7 Adaptive multi-rate speech channel Voice Activity Detection (VAD)

06.713GPPAdaptive Multi-Rate speech processing functionsGeneral descriptionTS

The adaptive multi-rate VAD function is described in GSM 06.94 [11].

The input to the VAD is a set of parameters computed by the adaptive multi-rate speech encoder defined in GSM 06.90 [7]. The VAD uses this information to decide whether each 20 ms speech coder frame contains speech or not. Note that the VAD flag is an input to the TX DTX handler and does not need to control the transmitter keying directly.

GSM 06.94 [11] describes the VAD algorithm and GSM 06.73 [5] defines the C code. The verification of compliance to GSM 06.94 [11] is achieved by use of digital test sequences (see GSM 06.74 [6]) applied to the same interface as the test sequences for the speech codec.