P-Video-Replace

P-Video-Replace is the prank that became a tool: you give it a video and a reference image, and it puts the image's subject into the video - replacing the original actor or object while keeping the performance, the camera moves, and the timing. Required inputs are referenceImages (the new subject) and video (the clip to re-enact). It runs on Runware's cloud and returns a native VIDEO of the substituted scene.

The name says "replace" and the mechanism is exactly that - this isn't a face-swap or a style transfer, it's a full subject replacement that re-renders the motion onto the new look. That's the capability behind the funny demos (a cartoon character dancing in a live-action clip) and it's also genuinely useful for product videos and character shots where you want to iterate on the subject without reshooting the performance.

What you actually set

• referenceImages - required, IMAGE socket. The new subject that replaces whoever's in the source video.
• video - required, a STRING taking a UUID or URL of the source clip. Cloud-side reference, not a local path.
• positivePrompt - optional, for steering the replacement beyond what the reference implies.
• resolution - 720p or 1080p (default 720p); matches the input's aspect ratio.
• settings.sourceAudioSync - default True: drive lip and motion sync from the source video's audio. This is the setting that makes a talking-head replacement actually talk in sync. Independent of preserveAudio.
• settings.preserveAudio - default True: keep the source audio in the final output.
• settings.turbo - faster generation, may drop subtle details.
• fps - model default, 24, or 48.
• seed, numberResults - the usuals.

Output: one video socket, type VIDEO.

Install

One-time pack install: ComfyUI Manager → search Runware → install → restart, or

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

API key into ComfyUI Settings → Runware API key or RUNWARE_API_KEY. Light dependencies, no model downloads.

Where people get burned

• The source video must be reachable by the cloud. The video string wants a hosted URL or an uploaded UUID, not C:\videos\clip.mp4. This is the #1 failure with the media-input nodes in this pack.
• Reference quality sets the result. A clear, well-lit reference of the subject gives a clean replacement; a muddy one gives a muddy one.
• Turbo breaks sync. If you flip settings.turbo on for speed, check that sourceAudioSync still holds - that's the first detail to degrade.
• safety.mode defaults to none. Same opt-in guardrail story as the rest of the video nodes.

The verdict: P-Video-Replace is the pack's most show-off capable node and it earns the attention. Use it when you want the performance but a different performer, and keep the source clip clean and reachable.