Picked sound_bank rather than tie, where three discriminators have now come back
negative and a fourth would be guesswork.
The body after the 24-byte head opens with twelve words. Six are settled across
all 27 levels:
word value note
0 varies per level not identified; 27 distinct
1 60 constant
2 varies per level not identified; 23 distinct
3 0 constant
4 daw_size == the header's daw_size, exactly
5 daw_size the same value again
6,7,8 0 constant
9 127 constant
10 1 constant
11 0 constant
Level 0's words 4 and 5 are both 1,482,000, and daw_size is 1,482,000.
THE POINTER THAT WAS NOT ONE
Words 4 and 5 were briefly recorded as pointers into the DAW region. They are not.
The test that promoted them was "does this value fall inside [daw_offset,
daw_offset + daw_size)" -- and the DAW region is ~1.5 MB starting near the front of
a ~1.5 MB extent, so almost any plausible 32-bit word lands inside it. 1,482,000 is
merely just under the top of exactly that range.
A range test is not an identification. What survives is EQUALITY with daw_size,
exact on all 27 levels and asserted, which is a claim that can fail rather than one
that is almost always true.
That is the fourth time this session a plausible reading of a single number has had
to be withdrawn for something falsifiable: the 305x class-ID slot, the UV-corner
texcoords, the VIF code word, and now this. The pattern is consistent enough to be
worth stating as a rule -- a test that passes almost always is measuring the shape
of the data, not a property of it.
Word 0 gets one note: levels 1 and 4 hold 13,042,052 and 13,042,054, two apart,
while their daw_sizes differ by 63,504. Whatever it is, it is not a size.
The remainder of the SBlk body -- the per-sound record table -- is still undecoded,
so sound_bank stays open. A SBlkBodyHead struct carries the twelve words with the
constants asserted in its docs.
259 tests.
sound_bank's head was parsed but never characterised. Across all 27 levels the
SBlk region opens identically for its first twelve bytes:
+0x00 "SBlk" +0x04 1 +0x08 4 +0x0c "DAW\0" +0x10 0
and +0x14 is the only word that varies. It varies with its low sixteen bits zero
on all 27, leaving 0x0092..0x0103 -- 146 to 259.
That is the shape of a record count, and it tracks the body length at close to
100 bytes per unit. It is not one:
body / field_14 91.2 .. 110.8 across 27 levels
any stride 0..80 with body = stride*word + constant exactly: no
So the test asserts the negative too. If a stride ever makes the relation exact
on all 27, sound_bank_sblk_head_is_constant_apart_from_one_word fails and asks
for the record size to be revisited. A near-miss at 100 bytes/record is exactly
what hardens into a name the next time somebody glances at it; the constants are
also checked individually so a real deviation names which one moved.
The DAW region begins with sixteen zero bytes then block-structured data with
16-byte periodicity and slowly varying nibbles -- consistent with block
compressed audio, not decoded. Recorded as such.
Two mistakes, both mine, both the same shape as earlier ones:
1. The constructor bound `format_tag` with a `let` BEFORE the two words that
precede it in the file, consuming bytes 4..8 and shifting every field after
it. The struct literal listed the names in the right order; the statements did
not. A scratch script reading the same bytes gave the opposite answer, which
is what exposed it. Fixed, with a comment, because "read the lets in file
order" gets undone otherwise.
2. Inserting the new test ahead of an existing one stranded that test's #[test]
on my doc comment -- silently unregistering
tie_vertex_element_is_16_bytes_with_fixed_texcoords. This is the SAME mistake
as two commits ago and I made it again. It again surfaced only as clippy's
"never used" rather than as a missing test. Restored and verified by listing
the registered tests rather than trusting the count.
240 tests, clippy clean, both tie vertex tests confirmed present.
A level's sound extent is two regions: an `SBlk` descriptor table and the
sample data that follows it. Four u32 at the head describe the layout, and
the invariant that establishes it is sblk_offset + sblk_size == daw_offset,
which holds on all 27 levels. That is what pins the field meanings; the
numbers alone are ambiguous about which of them is the offset.
DAW is a format tag inside the SBlk header, not a region signature. It
occurs exactly once in the entire extent, at sblk_offset + 12, naming the
sample format -- the sample data itself starts at daw_offset with no
signature at all, roughly 19 KB away on level 0. Reading it as a region
magic is the obvious reading and it is wrong.
daw_size never reaches the end of the file. The tail is positive on all 27
levels, 232 to 1,848 bytes, so the field describes less than the region
it names; the test asserts that direction rather than inventing a size
that fits.
523,720 SBlk and 37,649,008 DAW bytes across the 27 levels.
The sample format inside DAW is not decoded. It looks like VAG/ADPCM from
the nibble packing, and it has no bearing on drawing anything, so it stays
open rather than getting a half-answer.
ReaperOfVeriod