Question: In the EVS codec's frame loss concealment for the frequency domain core, how is a smooth time evolution ensured when extrapolating the last received MDCT coefficients?
Option 1: By updating the codec memory with predicted MDCT coefficients before processing the missing frame.
Option 2: Through additional processing that guarantees a smooth transition from the last received frame to the extrapolated signal in the time domain.
Option 3: By fading the extrapolated signal to background noise if no reasonable continuation can be assumed.
Option 4: By always reducing the energy of the extrapolated signal until a good frame is received.
Explanation: This is correct because, according to the EVS codec's frame loss concealment mechanism for the frequency domain core, not only are the last received MDCT coefficients extrapolated in some cases, but also, the resulting time domain signal is specifically processed to ensure a smooth time evolution from the last received frame into the missing frames. This highlights the importance of maintaining audio continuity and quality during packet loss conditions in VoIP systems.