Question: In an Adaptive Multi-Rate (AMR) speech codec using Source Controlled Rate operation, what triggers the transmission of a SID_UPDATE frame during speech pauses in the TX part of the Adaptive Noise (AN) handler?
Option 1: Detection of background noise exceeding a certain threshold
Option 2: Regular time intervals to update comfort noise on the Receiver (RX) side
Option 3: Receipt of a new SPEECH_GOOD frame from the speaker's audio stream
Option 4: Change in network congestion requiring adjustment of transmission rates
Explanation: During speech pauses, the TX part of the Adaptive Noise (AN) handler resumes transmission at regular intervals specifically to send one SID_UPDATE frame. This is done to update the generated comfort noise on the Receiver (RX) side, ensuring a more natural audio experience during periods of silence in the conversation.