Modules

The repository is a Cargo workspace for the Rust side and a pnpm workspace for the web side.

crates/   core · proto · net · capture · gpu · codec · render · input · audio · secure
apps/     host-agent · client · client-ui · desktop
web/      ui · viewer · e2e
tests/    e2e (host and client through an impaired network)
fuzz/     cargo-fuzz targets
dev/      Distrobox containers for Bazzite, GPU runner setup
packaging/ AppImage, install scripts, systemd unit

How they depend on each other

flowchart BT
    core["core"]
    proto["proto"]
    net["net"] --> core & proto
    capture["capture"] --> core
    gpu["gpu"] --> capture
    codec["codec"] --> capture & gpu & core & proto
    render["render"] --> codec & gpu
    input["input"] --> proto
    audio["audio"] --> core
    secure["secure"]
    host["apps/host-agent"] --> net & codec & input & audio & secure
    client["apps/client"] --> net & render & input & audio & secure
    desktop["apps/desktop"] --> client & host & secure

Crates

Crate	What it does
core	The slot with capacity 1 (latest frame wins, buffer recycling), the monotonic clock, latency statistics per stage, hot threads (real-time where allowed, else raised priority; precise sleeps), system info for discovery
proto	The UDP packet format v1: video shards with stage timestamps, feedback, clock ping/pong, hello/ack with the codec set, bye, pointer, input, audio, handshake, sealed packets, pairing, discovery, monitors. The parser never panics and never allocates (protocol)
net	Reed-Solomon FEC (reed-solomon-simd), one group per frame up to 512 shards, balanced and interleaved beyond; recovery shards per group sized binomially from the measured loss (group failure ≤ 10⁻⁵); reassembly with keyframe requests and hard size limits; the pacer; NTP-style clock sync; UDP sockets with 4 MiB buffers; bitrate adaptation; loss simulation
capture	The FrameSource trait, the test pattern (NV12, a moving bar, a circling pointer), the DMA-BUF description, KMS capture at vblank with the cursor plane and monitor switching (feature kms, pure Rust)
gpu	The Vulkan device and DMA-BUF import without a copy (for the renderer and the encoder); RGB DMA-BUF → NV12 by a compute shader, exported to CUDA for NVENC; test images exported as DMA-BUFs
codec	The Encoder/Decoder traits, the synthetic codec, VAAPI encode and decode of H.264, HEVC and AV1 through FFmpeg (feature vaapi, DMA-BUF import, RGB → NV12 and scaling by scale_vaapi), NVENC/NVDEC (feature nvidia, screen through Vulkan → CUDA, decoded pictures exported from CUDA to Vulkan), hardware capability queries
render	The Presenter trait, overlay formatting, the Vulkan renderer (NV12 from the CPU or a DMA-BUF → RGB, letterboxing, the pointer) and the window presenter (feature window)
shader	WGSL to SPIR-V for the build scripts of gpu and render: the shaders compile when the crate builds, the programs carry SPIR-V and no shader compiler
input	Input events, the duplicate filter, uinput devices on the host (mouse, keyboard, Xbox 360 pads with rumble), DualSense pads through uhid (gyro, touchpad), gamepads on the client (SDL3, else evdev)
clipboard	The clipboard: a Wayland desktop's through data control (ext-data-control-v1, else wlroots' zwlr-data-control), and a text across the link in acknowledged pieces
audio	Capture and playback through PipeWire's PulseAudio interface, Opus (48 kHz stereo, 5 ms frames, low delay), the client's jitter buffer, a test tone; libopus and libpulse are loaded at runtime
secure	Device keys (X25519), the list of paired devices, pairing with SPAKE2, Noise IK sessions, the replay window (security)

Apps

App	What it does
apps/host-agent	fernsicht-host-agent: the control loop (lib.rs, its steps in dispatch.rs) and its answers (requests.rs), starting a session (start.rs) and its threads (capture.rs, encode.rs, send.rs, audio.rs), the way to the client (link.rs: our UDP protocol or a browser's WebRTC), keys and pairing (security.rs), the control socket (control.rs), the web viewer and WebRTC (web/), the monitor arrangement for input mapping (layout.rs), GPU clocks during sessions (power.rs)
apps/client	fernsicht-client: the network thread (network.rs), decoding and presenting (present.rs), sound (audio.rs), hosts and pairing (hosts.rs), discovery (discover.rs), the pointer (cursor.rs), the window with its keys and system-shortcut lock (window.rs, shortcuts.rs)
web/client-ui	The app's interface (React 19, TanStack Router and Query, Tailwind, shadcn-style components); demo data in a browser, the real backend in the app
apps/desktop	The Tauri app around client-ui: devices, pairing, sessions through the client (backend.rs), sharing this computer from the AppImage (share.rs). Its own Cargo workspace (it needs WebKitGTK)

Web

Package	What it does
web/ui	Shared components: the session view with toolbar and menus, the latency overlay, primitives, demo data
web/viewer	The web viewer: connect page, WebRTC session, pointer, mouse, keyboard, gamepads, touch gestures (lib/touch.ts), on-screen keyboard (lib/textkeys.ts), fullscreen with Keyboard Lock
web/e2e	Playwright tests (desktop, phone, phone in landscape, accessibility with axe) and the screenshot script

Build features

Feature	Crates
vaapi	codec, host-agent, client, render (GPU tests), e2e	hardware video on AMD/Intel; needs FFmpeg and libva headers
nvidia	codec, host-agent, client, render (GPU tests), e2e	NVENC/NVDEC; CUDA is loaded at runtime, builds without the driver
kms	capture, host-agent	screen capture over KMS
window	render, client	the Vulkan window (winit)
vulkan	render	the renderer without a window (tests)

Without features the whole pipeline runs with the test pattern and the synthetic codec, so CI and machines without a GPU test transport, FEC, pacing and latency for real.