4k-vfx

Maps a video-to-video VFX move onto the Pika MCP's Seedance 4K reference-to-video. The user hands you a clip + the change they want; you read EVERY frame (locally extracted with ffmpeg and tiled into contact sheets) and understand the audio (speech + music + SFX + ambience), author a Seedance-faithful prompt that locks the original (face, gestures, camera move) and time-codes the change to the right beat, then re-render the same shot in 4K with the VFX baked in. One run produces one 4K clip for one requested change.

How it works — why reading EVERY frame (and the audio) is the mechanism (do not skip the reading pass)

Seedance treats the reference video as a motion/style anchor, NOT a pixel-locked base — it does not copy the input frame-for-frame, it re-generates the shot guided by your prompt. So fidelity comes from the PROMPT: the more exhaustively the prompt describes the original (subject identity, exact gestures, camera move, framing, lighting, palette, wardrobe) and the audio (dialogue + lip-sync, music/SFX beats), the more the 4K output reads as the same shot with the change layered on. Reading EVERY frame — not a sample — is how you build that exhaustive description: you locally extract all frames with ffmpeg, tile them 25-to-a-contact-sheet (5×5), and analyze every sheet so the prompt is built from the entire timeline rather than a handful of stills. Skip the read (or read only a sample) and the output drifts — a different face, a different camera move, a different room, a missed motion beat. The reading pass — all frames + the audio — IS the skill.

Prerequisites

pika MCP available, and local ffmpeg in the run environment (used to extract every frame and build the contact sheets). Two inputs from the user: (1) a video clip (a local file or a public URL) and (2) the VFX change they want made to it. Tools used: upload_asset, probe_media, analyze_media, transcribe_audio, estimate_cost, generate_reference_video, task_status (frame extraction + tiling is done locally with ffmpeg, not an MCP tool).

Stage 0 — Gather inputs (settle this first)

You need exactly two things before generating:

1. The video — the original clip to transform. If they gave a local file, you will upload it (Step 1); if they gave a public URL, keep it.
2. The change / VFX — what should be different in the output (e.g. "turn the plaza into an open desert on a finger snap", "make it snow", "set the room on fire behind me", "morph my jacket into glowing armor").

If either is missing, ask for it before doing anything else — do not invent a change, and do not proceed on a clip you cannot reach. Once both are in hand, say in one line what you're about to do ("Reading every frame of your clip to build the desert-on-snap 4K prompt…") and run Steps 1–5 without further check-ins — but stop at the Step 6 agreement gate before generating: the 4K render is the expensive, irreversible step, and it only fires after the user approves the prompt and cost.

Step 1 — Upload the clip (upload_asset)

Real video must be uploaded — inline base64 only works for tiny assets (<~3MB), so any actual clip goes through the presigned-upload path.