Periodic-combined-envelope-sequence generation device, periodic-combined-envelope-sequence generation method, periodic-combined-envelope-sequence generation program and recording medium

A periodic-combined-envelope-sequence generation device comprising:

• processing circuitry configured to:
• execute a spectral-envelope-sequence calculating processing which takes, as an input audio signal, a time-domain audio digital signal in each frame which is a predetermined time segment, and calculates a spectral envelope sequence of the input audio signal on the basis of time-domain linear prediction of the input audio signal;
• and
• execute a periodic-combined-envelope generating processing which transforms the spectral envelope sequence to a periodic combined envelope sequence on the basis of a periodic component of the input audio signal in the frequency domain;
• wherein the periodic-combined-envelope generating part modifies the periodic combined envelope sequence based on a value that determines a mixture ratio between the spectral envelope sequence and the periodic component;
• and
• the value that determines the mixture ratio is chosen such that the shape of the periodic combined envelope sequence and the shape of absolute values of a coefficient string which is transformed from the input audio signal in the frequency domain becomes similar to one another.