Question: In the EVS codec, when using ACELP core for WB, SWB, or FB signals at bitrates above 13.2 kbps, what happens to the pre-emphasis process due to the internal sampling rate change?
Option 1: The pre-emphasis factor is adjusted to 0.5 to compensate for the increased sampling rate.
Option 2: The pre-emphasis step is skipped entirely to avoid over-amplification of high frequencies.
Option 3: The pre-emphasis is re-applied at the end of the pre-processing chain with the original input signal (x[n]).
Option 4: The sampling rate is converted back to 12.8kHz before applying pre-emphasis to maintain consistency.
Explanation: When ACELP core is selected for WB, SWB, or FB signals at higher bitrates (>13.2 kbps), leading to an internal sampling rate of 16kHz, the pre-emphasis is re-done at the end of the pre-processing chain. This ensures the signal undergoes necessary high-pass filtering to emphasize higher frequencies appropriately for the changed sampling context.