prosolis
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FINDINGS 26 stopped the session-5 rate controller before it shipped: it built a lam-ladder of independent whole-sequence encodes and picked frames off it, so SKIP blocks referenced reconstructions the decoder never saw -- 111 of 120 frames drifted. The fix is the structural one 26.1 said it had to be. vq_hybrid is now frame-drivable -- frame_ctx / decide / paint -- and encode() is a thin loop over it. Rate control drives the same three calls, bisects lam per frame under the leaky bucket, and feeds back the frame it actually emitted. The desync has no way to occur, and 09_ratectl_drift.py goes 111/120 -> 0/120. That test is now part of check.sh, which is ~2 min rather than ~40 s. Both overshoots on the worst sustained window are closed for under 1 dB, totals including audio: sasi 137.4 -> 109.5 KB/s (-0.60 dB), scsi 381.6 -> 280.0 KB/s (-0.91 dB). Zero frames hit the lam=800 cliff, so nothing was destroyed to get there. Rate control also makes the display path cheaper -- scsi's median drops 53.6% -> 47.1% -- because raising lam moves blocks to SKIP and V1. Two knobs measured rather than guessed. --rc-floor is worth 0.00 dB on that window and defaults to the profile lam, so rate control cannot regress content that already fits. --prefill defaults to 0 and is documented as a trap: it buys a permission to overshoot of exactly bucket/nframes, and on a 14-frame clip it disables the controller outright. FINDINGS 26.5 was wrong in both halves and 27.6 records it. _paint was not the bottleneck (14% of a frame, though vectorising it was still right at 17.1x) and the ladder was never "minutes" -- those were k-means in build(). What makes per-frame rate control affordable is that VQ.assign depends on neither lam nor prev, so it is cached one frame deep: a 12-step search over 120 frames costs 0.31 s against 49.1 s. Also caught: fixed-lam sasi was already 5% over target on 00020, the clip everyone called easy. Nothing noticed because the profile table quotes PSNR and not bitrate. check.sh: ALL GREEN. Claude-Session: https://claude.ai/code/session_01194oWYW8DQXK1SZ2DnChW6
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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 (~2 min, needs the Blu-ray
mounted) re-runs both display regression tests plus the rate-control drift test
and 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.
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.
tools/vasm/ vasm m68k assembler (built from source)
tools/encoder/ hybrid VQ encoder + DLX1 container writer (working)
src/player/ 68000 player (not yet written)
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.