For 16:9 to 9:16 (or reverse), when should I crop and reframe versus outpaint, what do video outpainting tools document, and how do headroom and lead room constrain it?

Problem. Delivering a clip in another aspect ratio without losing the framing intent. Conditions. Source clip with fixed composition; vertical (9:16) social delivery as in C3-B573. Tool statements. WaveSpeed's Video Outpainter takes a required video, an optional prompt and an aspect_ratio, expands the video in any direction while preserving motion, identity and scene coherence, and converts ratios without cropping; VACE lists Expand-Anything for video. For stills, getimg.ai says outpainting generates new content around the source while keeping the original pixels unchanged. Craft constraints (Wikipedia). Headroom is the space between the top of the head and the top of the frame and too much creates dead space; lead room is space in front of a subject in the direction it faces or moves. Method (inference). (1) Arithmetic: a centre 9:16 crop of a 16:9 frame keeps (9/16)/(16/9) = 31.6% of the width; if the shot is a wide with several subjects that loses them, so choose reframing by tracking the crop window across the shot, or outpaint. (2) Outpainting a 1920x1080 clip to 9:16 at full width needs a 1920x3413 canvas, so about 68% of the output height is invented; prefer it for backgrounds, sky and floor extensions, not for new subjects. (3) Check after the operation: headroom still sensible, lead room kept in the facing/moving direction, nothing important in the top and bottom UI-safe margins of the platform (the WaveSpeed page itself mentions 'adding safe margins'). (4) Verify that temporal consistency of the invented area holds across the clip; reject flicker. Failure modes. Invented regions flicker or change between frames; identity or props at the edge can be cut or extended wrongly (inference). Limitations. Vendor page gives no quality data; pricing not recorded. Version/date. Fetched 2026-10-23. Curator qualifications: All cited documentation excerpts located on the live pages by curator GET; no video sources. Limitations: Arithmetic and workflow are mine; vendor claims unverified; no quality metrics. Platform safe-zone numbers not given here (see C3-B573). Evidence status: statements located in the cited sources by a correlated desk review (Claude); not executed; not independently reviewed.

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