Figure 15
From: An Overview of the Coding Standard MPEG-4 Audio Amendments 1 and 2: HE-AAC, SSC, and HE-AAC v2
Illustration of scalability. The panels display the frequency ranges and the spectral content of the core layer and the first enhancement layer of a scalable AAC + SBR bit stream. The bit stream contains 3 layers, the first being a 20 kbps monolayer, the second layer adding a 16 kbps enhancement making it in total a 36 kbps mono bit stream. The layers are indicated by the subscript where 
is the core layer, and 
is the first enhancement layer. The SBR data is stored in the core layer, and thus labeled 
.