prosolis
06b98d4b47
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
96 lines
4.2 KiB
Python
96 lines
4.2 KiB
Python
#!/usr/bin/env python3
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"""REGRESSION TEST for the ratectl lam-ladder desync (FINDINGS 26). PASSES as
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of session 6 -- keep it passing.
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Exits non-zero if the encoder ever again reports a reconstruction that a
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decoder would not produce. That is the acceptance criterion for any change to
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rate control, and it is not a property a PSNR number can show you.
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The bug it was written for: encode_rate_controlled() ran H.encode() once per lam
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over the WHOLE sequence, then picked each frame from whichever rung fit the
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budget. H.encode() is temporally recursive -- a frame's SKIP blocks are copied
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from the PREVIOUS RECONSTRUCTION of that same rung -- so when frame f came from
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rung i and frame f-1 was emitted from rung j != i, the SKIP blocks in f
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referenced a frame the decoder never saw. 111 of 120 frames drifted, worst frame
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43.4%. The fix was structural: the encoder is now frame-drivable and rate
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control feeds back the frame it actually emitted (vq_hybrid.frame_ctx/decide/
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paint), so drift is zero by construction rather than by tuning.
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This replays what a real decoder does -- SKIP copies the ACTUALLY EMITTED
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previous frame -- and compares it to the reconstruction ratectl recorded.
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Session 8 added a SECOND controller (mu, the per-frame 68000 decode ceiling)
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that also varies the mode map frame to frame, so it is exposed to exactly the
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same failure and is tested here too. Both configurations must show zero drift.
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Needs tmp/fr_singe (see docs/STATUS.md, reproducing the sustained-action
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result). ~55 s, nearly all of it the k-means in H.build; the rate-controlled
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encode of 120 frames is ~2 s.
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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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import vq as VQ, vq_hybrid as H, ratectl as RC
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m = H.build("tmp/fr_singe", k1=256, k4=256, iters=16)
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def check(label, cycle_budget):
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"""Encode, replay as a decoder would, and return the drift in pixels."""
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print(f"\n=== {label} ===")
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m.pop("_sym", None)
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# lam_lo=1.0: let quiet frames spend the whole allowance, which is the
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# harder case for this test -- it maximises how often lam moves frame to
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# frame.
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enc = RC.encode_rate_controlled(m, target_kbps=110, lam_lo=1.0,
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cycle_budget=cycle_budget)
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lam = enc["lam"]
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sw = int((np.diff(lam) != 0).sum())
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print(f"frames={len(lam)} distinct lam used={len(set(lam.tolist()))} "
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f"lam changes frame-to-frame={sw} "
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f"overruns={int(enc['overrun'].sum())}")
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pal, nbx = m["pal"], m["W"] // 4
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emitted = []
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drift_px, drift_db = [], []
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for f, (rec, mode) in enumerate(zip(enc["recon"], enc["modes"])):
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out = rec.copy()
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if f > 0:
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prev_true = emitted[-1]
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for b in np.flatnonzero(mode == 0): # SKIP blocks
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by, bx = divmod(int(b), nbx)
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y, x = by*4, bx*4
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out[y:y+4, x:x+4] = prev_true[y:y+4, x:x+4]
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emitted.append(out)
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d = (out != rec).sum()
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drift_px.append(d)
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drift_db.append(VQ.psnr(pal[rec], pal[out]))
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drift_px = np.array(drift_px)
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print(f"pixels differing from what the encoder recorded:")
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print(f" frames with ANY drift: {int((drift_px>0).sum())}/{len(drift_px)}")
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print(f" max {drift_px.max()} px ({100*drift_px.max()/(m['H']*m['W']):.1f}% of frame)")
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print(f" mean {drift_px.mean():.0f} px")
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fin = [d for d in drift_db if np.isfinite(d)]
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if fin:
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print(f" encoder-vs-decoder agreement: min {min(fin):.1f} dB "
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f"(inf = identical on {len(drift_db)-len(fin)} frames)")
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r = RC.summarise(m, enc, 110)
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print(f"\nratectl reports PSNR {r['psnr']:.2f} dB, {r['kbps']:.1f} KB/s "
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f"(target 110), {r['over']:.0f}% of frames over budget")
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tp = np.mean([VQ.psnr(o, pal[e]) for o, e in zip(m["rgb"], emitted)])
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print(f"what a decoder actually reconstructs: {tp:.2f} dB "
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f"-> overstated by {r['psnr']-tp:.2f} dB")
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return drift_px
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# Acceptance criterion for the fix: a decoder replaying the emitted stream must
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# reconstruct exactly what the encoder recorded -- under either controller.
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bad = 0
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for label, cb in (("bytes only (session 6)", None),
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("bytes + CPU ceiling (session 8)", RC.FRAME_CYCLES)):
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d = check(label, cb)
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bad += int((d > 0).any())
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sys.exit(1 if bad else 0)
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