Question: In the context of Enhanced Voice Services (EVS) codec, what is the primary purpose of computing the 'pitch stability counter' (pc) parameter during signal classification at the encoder?
Option 1: To assess the average energy of consecutive speech frames
Option 2: To evaluate the spectral balance of the audio signal
Option 3: To measure the variation in pitch period across successive OL pitch estimates
Option 4: To determine the voicing measure through normalized correlation analysis
Explanation: The pitch stability counter (pc) is specifically designed to assess how the pitch period varies. This is crucial for signal classification, as it helps in distinguishing between different types of audio inputs (e.g., voiced, unvoiced, or transient signals). By evaluating the variation in pitch estimates, the encoder can make more informed decisions about the appropriate coding strategy to apply, ensuring optimal voice quality over various network conditions.