Caption Build Animation

Controls the per-word fade-in animation window for burn-in captions.

video-caption-build accepts either:

• A duration in milliseconds — each word fades in over the specified time window as it appears.
• true — enables fade-in with a default duration.
• false — disables the fade-in animation (words appear instantly).

This animation applies in word-pop and karaoke styles where words appear individually. In plain style, the effect applies to the entire caption line appearing as a unit.

Combine with video-caption-bounce for a combined fade-and-scale entry effect.