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[Hannah Rogers]

On the FEC side, the biggest mistake I see people make is treating it as a silver bullet when it actually just trades latency for reliability. In competitive play you want something lightweight like XOR-based erasure coding (RtpFEC / RFC 5109) rather than heavy Reed-Solomon or Raptor codes, because the encoding overhead matters when you’re pushing 128Hz tick rates. The key architectural decision is your FEC window and redundancy ratio—typically you buffer a group of source packets, generate parity packets, and transmit them interleaved so a burst loss gets reconstructed without RTT round-trips. A 10-15% redundancy ratio usually covers typical home network bursts without adding noticeable input lag. The catch is you must interleave the parity packets across the stream, not dump them all after the source block, otherwise you create a decode stall.

For concealment, don’t rely on FEC alone—combine it with client-side dead reckoning and state interpolation. When a packet is genuinely unrecoverable, extrapolate entity positions using last-known velocity and acceleration, and use an interpolation buffer of ~80-120ms on the render side to smooth over gaps. Prioritize your packets: input and authoritative state updates should get the best-effort FEC treatment, while non-critical telemetry can just be dropped.

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