Fixed code book search device and fixed code book search method

• US 8,352,254 B2
• Filed: 12/08/2006
• Issued: 01/08/2013
• Est. Priority Date: 12/09/2005
• Status: Active Grant

• Current Assignee: Optis Wireless Technology, LLC (Brevet Capital)
• Original Assignee: Panasonic Corporation (Panasonic Holdings Corporation)
• Inventors: Ehara, Hiroyuki
• Primary Examiner(s): Desir, Pierre-Louis
• Assistant Examiner(s): BAKER, MATTHEW H
• Application Number:
  US12/096,424
• Publication Number:
  US 20090292534A1
• Time in Patent Office: 2,223 Days
• Field of Search: 704/219, 704/222
• US Class Current: 704/223
• CPC Class Codes: G10L 19/08 Determination or coding of the excitation function; Determination or coding of the long-term prediction parameters
• CPC Class Codes: G10L 2019/0013 Codebook search algorithms

Abstract

A fixed code book (FCB) search device simplifies an error minimizing process and reduces a calculation amount so as to prevent deterioration of a coding performance. The FCB search device includes a pulse shape convolution inverse filter having an inverse feature of a pulse diffusion filter and supplied with an ideal residual signal; a pulse candidate preparatory selector that pre-selects a plurality of pulse candidates from the ideal residual signal to which the inverse filter is applied; and a pulse candidate final selector that finally selects one pulse from the selected candidates. Using this configuration, a search is made for an algebra code book to which the pulse diffusion is applied.

Claims

1. A fixed codebook search method for searching a fixed codebook that generates a fixed codebook vector by convolving a shape vector with a pulse, comprising:

filtering a linear prediction residual signal using a filter having opposite characteristics with respect to a pulse dispersion filter that convolves the shape vector;

limiting pulse position candidates in a pulse vector using a first evaluation function that minimizes an error between a signal acquired by filtering using the filter having the opposite characteristics and the pulse vector; and

searching the fixed codebook using the limited pulse position candidates and a second evaluation function.

2. The fixed codebook search method according to claim 1, wherein the second evaluation function comprises a value calculated by normalizing a cross-correlation between a target vector and a synthesized signal using energy of the synthesized signal.

3. The fixed codebook search method according to claim 1, wherein a following equation is used as the second evaluation function:

second evaluation function=x^tHDc/(c^tD^tH^tHDc)

where

x;

target vector;

H;

lower triangular matrix expressing impulse response convolution in an auditory weighting synthesis filter;

D;

convolution matrix for a dispersion vector;

c;

pulse vector; and

t;

subscript expressing a transposed matrix or a transposed vector.

4. A fixed codebook search apparatus that searches a fixed codebook that generates a fixed codebook vector by convolving a pulse with a shape vector, the fixed codebook search apparatus comprising:

an inverse filter including a processor that has opposite characteristics with respect to a pulse dispersion filter that convolves the shape vector and filters a linear prediction residual signal;

a first selector that minimizes an error between a signal acquired by filtering using the inverse filter and a pulse vector, and selects a plurality of pulse position candidates for the pulse vector; and

a second selector that minimizes an error between a target signal and an auditory weighting synthesized signal using a second evaluation function, and selects a set of pulse positions from the plurality of pulse position candidates.

5. The fixed codebook search apparatus according to claim 4, further comprising:

a determiner that determines the shape vector based on adaptive parameters; and

a calculator that calculates opposite characteristics with respect to the filter that convolves the shape vector,

wherein the inverse filter performs filtering using the opposite characteristics calculated in the calculator.

6. A communication terminal apparatus comprising the fixed codebook search apparatus according to claim 4.

7. A base station apparatus comprising the fixed codebook search apparatus according to claim 4.