The present invention relates to a decoding apparatus, a decoding method, an encoding apparatus, an encoding method, and programs that can shorten the delay time caused by the band extension at the time of decoding, and restrain increases in resources on the decoding side.A higher frequency component generating unit (73) generates a pseudo higher frequency spectrum by using a lower frequency spectrum (SP-L) and a higher frequency envelope (ENV-H). A phase randomizing unit (74) randomizes the phase of the pseudo higher frequency spectrum, based on a random flag (RND). An inverse MDCT unit (75) denormalizes the lower frequency spectrum (SP-L) by using a lower frequency envelope (ENV-L), and combines the pseudo higher frequency spectrum supplied from the phase randomizing unit (74) with the denormalized lower frequency spectrum (SP-L). The combination result is used as the spectrum of the entire band. The present invention can be applied to a decoding apparatus that performs band extension decoding, for example.