Question: In a Transparent end-to-end Packet-switched Streaming Service (PSS), what does the 'Value' field for the 'Metrics-Name Rebuffering_Duration' in the QoE-Feedback header specifically represent, and what is its unit of measurement?
Option 1: The number of rebuffering events, measured in milliseconds.
Option 2: The total playback time saved due to buffering, measured in seconds.
Option 3: The average bitrate during rebuffering periods, measured in kilobits per second.
Option 4: The duration of rebuffering, which can be a fractional value, measured in seconds.
Explanation: This is correct because the 'Value' field for 'Rebuffering_Duration' specifically indicates how long the playback was stalled due to involuntary events at the client side. The unit of measurement for this metric is in seconds, and it can take on fractional values to accurately represent the duration of such events, which may occur multiple times during a measurement period.