Patent ID: 8688442

Claim:
An audio coding apparatus comprising: coding units; a signal classifying unit configured to determine a classification of a property of an input signal as a classification of the input signal, according to the property; and a selecting unit configured to select a coding unit based on the classification determined by said signal classifying unit and an index specified for said selecting unit, irrespective of the property of the input signal, from among said coding units and cause said selected coding unit to code the input signal, wherein: said coding units are ranked from first to Nth, N being greater than 1 and a lower number indicating a higher rank, the index indicates a bit rate of a coded signal to be generated from the input signal by said coding unit, the classification includes a value S which increases as a degree of speech signal components in the input signal increases, a lowest coding unit that is ranked first is configured to code a frequency spectrum signal of the input signal, a highest coding unit that is ranked Nth is configured to separate the input signal into a linear prediction coefficient and an excitation signal, and code each of the linear prediction coefficient and the excitation signal, and said selecting unit is configured to: select, from the coding units, a coding unit that is ranked higher than a predetermined rank, when (i) the bit rate indicated by the index is a first bit rate and (ii) the value S is smaller than or equal to a predetermined value A; and select, from the coding units, a coding unit that is ranked higher than the predetermined rank, when (i) the bit rate indicated by the index is a second bit rate higher than the first bit rate and (ii) the value S is smaller than or equal to a predetermined value B, the predetermined value B being larger than the predetermined value A.