The impact of differences in facial features between real speakers and 3D face models on synthesized lip motions

Lip motion accuracy is important for speech intelligibility, especially for users who are hard of hearing or second language learners. A high level of realism in lip movements is also required for the game and film production industries. 3D morphable models (3DMMs) have been widely used for facial analysis and animation. However, factors that could influence their use in facial animation, such as the differences in facial features between recorded real faces and animated synthetic faces, have not been given adequate attention. This paper investigates the mapping between real speakers and similar and non-similar 3DMMs and the impact on the resulting 3D lip motion. Mouth height and mouth width are used to determine face similarity. The results show that mapping 2D videos of real speakers with low mouth heights to 3D heads that correspond to real speakers with high mouth heights, or vice versa, generates less good 3D lip motion. It is thus important that such a mismatch is considered when using a 2D recording of a real actor's lip movements to control a 3D synthetic character.