| 摘要 |
PURPOSE: A method for retrieving a fixed codebook through global pulse replacement is provided to reduce computation quantity required for retrieving the fixed codebook in a voice encoder by determining an initial codebook vector on the basis of a track-classified absolute value, replacing pulses in each track by one pulse, and determining a codebook vector. CONSTITUTION: An absolute value of a factor in a pulse position possibility estimation vector with respect to each track-classified pulse position is computed and acquired(100). A pulse position is selected from a position with a great absolute value of the factor in the estimation vector, a codebook vector is temporarily determined(110). Pulses are replaced in each track from the codebook vector by one pulse. A certain value is obtained by selectively using a codebook vector according to the pulse replacement, the entire pulse position number of sub-frames, an object signal for retrieving a fixed codebook, an impulse response of an LP(Linear Prediction) synthesis filter, the pulse number of the sub-frames and the pulse position possibility estimation vector(120). It is confirmed whether a value which is greater than a value by the codebook vector before replacing the pulses exists among a plurality of values obtained by the pulse replacement(130). If the value exists, a pulse is replaced to a pulse position generating the maximum value among a plurality of the values obtained by the pulse replacement, and a new codebook vector is determined(140).
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