Question: In EVS (Enhanced Voice Services) codec, when internal sampling rate switching occurs, how are the analysis CLDFB states resampled for both the decoded signal and the error signal from the Bass post-filter?
Option 1: Using linear interpolation as described in the EVS algorithmic specifications.
Option 2: Employing a polyphase resampling approach to maintain signal integrity.
Option 3: Through a simple hold-and-repeat method for state transition.
Option 4: By recalculating the states from the original input signal.
Explanation: In the context of Enhanced Voice Services (EVS) codec, specifically when dealing with internal sampling rate switching, maintaining the integrity of the analysis CLDFB (Complex Low-Delay Filter Bank) states is crucial. The correct approach, as aligned with telecom standards for such scenarios, involves utilizing linear interpolation. This method ensures a smooth transition between sampling rates, preserving signal quality by accurately estimating intermediate state values. This is particularly important for both the decoded signals (from CELP or MDCT-based TCX decoded modules) and the error signals provided by post-filtering processes like the Bass post-filter, to prevent artifacts and maintain voice clarity.