A code excited linear prediction speech decoder is provided. An adaptive codebook generates an adaptive code vector. A random codebook generates a random code vector. A synthesis filter receives a signal based on the adaptive code vector and the random code vector, and performs linear prediction coefficient synthesis on the signal. The random codebook includes a pulse vector provider that provides a pulse vector having a signed unit pulse, a comparator that compares a value of adaptive codebook gain with a preset threshold value, a selector that selects a dispersion pattern from a plurality of dispersion patterns stored in a memory in accordance with a result of the comparison, and a generator that generates the dispersed vector by convoluting the pulse vector and the selected dispersion pattern.
CROSS-REFERENCE TO RELATED APPLICATION
This application is a continuation of U.S. application Ser. No. 10/133,735, filed Apr. 29, 2002 now U.S. Pat. No. 7,024,356, which is a continuation of U.S. patent application Ser. No. 09/319,933, filed on Jun. 18, 1999, which is now U.S. Pat. No. 6,415,254, issued Jul. 2, 2002, which is the National Stage of International Application No. PCT/JP98/04777, filed Oct. 22, 1998, the content of which is expressly incorporated by reference herein in its entirety. The International Application was not published under PCT 21 (2) in English.
Priority Data
Oct 22, 1997 [JP] 9-289412 Oct 28, 1997 [JP] 9-295130 Mar 31, 1998 [JP] 10-85717
