Question: In a Transparent end-to-end Packet-switched Streaming Service (PSS), what is the primary condition under which servers MUST include video buffering header fields (e.g., `x-predecbufsize`, `3gpp-videopostdecbufsize`) in an SP PLAY response for H.264 or H.265 streams?
Option 1: When the client explicitly requests these headers in the SP PLAY request.
Option 2: Whenever the values are available in the 3GP file used for the streaming session.
Option 3: Only if the server has previously indicated support for these headers in its capabilities announcement.
Option 4: If the network conditions suggest a need for additional buffering to ensure smooth playback.
Explanation: According to the specifications, for H.264 or H.265 (HEVC) streams, servers are required to include these video buffering header fields in an SP PLAY response if the values are available in the 3GP file being used for the streaming session. This ensures that the client can appropriately manage its buffers based on the actual stream requirements, enhancing playback quality and stability.