prosolis
31c4c1aba1
The profiles were chosen against disk bandwidth and say nothing about CPU. The locked CPU target is a stock 10MHz 68000 for both of them, so both must fit 833,333 cycles -- picking sasi does not rescue it, it still misses 31% of frames against scsi's 42%. Splits the miss into what the encoder can fix and what it cannot: re-coding every non-SKIP block as V1 is the floor, and it still misses 11 frames at sasi and 12 at scsi, all of them above ~90% non-SKIP. So a cost-aware mode decision can reach about three quarters of the misses; the rest need a structural answer, not a better encoder. Also: V4 is 448 cycles against RAW's 400, and RAW is pixel-exact. On the CPU axis V4 is strictly dominated and the byte lagrangian's mode preference inverts. Only the byte-rich profile can take that escape, so the cycle ceiling should cost sasi MORE quality than scsi despite costing it fewer cycles. FINDINGS 28.7/28.8. Claude-Session: https://claude.ai/code/session_01194oWYW8DQXK1SZ2DnChW6
Dragon's Lair — Sharp X68000 port
Porting Dragon's Lair to a stock X68000 (68000 @ 10MHz, 2MB, SASI/SCSI).
This is fundamentally a video codec problem, not a game-logic problem: the game logic is a scene table with branching input windows; the difficulty is pushing ~22 minutes of Don Bluth animation through a 10MHz 68000.
Green-light check: ./tools/bench/check.sh (~3 min, needs the Blu-ray
mounted) re-runs both display regression tests, the rate-control drift test, the
display-path coherency counterexample and a 120-frame 68000 decode, then prints
ALL GREEN.
Read first
docs/FINDINGS.md— measured hardware facts, content statistics, codec decision, and a section on measurement traps that produced three separate false results. Read §4 before trusting any pipeline number.docs/STATUS.md— current state, working setup, blockers, next steps. Start here. It also lists what has been explicitly abandoned, so old ideas do not get re-proposed.docs/BENCHMARK.md— how to measure the storage subsystem, and why a bandwidth figure out of MAME would be meaningless.docs/HARDWARE.md— X68000 GVRAM/CRTC reference.
Layout
docs/ findings, status, hardware reference
tools/analysis/ measurement scripts, numbered in the order they were written
(01/02 marked BROKEN deliberately, kept as regression refs).
Run from the repo root — they import from tools/encoder/.
07 finds the hottest sustained window in a stream; 08 renders
source | decoded | block-mode map as .webm; 09 is the
rate-control drift gate (FINDINGS 26/27) and is part of
check.sh -- it exits non-zero if the encoder ever again
reports a reconstruction no decoder would produce.
10 is a COUNTEREXAMPLE, and exits non-zero by design: it
demonstrates that the two-display-path plan of FINDINGS
24.5/25.6 corrupts 70 of 120 frames (FINDINGS 28.1).
11 scores a container against the MEASURED per-mode block
costs without needing MAME.
tools/bench/ MAME Lua injection harness + 68000 benchmark sources.
`check.sh` re-runs both display regression tests (~40 s).
`blit.s`/`blit.lua` time the full-frame GVRAM blit on the
68000 itself (FINDINGS 24) — not part of check.sh, because
wall timings would make the green-light check host-sensitive.
`crtc_mode.lua` is the single source of truth for CRTC R00-R08
and R20 — do not write CRTC values anywhere else.
`prep_dlx.py`/`decode.lua`/`verify_decode.py` load, time and
verify `src/player/decode.s`; the verify pass is in check.sh.
tools/vasm/ vasm m68k assembler (built from source)
tools/encoder/ hybrid VQ encoder + DLX1 container writer (working).
dlx.py is the reference DECODER -- ground truth for the 68000.
src/player/ decode.s: the 68000 DLX1 decoder. Pixel-exact, and 31% of
frames over the 12fps CPU budget. See FINDINGS 28.
assets/ extracted frames/audio (gitignored)
Encoder
python3 tools/encoder/extract.py 00020 /tmp/fr 12 crop
python3 tools/encoder/encode.py /tmp/fr out.dlx --profile sasi --preview p.png
Two quality profiles ship from one codec and one decoder — sasi (110 KB/s) and
scsi (280 KB/s) are two points on the same rate-distortion curve. Both are
ceilings: lam is bisected per frame under a leaky bucket, so the profile's
lam is a quality floor rather than a setting (--fixed-lam opts out). The codec is
a Cinepak-style hybrid: each 4x4 block is coded as SKIP, one 4x4 codeword, four
2x2 codewords, or RAW literal pixels, chosen per block by rate-distortion.
The RAW escape means lam=0 is pixel-exact against the palettised frame, so the
quality knob spans lossless to heavily-compressed without changing the bitstream.
Profiles are derived from a bandwidth figure, not chosen by eye:
python3 tools/encoder/profile_gen.py --bw-mbps 4 --name scsi
On reading
docs/FINDINGS.md: it is append-only and several later sections overturn earlier ones. Superseded sections carry a blockquote at the top pointing to the correction — heed those, especially 18 (reversed by 21).
Source media (DRAGONS_LAIR.iso) and ROMs are gitignored — supply your own.
Not every large stream is game footage. 00216 is the feature with a
burned-in commentary picture-in-picture and 00215 is the commentary itself —
the two largest files on the disc. The clean 9.4-minute animation is 00223.
See FINDINGS 25.1 before running any size-ranked survey.