| 摘要 |
The present invention simplifies a codebook search in the vector quantization according to the VSELP method for coding an audio signal or the like, enhancing the vector search speed. Each of the M basic vectors in a noise code book 260 is multiplied by a factor +/-1 in a sign adder 270 and combined in an adder 280 to create 2<M> noise signed vectors. Here, the characteristic of the binary Gray code is utilized as follows. A change DELTA Gu obtained between a noise signed vector based on a signed word i of the binary Gray code and a noise signed vector based on a sign word u adjacent to the sign word i and different from the sign word i only in a predetermined bit position v is used in such a manner that a sign word u' which is next to reverse the bit position v on the Gray code sequence can express a change DELTA Gu' from the noise signed vector by utilizing the fact that the sign word u' differs from the sign word u only in one bit position w excluding the bit position V. Thus, calculation is simplified, increasing the vector search speed. <IMAGE> |
