In a network system for sending data to a plurality of terminals, a data processing apparatus has a plurality of coding units that code outgoing data including at least video or voice data for transmission to terminals over a network. The data processing apparatus obtains information about the terminals, groups the terminals according to the information, and transmits the coded outgoing data obtained from each coding unit to a different group of terminals. Appropriate grouping of the terminals conserves both network and coding resources and enables the quality of the data transmitted to the terminals to be improved at a low cost.