Karaoke playback (Transcript viewer)

Theme D adds clip-scoped karaoke reading on the Transcript page.

Behaviour

  1. Press ▶ on a Turns/Segments line (or chapter Play).

  2. The sticky player loads that segment clip (same ffmpeg extract path as before).

  3. When imported words[] timings align and cover enough of the clip, the player highlights word-by-word from the browser playhead and supports click-a-word → seek.

  4. When timings are missing, incomplete, or nulled by corrections, the player uses segment-level highlight only and shows an honesty caption — timings are never invented.

  5. The list marks the active line with a Playing badge and scrolls it into view once.

Honesty / limits

  • Playhead stays browser-local (iframe); it is not streamed into Streamlit session state.

  • Clips remain capped at the existing ClipService window (60s); words outside that window are not timed for karaoke.

  • Continuous full-file karaoke and a CCv2-native reader surface are follow-ons (see ROADMAP Theme D).