Question: When utilizing the PSS timeshift feature with a live stream, how does a PSS client determine the current valid boundaries of the timeshift buffer?
Option 1: The PSS client receives explicit boundary notifications from the PSS server via dedicated headers in server-to-client messages.
Option 2: The PSS client calculates the boundaries based on the initial SP SETUP response alone, without needing further updates.
Option 3: The PSS client uses the Accept-Ranges header field to infer the buffer boundaries for both NPT and UTC time ranges.
Option 4: The boundaries are predefined in the PSS protocol and do not vary, thus requiring no calculation or server indication.
Explanation: According to specifications, for ongoing validity in a live stream, the PSS client relies on dedicated headers in subsequent server-to-client messages to accurately calculate current valid boundaries, ensuring up-to-date information for effective time-shifting operations.