Question: What is the primary purpose of applying a high-pass filter with an 80 Hz cut-off frequency in the pre-processing stage of the Adaptive Multi-Rate (AMR) speech codec?
Option 1: To reduce the bitrate of the encoded speech signal
Option 2: To enhance the audio quality by amplifying low-frequency components
Option 3: To synchronize the speech signal with other media streams
Option 4: To prevent undesired low-frequency components from affecting the encoding process
Explanation: In the context of speech codec pre-processing, high-pass filtering is utilized to remove or attenuate unwanted low-frequency components that could potentially degrade the encoding quality or introduce unnecessary artifacts. By setting a cut-off frequency of 80 Hz, the filter ensures that the encoding process focuses on the more relevant frequency range for human speech, thereby protecting the integrity of the encoded signal.