enricobuehler
20f4d23f2d
PW6 shipped behind a knob because one pre-registered risk was unmeasured: a streamed frame whose FINAL block is lost has no totals, so where the whole-AU path hands the consumer a usable blurred partial, a streamed frame may deliver nothing. PyroWave clients opt into partial delivery unconditionally, so this would have been a live behaviour change for every one of them. Measured now, three ways, instead of reasoned about. `tools/loss-harness` gains a partial-delivery leg: FEC pinned OFF, chunk-aligned AUs, deliver_partial ON, realistic 1408/200 geometry, and AU sizes swept across the whole 1..=200-shard range of FINAL-block sizes — because the final block's size is what bounds the exposure. Loss is injected per packet from a seeded xorshift rather than through `loopback_drop_period`, whose deterministic 1-in-N would systematically always-or-never hit the final block, which is the entire question. `tc netem` on `lo` was deliberately not used: the in-process model gives exact per-frame attribution, needs no sudo, cannot disturb a box running a live desktop session, and — decisively — can drop precisely the final block. Leg 1, deterministic (drop exactly the last block, 200 frames): whole-AU delivers 200 partials and 0 losses; streamed delivers 0 partials and 200 total losses. The trap is real and, when it fires, total. Leg 2, random loss, 20 000 frames per cell, same seed and sizes for both shapes. At 2 % the two are indistinguishable — 20000/20000 partials and ZERO vanished frames on both, matching the analytic bound E[loss^k] over final-block sizes k (~1e-4). The gap only appears at 30 % (99.94 % vs 100 % rescue) and 50 % (99.79 %). `complete` is 0 throughout by construction: with FEC off and ~500 packets per AU, essentially every frame is damaged — which is the regime the partial path exists for. The spike gains `--wire-chunk` and a streamed loopback path, so the wire shape is reachable end to end outside a real client: `poll_chunk` drains the AU, `begin_streamed_frame_at`/`seal_streamed_chunk`/`seal_streamed_finish` seal each piece, and the client byte-compares the reassembly. On 120 real PyroWave AUs the streamed legs (56.5 and 2.0 chunks/AU) and the whole-AU control emit a byte-identical 47 373 568-byte stream with 0 mismatches — the cut changes the wire shape and not one byte of content, and with the knob unset it does not engage at all. A new `#[ignore]`d GPU test closes the picture question on real hardware with a BUSY card (gradients + checker + noise), never a flat fill: chunks are whole windows, exactly one `first` and one `last`, the AU decodes through the client's own window walk, and luma PSNR lands at 40.2 dB. Unset the knob and the test refuses to run, which is the default-off claim verified rather than asserted. Verdict recorded in the plan: KEEP IT OFF. The 2 % tie is an argument about typical loss, but the failure is not graceful when it fires and the measured win is host send-side pipelining that nobody has yet put a millisecond number on.
loss-harness
A FEC loss-resilience sweep for punktfunk-core. It
drives access units through the in-process loopback at increasing packet-loss rates — for both FEC
schemes (GF(2⁸) and GF(2¹⁶)) — and reports how many frames survive.
It's a pure-software stand-in for tc netem: no network, no root, runs anywhere punktfunk-core
builds. Use it to sanity-check the FEC before reaching for the real punktfunk/1 harness (which adds
tc netem jitter/reorder on the UDP path).
cargo run -p loss-harness # from the repo root
Part of the measurement tooling (punktfunk-planning: implementation-plan.md §10), alongside
latency-probe.