Method and apparatus for improved weighting filters in a CELP encoder

A speech encoder comprising:

• a first error weighting filter configured to accept a speech signal as input, to output a weighted speech signal, and to minimize a magnitude of a first weighted error signal generated by taking the difference between said weighted speech signal and a first weighted synthesized speech signal;
• a first signal path configured to generate a first synthesized speech signal;
• a second error weighting filter coupled with the first signal path, said second weighting filter configured to generate the first weighted synthesized speech signal from the first synthesized speech signal and configured to minimize the magnitude of the first weighted error signal generated by taking the difference between the weighted speech signal and said first weighted synthesized speech signal;
• a first subtractor coupled with the first and second error weighting filters, said first subtractor configured to take the difference between the weighted speech signal and the first weighted synthesized speech signal and to output the first weighted error signal;
• a second signal path configured to generate a second synthesized speech signal;
• a third error weighting filter coupled with the second signal path, said third error weighting filter configured to generate a second weighted synthesized speech signal from the second synthesized speech signal and configured to minimize a magnitude of a second weighted error signal generate by taking a difference between the first weighted error signal and said second weighted synthesized speech signal;
• a second subtractor coupled with the first subtractor and the third weighting filter, said second subtractor configured to take the difference between the first weighted error signal and the second weighted synthesized speech signal, and to output a second weighted error signal;
• and
• a feedback means coupled to the second subtractor, said feedback means configured to use the second weighted error signal to control the generation of subsequent first and second synthesized speech signals.

A method of speech encoding comprising:

• a) performing error weighting on a speech signal to create a weighted speech signal;
• b) generating a first synthesized speech signal from a first excitation signal multiplied by a first gain term;
• c) performing error weighting on the first synthesized speech signal to create a weighted first synthesized speech signal;
• d) taking the difference between the weighted speech signal and the weighted first synthesized speech signal in order to generate a first error signal;
• e) generating a second synthesized speech signal from a second excitation signal multiplied by a second gain term;
• f) performing error weighting on the second synthesized speech signal to create a weighted second synthesized speech signal;
• g) taking the difference between the first error signal and the weighted second synthesized speech signal in order to generate a second error signal;
• and
• h) using the second error signal to control the generation of subsequent first and second synthesized speech signals.

A transmitter comprising:

• a speech input means configured to receive a voice input signal;
• a speech encoder coupled with said voice input means, said speech encoder configured to generate parameters associated with a synthesized speech signal that represents the voice input signal, said speech encoder including:
• a first error weighting filter configured to accept a speech signal as input, to output a weighted speech signal, and to minimize a magnitude of a first weighted error signal generated by taking the difference between said weighted speech signal and a first weighted synthesized speech signal;
• a first signal path configured to generate a first synthesized speech signal;
• a second error weighting filter coupled with the first signal path, said second weighting filter configured to generate the first weighted synthesized speech signal from the first synthesized speech signal and configured to minimize the magnitude of the first weighted error signal generated by taking the difference between the weighted speech signal and said first weighted synthesized speech signal;
• a first subtractor coupled with the first and second error weighting filters, said first subtractor configured to take the difference between the weighted speech signal and the first weighted synthesized speech signal and to output the first weighted error signal;
• a second signal path configured to generate a second synthesized speech sample;
• a third error weighting filter coupled with the second signal path, said third error weighting filter configured to generate a second weighted synthesized speech signal from the second synthesized speech signal and configured to minimize a magnitude of a second weighted error signal generate by taking a difference between the first weighted error signal and said second weighted synthesized speech signal;
• a second subtractor coupled with the first subtractor and the third weighting filter, said second subtractor configured to take the difference between the first weighted error signal and the second weighted synthesized speech signal, and to output a second weighted error signal;
• and
• a feedback means coupled to the second subtractor, said feedback means configured to use the second weighted error signal to control the generation of subsequent first and second synthesized speech signals;
• and
• a transceiver coupled with said speech encoder, said transceiver configured to transmit the parameters through a transmission means.