Nebulus

Nebulus is a pure-Rust OpenIPC FPV ground station built with egui. It opens one or more supported Realtek USB WiFi adapters, reconstructs WFB video, decodes H.264 or H.265 with the operating system's video API, and always presents the newest decoded frame. Native builds can instead receive an already-recovered RTP stream from UDP.

It shares the same Rust application, protocol pipeline, settings, metrics, and UI across desktop, Android, and the browser. USB access, native UDP sockets, and video-surface presentation are target-specific.

Nebulus is the primary ground station distributed by this repository. Tagged releases include Linux x64/arm64 executables, macOS Apple Silicon/Intel disk images, Windows x64/arm64 installers, and one universal Android APK. The hosted browser build is available at nebulus.openipc-rs.neels.dev. The source package is published at crates.io/crates/nebulus.

Run On Desktop

cargo run -p nebulus --bin nebulus --release

Or install the published package from crates.io:

cargo install nebulus
nebulus

On Linux, install the VA-API build dependencies listed in the openipc-video README. The app uses nusb directly; it does not need the Tauri backend or the devourer library.

macOS and Windows builds add a Nebulus system-tray icon. Its menu can show or hide the window, start or stop RX, enable VPN for the next receiver start, open the full VPN panel, and quit. macOS displays it in the menu bar; Windows uses the notification area and may place it under the overflow arrow.

After monitor initialization succeeds, Settings shows a connected-receiver summary with the actual USB VID:PID, probed Realtek family, RF path layout, cut revision, USB speed, selected bulk endpoints, initialization result, firmware download status, and active RF/Link ID configuration. The summary is cleared when the receiver disconnects.

Receive RTP From UDP

In Settings → Receiver, select UDP RTP and choose a local bind address and port. The default is 0.0.0.0:5600. Each UDP datagram must contain one complete RTP packet. H.264 and H.265 payloads use the same reorder, depacketizer, decoder, metrics, OSD, and MP4 recording path as USB reception; Opus carried on the configured mixed-audio RTP payload type uses the normal audio route.

UDP input is available on desktop and Android. It receives RTP after the radio transport, so it intentionally bypasses Realtek initialization, 802.11/WFB filtering, decryption, and FEC. Adaptive-link uplink, VPN/TUN, diversity, channel scanning, and routes on non-video radio ports therefore require the USB source. Browsers cannot bind arbitrary UDP sockets and continue to use WebUSB.

The GUI tab contains presentation-only settings. It offers Catppuccin Latte, Frappé, Macchiato, and Mocha themes, a persistent 75–150% interface scale, an editable video OSD, control-panel visibility, and a one-click GUI reset. Each indicator can be hidden or dragged to normalized video coordinates, so one layout remains usable at different window sizes. Its icon, label, value, status coloring, background, size, and opacity can be configured independently. Supported indicators can optionally include a mini graph with a configurable history window and dimensions; RSSI can optionally include signal bars. Graphs and bars are off by default. Changes apply immediately on desktop, Android, and the browser. OSD layouts have their own named profiles. Duplicate starts a new layout from the current one, edits auto-save to the selected layout, and the same OSD profile can be reused with any receiver profile.

Settings includes named receiver profiles. A profile snapshots the primary and diversity adapters, radio, Link ID, keys, routes, telemetry policy, audio, VPN, decoder choices, and a reference to a reusable OSD profile; GUI appearance stays global. Use Save current after changing a profile. Run preflight checks the selected adapters, keys, radio values, routes, decoder state, VPN, and adaptive-link configuration before RX starts.

Settings → Preset packs installs and exports versioned community JSON packs. Packs can contain OSD, theme, route, telemetry, and performance components, but their schema cannot represent keys, USB identities, radio configuration, local paths, or concrete UDP destinations. Installation shows a component preview; versions are pinned and never update a receiver profile automatically. Packs can be opened from a local file or HTTPS URL, and static registry indexes can be browsed directly. GitHub blob links are accepted and checksum-pinned registry entries are verified before preview. See the preset documentation and bundled schema under apps/nebulus/presets.

Scan channels opens an idle-only survey. The Rust driver initializes the adapter once, retunes it across the selected channels, and reports traffic, WFB frames, RSSI, and observed bitrate. The adapter is shut down after the survey. A scan and normal RX never run at the same time.

Run In A Browser

Install Trunk, then serve the app from a secure context or localhost:

rustup target add wasm32-unknown-unknown
cargo install trunk --locked
cd apps/nebulus
trunk serve --release --open

Use Add adapter to authorize each WebUSB radio, select a primary and any diversity receivers, then press Start RX. With no authorized selection, Start RX opens the browser's WebUSB device picker for one adapter. Browser builds use the same Rust Realtek initialization and WFB/FEC/RTP pipeline as native builds. WebCodecs performs H.264/H.265 decoding and WebGL uploads the retained browser VideoFrame directly, without copying decoded pixels through WASM. Recovered RTP batches are transferred to a Rust/WASM RTP worker. Complete access units then cross a direct MessageChannel to a separate WebCodecs worker, so a slow decoder cannot stall RTP ingest. Both handoff queues are bounded and discard dependent frames until a keyframe after overload. Only the newest transferable VideoFrame crosses back for presentation. The Metrics tab reports receive, decoder-output, and presentation rates separately.

The worker is the feature-gated nebulus-decode-worker binary inside this same Cargo package, not another app or crate. Trunk enables it automatically; normal native builds and cargo install nebulus only build the main binary.

Create deployable files with:

cd apps/nebulus
trunk build --release

The output is written to apps/nebulus/dist/ and is intentionally ignored by Git.

Build For Android

Nebulus uses NativeActivity; it does not need a Kotlin application shell. After installing the Android SDK, NDK, and cargo-apk2, run from the repository root:

./scripts/android-nebulus-dev.sh

This starts or reuses an emulator, waits for boot completion, selects the Rust target matching the AVD ABI, builds and installs Nebulus, and follows Logcat. Use --help for AVD, release, cold-boot, and no-Logcat options.

To only build the library target:

rustup target add aarch64-linux-android
cargo install cargo-apk2 --locked
cargo apk2 build -p nebulus --lib --target aarch64-linux-android

The manifest metadata requests android.hardware.usb.host. At runtime the Rust JNI bridge uses Android UsbManager to request permission and open the adapter, duplicates its file descriptor, and hands that descriptor to nusb::Device::from_fd. All later USB control and bulk transfers still run through nusb and openipc-rtl88xx.

Rust log output is mirrored to standard Android application output and the in-app Logs tab.

Android settings use an app-private eframe RON file under the activity's internal data directory. Receiver profiles, OSD profiles, the selected key, routes, and GUI preferences therefore survive process death and device restart without requiring storage permission. Support bundles use Android's document picker, so the user chooses where the ZIP is written.

That command creates an installable APK with the normal Android debug key. Add [package.metadata.android.signing.release] keystore settings outside source control before adding --release for distribution builds.

Data Path

USB: bulk IN from each selected adapter
  -> openipc-rtl88xx RX descriptor parsing and optional diversity
  -> openipc-core 802.11 filtering, WFB crypto, and FEC

UDP: one already-recovered RTP packet per datagram

Either source -> openipc-core route fanout
     -> video RTP depacketizing -> openipc-video H.264/H.265 decoder
     -> telemetry route -> MAVLink/MSP/CRSF decoder -> video OSD
     -> audio route -> Opus decoder -> audio device
  -> newest decoded video frame -> platform GPU presenter

Desktop and Android keep one bulk-IN capture worker per adapter and one shared protocol/decode worker. The egui event loop only updates state and uploads the newest presentable frame. The browser keeps WebUSB and WFB recovery on the app executor, then transfers recovered RTP batches to an RTP worker. A second worker owns WebCodecs, and a direct MessageChannel carries complete access units between them; application-written JavaScript callbacks are not part of the receive path.

Enabled payload routes share the receiver's WFB runtimes whenever they use the same channel and key slot. The default mixed-audio route therefore taps Opus RTP payload type 98 from the video channel without decrypting or FEC-decoding the packet twice. Opus decoding uses the pure-Rust ropus implementation. CPAL feeds native and Android audio devices; browser builds schedule PCM with Web Audio. Output volume can be adjusted while the receiver is running and is applied to every active audio route without restarting RX.

The default telemetry route reads raw payloads from OpenIPC radio port 0x10. Its Telemetry to OSD action can auto-detect checksum-valid MAVLink, MSP, or CRSF frames, or be pinned to one format. The radio port remains editable for custom VTX layouts. Decoding belongs to Nebulus rather than openipc-core: the shared core still returns protocol-neutral payload bytes, so applications using the libraries can choose different telemetry parsers. Nebulus normalizes common flight values into one OSD state and hides stale telemetry indicators after three seconds by default.

MAVLink support uses the mavlink crate's generated Common dialect. The crate provides current message layouts, enums, CRC extras, and MAVLink 2 payload handling; Nebulus only keeps the bounded incremental framer needed for payloads that may be split across WFB packets and maps selected messages into its protocol-neutral OSD state.

The Telemetry tab shows the detected protocol, source identity, frame age, and accepted/rejected/filtered counters. It also controls the stale-data timeout, MAVLink system/component filters and signing policy, MSP version and direction filters, and CRSF device-address filtering. MAVLink signing accepts a 32-byte binary key or a file containing 64 hexadecimal digits. Verify signed authenticates signed packets while allowing unsigned traffic; Require signed also rejects MAVLink 1, unsigned MAVLink 2, invalid signatures, stale signing timestamps, and replays. The MAVLink key is separate from the WFB gs.key.

Pending frame events use a one-frame replacement slot. USB buffers are re-armed before decode or route work, encoded frames move into the decoder without a playback copy, and diagnostic batches are emitted at 20 Hz. Rendering stalls therefore drop old pictures instead of growing a delayed playback queue. Codec configuration and keyframe detection share one allocation-free Annex-B scan. The macOS path also converts the normal uniquely owned Annex-B buffer to VideoToolbox length prefixes in place.

Adaptive-link/VPN transmit and Jaguar3 maintenance do not run on the native RX thread. Browser adaptive feedback uses a retained bounded WebUSB OUT queue, and browser Jaguar3 maintenance runs as a separate local async task. Auxiliary TX is dropped under sustained overload rather than delaying incoming video.

The default Metrics view focuses on six operational signals: best-path link score, unrecoverable post-FEC loss, FEC recovery percentage, encoded video bitrate, delivered video FPS, and local receive-through-decode processing latency. Loss and recovery use deltas from each sampling window rather than lifetime counters, so old link damage does not distort the current graph.

On macOS, Linux, and Windows, Nebulus keeps decoder-native frames in a latest-only queue, uploads NV12 Y and UV planes into persistent wgpu textures, and converts to RGB in the GPU shader. This avoids CPU color conversion and reduces a 1080p upload from about 8.3 MB of RGBA to 3.1 MB of NV12. Linux maps the newest VA-API DMA surface and Windows reads the newest D3D11 surface only after stale frames have been discarded. Direct IOSurface, DMA-BUF, and D3D11 texture import remain optional future zero-copy optimizations.

Android sends MediaCodec output directly to a SurfaceTexture backed by an external OpenGL ES texture. The egui Glow paint callback latches the newest decoder image, so decoded planes are never mapped or copied through Rust. The browser keeps WebCodecs VideoFrame objects inside Rust/WASM and uploads them directly into a persistent WebGL texture; decoded pixel arrays never cross the WASM boundary.

Desktop builds request non-vsynced wgpu presentation with one frame of surface latency. Android requests its fastest same-resolution display mode, disables egui vsync, raises the receive thread priority, and configures MediaCodec for low latency. Physical Android devices retain a three-frame decoder bound; the SDK emulator alone gets a larger allowance for Goldfish's delayed software codec. Native audio requests a 256-frame output buffer and keeps no more than 40 ms of queued PCM.

Included Controls

• Supported-adapter discovery and refresh
• Native direct H.264/H.265 RTP reception from a configurable UDP listener
• Packet-level receive diversity across multiple adapters of the same or mixed supported Realtek families
• RF channel, width, offset, link ID, epoch, and USB transfer size
• Built-in default gs.key, native file picker, and key-file drop
• Optional RTP reorder buffer
• Adaptive-link quality tracking, uplink feedback, and TX power override
• H.264/H.265 playback, video-only fullscreen, and a configurable video OSD
• Drag-and-drop OSD editor for link, battery, GPS, flight-mode, motion, attitude, and status indicators
• Named receiver profiles shared by desktop, Android, and browser builds
• Preflight validation and native automatic reconnect with bounded backoff
• Idle channel survey with per-channel WFB traffic and RSSI
• Keyframe-aligned H.264/H.265 MP4 recording without re-encoding
• Live bitrate, receive/decode/render FPS, RSSI, loss, and latency plots
• Pipeline-health, RTP, per-stage latency, and environment diagnostics
• Level-controlled library logging with target/text filtering and trace capture
• Configurable inspect, rate-limited log, telemetry-to-OSD, audio, and UDP payload routes
• Opus playback with volume, queue depth, and decoder/error metrics
• Native OpenIPC VPN/TUN bridging on macOS, Linux, Windows, and Android
• Catppuccin Macchiato theme and persisted receiver settings
• Sanitized ZIP support bundle with build, platform, pipeline, scan, and logs

Direct UDP input, UDP forwarding, and VPN/TUN are native-only. Their controls are unavailable in browser builds. Android requests VpnService consent and passes the resulting TUN file descriptor into the same Rust bridge used by desktop targets. Automatic receiver recovery is native-only because starting a WebUSB device selection requires a browser user gesture. Native recovery begins only after a receiver had reached Ready or Receiving; an initially invalid configuration does not create a retry loop. Delays increase from one to eight seconds and reset after 30 seconds of stable reception.

Recording writes the original encoded access units and the first enabled Opus audio route into MP4 without re-encoding. It waits for an H.264/H.265 keyframe, so the result begins at a valid random-access point. Video and audio timing come from their RTP clocks. Native muxing runs on a bounded recorder worker; browser recordings download when stopped. Both targets cap retained encoded media at 512 MiB. On desktop, Record never opens a file dialog: it writes a unique timestamped MP4 to the folder selected under Settings → Recording. The default is Nebulus inside the user's Videos directory, with Documents or the home directory as fallbacks. Android uses app-owned storage without prompting.

The VPN / tunnel section under Settings bridges recovered IP packets from radio port 0x20 into a native L3 interface at 10.5.0.3/24. Packets read from that interface are encrypted, FEC-wrapped, injected through the userland Realtek driver, and transmitted on radio port 0xa0. Linux may require elevated network-device permissions; Windows uses Wintun through rust-tun; Android uses its system VpnService.

The Windows release installer includes the matching wintun.dll. A cargo install nebulus installation detects when the DLL is absent and shows Install Wintun in Settings. Nebulus downloads the official signed 0.14.1 archive, verifies its published SHA-256, and installs the architecture-matched DLL under %LOCALAPPDATA%\Nebulus\wintun\0.14.1. The installer runs outside the receiver thread. Adaptive-link feedback injects WFB packets directly through the Realtek driver and does not require Wintun or an enabled VPN route.

Debug native and WASM builds also show Codec mock. It loops embedded, pre-recorded 1920x1080 H.264 and 48 kHz Opus fixtures, packetizes both tracks as RTP, and interleaves them on their media clocks. Native debug builds can start it automatically for profiling:

NEBULUS_CODEC_MOCK=1 cargo run -p nebulus --bin nebulus

Video passes through the normal RTP depacketizer and openipc-video; audio passes through the configured mixed-audio RTP tap, ropus, and the normal output queue. The native build uses its platform video decoder and WASM uses WebCodecs decoding; neither mock uses an encoder. Release builds omit the button and mock assets.

Validate

cargo fmt --all --check
cargo clippy -p nebulus --all-targets --no-deps -- -D warnings
cargo test -p nebulus --all-targets
cargo check -p nebulus --target wasm32-unknown-unknown
cargo check -p nebulus --bin nebulus-decode-worker --features web-decode-worker --target wasm32-unknown-unknown
cargo check -p nebulus --target aarch64-linux-android --lib

License

MIT