Question: In EVS (Enhanced Voice Services) codec, what is the primary purpose of performing local CNG (Comfort Noise Generation) synthesis at the encoder for low-band signals?
Option 1: To enhance voice quality by adding background noise to the transmitted signal.
Option 2: To update filters, adaptive codebook memories, and guide high-band analysis and DTX hangover control.
Option 3: To reduce bitrate by only transmitting comfort noise during silent periods.
Option 4: To improve error resilience in packet loss scenarios.
Explanation: The correct answer is Option 2 because local CNG synthesis at the encoder for low-band signals serves multiple internal purposes: updating filters, refreshing adaptive codebook memories, and guiding both high-band analysis and DTX hangover control. This is crucial for maintaining voice quality and efficient encoding/decoding processes.