Packet loss concealment fills the hole left by a lost or too-late audio frame with a plausible synthetic reconstruction, so the listener hears a brief smooth stretch instead of a click, a gap, or silence. The simplest schemes repeat and fade the previous frame; codec-integrated PLC (as in Opus) extrapolates from the signal's recent pitch and spectrum for a far more natural patch; and the newest neural approaches, like Opus's deep PLC, actually generate missing speech. Concealment works well for isolated losses but degrades as loss grows and bursts, which is why it works hand in hand with FEC and the jitter buffer rather than alone.
