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docs: mark Phase 3e (playback prefetch) done

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Skyler Lehmkuhl 2026-06-20 22:45:56 -04:00
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STREAMING_TO_DISK_PLAN.md
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@ -370,7 +370,15 @@ correct because a clean evicted frame's container bytes == its logical state. No
skip (no corruption). Unit-tested round-trip. *(Refinement: compress full-canvas-fill diffs, whose
bbox is the whole frame.)*
### 3e. Prefetch frames *(future, after 3d — pure latency win, no correctness need)*
### 3e. Prefetch frames **[DONE for playback]**
Implemented for playback: each update during playback, page in the next `PREFETCH_AHEAD=4`
upcoming keyframes per raster layer (reusing the async worker + `raster_loads_inflight` dedup), so
full frames are resident before the playhead arrives — fixes "proxy on every frame"/flicker during
playback. *(Caveat: with many simultaneous raster layers the 12-frame resident budget may evict a
prefetched frame before it's shown — raise budget or scale prefetch if that surfaces. Scrub-direction
prefetch still TODO.)*
Original note: *(future, after 3d — pure latency win, no correctness need)*
Fault-in is reactive (page in only on a render miss), so a never-visited frame still shows the
proxy for a beat before the full lands. **Prefetch the full pixels for frames about to be shown**:
on scrub/playback, dispatch background page-ins for the active keyframe ±N in the direction of