What is an Audio Object in MPEG-4?
MPEG-4 defines audio objects as “realistic” objects. A “real-world” audio object can be defined as an audible semantic entity (voice of one or more speakers, one or more instruments, etc.). It can be recorded with one microphone in case of a mono recording or with more microphones, at different positions, in case of a multichannel recording. Audio objects can be grouped or mixed together, but objects can not easily be split into sub-objects. One single audio object can consist of more than one audio channel, if we define audio channels as information, specific for one loudspeaker position. For example, one MPEG-1 audio bitstream will be the coded representation of one object in MPEG4. This object contains either 1 channel (mono mode) or 2 channels (dual, stereo or joint stereo mode).
