Audio encoding device using concealment processing and audio decoding device using concealment processing

摘要

Disclosed are an audio encoding device and an audio decoding device which reduce degradation of subjective quality of a decoding signal caused by power mismatch of a decoding signal which is generated by a concealing process upon disappearance of a frame. When a frame is lost, a past encoding parameter is used to obtain a concealed LPC of the current frame and a concealed sound source parameter. A normal CELP decoding is performed from the obtained concealed sound source parameter. Correction is performed by using a conceal parameter on the obtained concealed LPC and the concealed sound source signal. The power of the corrected concealed sound source signal is adjusted to match a reference sound source power. A filter gain of the synthesis filter is adjusted so as to adjust the power of a decoded sound signal to the power of a decoded sound signal during an error-free state. Moreover, a synthesis filter gain adjusting coefficient is calculated by using an estimated normalized residual power so that a filter gain of a synthesis filter formed by using a concealed LPC is a filter gain during an error-free state.

主权项

1. A speech encoding and decoding apparatus comprising:
an LPC analyzer that performs linear predictive analysis on each of a first frame and a second frame of an input speech signal to generate an LPC parameter of each of the first frame and the second frame, the input speech signal including the second frame and the first frame preceding the second frame; an LPC encoder that encodes the LPC parameter of the second frame; an excitation generator that generates an excitation signal and an excitation parameter of each of the first frame and the second frame; an excitation parameter encoder that encodes the excitation parameter of the second frame; an excitation power calculator that calculates power of the excitation signal of the first frame; a normalized predicted residual power calculator that calculates normalized predicted residual power based upon the LPC parameter of the first frame; a vector quantizer that performs vector quantization of first parameters of the first frame to obtain encoded first parameters of the first frame, wherein the first parameters of the first frame include the calculated excitation signal power of the first frame and the calculated normalized predicted residual power of the first frame; and a multiplexer that multiplexes the encoded first parameters of the first frame with an encoded second parameter of a second frame to output the multiplexed data as second frame encoded data, wherein the encoded second parameter of the second frame includes the encoded LPC parameter of the second frame and the encoded excitation parameter of the second frame, wherein the normalized predicted residual power calculator calculates the normalized predicted residual power Pz(n) of frame n byPz⁡(n)=∏j=1M⁢(1-r⁡[j]2) where M is a prediction order and r[j] is a j-order reflection coefficient, wherein the encoded first parameters, multiplexed with the encoded second parameter by the multiplexer, are transmitted to a speech decoding apparatus, and the speech decoding apparatus calculates a synthesis filter gain adjustment coefficient from a ratio of a decoder normalized predicted residual power calculated in the speech decoding apparatus in an event of a frame loss and the normalized predicted residual power transmitted from the speech coding apparatus, wherein the synthesis filter gain adjustment coefficient is multiplied with the excitation signal to derive a decoded speech signal, and wherein each of the LPC analyzer, the LPC encoder, the excitation generator, the excitation parameter encoder, the excitation power calculator, the normalized predicted residual power calculator, the vector quantizer, and the multiplexer is implemented individually in integrated circuits.