Question: In the EVS (Enhanced Voice Services) codec, what is the primary purpose of passing the modified excitation through the synthesis filter in the CELP (Code-Excited Linear Prediction) decoding process?
Option 1: To generate a new set of LPC (Linear Predictive Coding) coefficients for the next frame.
Option 2: To enhance the noise robustness of the decoded speech signal.
Option 3: To obtain a modified synthesis that overwrites the initially decoded synthesis for the current frame.
Option 4: To adjust the bit rate of the encoded voice stream in real-time.
Explanation: In the context of EVS codec's CELP decoding, the synthesis filter refines the excitation signal. Passing the modified excitation through this filter produces a more accurate synthesis output for the current frame, replacing the initial decoded synthesis, which is essential for maintaining and enhancing voice quality in real-time communications.