Coding method for using multi channel audio signals

DETAILED DESCRIPTION The present invention has been made in consideration of the above circumstances, and has as its object to provide a coding method and a coding apparatus which can prevent generation of a pre-echo and a post-echo and can perform effective coding by applying an psycho-acoustic model.
The coding method and coding apparatus according to the present invention solve the above problem by the following manner.
That is, an attack portion in which the levels of the waveform elements of the waveform signal sharply rise and a release portion in which the levels of the waveform elements of a waveform signal sharply lower are detected, and gain control is performed to at least a waveform element before the attack portion and an waveform element of the release portion by using a gain control amount which is adaptively selected depending on the characteristics of the waveform signal from a plurality of gain control amounts.
A masking level based on an psycho-acoustic model is calculated from the waveform signal, a plurality of frequency components are coded using the masking level, and control information for the gain control is coded.
More specifically, according to the present invention, the gain control is performed to prevent a pre-echo and a post-echo from being generated.
When the plurality of frequency components obtained by transforming the waveform signal, a masking level obtained on the basis of the psycho-acoustic model is used to avoid coding from being performed using an improper masking curve obtained by gain control.