Speech coding system and method using time-separated coding algorithm

A time-separated speech coding method for coding the transitional signal of voiced/unvoiced sound through harmonic speech coding, comprising the steps of:

• a transitional point detecting step for detecting the transitional point of the transitional signal;
• a window applying step for extracting harmonic model parameter of each block by applying TWH window to the central point of left/right block after dividing LPC residue signal out of inputted signals centering said transitional point;
• and
• a synthesis step for adding said harmonic model parameter.

A time-separated speech coder for coding a transitional signal of voiced and unvoiced sound through harmonic speech coding, the time-separated speech coder comprising:

• an excitation signal transitional analyzer, comprising:
• a transitional point detector configured to detect a transitional point of the transitional signal by measuring abruptly varying degrees of the energy ratio of a left and right signal block after computing a left and right energy ratio value Erate(n) for a time n, a computation using the following equation:
• E min ⁢ ( n ) = min ⁡ [ ∑ i = 0 P ⁢ s 2 ⁢ ( n + i ) , ∑ i = 0 P ⁢ s 2 ⁢ ( n - i ) ] E max ⁡ ( n ) = max ⁡ [ ∑ i = 0 P ⁢ s 2 ⁢ ( n + i ) , ∑ i = 0 P ⁢ s 2 ⁢ ( n - i ) ] E rate ⁡ ( n ) = [ E max - E min E max ] 2
• where, P is the pitch period, s(n) represents the speech signal after passing a Direct Current removal filter, min(x,y) is the function selecting the smaller number out of x and y, and max(x,y) is the function selecting the larger number out of x and y;
• a harmonic excitation signal analyzer for extracting a harmonic model parameter of each left and right block;
• and
• a harmonic excitation signal synthesizer for adding the harmonic model parameter.