Question: In EVS (Enhanced Voice Services) codec, what technique is employed to prevent signal discontinuities when transitioning from MDCT-based TCX to CELP decoding at the output sampling rate during MC3 (MDCT to CELP transition 3)?
Option 1: Cross-fading
Option 2: Time-domain interpolation
Option 3: Frequency-domain smoothing
Option 4: Adaptive gain adjustment
Explanation: To maintain signal continuity and avoid artifacts at the transition point, cross-fading is utilized. This technique gradually blends the output of the MDCT-based TCX decoding with the CELP decoding over a short period, ensuring a seamless transition and preventing audible discontinuities in the reconstructed audio signal. This approach is particularly crucial in voice services to preserve perceptual quality.