One RTX 5090 renders a 3:20 AI music video: LTX 2.5 lip-sync + Wan 2.2 in ComfyUI
keto_brain · reddit · 2026-11-05
A 3:20 AI music video on a single RTX 5090
The author made the second music video for an openly AI music act — Low Battery, 3:20, two characters, 42 shots — rendered entirely on one RTX 5090 via ComfyUI's HTTP API. No video editor was opened; Claude Code writes the scripts that build the graphs and cut the result.
The core trick: make LTX lip-sync to YOUR vocal
LTX is a joint audio+video model that generates its own audio if asked to sing. The fix: split the vocal with Demucs, encode it via LTXVAudioVAEEncode, and apply SetLatentNoiseMask with mask=0 so the sampler only generates video. All core nodes, no custom ones. Key settings:
- LTX 2.5 distilled int8 (transformer + Gemma encoder), 2x faster than 2.3 with more natural arm movement
- 1280x704@24fps, frames 8k+1; audio must exactly match frame count or the mouth drifts at the end
- VAEDecodeTiled with temporalsize 96 / overlap 16 to avoid OOM on 32GB
- CFG=1 on the distilled path, so negative prompts do nothing
Wan 2.2 for non-singing shots
LTX barely moves the body; Wan 2.2 (14B I2V + Lightning LoRA 0.3, 5 steps split 2+3, RIFE x2 to 24fps) handles walking, sitting, picking things up. Lessons: 121 frames is the sweet spot (longer drifts back to frame 0); prompt action sequences from the still's pose, not states; let Wan handle entering the frame; pre-crop inputs; a Wan frame can seed the next LTX sing shot.
Pitfalls and cost
"Slow push-in" in LTX prompts runs away into extreme close-ups; calm prompts win; never seed from darkened mp4 frames (h264 blocks get animated into crawling squares) — use lossless PNGs. 42 shots took 61 LTX takes and 33 Wan takes. Total cost: ElevenLabs Starter (8,800 credits), a Claude subscription, and $1 of electricity — every model is free and open source.
Related event: Creator Renders 3:20 AI Music Video Entirely on a Single RTX 5090(2 posts)→
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