An input data is divided into blocks of predetermined time units and then further divided into a plurality of bands. Each band is coded and compressed to prepare a basic sub-block essential for data reproduction and a plurality of extension sub-blocks contributing to improvement of the quality of the reproduced data. A transmission timing during streaming delivery, remaining extension sub-blocks are delivered if the time period is still within a time period for delivering the same data block, but the remaining extension sub-blocks are not delivered and delivery of the basic sub-block of the subsequent data block begins if the delivery timing for the subsequent data block has arrived. In this way, a stable streaming delivery is achieved by a scalable data compression.