AUDIO SIGNAL CODING METHOD, DECODING METHOD, AUDIO SIGNAL CODING APPARATUS, AND DECODING APPARATUS WHERE FIRST VECTOR QUANTIZATION IS PERFORMED ON A SIGNAL AND SECOND VECTOR QUANTIZATION IS PERFORMED ON AN ERROR COMPONENT RESULTING FROM THE FIRST VECTOR QUANTIZATION

摘要

A coding unit codes an audio signal by using a vector quantization method to reduce the quantity of data. An audio code having a minimum distance among auditive distances between sub-vectors produced by dividing an input vector and audio codes in a transmission-side code book is selected. A portion corresponding to an element of a sub-vector having a high auditive importance is handled in an audio code selecting unit while neglecting the codes indicating phase information and subjected to comparative retrieval with respect to audio codes in a transmission-side code book. Extracted phase information corresponding to an element portion of the sub-vector is added to the result obtained and output as a code index. Thereby, the calculation amount in the code retrieval of vector quantization and the number of codes in the code book are decreased without lowering the quality of an audio signal.