Patent ID: 8666754

Claim:
An audio signal encoding method for encoding an audio signal including a plurality of frames, using a first encoder operating under a linear predictive coding scheme and a second encoder operating under a coding scheme which is different from the linear predictive coding scheme, the audio signal encoding method comprising: a switching step of switching, to encode a second frame immediately succeeding a first frame, from the second encoder to the first encoder after the first frame of the audio signal is encoded by the second encoder; and an initialization step of initializing an internal state of the first encoder according to a predetermined method after the switching step, wherein, in the initialization step, an internal state of the first encoder is initialized by setting a residual signal as a content of an adaptive codebook of the first encoder, wherein the residual signal is obtained by applying a linear predictive inverse filter to either the first frame yet to be encoded by the second encoder or a signal obtained by decoding an encoded result of the first frame generated by the second encoder, and wherein linear predictive coefficients of the first frame are included in codes of the second frame, and, in the initialization step, the linear predictive coefficients are utilized for the linear predictive inverse filter.