Lip synchronization maps speech timing and phonetic content to facial movement. A strong result coordinates lips, jaw, cheeks, expression, pauses, and head motion while preserving the speaker's identity.
Multilingual dialogue is challenging because languages use different sound patterns and timing. Evaluation should inspect fast speech, pauses, profile views, facial occlusion, emotional delivery, and whether the audio and mouth remain aligned throughout the clip.
ELI5
Lip synchronization makes a person's mouth movement match spoken audio. The lips and face should form the right shapes at the right time so the speech looks believable.
For example, a generated speaker saying the same sentence in English and Japanese needs mouth motion that fits each language's sounds and timing. A small delay or repeated wrong shape can make the clip feel unnatural.
