prosolis
e4062ed294
Answers session 1's critical-path question. Flat 4x4 VQ at k=256 was prototyped and REJECTED by eye: Dirk's face disintegrates and ink outlines break into 4-pixel stair-steps. The 256-colour palettised frame is excellent, so the palette was never the problem -- block VQ was. Replaced it with a Cinepak-style hybrid: each 4x4 block is SKIP, one 4x4 codeword, four 2x2 codewords, or RAW literal pixels, chosen per block by rate-distortion. The RAW escape makes lam=0 pixel-exact (measured 0.00 dB loss), so the quality knob spans lossless to heavily-compressed in one bitstream. Per the user's decision, ships TWO quality profiles from that one codec, one decoder and one bitstream -- only the rate knob differs: sasi 45 KB/s lam=300 34.8 dB stock 10MHz ACE/EXPERT scsi 75 KB/s lam=100 35.9 dB Super/XVI or CZ-6BS1 Three corrections to earlier numbers: 1. Session 1's "183 KB/s at 12fps" was a bad extrapolation. Halving the framerate does not halve the bitrate -- decimation roughly doubles the per-frame delta. Re-measured directly: 340 KB/s for session 1's own RLE, 247 KB/s for changed-spans+deflate. The lossless floor is 319 MB. 2. A FOURTH false-good result, same family as the three in FINDINGS 4: k=1024 codebooks appeared to buy +2.4 dB free, because the rate model charged 1 byte for a 10-bit index. Charging the true cost reverses the verdict -- k=256 wins at every matched bitrate, and by 5 dB at the low end where the SASI profile lives. k=256 ships. 3. Stream inventory: the ~3-5MB clips are 1.2-1.7s, not ~60s, and some 60s streams are menus, not content. Any survey must classify before averaging. Also cleared both candidate sources for the game-logic layer: the SNES project is MIT and DirkSimple is zlib, so the arcade scene graph can be imported and the two transcriptions diffed against each other. Encoder is working end-to-end: extract.py -> vq/vq_hybrid/ratectl -> encode.py, emitting a big-endian DLX1 container the 68000 can parse with plain moves. Claude-Session: https://claude.ai/code/session_01194oWYW8DQXK1SZ2DnChW6
43 lines
1.8 KiB
Markdown
43 lines
1.8 KiB
Markdown
# Dragon's Lair — Sharp X68000 port
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Porting Dragon's Lair to a stock X68000 (68000 @ 10MHz, 2MB, SASI/SCSI).
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This is fundamentally a **video codec problem**, not a game-logic problem: the
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game logic is a scene table with branching input windows; the difficulty is
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pushing ~22 minutes of Don Bluth animation through a 10MHz 68000.
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## Read first
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- **`docs/FINDINGS.md`** — measured hardware facts, content statistics, codec
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decision, and a section on measurement traps that produced three separate
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false results. Read §4 before trusting any pipeline number.
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- **`docs/STATUS.md`** — current state, working setup, blockers, next steps.
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- **`docs/HARDWARE.md`** — X68000 GVRAM/CRTC reference.
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## Layout
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```
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docs/ findings, status, hardware reference
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tools/analysis/ frame-analysis scripts (01/02 marked BROKEN as regression refs)
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tools/bench/ MAME Lua injection harness + 68000 benchmark sources
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tools/vasm/ vasm m68k assembler (built from source)
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tools/encoder/ hybrid VQ encoder + DLX1 container writer (working)
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src/player/ 68000 player (not yet written)
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assets/ extracted frames/audio (gitignored)
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```
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## Encoder
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```
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python3 tools/encoder/extract.py 00020 /tmp/fr 12 crop
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python3 tools/encoder/encode.py /tmp/fr out.dlx --profile sasi --preview p.png
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```
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Two quality profiles ship from one codec and one decoder — `sasi` (45 KB/s) and
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`scsi` (120 KB/s) are two points on the same rate-distortion curve. The codec is
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a Cinepak-style hybrid: each 4x4 block is coded as SKIP, one 4x4 codeword, four
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2x2 codewords, or RAW literal pixels, chosen per block by rate-distortion.
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The RAW escape means `lam=0` is pixel-exact against the palettised frame, so the
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quality knob spans lossless to heavily-compressed without changing the bitstream.
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Source media (`DRAGONS_LAIR.iso`) and ROMs are gitignored — supply your own.
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