Provided are an apparatus and method for decoding audio, The method includes receiving a bitstream consisting of audio packets; decoding an audio packet included in the received bitstream, extracting a type of the decoded packet; obtaining system data from a packet of which system metadata corresponds to the extracted packet type; and transmitting the obtained system data to a system engine, wherein the system data includes at least one of information regarding a type of the system engine and a length of the system data.