Question: In EVS (Enhanced Voice Services) codec, how is the quantized low-band excitation energy transformed after being decoded from an LP-CNG SID frame?
Option 1: It remains in logarithmic domain for direct synthesis.
Option 2: It is converted from logarithmic to linear domain using a predefined procedure.
Option 3: It undergoes a spectral analysis before transformation.
Option 4: The transformation depends on the receiver's device capabilities.
Explanation: In the context of EVS codec, specifically for LP-CNG (Low-Priority Comfort Noise Generation), the decoded low-band excitation energy is not used directly in its logarithmic form. Instead, it undergoes a transformation to linear domain. This conversion is crucial as it prepares the energy value for further processing, such as smoothing, which is essential for generating natural comfort noise in voice communications. The linear domain representation allows for more intuitive and effective signal manipulation, ensuring high-quality synthesized low-band CNG.