8b5f51704c4b31a0428fe379cebbc21af5d682ff
3
Commits
| Author | SHA1 | Message | Date | |
|---|---|---|---|---|
 prosolis
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ab15c0749a |
Measure the level off the whole disc, and find the headroom is not worth buying
FINDINGS 69, ROADMAP P6 -- the item 66.3 reopened in session 34 and sessions 35 and 36 both deferred. The chip clamps its accumulator at 10 bits INSIDE the recursion, and the ten seconds every audio figure in this tree is quoted on peak at 435 of 511: it fits, and it fits by accident, because that window is a -13.4 dBFS passage. Nothing knew what the loudest passage of the game was. tools/analysis/35_audio_level.py reads every stream of the unique scene footage (00000-00201) through extract_audio.py's own chain -- 1,291.6 s, 201 of 202 streams -- and encodes windows of it with adpcm.CHIP. The disc peaks at 946 of 2048 = -6.71 dBFS (00200 @ 2.11 s), which is 5.35 dB over the clamp, and the census behind that peak is 687 samples of 20,182,000 (0.0034%) in 402 events, 44.0 ms, longest 0.90 ms. THE HEADLINE IS A NEGATIVE: THE LEVEL DOES NOT CHANGE. Forty 2 s windows drawn over the game's timeline at six gains -- the disc's own level (gain 1.0) has the best mean SNR (22.03 dB) and the best median, and loses the worst-window column to -3 dB by 0.04 dB. The gain that guarantees zero clamping disc-wide (0.5402) costs 0.85 dB of mean SNR across the whole game to buy back 1.90 dB on the 2.11 s that clamp, because the OKI step table's floor is a constant 16 and does not scale with the signal. AND 66.3's MECHANISM DOES NOT SURVIVE A CONTROL. Error after a clamp run is elevated ~5x -- and so is the same window at a gain that never clamps, read at the same indices, because those samples are simply loud. Worst ratio 1.28 over 64 offsets, and the clamped encode's whole-window mean |error| is the LOWER of the two (4.71 vs 5.05). adpcm.encode runs the chip's clamp inside its own sixteen-way search, so it never loses the chip's state. The worry was right about the mechanism and aimed one layer too late: an encoder clamping at 12 bits while the chip clamps at 10 is exactly that divergence, and 66 closed it. pack.py gains --audio-gain (default 1.0) so the level is a named parameter with a measurement behind it instead of a shift buried in a list comprehension, and prints the encoded window's peak against the clamp. tmp/packed_singe.dlxp rebuilds byte-identical, all 6,039,040 B. New check.sh stage, ~18 s. Three rig facts in 69.4, because a shipping encoder meets all three: 00176 has no audio track at all; 00199 is 61.31 s of video with 1.25 s of audio; and 18 stream pairs share duration, peak and RMS, 7 of them byte-identical. The 10-bit clamp is a DRIVER SETTING, not a chip constant -- x68k.cpp:1089 sets OUTPUT_10BITS -- so it is MAME's reading of the board, and hardware item 5 is what settles it. Claude-Session: https://claude.ai/code/session_01194oWYW8DQXK1SZ2DnChW6 |
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prosolis
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e3778f62b0 |
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 |
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prosolis
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f1007a0dbc |
Put the frame in a container with no decoder, and find the palette is not free
ROADMAP K2. DLXP1: a 49,664 B record that is 97 sectors exactly, no index and no length word, because a packed record's length is geometry rather than content. 582.0 KB/s, which is what FINDINGS 61.9 predicted to the tenth, and it encodes in 3.3 s because there is no k-means in it. px68k's own x68k/gvram.c renders the container's bytes index-exact with the harness computing no interleave -- the only test that can catch an encoder whose byte order is wrong, since a container round-trips against its own inverse either way. Both negative controls fail as they must. The picture is re-derived against this project's builder rather than PIL's (34.05 dB against 61.9's 34.08) and the GGGGGRRRRRBBBBBI word is charged for the first time in this tree: 0.53 dB, on every row, so it moves no comparison. What the control found is the finding. A packed container on a SCENE palette lands exactly on the codec's ceiling, so the whole +2.31 dB is the per-frame palette and nothing else -- and 231 of 256 entries change every frame, which makes a mismatched paint 12.8 dB worse than the correct pairing, on screen for roughly half of every frame slot if buffer mode does not blank. So B2 now decides which packed CONTAINER ships, not only which player. The fallback is already a flag: --scene-palette --no-palette is 30.79 dB, zero churn, 576.0 KB/s and still +2.07 dB on the shipping codec. 62.5 is priced and is a wash: palette first 20.32 dB, palette last 20.33. Claude-Session: https://claude.ai/code/session_01194oWYW8DQXK1SZ2DnChW6 |