Question: For an ACELP core operating at bitrates higher than 13.2 kbps for Wideband (WB) or Super-Wideband (SWB) signals, what happens to the input signal's sampling rate if it is initially sampled at 32 kHz?
Option 1: The input signal's sampling rate is converted to 16 kHz using FIR filtering with a specific set of LP filter coefficients.
Option 2: The input signal's sampling rate remains unchanged at 32 kHz, as no conversion is required for WB or SWB signals.
Option 3: The input signal undergoes a direct conversion to 25.6 kHz without any intermediate steps, regardless of the bitrate.
Option 4: The input signal is first downsampled to 8 kHz and then upsampled to match the ACELP core's internal rate.
Explanation: According to the principles outlined for handling different input sampling rates in relation to the ACELP core's operation, when the input signal is sampled at a higher rate (like 32 kHz), it undergoes resampling to match the core's internal operating rate of 16 kHz for WB and SWB signals at bitrates above 13.2 kbps. This process involves FIR filtering with specific LP filter coefficients tailored for this conversion, ensuring alignment and optimal processing.