Question: In EVS (Enhanced Voice Services) codec, transitioning from CELP to MDCT coding mode, what issue arises at the beginning of the MDCT encoded frame due to the preceding CELP encoded frame?
Option 1: Insufficient Bitrate Allocation
Option 2: Increased Packet Loss Susceptibility
Option 3: Incompatibility with HQ MDCT Mode
Option 4: Aliasing Distortion Affecting Frame Reconstruction
Explanation: When switching from CELP to MDCT coding mode in EVS, the absence of a preceding MDCT frame introduces aliasing. This aliasing specifically affects the proper reconstruction of the initial portion of the first MDCT encoded frame, leading to distortion.