
pub i: usize,
pub spread: usize,
pub remaining_bits: i32,
pvq_v: Vec<u64>,
iy: Vec<i32>,
tmp: Vec<f32>,
}
@@ -287,7 +307,7 @@ impl BandEnc<'_, '_> {
iy.clear();
iy.resize(n, 0);
pvq_search(&tmp, k, &mut iy);
encode_pulses(&iy, k, self.enc, &mut self.pvq_v);
encode_pulses(&iy, k, self.enc);
self.iy = iy;
self.tmp = tmp;
}
@@ -316,7 +336,7 @@ pub fn quant_all_bands(
) {
let mm = 1usize << lm;
debug_assert!(c == 1 || dual_stereo || intensity <= start, "stereo frames are coded as dual stereo");
let mut ctx = BandEnc { m, enc, i: 0, spread, remaining_bits: 0, pvq_v: Vec::new(), iy: Vec::new(), tmp: Vec::new() };
let mut ctx = BandEnc { m, enc, i: 0, spread, remaining_bits: 0, iy: Vec::new(), tmp: Vec::new() };
for i in start..end {
ctx.i = i;
let xo = mm * EBANDS[i] as usize;
@@ -466,12 +486,11 @@ mod tests {
#[test]
fn pvq_index_roundtrip_exhaustive() {
let mut v = Vec::new();
for n in 1..6usize {
for k in 1..6usize {
for y in all_codewords(n, k) {
let mut e = RangeEncoder::new();
encode_pulses(&y, k, &mut e, &mut v);
encode_pulses(&y, k, &mut e);
let buf = e.done(16);
let mut d = RangeDecoder::new(&buf);
assert_eq!(decode_pulses(n, k, &mut d), y, "n={n} k={k}");
@@ -480,6 +499,82 @@ mod tests {
}
}
/// The per-call table encoder this module used before the shared table.
fn encode_pulses_reference(y: &[i32], k: usize, enc: &mut RangeEncoder) {
let n = y.len();
let w = k + 1;
let mut v = vec![0u64; (n + 1) * w];
v[0] = 1;
for nn in 1..=n {
v[nn * w] = 1;
for kk in 1..=k {
let a = v[(nn - 1) * w + kk];
let b = v[nn * w + kk - 1];
let c = v[(nn - 1) * w + kk - 1];
v[nn * w + kk] = a.saturating_add(b).saturating_add(c);
}
}
let total = v[n * w + k];
let vv = |nn: usize, kx: usize| v[nn * w + kx];
let mut index = 0u64;
let mut kk = k;
for j in 0..n {
if kk == 0 {
break;
}
let rem = n - j;
let t = y[j].unsigned_abs() as usize;
let mut base: u64 = (0..kk - t).map(|m| vv(rem - 1, m)).sum();
if y[j] < 0 {
base += (vv(rem - 1, kk) + vv(rem, kk)) / 2;
}
index += base;
kk -= t;
}
if total >= 2 {
enc.uint(index as u32, total as u32);
}
}
#[test]
fn pvq_table_encode_matches_per_call_table() {
let mut seed = 0x9E37_79B9_7F4A_7C15u64;
let mut next = move |m: u64| {
seed ^= seed << 13;
seed ^= seed >> 7;
seed ^= seed << 17;
seed % m
};
let mut checked = 0;
for n in (1..=PVQ_MAX_N).step_by(5).chain([PVQ_MAX_N]) {
for k in (1..=PVQ_MAX_K).step_by(3).chain([PVQ_MAX_K]) {
if crate::rate::pvq_v(n, k) > u32::MAX as u128 {
continue;
}
for _ in 0..4 {
let mut y = vec![0i32; n];
for _ in 0..k {
let at = next(n as u64) as usize;
y[at] += if next(2) == 0 { 1 } else { -1 };
}
// Opposite pulses cancel; top up so that sum |y| = k again.
let mut have: usize = y.iter().map(|v| v.unsigned_abs() as usize).sum();
while have < k {
let at = next(n as u64) as usize;
y[at] += if y[at] < 0 { -1 } else { 1 };
have += 1;
}
let (mut a, mut b) = (RangeEncoder::new(), RangeEncoder::new());
encode_pulses(&y, k, &mut a);
encode_pulses_reference(&y, k, &mut b);
assert_eq!(a.done(16), b.done(16), "n={n} k={k}");
checked += 1;
}
}
}
assert!(checked > 100, "{checked}");
}
#[test]
fn pvq_search_finds_good_direction() {
let x: Vec<f32> = (0..32).map(|i| ((i as f32) * 0.7).sin()).collect();