Mpeg audio decoding method

In a compression process (S 10 ), each allocation table is converted by reducing each group of subbands sharing a common pattern to one (S 11 ), and the allocation tables are further converted into a single table (S 12 ). Then, offset values each corresponding to one subband are defined in a table (S 13 ), and these tables are stored in the memory (S 14 ). In a decoding process (S 20 ), an offset value is obtained using a subband as a key (S 21 ), and the number of quantization steps is obtained from a pattern read out from the table using the offset value (S 22 ).