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
M1 — punktfunk-core + C ABI	✅ done & tested (FEC, packetization, crypto, session, punktfunk_core.h)
M0 — pipeline spike (wlroots→PipeWire→NVENC→file→punktfunk-core)	✅ done & verified on NVIDIA (RTX 5070 Ti / driver 595)
M2 — P1 host → stock Moonlight	🟡 capture+encode landed in M0; pairing/RTSP/vdisplay pending
M3 — measurement harness	🟡 tools/loss-harness runs; latency-probe scaffolded
M4 — P2 transport + Rust client	🟡 GF(2¹⁶) core done; punktfunk-client-rs scaffolded
M5 — Apple client	🟡 macOS first light: HEVC on glass + input over punktfunk/1 (clients/apple)

punktfunk-core is complete and verified: it builds and its full test suite (FEC recovery, loopback round-trip under loss, property tests, and a C ABI harness) passes on macOS/aarch64. M0 is done: punktfunk-host captures a headless wlroots output via the ScreenCast portal + PipeWire, encodes it with NVENC, writes a playable H.265 file, and round-trips every access unit through a punktfunk_core host→client session (see docs/linux-setup.md). M2 is in flight: the GameStream control plane (gamestream/) and the management REST API (mgmt.rs, OpenAPI spec in docs/api/) are implemented; the remaining Linux host backends (KWin/Mutter virtual displays, libei input) are #[cfg(target_os = "linux")] seams — defined and compiling, implementations pending.

Layout

crates/
  punktfunk-core/        protocol · FEC · pacing · crypto — the C ABI (lib + cdylib + staticlib)
  punktfunk-host/        Linux host: vdisplay · capture · encode · inject · gamestream · mgmt
  punktfunk-client-rs/   reference client (M4): VAAPI decode + wgpu present
clients/{apple,android}/   native client scaffolds (import punktfunk_core.h)
include/punktfunk_core.h       cbindgen-generated C header (checked in)
tools/{latency-probe,loss-harness}/   measurement (plan §10)
docs/implementation-plan.md

Build & test

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-core exactly once, exposed over a stable, versioned C ABI (punktfunk_abi_version(), PunktfunkConfig carries its own struct_size).
• No async on the hot path. The per-frame pipeline uses native threads only; tokio/quinn are gated behind the off-by-default quic feature (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.