enricobuehler
ffc0b07b46
Phase 1 of codec negotiation, and the Linux software H.264 encode path it unblocks. **Codec negotiation (core `quic`):** - `Hello.video_codecs` (bitfield: CODEC_H264/HEVC/AV1) — the client advertises what it can decode; appended as a trailing byte (older client → 0 = HEVC-only, back-compat). - `Welcome.codec` — the single codec the host resolved and will emit; trailing byte (older host → HEVC). - `resolve_codec(client, host_capable)` picks the shared codec (precedence HEVC > AV1 > H.264) or `None` → the host refuses honestly rather than sending an undecodable stream. - Roundtrip + back-compat tests; cbindgen exports the CODEC_* constants. **Software encoder (host):** - The openh264 `OpenH264Encoder` (was Windows-only) is now built on Linux too — it's platform-agnostic (consumes CPU RGB `CapturedFrame`s, statically-bundled openh264). `openh264` moved to the shared linux+windows Cargo target. - `PUNKTFUNK_ENCODER=software` selects it: `open_video` gains a `software` branch (H.264 only), and `session_plan::resolve_encoder` / `capture::gpu_encode` resolve `EncoderBackend::Software` → `output_format().gpu = false`, so the portal capturer delivers CPU RGB. Explicit-only (auto never picks it — a box with a dead driver still has /dev/nvidiactl and would mis-resolve NVENC). **Host codec resolution (`punktfunk1`):** - The native path no longer hardcodes HEVC: it resolves the codec from the client's advertised set ∩ the host's capability (`Codec::host_wire_caps`: software→H.264, else HEVC), threads it through `SessionPlan.codec`, and opens the encoder + validates reconfigures at that codec. A software host + HEVC-only client is refused with a clear error. - 4:4:4 is gated on HEVC (it's HEVC-only). **Probe:** advertises H264|HEVC|AV1 and logs the resolved codec. Validated on the GPU-less dev box: negotiation is live end-to-end (probe advertises 0x07 → host resolves H.264 → Welcome reports it → plan = Software/H264), and the openh264 unit test (CPU RGB → AnnexB IDR) now runs on Linux. Full capture→encode still needs a GPU on this box — every compositor screencast path (KWin GL, gamescope VK_EXT_physical_device_drm, wlroots EGL) requires one; software render (llvmpipe/pixman) can't be captured — so this box exercises negotiation + encoder, not live capture. The software path unblocks GPU-less-*encode* boxes that still have a display GPU. Phase 2 (clients advertising real codecs + decoding per Welcome.codec) is a follow-up. Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>
punktfunk-core
The shared protocol core — the one place where punktfunk's transport, forward error correction, and crypto live. It's linked into the host and every native client, so there's exactly one implementation of the wire format everywhere.
Written in Rust with no async on the per-frame path (native threads only). It exposes both a normal Rust API and a stable, versioned C ABI, so the Swift and Kotlin clients — and any C embedder — link the same code as the Rust ones.
What's in here
- Transport & session (
session.rs,transport/,packet.rs) — thepunktfunk/1data plane over raw UDP: packetization, reassembly (with attacker-bounded limits), pacing, and socket tuning. - FEC (
fec/) — the wall-breaker. Two codes:- GF(2⁸) classic Reed–Solomon with the Cauchy generator matrix — byte-identical to the
nanorslibrary Moonlight uses, so our parity is decodable by a stock Moonlight client. - GF(2¹⁶) Leopard-RS (SIMD, O(n log n)) — up to 65535 shards/block, which removes the ~1 Gbps
FEC ceiling.
punktfunk/1negotiates this one.
- GF(2⁸) classic Reed–Solomon with the Cauchy generator matrix — byte-identical to the
- Crypto (
crypto.rs) — AES-128-GCM session encryption with per-direction nonce salts and sequence-as-AAD; SPAKE2 PIN pairing lives behind thequicfeature. - QUIC control plane (
quic.rs,client.rs, featurequic) — the Hello/Welcome/Start handshake, cert pinning/TOFU, reverse audio, and the embeddableNativeClientconnector. This is the only placetokio/quinnare allowed; the feature is off by default so the core stays runtime-free. - C ABI (
abi.rs) — the versioned surface (punktfunk_abi_version(),PunktfunkConfigcarrying its ownstruct_size) that generatesinclude/punktfunk_core.hvia cbindgen at build time.
Build outputs
The crate builds three ways at once (crate-type = ["lib", "cdylib", "staticlib"]):
| Output | Used by |
|---|---|
lib (rlib) |
the host, probe, and tools link it as a normal Rust crate |
cdylib (.so/.dylib) |
the Swift / Kotlin clients via the C ABI |
staticlib (.a) |
the C test harness and static embedding |
Test
cargo test -p punktfunk-core # unit + proptest + loopback
cargo run -p loss-harness # FEC loss-resilience sweep (no network needed)
bash crates/punktfunk-core/tests/c/run.sh # standalone C-ABI link + round-trip proof
Design invariants (do not regress)
- One core, linked everywhere — protocol/FEC/crypto live only here, behind the stable C ABI.
- No async on the hot path — the per-frame pipeline is native threads only;
quic(tokio/quinn) is control-plane only, feature-gated, off by default. - Security hardening stays intact — the reassembler bounds attacker-controlled fields before
allocating; AES-GCM keeps per-direction nonce salts + seq-as-AAD; the ABI checks
struct_size. Regression tests exist — keep them green.
Related
punktfunk-host— the streaming host built on this core- Clients — the apps that link this core over the C ABI (or directly, in Rust)
design/implementation-plan.md— why GF(2¹⁶) FEC, the latency budget, and the architecture thesis