Question: What happens to the MA (Moving Average) memory of the ISF (Inverse Sinusoidal Filtering) quantizer when an inactive signal frame is encoded in the EVS (Enhanced Voice Services) codec?
Option 1: It is set to its previous active value to maintain continuity.
Option 2: It is updated with the mean values for UC (Unconstrained Complexity) mode, WB (Wideband) case.
Option 3: It is set to zero to reset the quantizer state.
Option 4: It remains unchanged to preserve signal integrity.
Explanation: When encoding an inactive signal frame in the EVS codec, resetting the MA memory of the ISF quantizer to zero is crucial for accurately representing the absence of signal. This action prevents any residual or previous signal characteristics from influencing the encoding of the inactive frame, ensuring a clean representation of silence or background noise. This approach aligns with the detailed algorithmic descriptions for handling inactive frames in voice codecs, emphasizing the importance of state resets for maintaining audio quality and integrity.