5.1 Overview

26.4033GPPAdvanced Audio Coding (AAC) partEncoder specificationEnhanced aacPlus general audio codecGeneral audio codec audio processing functionsRelease 17TS

The AAC encoder acts as the core encoding algorithm of the aacPlus system encoding at half the sampling rate of aacPlus. Since aacPlus implements the High Efficiency AAC Profile at Level 2 as defined in [3], the AAC LC object type is used. The AAC LC object type does not implement the Long Term Predictor (LTP) tool. The Level 2 implies a restriction to a maximum of two channels. Furthermore in case of SBR being used, the maximum AAC sampling rate is restricted to 24 kHz whereas if SBR is not used the maximum AAC sampling rate is restricted to 48 kHz.

The basic layout is depicted below.

Figure 1: AAC Encoder Block Diagram