prosolis
2f9f5cc995
Two sessions that were never separated in the working tree, so they land as one commit. check.sh ALL GREEN before and after both. SESSION 19 -- the ring rig gets a frame clock (FINDINGS 51). src/player/stream.s had no frame clock: it asked for record i the instant it finished i-1, outran any finite pipe, and never let the ring back up. The 49.1 sweep passing at 48 KB was therefore a wrap-correctness result and nothing else. PACE/PACEON ($18034/$18038) hold the decoder to 12 fps, so FR_HEAD-FR_TAIL finally means what it reads as: whole frames the decoder could still draw with delivery stopped dead. PACEON=0 free-runs and is what the wrap gate still uses, so every figure in 49 is unmoved. Paced, on the gate container: 64 KB holds 2 frames, 256 KB holds 7-8, 512 KB holds 14-15, all pixel-exact. Tolerance is ceiling-1, measured by cutting the pipe: 256 KB buys 500 ms of dead pipe, not 583. SLACK IS ACCUMULATED, NOT OWNED. It is built out of pipe-wire and a seek spends all of it. At 488 KB/s a 256 KB ring needs 4.83 s of play to reach its ceiling from empty; 512 KB needs 8.42 s to reach 14. A bigger ring raises the ceiling AND lengthens the climb, so a branch point does not ask "is the buffer big enough" but "has there been enough play since the last one" -- and Dragon's Lair's decision points are seconds apart. The rig now also says WHICH resource is binding: at 460 KB/s every ring from 192 KB to 512 KB is rate-bound at ceiling 4 and never fills, so larger rings are dead RAM in that scene. 20_seek_slack.py is the same model rewritten in Python from record sizes, sharing no code with the Lua producer: 35/35 ceilings inside its bracket. SESSION 20 -- the DMAC configuration was in the IPL ROM the whole time (FINDINGS 52). ROADMAP's "do this first" was to put the ADPCM stream on the bus. That needs a clocks-per-byte figure for the audio channel, and 11_cpu_budget.py was charging audio the DISK's rate -- 5 clk/B, its own help text calling it "single-address, bus held". Audio was being charged the favourable end of B3, a 242 KB/s open question. It never had to be a guess. The IPL ROM programs all four HD63450 channels itself and MAME boots the rig with it, so 21_iplrom_dmac.py reads the configuration out of the image and decodes the MC68450 fields. Eight (address, expected bytes, meaning) sites; a mismatch or an unknown revision exits non-zero. In check.sh, no emulator, milliseconds. ch3 DCR=$80, OCR=$32: dual address, 8-bit port, cycle steal WITHOUT hold, REQG=10 external request. The DMAC arbitrates once per byte with no burst to amortise the 5..8 + 2 over, so an audio byte is 16..19 clocks, not 5 -- the old debit was 3.2x..3.8x small. And on the bus it is still nothing: 651 B/frame is 1.25%..1.48% of a frame, about 4% of what the decoder leaves. P6's bus risk does not materialise. The unit worry was worth checking and nearly right: 15.6 kHz is 8 MHz/512 = 15,625 samples/s, two 4-bit samples to a byte = 7,812.5 B/s exactly, and AUDIO_KBPS=7.8 is that in decimal kB while the tool multiplied by 1024. THE DISK CHANNEL IS PROGRAMMED IDENTICALLY. ch1 (SASI) is DCR=$80 too, and so is ch0. That is 16..19 clocks per delivered byte, where 42.4 brackets W at 5..12 and 42.5 has W=8 already missing 47/120 frames. The only worked example of a disk DMA configuration on this machine sits above the entire bracket, and at that price nothing fits at any container size. It is not scsiexrom.bin so B3 stays open -- what changed is that a cheap configuration is now the thing that has to be SHOWN. W <= 12 is a requirement on the player's DMAC programming, not a range the hardware hands us, and it is now the largest open number in the project, ahead of the rate. An unforced cross-check fell out: 15_bus_occupancy.py's new W sweep puts W=8 at 105.7% of the frame, agreeing with 42.5's 47/120, from mode histograms and bus clocks respectively, two models sharing no code. Also: ADPCM outranks the disk at the arbiter (CPR 1 against 2), so an audio byte never waits and a video byte does -- relevant to 51's smooth-rate delivery model. README MEDIA. stream.lua gains DLX_SNAP_EVERY=1 (needs DLX_PACE, off by default, on no path check.sh takes) and tools/media/make_readme_media.py turns the PNGs into docs/img/. The stills and both clips are MAME's own screen pixels. Building it turned up something worth recording. 116 of 119 captured frames are pixel-exact against dlx.py; three are TORN -- frame n on top, frame n-1 below the tear line -- because MAME captured the screen while the block loop was partway down it. decode.s writes straight to the displayed page (one display path, 28.1), so a real player tears the same way, and this is the first time that consequence has been visible rather than argued. The script ASSERTS the tear and refuses to build otherwise, rather than trimming three frames and reporting "every frame I kept is exact". Second correction the capture forced: the snapshot fires before frame n is decoded, so the obvious reading is that it holds frame n-1 -- it does not, because MAME renders the screen at the end of the machine frame, by which time the 68000 has finished frame n. 11_cpu_budget.py's "validated to within 1 pt" line is also corrected: the model reads 2..10 pt HIGH and by more as the frame gets harder, which was already true before either session. src/player/decode.s is unchanged; decode.bin is still 1,296 B at the same MD5. Claude-Session: https://claude.ai/code/session_01194oWYW8DQXK1SZ2DnChW6
89 lines
4.1 KiB
Python
89 lines
4.1 KiB
Python
#!/usr/bin/env python3
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"""What 256 -> 16 colours actually costs, on real frames.
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python3 tools/analysis/18_text_plane_16col.py [frames_dir]
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FINDINGS 46.3 opened a lead and could not price it: the X68000 text plane is
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4bpp planar -- 0.5 bytes/pixel against the graphics planes' 2.0 -- so a LITERAL
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uncompressed 16-colour frame is 288.0 KB/s against the shipping compressed
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256-colour container's 496.7 KB/s. 42% cheaper on the wire, with no decoder.
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The whole lead turns on one number nobody had computed: the quality cost of 16
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colours. This computes it, and it is deliberately generous to the 16-colour
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side on every axis where the hardware allows it:
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* PER-FRAME palettes are legitimate here. The text palette is 16 entries and
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reloading it is 16 words a frame -- nothing, against a 833,333-clock budget.
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The 256-colour path cannot do this: its palette is shared scene-wide
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(vq.scene_palette) because the codec's codebooks are indices INTO it.
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* DITHERING is free here, and only here. The tree does not dither (vq.py:32,
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"cel art is flat") because dither destroys the inter-frame coherence SKIP
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blocks and v7 spans are built on. A literal frame has no codec to wreck, so
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Floyd-Steinberg is available to this path at zero runtime cost.
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Both are measured, so the comparison cannot be accused of hobbling the option it
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is testing. Reported against the 256-colour scene-palette ceiling (the tree's
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existing "palette ceiling" figure) and against the shipping container's PSNR.
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"""
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import sys, os
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sys.path.insert(0, "tools/encoder")
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import numpy as np
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from PIL import Image
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import vq as VQ
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FRAMES = sys.argv[1] if len(sys.argv) > 1 else "tmp/fr_singe"
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SHIPPED_PSNR = 29.19 # docs/STATUS.md, --spans all, c=5, 496.7 KB/s
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rgb = VQ.load_frames(FRAMES)
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H, W = rgb[0].shape[:2]
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n = len(rgb)
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print(f"{FRAMES}: {n} frames, {W}x{H}")
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print()
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def recon_scene(colors, dither):
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"""One palette for the whole scene -- what the 256 path is forced to do."""
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d = Image.FLOYDSTEINBERG if dither else Image.NONE
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samp = np.concatenate([r.reshape(-1, 3) for r in rgb[::3]])
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ref = Image.fromarray(samp.reshape(-1, 1, 3)).quantize(
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colors=colors, method=Image.MEDIANCUT, dither=Image.NONE)
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pal = np.array(ref.getpalette()[:colors * 3], np.uint8).reshape(-1, 3)
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return [pal[np.asarray(Image.fromarray(r).quantize(palette=ref, dither=d),
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np.uint8)] for r in rgb]
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def recon_perframe(colors, dither):
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"""A fresh palette every frame -- what the text plane can afford."""
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d = Image.FLOYDSTEINBERG if dither else Image.NONE
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out = []
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for r in rgb:
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q = Image.fromarray(r).quantize(colors=colors, method=Image.MEDIANCUT,
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dither=d)
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pal = np.array(q.getpalette()[:colors * 3], np.uint8).reshape(-1, 3)
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out.append(pal[np.asarray(q, np.uint8)])
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return out
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def report(name, recon):
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per = np.array([VQ.psnr(a, b) for a, b in zip(rgb, recon)])
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print(f" {name:<42s} {per.mean():6.2f} dB "
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f"(min {per.min():5.2f} max {per.max():5.2f})")
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return per.mean()
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print("PSNR vs the 24-bit source, mean over frames:")
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c256 = report("256 colours, scene palette [the tree's]", recon_scene(256, False))
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report("256 colours, per-frame palette", recon_perframe(256, False))
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print()
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s16 = report("16 colours, scene palette", recon_scene(16, False))
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p16 = report("16 colours, per-frame palette", recon_perframe(16, False))
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p16d = report("16 colours, per-frame + FS dither", recon_perframe(16, True))
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print()
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print(f" the 16-colour ceiling is the best of those: {max(s16, p16, p16d):.2f} dB")
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print(f" cost of 256 -> 16, at each side's best: "
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f"{c256 - max(s16, p16, p16d):.2f} dB")
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print()
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print(f" for scale, the shipping container delivers {SHIPPED_PSNR:.2f} dB "
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f"at 496.7 KB/s")
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print(f" a 16-colour literal would deliver "
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f"{max(s16, p16, p16d):.2f} dB at 288.0 KB/s")
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delta = max(s16, p16, p16d) - SHIPPED_PSNR
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print(f" so the text-plane path is {abs(delta):.2f} dB "
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f"{'BETTER' if delta > 0 else 'WORSE'} at 58% of the bitrate")
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