Patent ID: 8265929

Claim:
A speech coding apparatus comprising: a core speech coding unit which presents a speech signal with an excitation signal; a transmission rate determination unit which allocates the number of bits that are additionally allowed due to a capacity change in a transmission channel; and an embedded excitation signal coding unit for determining which one of a multiple pulse excitation coding method and a gain compensation method is optimal for coding a residual excitation signal, that is not coded in the core speech coding unit, with the additionally allowed bits, and generating the residual excitation signal coded by the determined method, wherein the gain compensation method derives a gain compensation value for compensating a gain obtained from an algebraic codebook search, the gain compensation value being multiplied with the gain obtained from the algebraic codebook search to update the gain, wherein the embedded excitation signal coding unit comprises a multiple pulse search unit for selecting a position and a sign of multiple pulses that minimize a square error ε m of the residual excitation signal, the embedded excitation signal coding unit further comprises a gain compensation unit for determining the gain compensation value that minimizes a square error ε g of the residual excitation signal, and the embedded excitation signal coding unit compares ε m with ε g , selects the multiple pulse excitation coding method when ε m <ε g , and selects the gain compensation method when ε m >ε g .