Method and apparatus for decoding and changing the pitch of an encoded speech signal

A speech signal decoding apparatus comprising:

• first receiving means for receiving a value identifying a fundamental frequency of a speech signal at a first pitch;
• second receiving means for receiving a set of amplitude values identifying a spectral envelope of said speech signal at said first pitch by defining amplitudes of a predetermined band of harmonics;
• modifying means connected to said first receiving means for modifying said value identifying said fundamental frequency and forming a modified fundamental frequency value;
• interpolating means connected to said second receiving means for interpolating additional amplitude values identifying a modified spectral envelope corresponding to said modified fundamental frequency value to form an interpolated set of amplitude values;
• and
• synthesizing means connected to said interpolating means and to said modifying means for synthesizing said speech signal at a second pitch based on said modified fundamental frequency value and said interpolated set of amplitude values.

A speech synthesis method comprising the steps of:

• storing a value corresponding to a fundamental frequency of a speech signal at a first pitch;
• storing a set of amplitude values of a predetermined band of harmonics corresponding to a spectral envelope of said speech signal at said first pitch;
• retrieving said fundamental frequency value and said amplitude values;
• modifying said fundamental frequency value to form a modified fundamental frequency value;
• interpolating additional amplitude values corresponding to a modified spectral envelope based on said modified fundamental frequency value to form an interpolated set of amplitude values;
• and
• synthesizing said speech signal at a second pitch based on said modified fundamental frequency value and said interpolated set of amplitude values.

A speech synthesis apparatus comprising:

• storage means for storing a value corresponding to a fundamental frequency of a speech signal and amplitude values of a predetermined band of harmonics corresponding to a spectral envelope of said speech signal at a first pitch;
• modifying means connected to said storage means for retrieving said fundamental frequency value and for modifying said fundamental frequency value to form a modified fundamental frequency value;
• interpolating means connected to said storage means for retrieving said amplitude values and for interpolating additional amplitude values corresponding to a modified spectral envelope based on said modified fundamental frequency value to form an interpolated set of amplitude values;
• and
• synthesizing means connected to said modifying means and to said interpolating means for synthesizing said speech signal at a second pitch based on said modified Fundamental frequency value and said interpolated set of amplitude values.

A portable radio terminal apparatus comprising:

• amplifier means for amplifying a received analog radio signal to form an amplified analog signal;
• demodulation means connected to said amplifier means for demodulating said amplified analog signal to form a demodulated analog signal;
• conversion means connected to said demodulation means for converting said demodulated analog signal to a digital signal;
• transmission path decoding means connected to said conversion means for channel-decoding said digital signal to produce a speech encoded signal;
• speech decoding means connected to said transmission path decoding means for decoding said speech encoded signal to produce a decoded speech signal;
• and
• D/A conversion means connected to said speech decoding means for converting said decoded speech signal to produce an analog output speech signal,
• wherein said speech decoding means includes:
• first receiving means for receiving a first component of said encoded speech signal corresponding to a fundamental frequency value of said speech signal at a first pitch;
• second receiving means for receiving a second component of said encoded speech signal corresponding to a set of amplitude values of a predetermined band of harmonics defining a spectral envelope of said speech signal at said first pitch;
• modifying means connected to said first receiving means for modifying said first component corresponding to said fundamental frequency value to produce a modified fundamental frequency value;
• interpolating means connected to said second receiving means and said modifying means for interpolating additional amplitude values corresponding to a modified spectral envelope based on said set of amplitude values and said modified fundamental frequency value to form an interpolated set of amplitude values;
• and
• synthesizing means connected to said interpolating means and to said modifying means for synthesizing said decoded speech signal at a second pitch based on said modified fundamental frequency value and said interpolated set of amplitude values.