CS-ACELP speech compression system with adaptive pitch prediction filter gain based on a measure of periodicity

A speech processing system comprising:

• a first portion including an adaptive codebook and means for applying an adaptive codebook gain, and
• a second portion including a fixed codebook, a pitch filter, wherein the pitch filter includes a means for applying a pitch filter gain,
• and wherein the improvement comprises:
• means for determining said pitch filter gain, based on a measure of periodicity of a speech signal.

A method for use in a speech processing system which includes a first portion which comprises an adaptive codebook and corresponding adaptive codebook amplifier and a second portion which comprises a fixed codebook coupled to a pitch filter, the pitch filter. comprising a delay memory coupled to a pitch filter amplifier, the method comprising:

• delaying the adaptive codebook gain;
• determining the pitch filter gain to be equal to the delayed adaptive codebook gain, except when the adaptive codebook gain is either less than 0.2 or greater than 0.8., in which cases the pitch filter gain is set equal to 0.2 or 0.8, respectively;
• and
• amplifying samples of a signal in said pitch filter based on said determined pitch filter gain.

A speech processing system comprising:

• a first portion including an adaptive codebook and means for applying an adaptive codebook gain, and
• a second portion including a fixed codebook, a pitch filter, means for applying a second gain, wherein the pitch filter includes a means for applying a pitch filter gain,
• and wherein the improvement comprises:
• means for determining said pitch filter gain, said means for determining including means for setting the pitch filter gain equal to an adaptive codebook gain, said signal gain is either less than 0.2 or greater than 0.8., in which cases-the pitch filter gain is set equal to 0.2 or 0.8, respectively.