7 Output resampler tool
26.4023GPPAdditional decoder toolsEnhanced aacPlus general audio codecGeneral audio codec audio processing functionsTS
The audio output from an Enhanced aacPlus decoder using a downsampled synthesis filterbank (see 4.6.18.4.3 or 4.6.18.8.2.3 of [1]) is given at the AAC decoder sampling rate 
. If an output with lower sampling rate is desired, a downsampler tool is required in order to convert the audio output from the source sampling frequency 
to the target sampling frequency 
.
The downsampler tool consists of three parts connected to the final operations of the SBR decoder as in Figure 1. (Refering to Figure 4.44 of [1]). The QMF bandlimiter operates on QMF samples and is inserted prior to the QMF synthesis bank, the spline resampler and the postfilter operate on synthesised PCM audio samples.
Figure 1: Downsampler tool