Underline

A bar slides under the word being spoken, travelling from word to word while the text itself stays untouched

Installation

$ pnpm dlx shadcn@latest add @remocn/caption-underline

Usage

CaptionUnderline shows the whole page and keeps a single bar under the word being spoken. When the voice moves on, the bar slides across to the next word and stretches or shrinks to its width, so the eye follows one continuous mark rather than a flicker of separate ones. On the first word of a page the bar grows in from the left. The component renders only the text block, so place it inside your own AbsoluteFill — see Positioning.

import { AbsoluteFill } from "remotion";
import { CaptionUnderline } from "@/components/remocn/caption-underline";
import captions from "./captions.json";
 
export const MyScene = () => (
  <AbsoluteFill
    style={{
      justifyContent: "flex-end",
      alignItems: "center",
      paddingBottom: 108,
      paddingInline: 192,
    }}
  >
    <CaptionUnderline captions={captions} underlineColor="#facc15" />
  </AbsoluteFill>
);

Props

Prop	Type	Default	Description
`captions`	`Caption[]`	`—`	The timed transcript, in the `Caption` shape from `@remotion/captions`. Times are relative to the start of the surrounding `Sequence`.
`combineTokensWithinMilliseconds`	`number`	`1200`	How much speech one page may span before the next word starts a new page. Pages also break at the end of a sentence and on any pause of at least `holdMs` (300 ms minimum).
`holdMs`	`number`	`600`	How long a page stays after its last word when the next page is not already due. It fades out at the end of the hold.
`underlineColor`	`string`	`"#facc15"`	Colour of the bar under the active word.
`thickness`	`number`	`0.08`	Bar thickness in em, so it scales with the font size.
`underlineOffset`	`number`	`0.02`	Gap in em between the bottom of the word's line box and the bar. Negative values pull it up toward the baseline.
`fontSize`	`number`	`64`	Font size in pixels.
`fontWeight`	`number`	`800`	Font weight. The font itself is inherited.
`color`	`string`	`"#ffffff"`	Text colour. It does not change as words are spoken.
`shadow`	`boolean`	`true`	A tight text shadow that keeps the caption legible over bright footage.
`className`	`string`	`—`	Classes for the text block — width, font family, `uppercase`.

Active Pop

The word being spoken turns to the accent colour and springs up in scale, then settles back as the voice moves on

Dim Progress

The whole phrase sits on screen dimmed and each word brightens the moment it is spoken, with no motion at all