FEC/Reed-Solomon packetization ran inline on the encode loop (~3 ms/frame at 4K),
serializing behind encode and capping the GameStream frame rate below what the
encoder alone can sustain. Split it into a 3-stage pipeline, each stage on its own
thread joined by a depth-2 bounded queue:
encode loop → [raw AUs] → packetizer (FEC/RS) → [wire batch] → paced sender
- `spawn_packetizer`: turns each `RawFrame`'s access units into wire datagrams via
the stateful VideoPacketizer, off the encode loop. Above-normal priority (on the
per-frame critical path). Tallies goodput (bytes to the wire) for the stats window.
- Backpressure chains up: a slow sender blocks the packetizer, which fills the
encode→packetizer queue, which makes the encode loop drop the NEWEST frame — encode
itself never waits.
- A dropped frame now consumes no client-visible frameIndex (packetization is
downstream), so the host re-anchors the reference chain: a drop arms a keyframe on
the next iteration (`recover_after_drop`), routed through the same coalesce gate as
client IDR requests so a burst of drops (congestion) can't become an IDR storm.
- Perf/stats relabeled: `pkt` = AU drain, `send` = enqueue to the pipeline (both
should be near-zero now; nonzero = encode being stalled by pipeline backpressure).
Goodput read from the packetizer's atomic at the 1 s stats boundary.
Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>
enricobuehler
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