MPEG-4 Book, The

11.6. MPEG-4 HILN Parametric Audio Coding

The MPEG-4 parametric audio coding tools (called HILN) are defined in Version 2 of the MPEG-4 Audio standard [MP4V2-3]. By means of a parametric signal representation, they allow the coding of general audio signals at very low bit rates, down to about 4 kbit/s [PurM00]. Based on the general principles introduced in Section 11.5, the specific architecture and design of the HILN tools will now be described.

It should be noted that, as usual for MPEG standards, only the bitstream format and the decoding process are defined in the normative part of the MPEG standard, whereas for the encoding process only an example is given in an informative annex of the standard. This approach allows the optimization of ...