H3 long-video ghosting traced to averaged context-window overlaps; chained fix open-sourced

ReferenceFluffy6159 · reddit · 2026-11-10

A community developer diagnosed and fixed the ghosting that ComfyUI's MiniMax H3 context windows produce on long videos, open-sourcing the fix as chained context windows (CCW) in H3MD 0.4, validated on a 2:20 music video.

Root cause: ComfyUI 0.44 denoises the timeline as overlapping windows, averaging each overlap. When the picture changes a lot inside an overlap (fast motion, camera moves, new backgrounds), the two windows draw different content and the average shows both — e.g. a see-through railing, doubled lamp posts, a boardwalk dissolving into another building.

CCW: low-res windows run in time order, each taking over the overlap from the previous window instead of averaging, keeping hard cuts clean. The high-res pass still averages and didn't ghost, likely because both windows start from the same upscaled low-res result.

Measured (RTX 5090 32GB, 1920×1088, 48fps with RIFE): 2:20 video, 10 shots in 3 groups: 2h18m, VRAM peak 11.1GB, 25% slower than segment-by-segment. All 5 ghosted spots clean; frame-difference spikes only at the 6 planned hard cuts. Redrawing the last 18.6s with a changed prompt and extra outfit picture took 25m51s with everything outside the range unchanged. Limits: needs ComfyUI 0.44+; slower; system RAM approached 64GB decoding 1080p groups.

Open source (AGPL-3.0): github.com/1113800942/comfy-h3md-director; workflows on Civitai plus a YouTube walkthrough (Chinese voiceover, English subs).

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H3 long-video ghosting traced to averaged context-window overlaps; chained fix open-sourced

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