# Development Phases

This file breaks the project into incremental milestones. Each phase produces a
working, testable slice of functionality. Do not start a phase until the
previous one is validated.

## Phase 1 — Project Skeleton

**Goal**: configure, compile, and run tests with no real dependencies.

- [x] Meson build files (`meson.build`, `meson_options.txt`).
- [x] Public module headers with `namespace sc`.
- [x] Unit test that exercises a trivial utility function.
- [x] `README.md` with build instructions.

**Validation**: `meson setup build && meson compile -C build && meson test -C build`.

## Phase 2 — Software H.264 Encode / Decode

**Goal**: encode raw pixel buffers to H.264 and decode them back, purely with
FFmpeg software paths.

- [x] Add `libavcodec`, `libavutil`, `libswscale` dependencies.
- [x] Implement `EncoderFactory::create()` and `Encoder::encode()`.
- [x] Implement `DecoderFactory::create()` and `Decoder::decode()`.
- [x] Round-trip test: synthetic RGB frames → H.264 → decoded RGB.

**Validation**: unit test produces visually/structurally correct round-trip
frames.

## Phase 3 — PipeWire Screen Capture

**Goal**: capture the desktop and feed frames into the encoder.

- [x] Add `libpipewire-0.3` dependency.
- [x] Implement `CaptureFactory::create()` using the xdg-desktop-portal.
- [x] Wire `CaptureSession::next_frame()` → `Encoder::encode()` in a local smoke
  test that just writes a few encoded frames to disk.

**Validation**: manual run on a real Linux desktop session produces a valid
H.264 bitstream.

## Phase 4 — RTP Framing

**Goal**: packetize NAL units into RTP and depacketize them.

- [x] Implement `RtpHeader` and `RtpPacket` serialize/parse.
- [x] Add H.264 NAL splitting and FU-A fragmentation.
- [x] Unit test for serialization, fragmentation, and reassembly.

**Validation**: unit tests cover single-NAL and fragmented packet paths.

## Phase 5 — Local UDP Sender → Receiver Loopback

**Goal**: send RTP packets over UDP and render the result locally.

- [x] Implement `RtpTransport` with ASIO or raw UDP sockets.
- [x] Wire sender pipeline: capture → encode → RTP → localhost UDP.
- [x] Wire receiver pipeline: localhost UDP → RTP → decode → renderer.
- [x] Add SDL2/SDL3 dependency and a minimal `Renderer`.

**Validation**: `screencast --send` and `screencast --receive` on the same
machine show the captured desktop in a window.

## Phase 6 — LAN Signaling and Discovery

**Goal**: two peers on the same LAN can find each other and negotiate a
session.

- Implement mDNS/DNS-SD discovery with Avahi.
- Implement JSON WebSocket signaling.
- Extend CLI with `--peer-address` or `--discover`.

**Validation**: two machines on the same LAN connect without hard-coded IP
addresses.

## Phase 7 — Resilience and Polish

**Goal**: loss recovery, hardware acceleration, and packaging.

- NACK / PLI feedback loop.
- Jitter buffer on the receiver.
- VAAPI/NVENC hardware encode probes and fallback.
- Optional GUI target behind `meson -Dgui=true`.
- `.desktop` file, icon, packaging notes.

**Validation**: sustained streaming under packet loss; hardware accel smoke
where available.

## Current phase

Phase 6 — LAN Signaling and Discovery.