Question: In EVS (Enhanced Voice Services) codec, what influences the classification of a frame as critical for protection against loss, in addition to the input signal's characteristics?
Option 1: Previous frame loss history and configurable threshold based on network conditions
Option 2: Only the type of coder used for primary copy coding (e.g., speech, audio)
Option 3: Subframe pitch lag and factor M alone, without considering network conditions
Option 4: The quantization resolution of gain parameters in partial frame coding modes
Explanation: The correct answer is Option 1 because the criticality of a frame for protection against loss in EVS codec not only depends on the input signal's characteristics but also on whether previous frames were lost (history) and a configurable threshold. This threshold can be dynamically adjusted based on current network conditions, such as high Frame Error Rate (FER) conditions, to classify more frames as critical if needed. This approach ensures adaptive protection of speech quality under varying network reliability.