Question: What is the primary function of the Voice Activity Detector (VAD) in the Discontinuous Transmission (DTX) mechanism of the Adaptive Multi-Rate (AMR) speech codec?
Option 1: To analyze background acoustic noise and transmit its characteristic parameters to the receiver.
Option 2: To detect silent periods in speech, allowing for the temporary cessation of radio transmission.
Option 3: To generate comfort noise on the transmitter side during active speech.
Option 4: To perform error concealment for lost AMR speech frames.
Explanation: The Voice Activity Detector (VAD) is a crucial component of the DTX mechanism in the AMR codec. Its primary function is to identify periods of silence or low speech activity, enabling the transmitter to temporarily halt radio transmission during these periods, thus conserving resources without significantly impacting perceived voice quality.