b322e84cd4791582f4ad06d60496513de6adb901
6
Commits
| Author | SHA1 | Message | Date | |
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 prosolis
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b322e84cd4 |
Get a real Dragon's Lair frame onto the emulated X68000
First pixels on an actual X68000 screen. Everything up to now was Python-side or a headless -video none run, which cannot snapshot at all. The blocker was not the video controller. The IPL leaves CRTC R20 = 0x0B16, and bit 11 is "G-VRAM set to buffer", which makes MAME's draw_gfx() return early. GVRAM writes still land and read back correctly while the layer is invisible, so six attempts at $E82400/$E82500/$E82600 all rendered black with every register holding the value I intended. Two more facts, both confirmed against MAME 0.277 source rather than assumed: - $E8E001 monitor contrast is left at 14 by the IPL, scaling all output to 93.3%. The player must set it to 15. Contrast 0 blanks the screen, which is a free fade-to-black for scene transitions. - The palette word is GGGGGRRRRRBBBBBI with a shared LSB, expanded as pal6bit((field<<1)|I). With contrast at 15 the render is pixel-exact, not merely close, which also confirms the 1024-byte GVRAM line stride. That exactness gives a new quality ceiling: the 15-bit+I palette alone costs 38.88 dB against the 24-bit palettised source, the same order as the scsi profile's own codec error. scsi is close to display-transparent on hardware, which bounds how much further it is worth raising. Unblocks next step 2, the 68000 decoder skeleton, which now has a known-good reference image to diff against. Claude-Session: https://claude.ai/code/session_01194oWYW8DQXK1SZ2DnChW6 |
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prosolis
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64cd1ffd72 |
Handoff: reconcile docs and tooling with the corrections made this session
Session 2 reversed several of its own conclusions. The docs are append-only, so a reader could land on a superseded section and act on it. This pass makes the repo internally consistent. Defects found and fixed in STATUS.md: - claimed "Hybrid VQ with k=1024: no" as the answer to the linework question, directly contradicting FINDINGS 14, which rejected k=1024. Both profiles are k=256. - malformed profile table (six column separators, five columns). - next-steps list had two items numbered 3 and listed the full-disc survey twice. - the disk-benchmark section still read CRITICAL-PATH with "if SCSI sustains >=800 KB/s, ship pixel-exact". That was written while the bandwidth figure was misread as 4 MB/s. At 4 Mbps pixel-exact needs 92-97% of the pipe and is not available, and the ring-buffer result means the design no longer hangs on the benchmark at all. Rewritten with what it IS still worth doing: confirming the 4 Mbps provenance, and confirming DMA is used rather than PIO. FINDINGS now carries supersession blockquotes on 5, 8, 11, 17 and 18 pointing at the sections that correct them. 18 is the dangerous one -- its peak-vs- sustained test is reversed by 21 -- so it is marked DO NOT ACT ON THIS SECTION while noting the per-frame data itself remains valid. profile_gen.py had the same problem in code: it defaulted to the superseded peak sizing and returned lam=25 where the docs say lam=10. The buffered test is now the default and peak sizing is behind --size-for-peak as a bound only. A tool that contradicts the findings is worse than no tool. Also preserves the five measurement scripts that produced this session's numbers as tools/analysis/05-09, following the session 1 precedent, and adds an "explicitly abandoned -- do not re-propose" list to STATUS covering entropy coding, k=1024 codebooks and flat 4x4 VQ. Claude-Session: https://claude.ai/code/session_01194oWYW8DQXK1SZ2DnChW6 |
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prosolis
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48e912de8b |
Size against 4 Mbps: peaks break the scsi profile; DMA steal is not free
User clarified the bandwidth figure is 4 Mbps (488 KB/s), not 4 MB/s -- ~8x
tighter than the previous commit reasoned against. Two consequences, plus a
correction to session 1.
1. The scsi profile committed in
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prosolis
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f0f2f807a4 |
Raise both quality profiles; rule out entropy coding on CPU grounds
The profiles shipped in
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prosolis
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e4062ed294 |
Session 2: hybrid VQ codec, two quality profiles, three corrections
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 |
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reala-misaki
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65112b9305 |
Session 1: hardware research, content measurement, codec decision, MAME harness
Verified GVRAM is one word-access per pixel in ALL color modes; chose 256-color 256x192 with movem.l bursts (page 1 sacrificed as double-buffer). Measured 8 scenes from the Blu-ray source: blit costs under 8% of the 12fps cycle budget, so I/O is the bottleneck, not CPU. Naive delta+RLE reaches only 3.2:1 (365 KB/s, 470MB) -> decision to use 4x4 vector quantization (~30 KB/s). "Shot on twos" assumption failed: the transfer has zero duplicate frames, so 12fps requires explicit decimation. Documents three false measurement results and their root causes (per-frame Floyd-Steinberg dithering, temporal denoise, exact-match dedupe on noisy source). MAME Lua injection harness works and is reusable for cycle-cost measurement; the IOCS _B_READ disk benchmark is blocked returning -1. Claude-Session: https://claude.ai/code/session_01194oWYW8DQXK1SZ2DnChW6 |