| 摘要 |
<p>A plurality of encoding means performs a local decoding of a speech signal and extracts excitation information and vocal tract information from a speech signal for an encoding. The transmission rate ratios between respective encoded information are different. An evaluation/selection means evaluates the quality of respective decoded signals subjected to a local decoding in the encoding means, determines the most suitable encoding means from among a plurality of encoding means based on a result of the evaluation, and selects the most suitable encoding means, thereby outputting the selection result as selection information. The decoding means decodes a speech signal based on selection information, vocal tract information and excitation information. Evaluation/selection means selects the output from the encoding means in which the quality of a locally decoded signal is the most preferable. When vocal tract information changes little, the vocal tract information is not output, thereby causing the surplus of the quality of information. As much of the surplus of information as possible is assigned to a residual signal. Thus, the quality of a decoded speech signal is improved.</p> |
