Question: When ACELP core is used for WB, SWB, or FB signals at bitrates above 13.2 kbps, what is the internal sampling rate set to for LP analysis, and how many samples are used for the LP analysis window at this rate?
Option 1: 12.8 kHz with a 300-sample window
Option 2: 16 kHz with a 400-sample window
Option 3: 25.6 kHz with a 200-sample window
Option 4: 32 kHz with a 500-sample window
Explanation: According to the specified conditions for ACELP core usage (WB, SWB, or FB signals at bitrates higher than 13.2 kbps), the internal sampling rate is adjusted to 16 kHz from the standard 12.8 kHz. At this increased sampling rate, the LP analysis window length is set to 400 samples, which maintains a time frame of 25 ms (since 400 samples / 16,000 samples per second = 0.025 seconds or 25 ms). This adjustment ensures that the analysis captures the necessary signal characteristics at the higher bitrate.