c520a89e141071506768fe6ba7c1a4f1a263f49c
4
Commits
| Author | SHA1 | Message | Date | |
|---|---|---|---|---|
 prosolis
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7d365b3ff5 |
Drop SASI on capacity, then find the budget never had the disk in it
USER DECISION: drop the `sasi` profile. Not on bandwidth -- on capacity. A SASI volume is 40 MB, and the 22.8 min of unique scene footage on the source Blu-ray (streams 00000-00201, measured, not recalled) is 146 MiB at the LOWEST rate this codec makes -- more than the machine's whole 4-unit SASI space. `scsi` is the only profile now. FINDINGS 32. Then the user asked whether we were drawing the wrong conclusions about PIO vs DMA, and we were, more broadly than the question implied. Every CPU figure in FINDINGS 24-34 is scored against the full 833,333 cycles/frame with nothing subtracted for moving the bitstream off disk. Debiting the HD63450 cycle-steal at the long-standing 8 clk/word ESTIMATE, "1 frame of 120 misses" becomes 84 of 120, median 112.4%. PIO at the span rate is 99.8% of the machine. Spans buy cycles by spending bandwidth and the bandwidth returns as steal, so 31.6's "fits completely" becomes a worst frame of 114.3%. 10 fps absorbs it: median 93.7%, 1/120. FINDINGS 35. `11_cpu_budget.py` takes --io dma|pio|none, defaults to dma, and warns if asked for none. Also landed: - item 1 done: the cost model checked against the 68000 on a cost-aware container, -3.07% to +0.01%, whole-window mean -1.22%. FINDINGS 34. - item 4 done: the container carries its own 4-byte record alignment (DLX2). 94/120 record starts were on odd addresses -- an address error, not a slow read -- now 0/120 for 16 B/s. Re-encoding reproduces 31.1 exactly. FINDINGS 33. - a `scsi` window does not fit the 2 MB machine the rig emulates (2.84 MB of stream past a 0x200000 ceiling). The gate now verifies 80 of 120 frames and SAYS so, and fails loudly when the pass does not complete, instead of reporting a phantom 49,005-pixel diff. FINDINGS 36. Three near-misses this session had one shape: an unobservable run nearly produced a false finding. stdbuf -oL on any MAME job that prints progress -- a file is block-buffered too, and a run that is merely finishing looks exactly like one that is wedged. check.sh ALL GREEN. Claude-Session: https://claude.ai/code/session_01194oWYW8DQXK1SZ2DnChW6 |
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prosolis
|
06b98d4b47 |
Price cycles in the mode decision: 37 misses become 1, for 0.26 dB
The decoder has been CPU-bound since FINDINGS 28 while the mode decision
minimised D + lam*R -- distortion against BYTES. decide() now minimises
D + lam*bytes + mu*cycles, and ratectl bisects mu per frame against the
833,333-cycle budget with the lam bisection nested inside it. On the worst
sustained window:
sasi 27.22 -> 26.95 dB, 109.5 -> 109.4 KB/s, 37/120 misses -> 1
scsi 29.90 -> 29.27 dB, 280.0 -> 278.6 KB/s, 51/120 misses -> 1
Bitrate does not move: the byte controller still binds, and mu changes WHICH
modes are bought. V4 is what it stops buying -- 25.2 -> 20.3% of blocks at sasi
and 15.0 -> 5.3% at scsi, where RAW takes it. That is 28.8's inversion in
practice: RAW is dearer in bytes and cheaper in cycles, so only the byte-rich
profile can buy its way out of V4.
Three things worth knowing beyond the headline:
- The one frame that still misses, at both profiles, is FRAME 0 -- no previous
reconstruction, so 100% changed by definition, which is also what a scene
cut is. It comes out at the all-V1 floor of 110.6% and is emitted late on
purpose. Freezing a cut to make a deadline is the worse failure.
- 28.7's "11 frames are impossible" was too pessimistic. That floor held the
SKIP set fixed and asked how cheaply the drawn blocks could be drawn; the
real decision can also MOVE a block to SKIP, which above ~90% non-SKIP is
the only lever left.
- SKIP's price depends on its neighbours (13.25 cycles clustered, 45 mixed),
which a per-block lagrangian cannot see. The way out is that the two uses
need not share a cost function: a ranking constant inside decide(), the
exact clustered rule for the frame-level bisection. vq_hybrid.cycles() is
now the one definition of that rule and 11_cpu_budget.py imports it.
Gated: 09_ratectl_drift.py runs both controllers, both 0/120 drifting frames.
The cost-aware container decodes pixel-exact on the 68000 (120 frames). ON by
default in encode.py; --no-cpu-fit restores session 7. check.sh ALL GREEN.
Still a model, not a measurement, for THIS container: FINDINGS 31's cycle
figures come from vq_hybrid.cycles (within 1 point of the 68000 on four frames
of the session-7 container). Timing this one on the machine is step 1 of the
next session -- it was started and killed for time, and it is slow.
FINDINGS 31. tools/analysis/13_cpu_ratectl.py.
Claude-Session: https://claude.ai/code/session_01194oWYW8DQXK1SZ2DnChW6
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prosolis
|
ed353d24a9 |
Budget both profiles against both clocks: the CPU limit is the clock, not the profile
11_cpu_budget.py takes --machine. Clocks confirmed from MAME 0.277
x68k.cpp:1133/1194/1200, not recalled: x68000 AND x68ksupr are both
40_MHz_XTAL/4 = 10 MHz; only the XVI is faster at 33.33_MHz_XTAL/2.
sasi scsi
stock 10MHz 31% miss 42% miss
XVI 16.7MHz 0% miss 0% miss
sasi is the cheaper profile but it does not fit either at 10 MHz. The XVI
column is headroom, not a target: the profiles are an I/O-bandwidth axis and
say nothing about CPU, and the locked target CPU is a stock 10 MHz 68000 for
both of them. So both profiles have to fit the same 833,333-cycle budget, and
the cycle ceiling has to be enforced in the encoder regardless of which one
ships.
Model comparisons are now gated to the clock and framerate they were stated
at: quoting 24.5's 76.6% or the stock-machine 68000 timings against an XVI
budget compares a model to a measurement of a different machine.
Claude-Session: https://claude.ai/code/session_01194oWYW8DQXK1SZ2DnChW6
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prosolis
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e1aa26bb57 |
The 68000 decoder draws pixel-exact frames, and does not fit
src/player/decode.s parses DLX1 and decodes straight into GVRAM. Verified pixel-exact over a 120-frame sequential run of the worst sustained window on the disc -- all four block modes, full temporal recursion, so the last frame is only right if all 120 were. In check.sh. It costs a mean of 81.7% of a 12fps frame budget, and 31% of frames exceed 100% (42% at scsi). CPU is now the binding constraint. FINDINGS 28. Three things that were believed and are not true: - The dual-display-path plan of FINDINGS 24.5/25.6 is incoherent. The compose path needs a RAM copy of the previous reconstruction; the direct path's selling point is that it keeps none. Mixing them shows stale pixels on 70 of 120 frames, worst frame 18.8% of the screen. Every coherent repair is dearer than not mixing, and 24.5's two figures were both copies with no decode in either, so there was never a crossover to find. One path ships, and the 96KB reference frame is gone. tools/analysis/10_pathmix_drift.py keeps the counterexample runnable; check.sh asserts it still reproduces. - The four block modes do not cost the same. V1 300, V4 448, RAW 400 cycles against the old model's flat 207.8. V4 is 25% of blocks and 50% of the cycles, and the mode decision charges it bytes it does not charge cycles for. tools/analysis/11_cpu_budget.py reproduces all four frames timed on the 68000 to within 1 point. Hand-derived timings agree to 0.5% on V1. - The container is big-endian but not aligned. Variable-length records laid end to end put frame 1's length field at an odd address, and move.l (a0)+ there is an address error: frame 0 decoded perfectly and then vectored into the IPL for 59 emulated seconds looking like a hang. Found by dumping PC, not by reading the source. Also: an all-V1 frame, the cheapest possible full redraw, is 110.5% of budget. No mode assignment fits a scene cut at 12fps. That one needs a decision, not a measurement. Next: charge cycles in the mode decision and bisect against 833,333 per frame, the way session 6 bisects lam against bytes -- but with no bucket, because a late frame cannot be banked. Claude-Session: https://claude.ai/code/session_01194oWYW8DQXK1SZ2DnChW6 |