Question: In EVS (Enhanced Voice Services) codec, operating in a bandwidth-efficient mode, how is the linear-prediction residual typically analyzed and processed for transmission?
Option 1: By applying a fixed quantization scheme across all operational modes.
Option 2: Through a single parametric representation of the high-frequency signal portion, irrespective of bitrate.
Option 3: Using an adaptive bitrate-dependent quantization strategy for the low-frequency band only.
Option 4: By employing different quantization schemes dependent upon the nature of the residual, with parameters varying by bitrate.
Explanation: In the context of EVS codec's linear prediction based operation, especially when aiming for efficient bandwidth use (implied by 'bandwidth-efficient mode'), the processing of the linear-prediction residual is optimized by adapting to its nature. This involves selecting from multiple quantization schemes based on the characteristics of the residual signal and considering the bitrate of the operation. This approach ensures a balance between voice quality and bandwidth utilization, which is crucial for Enhanced Voice Services.