Speech coding method

A speech coding method according to conjugate-structure algebraic code excited linear prediction, hereinafter referred to as CS-ACELP, in which an LSP coefficient, a pitch component vector, a random component vector, and gain vectors which are applied to the pitch component vector and the random component vector are coded using an LSP codebook, an adaptive codebook, a random codebook and a gain codebook, respectively, such that a distortion relative to an input speech waveform vector is minimized for each frame;

• comprising the step of coding the random component vector such that each of random component vectors forming together the random codebook is formed of three or less pulses having a unit amplitude for each of a pair of subframes which form together a frame, the positions of the pulses being determined from a plurality of predetermined positions which a pulse can assume in a subframe so that a distortion in a synthesized speech is minimized;
• wherein each random component vector in the random codebook comprises a pair of sub-vectors, each sub-vector comprising three pulses having a unit amplitude.

A speech coding method according to conjugate-structure algebraic code excited linear prediction, hereinafter referred to as CS-ACELP, in which an LSP coefficient, a pitch component vector, a random component vector, and gain vectors which are applied to the pitch component vector and the random component vector are coded using an LSP codebook, an adaptive codebook, a random codebook and a gain codebook, respectively, such that a distortion relative to an input speech waveform vector is minimized for each frame;

• comprising the step of coding the random component vector such that each of random component vectors forming together the random codebook is formed of three or less pulses having a unit amplitude for each of a pair of subframes which from together a frame, the positions of the pulses being determined from a plurality of predetermined positions which a pulse can assume in a subframe so that a distortion in a synthesized speech is minimized;
• wherein each random component vector in the random codebook comprises two sub-vectors, which may be selectively defined by two or three pulses each having a unit amplitude.

A speech coding method according to conjugate-structure algebraic code excited linear prediction, hereinafter referred to as CS-ACELP, in which an LSP coefficient, a pitch component vector, a random component vector, and gain vectors which are applied to the pitch component vector and the random component vector are coded using an LSP codebook, an adaptive codebook, a random codebook and a gain codebook, respectively, such that a distortion relative to an input speech waveform vector is minimized for each frame;

• comprising the step of coding the random component vector such that each of random component vectors forming together the random codebook is formed of three or less pulses having a unit amplitude for each of a pair of subframes which form together a frame, the positions of the pulses being determined from a plurality of predetermined positions which a pulse can assume in a subframe so that a distortion in a synthesized speech is minimized;
• wherein a search for the random component vector using the random codebook takes place by a search in which the random component vector is orthogonalized with respect to the pitch component vector when an optimum pitch gain has a value which exceeds a predetermined value, and takes place by a search without orthogonalization when the pitch gain does not exceed the predetermined value.

A speech coding method according to conjugate-structure algebraic code excited linear prediction, hereinafter referred to as CS-ACELP, in which an LSP coefficient, a pitch component vector, a random component vector, and gain vectors which are applied to the pitch component vector and the random component vector are coded using an LSP codebook, an adaptive codebook, a random codebook and a gain codebook, respectively, such that a distortion relative to an input speech waveform vector is minimized for each frame;

• comprising the step of coding the random component vector such that each of random component vectors forming together the random codebook is formed of three or less pulses having a unit amplitude for each of a pair of subframes which form together a frame, the positions of the pulses being determined from a plurality of predetermined positions which a pulse can assume in a subframe so that a distortion in a synthesized speech is minimized;
• wherein the gain codebook comprises a 6-bit vector quantized gain codebook.

A speech coding method according to conjugate-structure algebraic code excited linear prediction, hereinafter referred to as CS-ACELP, in which an LSP coefficient, a pitch component vector, a random component vector, and gain vectors which are applied to the pitch component vector and the random component vector are coded using an LSP codebook, an adaptive codebook, a random codebook and a gain codebook, respectively, such that a distortion relative to an input speech waveform vector is minimized for each frame;

• comprising the step of coding the random component vector such that each of random component vectors forming together the random codebook is formed of three or less pulses having a unit amplitude for each of a pair of subframes which form together a frame, the positions of the pulses being determined from a plurality of predetermined positions which a pulse can assume in a subframe so that a distortion in a synthesized speech is minimized;
• wherein the gain codebook comprises a (3+3)-bit conjugate-structure gain codebook.

A speech coding method according to conjugate-structure algebraic code excited linear prediction, hereinafter referred to as CS-ACELP, in which an LSP coefficient, a pitch component vector, a random component vector, and gain vectors which are applied to the pitch component vector and the random component vector are coded using an LSP codebook, an adaptive codebook, a random codebook and a gain codebook, respectively, such that a distortion relative to an input speech waveform vector is minimized for each frame;

• comprising the step of coding the random component vector such that each of random component vectors forming together the random codebook is formed of three or less pulses having a unit amplitude for each of a pair of subframes which form together a frame, the positions of the pulses being determined from a plurality of predetermined positions which a pulse can assume in a subframe so that a distortion in a synthesized speech is minimized;
• wherein bits are allocated to the code of the pitch component vector without a parity bit.

A speech coding method according to conjugate-structure algebraic code excited linear prediction, hereinafter referred tp as CS-ACELP, in which an LSP coefficient, a pitch component vector, a random component vector, and gain vectors which are applied to the pitch component vector and the random component vector are coded using an LSP codebook, an adaptive codebook, a random codebook and a gain codebook, respectively, such that a distortion relative to an input speech waveform vector is minimized for each frame;

• comprising the step of coding the random component vector such that each of random component vectors forming together the random codebook is formed of three or less pulses having a unit amplitude for each of a pair of subframes which form together a frame, the positions of the pulses being determined from a plurality of predetermined positions which a pulse can assume in a subframe so that a distortion in a synthesized speech is minimized;
• wherein the LSP coding comprises the steps of coding in a first stage using a first LSP codebook, and coding in a second stage using a second LSP codebook, the number of bits in the second LSP codebook being less than the number of bits in the second LSP codebook according to ITU-T Recommendation G.279 which is equal to 10.