Question: What is the primary purpose of deriving the high-band LP synthesis filter from the weighted low-band LP synthesis filter in EVS (Enhanced Voice Services) codec, specifically in the context of transitioning between different sampling rates?
Option 1: To enhance audio quality by introducing artificial high-frequency noise
Option 2: To adapt the filter for effective signal processing when up-sampling from a lower (12.8 kHz) to a higher (16 kHz) sampling rate
Option 3: To reduce computational complexity in low-bandwidth transmission modes (< 6.6 kbit/s)
Option 4: To ensure backward compatibility with legacy voice codecs operating at 8 kHz sampling rates
Explanation: The correct answer highlights the practical implication of deriving the high-band LP synthesis filter in the context of EVS codec. This process is crucial for effectively adapting the filter to work seamlessly with an increased sampling rate (from 12.8 kHz to 16 kHz), ensuring that the voice service maintains its enhanced quality across different transmission scenarios.