Observed Choreography Transcription

Primary role: observed scroll-choreography transcription workflow.

Repository Boundary

This workflow turns an externally observed scroll-driven presentation into a transcription record written in the Scroll-Driven Story vocabulary: start, distance, scene_ranges, progress-derived state, and static path. It exists so that a reimplementation study, a review, or an automated capture pipeline can hand a builder one document instead of raw pixels.

It does not authorize copying an observed site's assets, copy, code, or brand into this repository or into a study; it does not add motion or decorative properties to reusable Layout pattern CSS; and a transcription record is an observation of an unaffiliated external artifact, not evidence about this repository's own examples. The consuming study owns its own imagery, copy, and visual values.

Reusable Method

Capture Protocol

Record the capture identity before transcribing: URL, capture date, viewport, tool, wait strategy, and total scroll height. Capture in two passes:

1. A coarse scene pass segments the page into scene y-ranges using layout landmarks (full-width blocks) and per-scene representative frames.
2. A dense timeline pass scrubs at a fixed step (small enough that at least three frames land inside the shortest choreography of interest) and records a frame-difference score between consecutive frames.

Difference-score plateaus near zero indicate static regions; sustained non-zero runs indicate scrubbed choreography; isolated spikes indicate discrete swaps. Keep every frame file; the transcription must cite frames by file name.

Transcription Record

For each observed scene, write:

• Scene identity: name, document y-range, one-sentence job.
• Pin observation: whether a stage visually holds position while the document advances (start and distance in document pixels), or the scene scrolls through normally (distance not applicable).
• Scene ranges: sub-segments as fractions of scene progress, each with the observed state it presents.
• Keyframe observations: for each boundary between sub-segments, the property-level change observed across adjacent frames — content swap, translation, scale, opacity, counter/number roll, media frame advance — stated as direction and rough magnitude, not invented exact values.
• Transition profile: for each sub-segment boundary, how the states mix — cut (adjacent frames show only completed states), blend (a mid-transition frame shows both states partially visible; record the observed blend width in scroll pixels, bounded below by the capture step), or slide (a mid-transition frame shows a state displaced along an axis; record the direction). A consumer without a profile defaults to whatever its own contract prefers, so an omitted profile is a gap worth naming.
• Static path: what a non-animated reading order of the same content would present, so the consumer can build the reduced-motion and no-script alternative required by the Scroll-Driven Story contract.
• Asset inventory: the kind of media carrying the effect (photograph, video, rendered UI, image sequence) and its role. Kinds only; the record never embeds or links a copy of the asset for reuse.
• Frame evidence: the frame files supporting each claim.

Mark anything the captured frames cannot establish as not observable in captured frames instead of interpolating a guess. A claim without a citable frame is a gap, not a fact.

Handoff

A transcription record travels with the capture manifest and difference curve. A consumer maps scene ranges onto the Scene Composition Contract: document scroll and sticky geometry stay with Layout responsibilities, progress mapping and teardown with Motion, and all visual values with the consuming product.

Opinionated Guidance

Transcribe jobs and relationships, not pixel values; a reimplementation that inherits observed exact timings inherits unverified choices. Derive every described state from scene progress so reversal and mid-entry stay well defined in the eventual build. Sampling density bounds what a record may claim: a 500px step cannot support statements about effects shorter than 500px of scroll.

Platform-Specific Guidance

Record the capture browser, OS, headless mode, and device scale separately from the observed site's behavior; headless rendering, missing fonts, and disabled video autoplay can all change what frames show. For client-rendered pages, note that DOM text accumulates as sections mount, so per-scene text dumps overstate what is visible; treat frames as the primary evidence for visibility.

Unsupported Absolutes

A transcription proves what frames show at sampled positions, never how the original is implemented — no easing curve, frame rate, library, or performance claim survives from frame differences alone. There is no universal scrub step, difference threshold, or scene count; each capture declares its own. Frame similarity in one direction does not prove reversibility. A transition profile is bounded by sampling: a capture step wider than a transition can prove blend only when a mid-transition frame happens to land inside it, and can never prove cut.

Verification Contract

A transcription record is usable when every scene declares a y-range and pin observation, every motion claim cites frame files, every scene has a static path, and every unknown is marked not observable in captured frames. Reversibility claims require frames captured in both scroll directions; otherwise mark reversal untested. The record is stale when the source site changes; re-verification means a fresh capture compared against the recorded capture date, never editing old observations in place.

Source, License, And Attribution

Locally authored workflow, generalized from an internal capture-and-reimplementation study of an external homepage on 2026-09-10. Transcription records describe unaffiliated external sites; they carry the capture identity for provenance and reproduce no external assets, copy, or code.

IA Navigation

Parent: Motion. Next: Scroll-Driven Story.