Vector estimation system, method and associated encoder

A vector estimation system for processing a sequence of input vectors, said input vectors each comprising a plurality of element values, and said system comprising:

• a digital filter with a filter vector input for receiving said sequence of input vectors and an observation noise variance input for controlling characteristics of said filter, said digital filter also having a current slowly evolving filter estimate output, a predictor error variance output and a previous slowly evolving filter estimate output, said current slowly evolving filter estimate output providing a current filtered estimate vector of current filtered estimate element values of a slowly evolving component of said sequence of input vectors, said predictor error variance output providing a current predictor error variance vector of current predictor error variance element values and said previous slowly evolving filter estimate output providing a previous filtered estimate vector of previous filtered estimate element values of said slowly evolving component of said sequence of input vectors;
• and
• a parameter estimator having an estimator vector input for receiving said sequence of input vectors and a previous slowly evolving filter estimate input coupled to said previous slowly evolving filter estimate output, said parameter estimator further includes a observation noise variance output coupled to said observation noise variance input and a predictor error variance input coupled to said predictor error variance output,
• wherein when said vector estimation system receives a current input vector that is one of said sequence of said input vectors, said parameter estimator provides a current observation noise variance vector of current observation noise variance element values at said observation noise variance input each of said current observation noise variance element values modifying one of said current filtered estimate element values at said current slowly evolving filter estimate output, each of said current observation noise variance element values being dependent upon said current input vector, said current predictor error variance vector and said previous filtered estimate vector.

A method for processing a sequence of input vectors each comprising a plurality of elements, said vectors being applied to a vector estimation system having a parameter estimator coupled to a digital filter, said method comprising the steps of:

• receiving said sequence of input vectors at inputs of said filter and said parameter estimator, said input vectors comprising a plurality of element values;
• determining a current predictor gain vector of current predictor gain element values, each of said current predictor gain element values being determined from said current input vector that is one of said sequence of said input vectors, said determining being effected by said parameter estimator;
• and
• applying said current predictor gain element values to said digital filter to thereby modify a current filtered estimate vector of current filtered estimate element values provided at an output of said digital filter, each of said current predictor gain element values being dependent upon a previous filtered estimate vector from said filter and said current input vector.

A method for processing a sequence of input vectors each comprising a plurality of elements, said vectors being applied to a vector estimation system having a parameter estimator coupled to a digital filter, said method comprising the steps of:

• receiving said sequence of input vectors at inputs of said filter and said parameter estimator, said input vectors comprising a plurality of element values;
• determining a current observation noise variance vector of current observation noise variance element values, each of said current observation noise variance element values being determined from said current input vector that is one of said sequence of said input vectors, said determining being effected by said parameter estimator;
• and
• applying said current observation noise variance element values to said digital filter to thereby modify a current filtered estimate vector of current filtered estimate values provided at an output of said digital filter, each of said current observation noise variance element values being dependent upon a said current input vector, a vector comprising current predictor error variance element values, and a vector of previous filtered estimate element values.

An encoder for processing a speech signal, said encoder comprising:

• a signal normalization module for processing the speech signal to provide a sequence of input vectors each comprising a plurality of element values;
• a digital filter with a filter vector input coupled to an output of the signal normalization module for receiving said sequence of input vectors, the digital filter also having an observation noise variance input for controlling characteristics of said filter, said digital filter also having a current slowly evolving filter estimate output, a predictor error variance output and a previous slowly evolving filter estimate output, said current slowly evolving filter estimate output providing a current filtered estimate vector of current filtered estimate element values of a slowly evolving component of said sequence of input vectors, said predictor error variance output providing a current predictor error variance vector of current predictor error variance element values and said previous slowly evolving filter estimate output providing a previous filtered estimate vector of previous filtered estimate element values of said slowly evolving component of said sequence of input vectors;
• and
• a parameter estimator having an estimator vector input for receiving said sequence of input vectors and a previous slowly evolving filter estimate input coupled to said previous slowly evolving filter estimate output, said parameter estimator further includes a observation noise variance output coupled to said observation noise variance input and a predictor error variance input coupled to said predictor error variance output,
• wherein when said vector estimation system receives a current input vector that is one of said sequence of said input vectors, said parameter estimator provides a current observation noise variance vector of current observation noise variance element values at said observation noise variance input each of said current observation noise variance element values modifying one of said current filtered estimate element values at said current slowly evolving filter estimate output, each of said current observation noise variance element values being dependent upon a said current input vector, said current predictor error variance vector and said previous filtered estimate vector.