Question: In EVS (Enhanced Voice Services) codec, what triggers an internal sampling rate switch from 12.8 kHz to 16 kHz in LP-based CNG (Comfort Noise Generation)?
Option 1: Increase in bit-rate from ≤ 8.0 kbps to ≥ 9.6 kbps
Option 2: Decrease in bit-rate from ≥ 13.2 kbps to ≤ 8.0 kbps
Option 3: Switching from active frames to LP-based CNG segments at any bit-rate
Option 4: Change in the type of input audio signal (e.g., music to voice)
Explanation: According to the EVS codec's operational specifications, in LP-based Comfort Noise Generation (CNG), the internal sampling rate switches from 12.8 kHz to 16 kHz when the bit-rate increases from ≤ 8.0 kbps to ≥ 9.6 kbps. This switch is crucial for maintaining optimal audio quality and efficiency at varying bit-rates, highlighting the codec's adaptability in different network conditions or application scenarios.