Put sound in the packed container, and find the padding is a rate error

ROADMAP P6b, FINDINGS 67.  DLXP2: a 64-byte header and then groups -- one
audio lump of A sectors, then F records -- so record i is at
off_frm + i*rec + (i//F)*A*512 and lump k at off_aud + k*(F*rec + A*512).
Still no index and still none needed, which is the packed branch's whole
claim surviving the one change that could have ended it.  The player carries
the third term in six instructions once a frame and zero parsing, and 120 of
120 records are still pixel-exact off a real MB89352 volume with the
interleave in, against a silent control that says no picture byte moved.

The finding is what 65.3 called padding.  A lump is 7,168 B of SPACE; eleven
frames of audio is 7,161.4583... B, so the payload alternates 7,161 and
7,162 and the rest is zero.  A player that fed the chip the whole lump --
which is what "14 sectors every 11 frames" invites -- runs 0.09% fast, and
that is not waste, it is drift: 0.84 ms a group, 1.25 s of lip-sync over the
game's 22.8 minutes.  What a player carries is one accumulator,
acc += 11*15625; n = acc//24; acc %= 24, which is clock.i's shape for
clock.i's reason and the third time this tree has met the pattern.

The four ADPCM axes ride in the header as fields rather than a version
number, and the gate flips each one to prove they earn it: nibble order
-31.99 dB, delta formula -24.86, clamp 0.00, accumulator -0.49.  Nothing
parses a packed container, so the gate partitions the whole file -- 131
spans, no overlap, no gap -- and asserts what a cadence-blind player would
read: exactly records 11..119 wrong, and frames 0..10 identical either way,
which is how an off-by-one like that survives a rig that checks frame 0.

Wire 582.0 + 7.64 = 589.6 KB/s, 65.3's prediction to the tenth.

Green light ALL GREEN before (tmp/check_s35_start.log) and after
(tmp/check_s35_end.log), with the new stage in it.

Claude-Session: https://claude.ai/code/session_01194oWYW8DQXK1SZ2DnChW6

tools/bench/packed.lua

@@ -68,6 +68,7 @@ local META = loadfile("packed_meta.lua")()
 local PG_FLAG, PG_NFR, PG_FPS, PG_LBA0 = 0x18900, 0x18904, 0x18908, 0x1890C
 local PG_RECS, PG_PALL, PG_HELD        = 0x18910, 0x18914, 0x18918
 local PG_PACEON, PG_ITER               = 0x1891C, 0x18920
+local PG_CADF, PG_CADA                 = 0x18924, 0x18928
 local PG_SHOWN, PG_ERR, PG_ERRAT       = 0x18930, 0x18934, 0x18938
 local PG_LATE, PG_LATE1, PG_LATEM      = 0x1893C, 0x18940, 0x18944
 local PG_VDISP, PG_VD0, PG_TSPIN       = 0x18948, 0x1894C, 0x18950
@@ -107,12 +108,28 @@ local function setup()
   SP:write_u32(PG_HELD, HELD and 1 or 0)
   SP:write_u32(PG_PACEON, PACED and 1 or 0)
   SP:write_u32(PG_ITER, ITERS)
+  -- DLXP2's cadence. Zero for a silent container, and the 68000 branches on the
+  -- zero: a player told the wrong cadence does not fail, it reads an audio lump
+  -- as a record and paints it.
+  SP:write_u32(PG_CADF, META.cad_f or 0)
+  SP:write_u32(PG_CADA, META.cad_a or 0)
   SP:write_u32(PG_SHOWN, 0)
   P(string.format("packed.bin=%d B, %dx%d %d fps, %d of %d frames, %d passes",
                   #code, META.W, META.H, META.fps, NFR, META.nframes, ITERS))
-  P(string.format("record %d B = %d sectors at LBA %d + i*%d, palette %s",
+  local cad = ""
+  if (META.cad_f or 0) > 0 then
+    cad = string.format(" + (i//%d)*%d", META.cad_f, META.cad_a)
+  end
+  P(string.format("record %d B = %d sectors at LBA %d + i*%d%s, palette %s",
                   META.rec_bytes, META.rec_sectors, META.lba0,
-                  META.rec_sectors, META.palette_last == 1 and "LAST" or "FIRST"))
+                  META.rec_sectors, cad,
+                  META.palette_last == 1 and "LAST" or "FIRST"))
+  if (META.cad_f or 0) > 0 then
+    P(string.format("DLXP2: %d B of ADPCM at %d Hz rides in %d lumps of %d sectors, "
+                    .."one in front of every %d records -- the third term above is the "
+                    .."whole cost of it on the video path",
+                    META.aud_bytes, META.aud_hz, META.n_lumps, META.cad_a, META.cad_f))
+  end
   P(string.format("channel: %s, %s",
                   HELD and "BUS HELD (burst, max rate)" or "CYCLE STEALING",
                   PACED and ("SELF-PACED at "..FPS.." fps off V-DISP"