Speech coder

A speech coder comprising:

• means for dividing a discrete input speech signal into signal components in units of frames each frame having a predetermined time length, and for generating a spectrum parameter representing a spectrum envelope of said discrete input speech signal;
• means for dividing the frame into subframes each subframe having a predetermined time length, and for generating a pitch parameter so as to maximize correlation between a subframe signal and synthetic speech calculated from an excitation signal generated from a previous discrete input speech signal;
• a first code book for storing code vectors formed by off-line training based on a speech signal data base;
• a second code book for storing code vectors having predetermined statistical characteristics;
• means for generating an excitation signal of the discrete input speech signal by a linear combination of code vectors respectively selected from said first and second code books;
• and
• means for quantizing gains of at least one of the pitch parameter and gains of said first and second code books by using a gain code book formed in advance by off-line training, and outputting a quantized gain.

A speech coder comprising:

• means for dividing a discrete input speech signal into signal components in units of frames each frame having a predetermined time length, and for generating a spectrum parameter representing a spectrum envelope of said discrete input speech signal;
• means for dividing the frame into subframes each subframe having a predetermined time length, and for generating a delay amount of a pitch parameter so as to maximize a correlation between a subframe signal and synthetic speech calculated from an excitation signal generated by a previous discrete input signal;
• means for quantizing a gain of the pitch parameter by using a fourth code book formed in advance;
• a first code book for storing code vectors formed by off-line training based on the discrete input speech signal;
• a second code book for storing code vectors having predetermined statistical characteristics;
• and
• means for generating an excitation signal of the discrete input speech signal by a linear combination of code vectors respectively selected from said first and second code books, and outputting an index of said code vectors.