Speech translation for Unwritten language using intermediate representation: Experiment for Viet-Muong language pair

The paper studies an automatic translation method that translates from the text of a language (L1) to the speech of an unwritten language (L2). Normally the written text is used as the bridge to connect a translation module that translates from the text of L1 to the text of L2 and a synthesis module that generates the speech of L2 from the text. In the case of unwritten language, an intermediate representation has to be used instead of the writing form of L2. This paper proposes the use of phoneme representation because of the intimate relationship between phonemes and speech in one language. The proposed method was applied to the Viet-Muong language pair. The Vietnamese text needs to be translated into Muong language in two dialects, Muong Bi - Hoa Binh and Muong Tan Son - Phu Tho, both unwritten. The paper also proposes a phoneme set for each Muong language and applies them to the problem. The evaluation results showed that the translation quality was relatively high in both dialects (for Muong Bi, the fluency score was 4.63/5.0, and the adequacy score was 4.56/5.0). The synthesized speaking quality in both dialects is acceptable (for Muong Bi, the MOS score was 4.47/5.0, and the comprehension score was 93.55%). The results also show that the applicability of the proposed system to other unwritten languages ​​is promising.