TASK 4 ship step 3: encoder + RTMP push — FFmpeg subprocess with probed H.264 picker, BGRA stdin feed, stderr health parsing, graceful stop — 122 tests passing, 0 warnings

TASKS.md

@@ -199,7 +199,7 @@ Preview shows the transition too (WYSIWYG). No wipes/slides/LUTs beyond the four
 
 1. ✅ **Ship step 1 — the output compositor SHIPPED** (2026-08-10)
 2. ✅ **Ship step 2 — the FFmpeg locator SHIPPED** (2026-08-10)
-3. ☐ **Encoder + RTMP push** — the FFmpeg subprocess: frames via stdin, stderr health parsing, FLV mux + push to the cached reusable stream's ingestion URL
+3. ✅ **Encoder + RTMP push SHIPPED** (2026-08-12) — the FFmpeg subprocess: raw BGRA frames via stdin, stderr health parsing, FLV mux + push to the ingestion URL (see the ship step 3 plan below)
 4. ☐ **WASAPI audio capture** — loopback (desktop/game) + the picked mic feeding `AudioLevel` so the realtime meter comes alive (req 7)
 5. ☐ **Frame-pipeline wiring** — `CameraManager`/`ScreenCaptureManager` → compositor resolver → encoder
 6. ☐ **Health stats** — bitrate, FPS, dropped frames reported live in the bottom bar (req 5)
@@ -361,6 +361,35 @@ Tests: the hermetic `FfmpegLocatorTests` integration test (PATH → cache → do
 fake downloader serving a real in-memory zip) + edge/unit cases (shared-build DLL extraction, zero-byte
 cache refresh, empty payload, missing zip entry, downloader failure) — **78 passing**.
 
+#### Ship step 3 — Encoder + RTMP push (the FFmpeg subprocess)
+
+**Goal:** encode raw BGRA master frames into H.264+AAC FLV and push them to the reusable stream's RTMP
+ingestion URL — one battle-tested subprocess doing encode + mux + push + reconnect, the app feeding
+frames via stdin and parsing stderr for health (req 2).
+
+**Decisions (locked):** the encoder is a thin orchestrator over `ffmpeg.exe` — no H.264/AAC code in the
+app. Arguments (pure `FfmpegArgs.Build`): `-re -f rawvideo -pix_fmt bgra -video_size WxH -framerate FPS
+-i pipe:0` (frames in), a **silent placeholder audio track** via `-f lavfi -i anullsrc` (the WASAPI
+capture step replaces this input), `-c:v <encoder> -b:v K -maxrate K -bufsize 2K` + **`-g fps×4`
+`-keyint_min fps×4` `-sc_threshold 0` `-bf 0` `-pix_fmt yuv420p`** (the keyframe ≤4s / closed-GOP /
+H.264 compliance), `-c:a aac -ar 48000 -ac 2`, `-f flv <rtmpUrl>`. Encoder choice is **probed from the
+binary's `-encoders` listing** (`FfmpegEncoderPicker`, pure): hardware NVENC → QSV → AMF, then OpenH264
+software fallback — **never libx264** (GPL; see `ai.md` → Licensing). The seam (`IFfmpegEncoder` +
+`IEncoderProcess`, constructor-injected locator + process factory) keeps it hermetic — tests fake the
+whole subprocess (probe + encoder), no real binary.
+
+**Behavior:** `StartAsync` (locate → probe → spawn → stderr loop), `SubmitFrameAsync` (serialized BGRA
+stdin writes, ~2 Hz health via `HealthUpdated`/`StreamHealth` — bitrate/FPS/duration/dropped-from-frame-
+count), `StopAsync` (stdin EOF → ffmpeg finalizes + exits by itself; 10s watchdog kill), `ProcessFailed`
+on a non-zero unexpected exit.
+
+**Built (2026-08-12):** `EncoderOptions` + `IFfmpegEncoder`/`FfmpegEncoder` + `IEncoderProcess`/
+`FfmpegEncoderProcess` + pure `FfmpegArgs`/`FfmpegProgressParser`/`FfmpegEncoderPicker` in
+`Services/Encoder/`. Not yet constructed by the app (the frame-pipeline wiring, ship step 5, owns it).
+Tests: `FfmpegEncoderTests` integration (probe → spawn with NVENC preferred → frames into stdin →
+progress parsed → graceful stop, no kill) + units (args compliance/GOP, progress parser, picker
+preference + GPL guard, no-URL/not-running/noop stops, process-death `ProcessFailed`) — **122 passing**.
+
 ---
 
 ## TASK 5 — YouTube Live Stream Management