Viseme
Viseme is a term used in linguistics and computer graphics to denote a visual unit of speech corresponding to the mouth shapes and facial movements associated with producing a phoneme. Phonemes are abstract sound categories; visemes describe what the lips, teeth, tongue, and jaw look like during articulation. Because many phonemes produce nearly identical visible articulations, a single viseme often covers multiple phonemes. The exact viseme set varies by language, speaker, and application, but many systems use a compact repertoire of visually distinctive units to represent speech visually.
In visual speech processing, visemes are used to support lip-reading, visual speech recognition, and lip-sync for
Challenges include speaker variability, lighting, camera angles, and facial appearance differences that affect visibility of lip