21. The method of claim 15 , wherein: the first phoneme string portion comprises a first phoneme, a second phoneme, and a third phoneme; and the first potential set comprises a first viseme unit and a second viseme unit, the first viseme unit corresponding to the complete first phoneme and first phoneme context of the complete first phoneme, the second viseme unit corresponding to the complete third phoneme and second phoneme context of the complete third phoneme.
21. The method of claim 15 , wherein: the first phoneme string portion comprises a first phoneme, a second phoneme, and a third phoneme; and the first potential set comprises a first viseme unit and a second viseme unit, the first viseme unit corresponding to the complete first phoneme and first phoneme context of the complete first phoneme, the second viseme unit corresponding to the complete third phoneme and second phoneme context of the complete third phoneme. 22. The method of claim 21 , wherein the first phoneme context is a first part of the second phoneme and the second phoneme context is a second part of the second phoneme.