Concepts and terminology
Phoneme = the smallest linguistic unit, so that the set of all phonemes allows the representation of all the words in a given language. (alternative definition: phoneme = the smallest distinguishable unit of audio speech)
Viseme = the smallest visibly distinguishable unit of visual speech.
Visual speech = total of visible transformations and movements in the vocal tract due to speech production (i.e. motion of lips, teeth, tongue, etc.)
Lipreading (=speechreading) = speech recognition using visual information, lip state and shape information in particular
ASR = Acoustic Speech Recognition
AVSR = Audio - Visual Speech Recognition
Department of Informatics
Aristotle University of Thessaloniki