| 摘要 |
PROBLEM TO BE SOLVED: To provide a vocoder capable of more accurately representing a fixed codebook response of a signal frame (or a subframe), in a state where the number of bit positions in a bit frame is limited, and a method of operating such a vocoder. SOLUTION: The vocoder 50 has a fixed codebook 52 having a plurality of entries of pulse trains for comparing with the residue signal of the signal frame. The entries of the fixed codebook 52 are set according to the signal frame to be encoded. Noise signal is stored in a transmitting vocoder 50. During encoding, the noise signal is shaped by filtering depending upon determined parameters featuring the signal frame or subframe. The shaped noise signal is passed through a threshold filter, to obtain a pulse train. The fixed codebook response is selected as a part (entry) that most matches the residue signal of the signal frame or subframe in the pulse train. COPYRIGHT: (C)2007,JPO&INPIT
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