enricobuehler
516efcc3a3
On a clean link the flat 20% FEC is pure waste: extra wire bytes AND extra
packets. On a packet-rate-bound uplink (the Steam Deck's WiFi tx caps ~22k pps
regardless of bitrate) those extra packets directly cost goodput — measured at
200 Mbps goodput, 20% FEC drove ~10% loss vs ~2.6% at 0% (it saturated the link).
Adaptive FEC closes the loop:
- Client measures the loss FEC is absorbing each ~750 ms window from session stats
(recovered shards / received, + a bump when a frame went unrecoverable) and sends
a periodic `LossReport { loss_ppm }` on the control stream (new message;
`window_loss_ppm` helper, shared + unit-tested). Connector (Apple/Linux/Windows)
and probe both report; suppressed during a speed test so its filler can't skew it.
- Host maps loss → recovery % (`adapt_fec`: ≈ loss×1.4 + 1pt, clamped 1..50) and
applies it live via `Session::set_fec_percent` (the wire is self-describing — each
packet carries its block's data/recovery counts, so the receiver needs no notice).
A clean link decays to ~1%; loss ramps it up and converges.
- `PUNKTFUNK_FEC_PCT`, when set, now PINS FEC static (disables adaptation) so
speed-test / measurement runs keep a fixed, known overhead. Unset ⇒ adaptive,
starting at 10%.
An older host ignores LossReport (unknown control message) and keeps static FEC;
an older client simply never reports and the host holds its start value. Builds +
clippy + fmt + tests green (adapt_fec / window_loss_ppm / loss_report unit tests).
Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>
punktfunk
A ground-up low-latency desktop streaming stack, built Linux-first, with a shared Rust protocol core and native clients per platform.
punktfunk is a placeholder codename. The bet: ship a Linux virtual-display streaming
host that speaks the existing Moonlight protocol (every Moonlight/Artemis client works
day one), then break the ~1 Gbps FEC wall with a GF(2¹⁶) Leopard-RS transport as a
negotiated extension. See docs/implementation-plan.md.
Status
| Milestone | State |
|---|---|
Core — punktfunk-core + C ABI |
✅ done & hardened (FEC, packetization, AES-GCM, session, adversarial-review fixes, punktfunk_core.h) |
| GameStream host → stock Moonlight | ✅ live end-to-end: pairing, RTSP, audio, per-client virtual output at native res, GPU zero-copy NVENC, gamepads |
Native protocol — punktfunk/1 |
✅ validated live: QUIC control + GF(2¹⁶) FEC/AES data plane, SPAKE2 PIN pairing, mid-stream mode renegotiation |
| Native clients — decode + present | 🟡 macOS first light: AnnexB→VideoToolbox HEVC on glass + input/pairing over punktfunk/1 (clients/apple); iOS + presenter next |
| Web console + management API | ✅ TanStack web console (web/) over the OpenAPI mgmt API: host status, paired devices, on-demand native pairing (arm → show PIN) |
The GameStream host works with a stock Moonlight client — validated live on NVIDIA
(RTX 5070 Ti & RTX 4090, driver 595): trust-on-first-use pairing that persists, an app
catalog, RTSP/ENet/audio, and video at the client's exact resolution and refresh via a
per-session virtual output (KWin, gamescope, Mutter, Sway backends), encoded with GPU
zero-copy (dmabuf → CUDA/Vulkan → NVENC) at up to 5120×1440@240. The native
punktfunk/1 protocol adds a QUIC control plane and a GF(2¹⁶) Leopard-FEC + AES-GCM data
plane (p50 ~0.8 ms capture→reassembled at 720p120). Its trust model is SPAKE2 PIN pairing by
default — a new host requires the PIN ceremony; trust-on-first-use is an explicit host opt-in
(punktfunk1-host --allow-tofu / serve --open, advertised as pair=optional) for fully trusted LANs. Both
run from one process (serve --native), managed through a REST API + web console. Builds
against FFmpeg 7 or 8; deployed live on Bazzite. Full status: CLAUDE.md;
roadmap, setup guides & progress: the docs site (docs-site/ — Fumadocs;
bun run dev), with the canonical roadmap and
status there. Design notes stay in docs/.
Install (host)
The package registries are the real distribution channel — pick your distro and run one command. Per-distro setup (add the repo, first-run, web console) lives in the linked READMEs.
| Distro | One-command happy path | Details |
|---|---|---|
| Ubuntu / Debian (apt) | sudo apt install punktfunk-host (after adding the repo) |
packaging/debian/README.md |
| Fedora / Bazzite (rpm-ostree) | rpm-ostree install punktfunk punktfunk-web (after adding the repo; or the bootc image) |
packaging/rpm/README.md |
| Arch / Steam Deck (PKGBUILD / sysext) | makepkg -si (Arch) · sysext .raw (SteamOS/Deck) |
packaging/arch/README.md |
punktfunk-host is the streaming host; punktfunk-web is the browser console (pairing + status);
punktfunk-client is the GTK4 desktop client (also shipped via apt/RPM/Arch/Flatpak). After install,
run punktfunk-host serve --native inside your desktop session, then pair from the web console.
Building from source (below) is a fallback.
Layout
crates/
punktfunk-core/ protocol · FEC · pacing · crypto · quic — the C ABI (lib + cdylib + staticlib)
punktfunk-host/ Linux host: vdisplay · capture · encode · inject · gamestream · punktfunk1 · mgmt · native_pairing
clients/
probe/ punktfunk/1 reference/probe client (headless test + latency measurement)
linux/ windows/ native desktop clients (Rust: GTK4 / WinUI 3, link punktfunk-core directly)
apple/ android/ Swift (macOS+iOS) · Kotlin app + native/ Rust JNI core
decky/ Steam Deck Decky plugin
web/ TanStack web console (host status · paired devices · pairing) over the mgmt API
packaging/ Fedora/Bazzite RPM · bootc image · COPR (see packaging/bazzite/README.md)
include/punktfunk_core.h cbindgen-generated C header (checked in)
tools/{latency-probe,loss-harness}/ measurement (plan §10)
docs/{implementation-plan,roadmap,windows-host,dualsense-haptics}.md
Build & test (from source)
For development, or as an install fallback where no package is available:
cargo build --workspace # green on Linux and macOS
cargo test --workspace # unit + loopback + proptest + C ABI harness
cargo clippy --workspace --all-targets
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
The C header regenerates from crates/punktfunk-core/src/abi.rs on every build (cbindgen via
build.rs) into include/punktfunk_core.h.
Design invariants
- One core, linked everywhere. Protocol/FEC/crypto/pacing live in
punktfunk-coreexactly once, exposed over a stable, versioned C ABI (punktfunk_abi_version(),PunktfunkConfigcarries its ownstruct_size). - No async on the hot path. The per-frame pipeline uses native threads only;
tokio/quinnare gated behind the off-by-defaultquicfeature (control plane only). - FEC is the wall-breaker. GF(2⁸) (≤255 shards/block) for Moonlight compat; GF(2¹⁶) (≤65535 shards/block, SIMD, O(n log n)) to push past ~1 Gbps.
License
MIT OR Apache-2.0.