4 General

26.4513GPPCodec for Enhanced Voice Services (EVS)TSVoice Activity Detection (VAD)

The function of the Enhanced Voice Services coder VAD algorithm, or more accurately the SAD algorithm, is to indicate whether each 20 ms frame contains signals that should be transmitted, e.g. speech, music or other audio. The output of the SAD algorithm is a Boolean flag () that is set to one for the active signal, which is any useful signal bearing some meaningful information. Otherwise, the flag is set to zero indicating an inactive signal, which has no meaningful information. The inactive signal is mostly a pause or background noise.

The procedure of the present document is mandatory for implementation in all network entities and User Equipment (UE)s supporting the EVS coder.

The present document does not describe the ANSI-C code of this procedure. In the case of discrepancy between the procedure described in the present document and its ANSI-C code specifications contained in [4] the procedure defined by the [4] prevails.