Methods and apparatus for performing signal processing. The signal processing comprises demultiplexing input encoded data into data including information for a segment including frames and coefficient information for a coefficient selected in the frames of the segment, and low band encoded data, decoding the low band encoded data to produce a low band signal, selecting a coefficient of a frame to be processed from a plurality of the coefficients based on the data, calculating a high band sub-band power of a high band sub-band signal of each sub-band constituting a high band signal of the frame to be processed based on a low band sub-band signal of each sub-band constituting the low band signal of the frame to be processed and the selected coefficient, and producing the high band signal of the frame to be processed based on the high band sub-band power and the low band sub-band signal.