# screen_cast

A native Linux peer-to-peer screencast application.

- **Send** your desktop or a window to another Linux machine.
- **Receive** a stream and render it in a window.
- Discover receivers on the LAN via **mDNS/Avahi**; negotiate sessions with
  **JSON signaling**; stream **H.264 over RTP/UDP**.

Built with **C++20**, **Meson**, **PipeWire**, **FFmpeg**, and **SDL3**.

## Quick start

Requirements:

- C++20 compiler with `<format>` (GCC 13+, Clang 18+)
- Meson >= 0.63, Ninja
- FFmpeg development packages (`libavcodec`, `libavutil`, `libswscale`)
- SDL3 development package (`sdl3`)
- nlohmann JSON (`nlohmann_json`) and Avahi client (`avahi-client`)
- For the sender only: PipeWire dev (`libpipewire-0.3`) and libportal

Build and run tests:

```sh
meson setup build
meson compile -C build
meson test -C build --print-errorlogs
```

Stream between two machines:

```sh
screencast --receive        # machine A: announces itself, opens a window
screencast --send          # machine B: discovers A, negotiates, streams
```

See `docs/RUNBOOK.md` for all modes, flags, and validation procedures.

## Receiver on a small ARM board (e.g. Raspberry Pi Zero 2 W)

The receiver does not need the sender's PipeWire/portal capture stack. On
the board, run:

```sh
sudo ./scripts/install-receiver.sh
screencast --receive
```

The script installs the dependencies, builds a receiver-only binary
(`-Dsender=false`), runs the test suite, and installs to `/usr/local/bin`
(override with `SC_RECEIVER_INSTALL_DIR`). It needs Raspberry Pi OS Trixie
or newer (GCC 13+ for C++20 `<format>`), builds SDL3 from source when the
distribution does not package it, and enables `avahi-daemon`. It also
installs and enables a systemd service so the receiver starts at boot —
`systemctl status screencast-receiver` to check on it.

Performance note: decoding is software H.264; on very small boards expect
smooth playback for modest resolutions and reduced frame rates at high
resolutions. Hardware decode is planned for Phase 7.

## Architecture

See `docs/ARCHITECTURE.md` for module boundaries and design rules.

## Roadmap

Development is split into phases in `docs/PHASES.md`.

Current phase: **Phase 7 — Resilience and polish**.

## License

MIT — see `LICENSE` (to be added).