Currently, there is no obvious solution for describing explicitly relationships between digital items as they are common in real application scenarios. Semantic search for these relationships is also not possible. N12246 Requirements for the extension of MPEG 21 DID to support the description of the relational situation of Digital Items describes requirements. However, a use case is still missing.
4Audio
4.1MPEG-4: Part 3 Audio
In order to enable low-delay applications such like Voice-over-IP using MPEG technology especially in case of multi-channel audio, N12218 Definition of Low Delay AAC V2 Profile was defined.
