In recent years, there exist a lot of researches about automatic captioning, and the techniques of automatic speech recognition (ASR) aimed for captioning have been developed (Boulianne et al., 2006;Holter et al., 2000;Imai et al., 2006;Munteanu et al., 2007;Saraclar et al., 2002;Xue et al., 2006).
this research was partially supported by the Grant-in-Aid for Scientific Research (B) (No.