Excitation vector generator, speech coder and speech decoder

An excitation vector generator, comprising:

• excitation vector storage means for storing old excitation vectors;
• excitation vector processing means for performing different processes on at least one old excitation vector, read from said excitation vector storage means, in accordance with externally supplied indices, to generate a new random excitation vector;
• and
• switch means for switching indices to be supplied to said excitation vector processing means.

A speech coder, comprising:

• seed storage means for storing a plurality of seeds;
• an oscillator that outputs a vector stream in accordance with a value of a seed;
• a synthesis filter that performs LPC synthesis on said vector stream output from said oscillator as an excitation vector, to produce a synthesized speech;
• and
• searching means for measuring a distortion of a synthesized speech produced in association with each seed, and specifying a seed number to maximize a measured value while switching a seed to be supplied to said oscillator from said seed storage means.

A speech coder, comprising:

• excitation vector storage means for storing old excitation vectors;
• excitation vector processing means for performing different processes on at least one old excitation vector, read from said excitation vector storage means, in accordance with indices, thereby generating new random excitation vectors;
• a synthesis filter that performs an LPC synthesis on said excitation vectors output from said excitation vector processing means to produce synthesized speech;
• and
• searching means for measuring a distortion of said synthesized speech produced in association with each index and specifying an index number to maximize a measured value while switching indices to be supplied to said excitation vector processing means.

A CELP type speech coder, comprising:

• an adaptive codebook that stores immediately previous excitation vector information as an adaptive code vector;
• a random codebook that generates a random code vector;
• and
• a synthesis filter that performs an LPC synthesis of said adaptive code vector and said random code vector, said random codebook comprising an excitation vector generator having seed storage means for storing a plurality of seeds, an oscillator that outputs different vector streams in accordance with values of seeds, and switch means for switching a seed to be supplied to said oscillator from said seed storage means.

A speech coder, comprising:

• seed storage means for storing a plurality of seeds;
• an oscillator that outputs a vector stream in accordance with a seed value;
• a synthesis filter that performs an LPC synthesis on said vector stream output from said oscillator as an excitation vector to produce synthesized speech;
• means for measuring a distortion of said synthesized speech produced in association with each seed and specifying a seed number to maximize a measured value while switching a seed to be supplied to said oscillator from said seed storage means;
• means for acquiring an optimal gain of a synthesized speech produced in association with said specified seed number;
• and
• vector quantizing means for performing a vector quantization of said optimal gain.

A speech coder, comprising:

• an excitation vector generator having a fixed waveform storage means for storing a plurality of fixed waveforms, a fixed waveform arranging means for arranging said fixed waveforms read from said fixed waveform storage means, at respective arbitrary start positions, and adding means for adding said fixed waveforms arranged by said fixed waveform arranging means to generate an excitation vector;
• a synthesis filter that synthesizes excitation vectors output from said adding means to produce a synthesized speech;
• means for measuring distortion of a synthesized speech produced in association with each combination of said start positions to specify a combination of said start positions to maximize a measured value while instructing a combination of said start positions to said fixed waveform arranging means;
• means for acquiring an optimal gain of a synthesized speech produced in association with said specified combination of said start positions;
• and
• vector quantizing means for performing a vector quantization of said optimal gain.

A speech coder, comprising:

• seed storage means for storing a plurality of seeds;
• a synthesis filter that performs an LPC synthesis on said vector stream output from said oscillator as an excitation vector to produce a synthesized speech;
• means for measuring a distortion of a synthesized speech produced in association with each seed and specifying a seed number to maximize a measured value while switching a seed to be supplied to said oscillator from said seed storage means;
• and
• a noise canceler that removes a noise component from an input speech signal.

A speech coder, comprising:

• an excitation vector generator having a fixed waveform storage means for storing a plurality of fixed waveforms, a fixed waveform arranging means for arranging said fixed waveforms read from said fixed waveform storage means, at respective arbitrary start positions, and adding means for adding said fixed waveforms arranged by said fixed waveform arranging means to generate an excitation vector;
• a synthesis filter for synthesizing excitation vectors output from said adding means to produce a synthesized speech;
• means for measuring a distortion of a synthesized speech produced in association with each combination of said start positions to specify a combination of said start positions to maximize a measured value while instructing a combination of said start positions to said fixed waveform arranging means;
• and
• a noise canceler that removes a noise component from an input speech signal.

A speech decoder, comprising:

• seed storage means for storing a plurality of seeds;
• an oscillator that outputs a vector stream in accordance with a value of a stored seed;
• a synthesis filter for performing LPC synthesis on said vector stream output from said oscillator as an excitation vector to thereby produce a synthesized speech;
• and
• means for acquiring a seed from said seed storage means based on a seed number included in a received speech code and supplying said seed to said oscillator.

A speech decoder, comprising:

• excitation vector storage means for storing old excitation vectors;
• excitation vector processing means for performing different processes on at least one old excitation vector, read from said excitation vector storage means, in accordance with indices, thereby generating a new random excitation vector;
• a synthesis filter that performs LPC synthesis on said excitation vector output from said excitation vector processing means to produce a synthesized speech;
• and
• means for supplying an index included in a received speech code to said excitation vector processing means.

A CELP type speech decoder, comprising:

• an adaptive codebook that stores immediately previous excitation vector information as an adaptive code vector;
• a random codebook that generates a random code vector;
• and
• a synthesis filter that performs LPC synthesis of said adaptive code vector and said random code vector, said random codebook including an excitation vector generator comprising seed storage means for storing a plurality of seeds, an oscillator that outputs different vector streams in accordance with values of said plurality of seeds, and switch means for switching a seed of said plurality of seeds to be supplied to said oscillator from said seed storage means based on a seed number included in a received speech code.