Question: In the EVS (Enhanced Voice Services) codec, how does the Signal-to-Noise Ratio (SNR) impact the transmission rate of SID (Silence Insertion Description) frames when using an adaptive rate?
Option 1: Increasing SNR increases SID frame frequency to enhance voice quality.
Option 2: Increasing SNR decreases SID frame frequency to reduce average data rate with minor quality degradation.
Option 3: SNR has no impact on the adaptive transmission rate of SID frames.
Option 4: Decreasing SNR has no effect on SID frame frequency in adaptive mode.
Explanation: In the context of EVS codec's adaptive SID transmission rate, as the Signal-to-Noise Ratio (SNR) increases, indicating a cleaner signal with less background noise, the codec responds by decreasing the frequency of SID frames. This reduction in SID frame transmission rate aims to lower the average data rate without significantly compromising voice quality. Conversely, when the SNR decreases (indicating more noise), the SID frame frequency increases to maintain the naturalness of the comfort noise. Thus, Option 2 correctly describes the relationship between increasing SNR and the adaptive transmission rate of SID frames.