Question: In an MBMS (Multimedia Broadcast/Multicast Service) receiver, when utilizing Forward Error Correction (FEC), what action is taken if at least one source packet is missing after receiving FEC source and repair packets?
Option 1: The receiver immediately discards the entire source block due to the missing packet.
Option 2: The receiver waits for a predefined timeout before attempting FEC decoding with the available packets.
Option 3: The receiver checks if there are enough symbols from the source and repair packets to perform FEC decoding, but only if non-empty repair packets were received.
Option 4: The receiver determines if the constructed encoding block contains sufficient symbols for FEC decoding and performs it if possible, otherwise considering procedures to conceal missing media data.
Explanation: This option accurately reflects the step in the FEC receiving process where, upon identifying a missing source packet, the receiver assesses the feasibility of FEC decoding based on the available source and repair packets. If sufficient symbols are present, it proceeds with decoding; otherwise, it may initiate procedures to mitigate the impact of the missing data.