filmcraft/crates/aac/tools/gen.py at main · hmmhmmhm/filmcraft

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import json

out = ['//! AAC Huffman codebooks (ISO/IEC 14496-3 §4.A.1, spectrum codebooks 1–11 and the scalefactor codebook).',

'//!',

'//! Each table is indexed by the codebook index defined in the standard and stores `(codeword, length)`.',

'//! Generated data: derived by black-box probing of an external decoder used purely as a test oracle',

'//! (every table is a complete prefix code — Kraft sum exactly 1 — covering every index once; see',

'//! `tests::codebooks_are_complete_prefix_codes`).',

'',

'#![allow(clippy::unreadable_literal)]',

'']

for cb in [0] + list(range(1, 12)):

d = json.load(open(f'cb{cb}.json'))

n = len(d)

arr = [None] * n

for s, i in d.items():

arr[i] = (int(s, 2), len(s))

name = 'SCALEFACTOR' if cb == 0 else f'SPECTRUM_{cb}'

out.append(f'pub(crate) static {name}: [(u32, u8); {n}] = [')

line = ' '

for (c, l) in arr:

item = f' (0x{c:x}, {l}),'

if len(line) + len(item) > 100:

out.append(line)

line = ' '

line += item

out.append(line)

out.append('];')

out.append('')

open('huffman_tables.rs', 'w').write('\n'.join(out))