LiveBroadcaster

A live streaming and recording studio in Rust: egui / wgpu UI in the Futureboard Sphere UI design system, with media decode, H.264 / AAC encode and MP4 / MOV mux by MediaKit Foundation (MKFF) — no FFmpeg.

cargo run --release

The first build downloads the Chromium Embedded Framework runtime for the browser source (~165 MB, into .cef/) and compiles its C++ wrapper, so it needs CMake, Ninja and the MSVC build tools. cargo build --no-default-features leaves the browser source out.

What it does

Area
Sources	Display capture (DXGI duplication + cursor), window capture (Windows Graphics Capture; GDI PrintWindow fallback), browser (CEF off-screen: URL or local page, size, fps, custom CSS, sound to the mixer), cameras (Media Foundation, format picker), media files (any container / codec mkff-codecs decodes, with sound, loop, speed, transport), images, text (system fonts, Thai, outline, from file), colour
Audio capture	System sound — every app except the studio, on any device (WASAPI process loopback); one application, or all but one; playback device loopback; mic / line in
Scenes	Sources shared across scenes, layers with move / resize / crop / opacity, snapping, Cut / Fade transitions
Audio	48 kHz mixer, per-source fader / mute, meters with peak hold, master bus, monitoring (per source: output only / monitor + output / monitor only, on a chosen playback device — browser sources are heard by default), adaptive jitter buffers
Encode	GPU H.264 — NVIDIA NVENC, Intel Quick Sync, AMD AMF (MKFF mkff-hwenc) — or MKFF software H.264; Auto picks a GPU and falls back to software
Output	One shared H.264 + AAC encoder → RTMP / RTMPS (YouTube, Twitch, Facebook, Kick, custom; reconnect, congestion drop) and recording (fragmented MP4, MP4, MOV)
Compositor	On the GPU (the window's wgpu device): sources uploaded only when they change, alpha-weighted bilinear + mips (same rules as the CPU blitter), the preview draws the program texture directly, encoders get NV12 converted on the GPU and read back asynchronously. CPU compositor as the fallback (LB_CPU_COMPOSITOR=1)
Preview	wgpu renderer on a chosen GPU / API (Settings → Preview & GPU; Auto = discrete GPU, DX12 on Windows — clearly faster than OpenGL), VSync, pacing stats in Health (LB_PERF=1 logs them)
Languages	English, ไทย, 简体中文, 日本語, Bahasa Indonesia — follows the system language, or Settings → Appearance; switches live (menus included). Catalogs in i18n/*.json (English text → translation); cargo test checks every text in the code is in every catalog
UI	Native window with a Win32 menu bar, Scenes / Layers sidebar, stage, Audio / Properties / Health tabs, settings modal, dark & light themes

Settings and scenes live in %APPDATA%\LiveBroadcaster\ (settings.json, scenes.json, the browser cache in browser\); set LB_CONFIG_DIR to use another folder.

Licences

Everything linked is MIT / Apache-2.0 / BSD / ISC / zlib — no GPL. The browser source ships CEF (BSD-3-Clause) with Chromium inside libcef.dll, which contains LGPL-2.1 components (FFmpeg built without --enable-gpl, Blink); they stay in that separately replaceable DLL. Ship CEF's BSD licence and CREDITS.html (in .cef/) with a release.

MKFF (mkff-codecs, mkff-hwenc) comes from futureboard/mediakit-foundation, pinned to a commit (rev in Cargo.toml): push MKFF first, then bump the rev here. To work on both at once, override it locally with a [patch."https://github.com/futureboard/mediakit-foundation"] section pointing at a checkout.

Layout

src/
  engine.rs        compositor thread + audio mixer thread
  gpu_compositor.rs  wgpu compositor, NV12 conversion + async read-back
  video.rs         RGBA images, MKFF frame → RGBA, CPU bilinear / mip blitter
  bin/lb-browser-helper.rs  CEF's helper processes
  audio.rs         taps, resampling, fader law
  sources/         one runtime per source kind
  output/          encoder thread (MKFF), recorder, RTMP client + AMF0
  ui/              the studio window (Sphere UI)
crates/sphere-ui/  Sphere UI for egui (see below)

Translating

Interface texts are written in English inside tr!("…") / trf!("… {name} …", name = value). To add or change a text, edit the code, then add the same English key to each i18n/<lang>.json (cargo test catalogs_cover_the_code lists what's missing or unused). Keep {placeholders} and the menu shortcuts; Win32 menu accelerators use (&F) style in Thai / Chinese / Japanese.

crates/sphere-ui

An egui port of SphereUIComponents (Futureboard, GPUI): the token system (palette loaded from Futureboard theme files — themes/Default.json, themes/Light.json, or any theme with the same schema via Palette::from_theme_json), radius / spacing / size / typography / state-layer ladders, the system font chain (Segoe UI → Leelawadee UI → CJK … on Windows), Lucide icons (vendored SVGs, ISC, rasterised with resvg) and components: Button, IconButton, Panel, ListRow, Fader, meter, Toggle, segmented, tabs, chip, title_bar, status_bar, dialog_frame, menus and popovers. To use another Lucide icon, copy its SVG into crates/sphere-ui/icons/ and add it to src/icon_set.rs.

Tests

cargo test --workspace                 # unit tests + end-to-end recording through MKFF (clips: MKFF_TESTDATA=<mkff>/testdata/codecs)
cargo test -- --ignored rtmp           # streams to `ffmpeg -listen 1` (needs ffmpeg on PATH)
cargo test --release -- --ignored perf_1080p60 --nocapture   # encode time per encoder at 1080p60
cargo test -- --ignored browser_renders_page --nocapture     # CEF picture + sound (after cargo build)
cargo test -- --ignored process_loopback --nocapture         # app audio capture (plays a soft beep)
LB_TEST_PAGE=page.html cargo test -- --ignored browser_audio_timeline --nocapture   # when a page's sound comes out
LB_TEST_PAGE=page.html cargo test --release -- --ignored browser_sound_recording --nocapture   # …and in a 1080p60 recording
cargo test --release -- --ignored window_capture_methods --nocapture   # WGC vs GDI cost
cargo run --release --example encode_bench -- 1280 720 2500