HunyuanVideo 1080p added 50 minutes per clip on a 4090 — sysmem fallback strikes again
Suspicious_Pizza9529 · reddit · 2026-11-03
A wedding-video project with HunyuanVideo 1.5 image-to-video in ComfyUI on an RTX 4090:
- 720p drafts looked fine on a monitor but soft on a projector, especially faces, so they switched to 1080p with SR upscale.
- The first 1080p clip took 50 extra minutes with no errors — Task Manager revealed 14GB in shared GPU memory: the notorious 2023-era sysmem fallback, silently crawling with no console warning.
- Finals were rendered on HyperAI's Hunyuan notebook with a 96GB card, but seeds didn't carry over, requiring re-picking every take.
- Wholesome ending: glad AI video exists for things like a sister's wedding.
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