Question: In EVS (Enhanced Voice Services) codec, how are gains per frequency band handled for quantization in cases of low bit rate and non-NB (Narrowband) content?
Option 1: All bands are quantized using a single VQ without interpolation.
Option 2: Only specific bands (0-8, 10, 12, 14) are quantized, with others (9, 11, 13, 15) interpolated from neighboring quantized bands.
Option 3: The first 5 bands are quantized, and the rest are discarded to save bitrate.
Option 4: A fixed set of bands is always quantized regardless of bitrate or bandwidth.
Explanation: In the context of Enhanced Voice Services (EVS) codec, efficient use of bitrate is crucial. For non-Narrowband content at low bit rates, balancing detail with bitrate constraints is key. Quantizing specific bands (0-8, 10, 12, 14) and interpolating others (9, 11, 13, 15) from neighboring quantized bands strikes this balance, ensuring sufficient audio quality while managing bitrate efficiently. This approach leverages the correlation between frequency bands to reconstruct unquantized bands accurately, thus optimizing the use of available bits (between 21 and 26 bits for gain quantization).