Wan VACE Video Edit (fal)

VACE is Alibaba's official control framework for Wan - the piece that turns Wan from a "generate a clip" model into a controllable one: reference-to-video, video extension, and video editing all live under it. This node is the video edit path: hand it a clip and a prompt, optionally some reference images, and it re-renders the video to match your instruction. It runs on fal.ai, which is handy because VACE is notoriously slow to run locally without a speed LoRA.

Cloud call, per-clip billing, no local GPU. VACE is open (Apache 2.0, part of the Wan family), but running the 14B version at reasonable speed is a real machine - fal takes that on.

How it works

You give it a source video and a text prompt describing the edit, and VACE regenerates the clip guided by both. Optionally you also feed reference images to steer the look. It's the video equivalent of prompt-driven image editing: keep the motion and structure of the original while changing what the prompt tells it to change. The video_type switch (auto/general/human) hints whether the footage is people-focused, which helps VACE apply the right handling.

The inputs and outputs that matter

• prompt (required, multiline) - describe the edit you want.
• the source video - as a video socket or input_video_url string.
• images (optional, IMAGE) - reference image(s) to guide the edited look.
• video_type - auto (default), general, or human. Set human for people-centric footage if auto misreads it.
• resolution - auto (default) through 240p…1080p. auto matches the source; pin it if you need a specific output size.

Performance and framing knobs, safe at defaults: acceleration (regular default, plus low/none/default - trades speed for quality), enable_auto_downsample with auto_downsample_min_fps (default 15) to keep long/high-fps clips manageable, aspect_ratio (auto/16:9/9:16/1:1), enable_safety_checker, and variations (1–10).

Output is video_url (a list - one URL per variation) on fal. Download with Fal Save Media from URL or chain via *_direct_url. Save before the URLs expire.

How to install it

From gokayfem's ComfyUI-fal-API pack. ComfyUI Manager: search ComfyUI-fal-API, install, restart. Manual:

cd ComfyUI/custom_nodes
git clone https://github.com/gokayfem/ComfyUI-fal-API.git
pip install -r ComfyUI-fal-API/requirements.txt

Add your fal key (copy config.ini.example → config.ini, paste from fal.ai/dashboard/keys, or export FAL_KEY=your_key), restart.

Common issues & troubleshooting

The edit changed too much / lost the original. VACE regenerates guided by your prompt, so an aggressive prompt drifts far from the source. Describe only what should change, and consider feeding a reference image to anchor the look you want preserved.

People in the footage look off. Set video_type to human if auto didn't pick it up - the human path handles bodies and faces differently.

It's slow or expensive on a long clip. Leave enable_auto_downsample on so high-fps/long footage gets normalized, and consider a lower acceleration setting only when you specifically need the extra quality. Test on a short segment before committing a long render.

Output won't preview. It's a URL (or list of URLs) - download via Fal Save Media from URL first.

Insufficient funds / credit lag. fal is pay-per-call and legit; top-ups have occasionally posted late. Wait for credits rather than repaying. fal errors print as text in ComfyUI.