Frequency band extension apparatus and method, encoding apparatus and method, decoding apparatus and method, and program

Provided is a frequency band extension apparatus and method, an encoding apparatus and method, a decoding apparatus and method, and a program. Band-pass filters obtain a plurality of lowband subband signals from an input signal. A frequency envelope extracting circuit extracts a frequency envelope from the plurality of lowband subband signals obtained by the plurality of band-pass filters. A highband signal generating circuit generates highband signal components on the basis of the frequency envelope obtained by the frequency envelope extracting circuit, and the plurality of subband signals obtained by the band-pass filters. A frequency band extension apparatus extends the frequency band of the input signal on the basis of the highband signal components generated by the highband signal generating circuit.