In one embodiment, a channel in a frame of the audio signal is subdivided into a plurality of blocks according to a subdivision hierarchy. The subdivision hierarchy has more than one level, and each level is associated with a different block length. At least two of the blocks have different lengths. First subdivision information indicating whether the channel has been subdivided is generated, and second subdivision information is generated if the subdividing has been performed. The second subdivision information indicates the subdivision of the channel into the blocks.