1. Science and Technology Research Laboratories, Japan Broadcasting Corporation, Tokyo, Japan
2. Graduate School of Information Sciences, Tohoku University, Sendai, Japan
3. harasawa.m-ii@nhk.or.jp
4. sawahata.y-jq@nhk.or.jp
5. komine.k-cy@nhk.or.jp
6. Research Institute of Electrical Communication, Tohoku University, Sendai, Japan
7. shioiri@riec.tohoku.ac.jp