This part of ISO/IEC 13818 describes the MPEG-2 audio non-backwards compatible standard called MPEG-2 Advanced Audio Coding, AAC , a higher quality multichannel standard than achievable while requiring MPEG-1 backwards compatibility. This MPEG-2 AAC audio standard allows for ITU-R indsitinguishablequality according to  at data rates of 320 kb/s for five full-bandwidth channel audio signals.
The AAC decoding process makes use of a number of required tools and a number of optional tools. Table 1 lists the tools and their status as required or optional. Required tools are mandatory in any possible profile. Optional tools may not be required in some profiles.