5.1.1 High-pass Filtering

26.4453GPPCodec for Enhanced Voice Services (EVS)Detailed algorithmic descriptionRelease 15TS

The input audio signal sampled at 8, 16, 32 or 48 kHz, being the sample index, is high-pass filtered to suppress undesired low frequency components. The transfer function of the HP filter has a cut-off frequency of 20 Hz (–3 dB) and is given by

(1)

The coefficients of the HP filter for a given input sampling frequency are given in the table below.

Table 1: Coefficients of the 20Hz HP filer

8 kHz

16 kHz

32 kHz

48 kHz

0.988954248067140

0.994461788958195

0.997227049904470

0.998150511190452

-1.977908496134280

-1.988923577916390

-1.994454099808940

-1.996301022380904

0.988954248067140

0.994461788958195

0.997227049904470

0.998150511190452

1.977786483776764

1.988892905899653

1.994446410541927

1.996297601769122

-0.978030508491796

-0.988954249933127

-0.994461789075954

-0.996304442992686

The input signal, filtered by the HP filter, is denoted as .