Question: In the context of EVS (Enhanced Voice Services) codec, for SWB and FB inputs at specific bitrates, how is the Non-transient signal classification into Normal and Harmonic modes determined in the 2400-13600 Hz frequency range?
Option 1: By analyzing the energy distribution across all 448 MDCT coefficients without sub-band splitting.
Option 2: Through a comparison of the average magnitudes of spectral coefficients across the entire frequency range.
Option 3: Based on the peak magnitude of spectral coefficients in the first 5 sub-bands only.
Option 4: By evaluating the frequency sharpness (ratio of peak to average magnitudes) within 14 equally split sub-bands, utilizing specific conditions for mode counters (N_h1, N_h2, and M).
Explanation: The correct answer is Option 4 because the Non-transient signal classification into Normal and Harmonic modes involves splitting the frequency range into sub-bands, calculating frequency sharpness in each, and utilizing mode counters (N_h1, N_h2, and M) based on specific conditions to determine the frame mode, reflecting a nuanced understanding of the EVS codec's operational intricacies.