ytLlive/TASKS.md

# ytLlive — Task List

> Task queue and authoritative research. Memory-map conventions: [`schema.md`](schema.md);
> architecture/decisions: [`ai.md`](ai.md). Update statuses here whenever a task moves.

## YouTube Live API — research facts (authoritative, v3 build)

Lifecycle: `created → ready → [testing] → live → complete` (transitional `liveStarting` / `testStarting`).

- **liveBroadcasts.insert** requires: `snippet.title`, `snippet.scheduledStartTime`, `status.privacyStatus`, `status.selfDeclaredMadeForKids` (COPPA).
- **liveStreams.insert** requires: `snippet.title`, `cdn.frameRate`, `cdn.ingestionType`, `cdn.resolution`. **None of the four (except title) can ever change after creation** — changing them means delete + recreate the stream. This is the hard constraint behind the quality grey-out.
- **Title / description / privacy**: editable at any time, including while live (`liveBroadcasts.update`, part=`snippet,status`).
- **contentDetails** (DVR, recordFromStart, monitorStream, embed, latency): editable only in `created` / `ready`.
- **Transition to live** only allowed when the bound stream's `status.streamStatus == active`.

### Two features that reshape the design

1. **enableAutoStart / enableAutoStop** — instant one-click go-live, no transition call. With `enableAutoStart=true` we never call `transition(live)`: the broadcast auto-goes-live the moment the encoder starts. Combined with `enableMonitorStream=false` (our preview pane replaces YouTube's monitor stream — the thing that forces a testing stage), the flow is **create → bind → Start Stream → encoder starts → YouTube brings it live**. No testing, no transition polling, no liveStarting stuck-state handling.
2. **`cdn.resolution=variable` / `cdn.frameRate=variable`** — free auto step-down. YouTube auto-detects what we send; since we ARE the encoder we can drop bitrate/resolution on the fly with zero API calls. Declaring an explicit resolution instead (e.g. 1080p) requires a new stream, which can't happen mid-broadcast. Variable is the enabler for the whole auto step-down feature.

### Compliance gotchas (maps perfectly to report-by-exception)

- `liveStreams.status.healthStatus`: `good | ok | bad | noData` plus `configurationIssues[]` with `type` + `severity` (`info|warning|error`). Literally built for report-by-exception — poll it, render nothing on good/ok, surface a banner only on warning/error. No need to invent our own health logic.
- Encoder must comply or YouTube flags it: keyframes ≤ 4s (`gopSizeLong`), closed GOP, H.264, audio AAC/MP3 @ 44.1/48kHz, mono/stereo only.
- Error codes to handle: `errorStreamInactive`, `invalidTransition`, `redundantTransition`, `liveStreamDeletionNotAllowed`, `liveStreamModificationNotAllowed`, `liveBroadcastBindingNotAllowed`.

### Tips we should take advantage of

- **Reusable streams** (`isReusable=true`): one stream per channel, cache its ingestion URL + stream name, reuse for every broadcast. No rebinding dance each go-live. This is exactly the manual-stream-key baseline.
- **Backup ingestion address**: YouTube provides a simultaneous-push backup — future hardening, not v1.
- **`recordFromStart` + `enableDvr` default true** → every live is auto-recorded and immediately replayable. Free VOD archive, matches the v0.2 recording goal.
- **`latencyPreference`: `normal | low | ultraLow`** — for homelab streamers talking to chat, `low` (or `ultraLow`, capped at 1080p) is a real feature.
- **Broadcast ID == Video ID** — one ID to track everything.

---

## TASK 1 — Initial Scaffold

**Goal:** Working C# / WPF project with MVVM architecture, dark-theme main window, and YouTube service stubs.

### Status: ✅ Done
- Models: Scene, Source, StreamConfig, StreamHealth, YouTubeChannel, ChatMessage
- Services: YouTubeAuthService (OAuth2), YouTubeStreamService (broadcast/health), YouTubeChatService (chat polling)
- MainViewModel: scene management, stream controls, chat
- MainWindow: scene/source panel, preview area, chat panel, status bar
- Clean build, 0 warnings (WSL + Windows)

---

## TASK 2 — YouTube OAuth2 Authentication

**Goal:** Fully working Google OAuth2 flow — user clicks "YouTube", browser opens, authorization callback lands, channel info is stored.

**Design constraint:** Sign-in must NEVER block core exploration. Users can build scenes, add sources, and audition the software without authenticating. But **going live requires authentication** — the "Start Stream" dialog is where the account sign-in lives, alongside all stream metadata.

**Two-state flow:** There is no separate "Connect" button. The top bar shows a single button — **Start Stream** when idle, **End Stream** when live. Clicking Start Stream opens one dialog that supplies everything: account (previously-saved account shown as default, with a Change Account action) + title/description/visibility.

**Live indicators (unmissable):** Top bar + window title bar flip red, a pulsing **● LIVE** badge with elapsed timer appears in the top bar, the preview area gets a red glow, and the taskbar icon shows a red overlay dot. Window title bar shows the stream title once validated.

### Requirements:

1. **Google Cloud OAuth credentials** — client ID + secret, **baked into `Helpers/OAuthCredentials.cs`** (desktop "Desktop app" OAuth client; loopback callback — no console redirect URI registration needed; creators never configure)
2. **Local HTTP listener** — `HttpListener` on `http://localhost:PORT/oauth2/callback` to catch the redirect
3. **Browser launch** — open the authorization URL in the default browser
4. **Token persistence** — store access/refresh tokens securely (Windows DPAPI), reload on startup
5. **UI state** — account shown in the Start Stream dialog; "Change Account" action triggers re-auth
6. **Go Live gated on auth** — Start Stream dialog requires sign-in to enable the Start button; scene building works without it

### Tests:

- Mock token exchange response, verify channel info parsed
- Verify token refresh triggers when near expiry
- Verify credential load/save roundtrip

### Status: ✅ Complete
- ✅ Two-state Start/End Stream button, go-live dialog (account + title/description/visibility), red top bar, pulsing LIVE badge + elapsed timer, preview glow, taskbar red dot
- ✅ Real OAuth2 wiring — baked-in Google credentials (desktop client; loopback callback) + `YouTubeAuthService` complete: browser launch, `HttpListener` callback, token exchange, refresh, channel fetch
- ✅ Token persistence via Windows DPAPI (`Helpers/TokenStore.cs` → `%APPDATA%\ytLlive\ytLlive.auth`), best-effort reload + proactive refresh at startup, saved after every exchange/refresh
- ✅ Account sign-in/change surfaced in the GoLive dialog (saved account shown with "Change Account"; "Sign in to YouTube" when none; Start disabled until signed in)
- ✅ **End Livestream signs out** — a graceful end completes the session: `StopStream()` calls `YouTubeAuthService.ClearSession()` + `TokenStore.Clear()` + `IsConnected = false`, so the next Start Stream dialog requires a fresh sign-in. A crash never runs End, so the DPAPI token survives and the creator stays signed in. Resume/reconnect after a midstream crash is deliberately deferred to TASK 3: the socket can't be resumed (it dies with the process), so "resume" = fast reconnect with a saved broadcast ID/stream key within YouTube's disconnect-grace window; too slow and `enableAutoStop` ends the broadcast
- ✅ Tests in `ytLive.Tests` (xUnit, net8.0-windows): TokenStore DPAPI roundtrip/corrupt/missing/clear + mocked exchange channel-parse + refresh expiry bump + `ClearSession` — 7 passing

---

## TASK 3 — Capture Pipeline (Scenes/Sources)

**Goal:** Real video preview in the center panel — the minimal source set below, composited per scene.

### The Minimal Source Set (design decision — do not expand casually)

ytLlive is YouTube-only and 90% of users are casual. OBS's long source list is off-putting; we ship
the hot few and nothing esoteric. If a user needs more, they've graduated to OBS.

1. **Webcam** — the face cam. Non-negotiable.
2. **Screen** — the main event (game, slides, browser). One source; a picker chooses a monitor *or* a
   window. (Window capture is absorbed here — no separate source type.)
3. **Background** — a full-canvas backdrop image. Fills the whole scene automatically, zero fiddling.
   Kept separate from Image on purpose: same pixels, but this one needs no positioning.
4. **Image** — a floating graphic/logo overlay (watermark, badge, corner branding). Free-positioned.
5. **Text** — live text ("Starting soon", "Back in 5", handle, callout). Casual streamers live on this.
6. **Chat box** — YouTube live chat rendered *on* the stream so viewers read along in-video. YT-native.
7. **Alerts** — Super Chat / membership / subscribe pop-ins. The dopamine source. **The one big lift**
   (Super Chat event streaming + on-stream rendering/animation); build after the six. **Also the one
   paid feature** — see Monetization in `ai.md`.

Deliberately NOT supported: game capture, browser source, media playlist, VLC, color-key voodoo, MIDI.

### Source memory model (design decision)

- A scene has resources. Resources can be shared across scenes.
- A resource exists exactly once in memory, no matter how many scenes use it (a logo in five
  scenes = one loaded bitmap).
- Every resource carries a **catalog of scenes**: one usage entry per scene it appears in, each
  entry dictating that scene's use — placement (X/Y/Width/Height), opacity, z-order, enabled,
  scale mode, crop.
- Usages are named `{resourceName}.{sceneName}` — whatever the user named the resource, dot, the
  scene name: `logo.starting`, `logo.live`, `myPic.brb`. Not a hardcoded "logo".
- A webcam in two scenes = one capture session, two catalog entries.
- Refcount by catalog size: the last usage removed → the resource is disposed and evicted.
- The resource (not a per-scene node) owns everything `IDisposable`.

### Scene transitions (design decision)

Scene switching while live must never stutter. Supported types, most → least economical:

1. **Cut** — instant switch. The default. Zero cost.
2. **Fade** — short crossfade (~300ms).
3. **Move** — a simple, economical move transition, done to perfection and memory-efficient. The
   smart streamer's bread and butter.
4. **Custom (media) transitions** — require media elements (video/stinger playback during the
   transition). Heavier, but creators pay for these, so we support them. Their media follows the
   same resource memory model: loaded once, catalogued by scene.

Preview shows the transition too (WYSIWYG). No wipes/slides/LUTs beyond the four above.

### Requirements:

1. **Screen** — Windows.Graphics.Capture (WinRT), enumerate displays/windows, picker
2. **Webcam** — MediaCapture (WinRT SDK projection) with device enumeration — ✅ **milestone 1 done**:
   - TFM bumped to `net8.0-windows10.0.19041.0` (app **and** tests) so the WinRT projection resolves from the SDK reference packs — no NuGet package, no capability manifest (unpackaged desktop app)
   - `MediaCaptureFrameSource` (CPU-first: `MemoryPreference = Cpu`, BGRA8 via `CreateFrameReaderAsync`), `MediaCaptureCameraEnumerator` (`DeviceInformation.FindAllAsync(DeviceClass.VideoCapture)`)
   - `CameraManager`: refcounted by `DeviceId`, one shared `WriteableBitmap` app-wide, dispatcher-coalesced UI updates (~render rate, latest-frame drop), placeholder/`AppLog` + warning on failure
   - `CameraPickerDialog` (mirror of `ReuseImageDialog`) — "Searching for cameras…" / list / "No cameras found" states
   - One webcam app-wide: Add → Webcam greyed out once one exists ("it's already in your stream" tooltip); persisted `DeviceId` re-acquires after layout load
   - Default placement 16:9 **480×270**, bottom-right, 32px margin; drag/resize/selection shared with Image sources
   - **Clip shapes: Traditional + Round** (phone view dropped — the 9:16 phone output is the vertical output-crop tier); **mirror**; both persisted in the layout DB (schema v2) and toggled from the source chip
   - **Background removal = milestone 2** (ONNX Runtime + DirectML, MediaPipe Selfie Segmentation) — not in this build
3. **Background / Image / Text** — static sources positioned/scaled/opacity
4. **Chat box** — rendered from the live chat poll (right panel is the same feed, raw)
5. **Scene compositing** — per-scene source layering (z-order = sources list order, top-to-bottom
   back-to-front), preview rendered via D3DImage or MediaElement
6. **Branding flash** — the topmost full-frame "made with ytLlive!" layer at ~25% opacity, ~1s on /
   300s off (see Monetization in `ai.md`), gated on `BrandFlashEnabled` + live/recording. Lives in the
   preview compositor now (`BrandFlashLayer` in `MainWindow.xaml` CanvasGrid, driven by
   `BrandFlashActive`/`BrandFlashTimer` in `MainViewModel`); the encoder output renders the same layer,
   and v0.2 local recordings carry it too
7. **Drag/drop placement & reorder** — intuitive, visual (per design principle):
   - **Preview:** click-drag a source in the center panel to reposition it; resize via handles
   - **Scenes list:** drag rows to reorder scenes
   - **Sources list:** drag rows to reorder sources (this *is* the z-order) — implemented

### Status: 🔶 In progress — milestone 1 (webcam) shipped; **schema v3 (Ship Branch A) shipped**: multi-scene webcam (singleton `Webcam` + per-scene `WebcamSceneConfig`), right-click border/context menu, static OSB-style borders, 50%-per-dimension webcam size cap, device-swap (`ReleaseAllAsync`); **schema v4**: round→rect restore persisted (`WebcamSceneConfig.RectWidth`/`RectHeight`) + one-time legacy-square 16:9 heal on load — 25 tests passing; **screen backdrop (ship task #1) shipped**: live desktop/game capture as a permanent, non-deletable bottom layer (`Source.IsBackdrop`, schema v5), auto-detecting the full-screen game at launch/focus (else the **primary display** — never assumed monitor 0) via `Win32FullScreenDetector` (now with `GetDisplays()`/`PrimaryMonitorIndex()` for the in-app display picker), content re-designated via the OS `GraphicsCapturePicker` ("Change Capture…") or the in-app "Capture Display" submenu, refcounted/shared capture sessions in `ScreenCaptureManager` mirroring `CameraManager` — 45 tests passing; **schema v6**: `Scene.HasBackdrop`, now **Live-only by policy** — the backdrop is enforced by scene name on every load (`EnforceBackdropPolicy`: Starting/BRB/Chat/Ending never carry one; the one-time v5→v6 backfill covers all four), the scene context-menu "Backdrop" checkbox is gone (policy owns the flag), preview watermark hides when the backdrop renders, capture changed to `WindowsRuntimeMarshal.TryGetDataUnsafe` (the CsWinRT-safe frame-read) + downscale to the 1920×1080 master + 5s-throttled error logging (was flooding `startup.log` with 5 MB of cast errors and burning CPU), round webcam no longer re-rasterizes an `ImageBrush` every frame (Image + EllipseGeometry clip) — the live-mode stutter fix; **the five-scene catalog (`SceneCatalog`)**: Starting/Live/BRB/Chat/Ending is the product — work with less, never more; the (+) button only shows when a canonical scene is missing and re-adds it (its menu lists only the missing ones); **webcam-after-session-start fix**: a webcam added to a scene after the camera was already running (e.g. Chat) previously rendered a transparent container — `CameraManager.GetPreviewBitmap` + propagation in `AddWebcamToActiveSceneAsync`/`ReacquireWebcam` now hands the running shared frames to any newly added `WebcamSceneConfig` — 62 tests passing; the **Chat scene's webcam size cap** is raised from 50%-per-dimension (960×540) to half the screen AREA (~1358×764 @16:9, `MaxWebcamWidthFor`/`MaxWebcamHeightFor` keyed by canonical name) so the viewer sees the creator better — 65 tests passing; **"Add Webcam" always opens the camera picker** (deleting one scene's webcam then re-adding used to resurrect the old camera when another scene still used it — `SwapWebcamIdentityAsync` now swaps the app-wide identity if a different camera is chosen, same path as "Change Webcam…"); scenes/sources UI (add/reorder/rename, image + background overlays with move/resize/opacity/reuse) built; **audio UX shipped (UI)**: the bottom-bar footer is now two lines (dropped/duration moved under bitrate/fps), with the mic's sound meter + mute button + volume slider grouped CENTERED on the footer's top line, beneath the preview panel (meter: 288px, muted slate track with ruler graduations + muted yellow/red zone tints, green→yellow→red fill; mute = speaker icon → red do-not-symbol when muted, and the slider and speaker stay in sync (volume 0 ⇔ muted — sliding off flips the speaker to muted, sliding up from 0 clears it); mic volume defaults to 80%, muting zeroes the meter and restores the prior volume on unmute (which flashes the meter to the restored position ~300ms before it returns to the live level); the meter is a READ-ONLY realtime level display (fill = live level × volume — volume is a gain on ambient noise; while the slider is dragged the bar previews the slider position and bounces back to the live level on release, which is 0 with no input — clicking the meter does nothing), clicking the MIC label opens a microphone picker whose chosen source shows left-justified inside the meter bar (fill at 75% opacity so the name + ruler markings show through); slim dimensional slider — gradient track/fill, gloss-sphere thumb; the old flat pink 18px-filled one is gone), everything else on line 2 (bitrate/fps/dropped/duration/health left, quality + gear right) — the creator's only audio control, desktop/game audio is automatic (KISS rule); the connected YouTube account's avatar/name shows in the top bar next to Start Stream (`SyncConnectedAccount`); the scenes list is content-height now (no dead space before SOURCES); window capture, compositing, encoding pending

---

## TASK 4 — RTMP Ingest to YouTube

**Goal:** Push encoded video to YouTube's RTMP ingest.

### Requirements:

1. **Encoding** — H.264 (hardware via NVENC/AMD, fallback x264) + AAC audio; **must comply**: keyframes ≤ 4s (gopSizeLong), closed GOP, AAC/MP3 @ 44.1/48kHz, mono/stereo only. **License posture (decided): GPL-free build** — NVENC (NVIDIA) / QSV (Intel) / AMF (AMD) + OpenH264 software fallback + built-in AAC; no libx264 (GPL contaminates a paid product). Output containers are identical either way (H.264+AAC in `.flv` for RTMP, `.mp4`/`.ts` for VOD) — the format is NOT the differentiator, the license and per-GPU quality are. **License guardrails (never violate — see `ai.md` → "Licensing — do not violate"):** only BtbN `lgpl`/`lgpl-shared` builds; never GPL (gyan.dev) or `nonfree` (fdk-aac); never static for distribution (LGPL §6 relink material); never link FFmpeg into the app; never drop `THIRD-PARTY-NOTICES.txt` from the app/About screen.
2. **RTMP push** — **FFmpeg subprocess (decided)**: app feeds raw frames via stdin, parses stderr for health; one battle-tested binary does encode + FLV mux + push + reconnect. **Binary distribution (decided): check-then-pull** — probe `where ffmpeg`/PATH at first go-live; if absent, download a **pinned** build (**BtbN LGPL win64 static** zip, ~75 MB — gyan.dev's builds are GPLv3 and ship libx264, which violates the license posture; BtbN's LGPL variant drops x264/x265 while keeping NVENC/QSV/AMF + libopenh264 + native AAC) to `%APPDATA%\ytLlive\tools\ffmpeg.exe` (extract just `ffmpeg.exe` from the zip) and cache it, offline-friendly. Behind an `IFfmpegLocator` seam so tests fake it (ship step 2, below). Push goes to the cached reusable stream's ingestion URL
3. **Quality ladder** — the offered tiers, with **1080p60 @ 8 Mbps as the standard/default**:
   - 720p30 @ 6 Mbps
   - 720p60 @ 6 Mbps
   - 1080p30 @ 8 Mbps
   - **1080p60 @ 8 Mbps** (default — mainstream ceiling, GPU hardware-encoded so the gaming
     machine never notices; upload headroom stays comfortable)
   - Vertical 1080×1920 @ 60fps @ 8 Mbps (9:16 phone tier)
   The composition master is always 1920×1080; a tier is an output rect + target resolution
   (see `ai.md` "Resolution tiers"). Vertical output = the centered 607×1080 crop of the master
   scaled to 1080×1920 (semi-crop preview is already implemented; the encoder applies the same rect).
   1080p60 is the ceiling by design — "if you want 1440 or 4K or 8K → OBS is your solution"; the app
   targets the most mainstream creator, not power users.
   Ladder is sculpted by a **cached probe** (IP-only TCP vs public ingest host; no auth required).
   Quality is greyed out while live because the declared resolution can't change mid-stream — but
   with `variable`, we can **auto step-down** bitrate/resolution on the fly with zero API calls
   (no stream recreation); 60fps presumes a hardware encoder — no hardware encoder → auto
   fallback to 720p60/1080p30
4. **Stream key management** — reuse the cached reusable stream (one per channel) instead of creating a new one per go-live; prefill default YouTube ingest URL `rtmp://a.rtmp.youtube.com/live2`
5. **Health stats** — bitrate, FPS, dropped frames reported live in the bottom bar (encoder-side)
6. **One-click go live** — defaults that work out of the box
7. **Audio capture (feeds the meter — this task ships the wiring)** — WASAPI loopback (desktop/game at unity, zero UI — "it just is") + the picked mic (`MicSourceName` from the `MicPickerDialog`). The mic capture feeds `AudioLevel` so the realtime meter comes alive (today it reads 0 — the mixer feed is pending, see `ai.md` audio notes). AAC mono/stereo @ 48 kHz per the compliance rules.
8. **Private-only go live until v1 (reputation guard, decided 2026-08-10)** — until the v1 release, go-live is **locked to private streams only** so a software error can never publish something public/unlisted that damages the creator's reputation. RTMP push itself has no privacy — privacy lives on the YouTube **live broadcast object**, which this app already controls via its OAuth API calls. So the lock is purely API-side: the Go Live flow always creates/updates the broadcast with `privacyStatus = "private"` and a guard **refuses** to set anything else (same spirit as the Live-only backdrop policy). The UI shows a clear "PRIVATE" badge next to the stream state so the creator always knows who can see them. Enforcement must be verifiable in the auth-service tests (fake the broadcast-insert/update call, assert `privacyStatus` is forced to private).
9. **v1 release gate: bundle the full license texts (decided 2026-08-10)** — `THIRD-PARTY-NOTICES.txt` currently links the canonical license texts rather than embedding them. At the **v1 (GA) release**, the full texts of every license it names (LGPL v2.1+, BSD-2-Clause, MIT, Apache-2.0) MUST be bundled alongside it (shipped in the app output, e.g. a `licenses/` folder next to the notices file, still reachable from the About screen). This is a **release blocker for v1, not a task to queue early** — do it in the release pass. The repo should treat this like the private-only go-live gate: a checkbox that cannot silently lapse.

### Status: 🔶 In progress — **ship step 1 (the output compositor) SHIPPED** (2026-08-10); **ship step 2 (the FFmpeg locator) SHIPPED** (2026-08-10); encoder/RTMP/audio follow it

The pipeline chain the encoder needs doesn't exist yet: **scene compositing** (the master 1920×1080 frame
without the preview's editing chrome) → **audio capture** (WASAPI, feeds the meter) → **H.264+AAC encode**
→ **vertical-tier crop/scale** → **RTMP push** → **health stats** into the bottom bar. Nothing can encode
until a frame source exists, so the compositor is ship step 1.

#### Ship step 1 — Scene compositor (the frame source)

**Goal:** a pure-CPU software compositor producing the encoder's master frame (BGRA8, the `VideoFrame`
seam) from the scene model. The preview stays XAML (the editing view); the compositor is the **output
view** — WPF's `RenderTargetBitmap` can't be used (software-rendered + captures chrome). Two renderers
must agree, so the XAML (`MainWindow.xaml` CanvasGrid + element DataTemplate) is the contract.

**Decisions (locked 2026-08-10):** **Path A CPU blitter** — GPU effort belongs to NVENC (the encoder),
not composition; with an FFmpeg subprocess the master crosses a CPU readback to the pipe every frame
anyway, so GPU compositing buys ~nothing at this layer count (2-3 live layers; static layers
pre-composite once). A D3D11 compositor can replace this one later **behind the same seam** (the CPU
master buffer stays the contract). **Render the output rect directly**: compositor is constructed with
`CompositorOptions {SourceRectX/Y/W/H, OutputWidth, OutputHeight}`; 16:9 tiers = full 1920×1080 1:1;
vertical (9:16) = composite the centered 607×1080 crop then bilinear-upscale to 1080×1920. Reuses
`MainViewModel.OutputRectX/Y/W/H` (note `(1920−607)/2 = 656.5` → align to integer pixels for output).

**Render spec (back → front, mirror the XAML exactly):**
1. Backdrop — the Live scene's `IsBackdrop` Source (`CaptureKey` → live frame), `UniformToFill`
   full-frame (XAML's separate `BackdropImage` layer; the backdrop *element* renders nothing — its
   DataTemplate Image is Collapsed for DisplayCapture).
2. Background — the scene's `Background` Source, `UniformToFill` full-frame (the `ActiveBackgroundImage`
   layer, not per-element).
3. Elements in `Scene.Elements` order (back→front), skip `IsVisible=false`. What actually renders:
   - `Source` Type `Image` → static asset, `UniformToFill` cover-crop into (X, Y, W, H)
   - `WebcamSceneConfig` → latest frame by `DeviceId`: Traditional = `UniformToFill` rect; Round = circle
     diameter `min(W,H)` (alpha 0 outside — true circle, not oval); mirror = horizontal flip around
     element center (`MirrorScale`); opacity = per-pixel multiply (content + border); border = stroked
     rect / centered circle at `RoundBorderSize`, width `BorderWidth`, alpha `BorderOpacity`
   - `Background` / `IsBackdrop` / `TextOverlay` are NOT per-element (layers above; Text not shipped)
4. Branding flash — pre-rendered full-frame "made with ytLlive!" at 25% alpha when live +
   `BrandFlashEnabled` + timer active. Passed in as a `VideoFrame?` (compositor core stays pure byte-math,
   no WPF; likely a bundled asset rather than runtime text rendering).
5. NOT in output (preview chrome only): SelectionOverlay, DimRects, output-rect outline, badge, placeholder.

**New files (all in `Services/Compositor/`):**
- `SceneCompositor.cs` — `Render(Scene, frameFor: Func<SceneElement, VideoFrame?>, flashFrame:
  VideoFrame?, CompositorOptions) → VideoFrame` (output-sized). The caller's `frameFor` resolver maps
  each element to its frame (webcam → DeviceId, image → AssetId via `StaticPixelCache`, backdrop →
  CaptureKey) — the compositor stays pure/hermetic/no WPF.
- `CompositorOptions.cs` — source-rect + output W×H.
- `StretchMath.cs` — `UniformToFill` cover-crop, ellipse mask, bilinear scale (pure, unit-tested).
- `StaticPixelCache.cs` — asset `byte[]` → cached BGRA `VideoFrame` (WPF `BitmapDecoder` + `CopyPixels`,
  decode once per content hash).

**Test plan (Good Dog Rule — ONE integration test):** `SceneCompositorTests` — a scene with backdrop
(solid red fake frame) + round webcam (solid green) + image (solid blue) → render 16:9 master → assert
per-layer probe pixels (corner = backdrop color, element center = webcam color, outside the round clip =
backdrop color, mirrored element swaps left/right); a vertical-tier variant asserts 1080×1920 output +
crop fidelity. Focused unit tests on `StretchMath`. Tests push frames directly — no capture managers
involved (they wire in a later step).

**Same-PR housekeeping:** fix the stale comment `MainViewModel.cs:324` ("shown under the meter on line 2"
→ "shown left-justified INSIDE the meter bar" — `ai.md` is the authority); this task's requirements now
include the explicit audio-capture/meter wiring (#7 above).

**Out of scope (later ship steps):** FFmpeg locator + license posture (covered in requirements 1-2),
encoder + RTMP push, WASAPI audio capture (loopback + mic) feeding `AudioLevel`, wiring
`CameraManager`/`ScreenCaptureManager` into the frame pipeline, brand-flash timer wiring, health stats
(bitrate/FPS/dropped).

**Built (2026-08-10):** all four files shipped in `Services/Compositor/`, `SceneElement.TryGetBorderColor`
made public (shared hex parse with the compositor — no duplicated color parsing), the stale
`MainViewModel.cs:324` comment corrected, and the pre-existing CS1998 in `YouTubeAuthServiceTests`
cleaned up — build **0 warnings**. Tests: the `SceneCompositorTests` integration test (full-scene master
pixels, vertical tier, flash) + 4 `StretchMath` units — **72 passing**.

#### Ship step 2 — FFmpeg locator (the encoder's binary)

**Goal:** resolve a usable `ffmpeg.exe` on demand (the encoder's one external dependency), never shipping
a binary in the repo. Returns an absolute path; downloads only when neither PATH nor the local cache
provides one.

**Decisions (locked 2026-08-10):**
- **BtbN LGPL-shared win64 build** — not gyan.dev (gyan's "essentials" is GPLv3 and ships libx264, which
  violates requirement 1's license posture) and **not the static lgpl build**: LGPLv2.1 §6 wants
  relinkable object files for static linking, but the **shared** (dynamic-DLL) variant sidesteps that —
  compliance is "license text + source offer + unmodified binaries" (see `THIRD-PARTY-NOTICES.txt` and
  `ai.md` → Licensing). Drops libx264/libx265 while keeping NVENC/QSV/AMF, libopenh264 (the LGPL-legal
  H.264 software fallback) and native AAC — exactly the requirement-1 encoder profile.
- **Pinned URL** — `https://github.com/BtbN/FFmpeg-Builds/releases/download/autobuild-2026-08-09-13-03/ffmpeg-master-latest-win64-lgpl-shared.zip`
  (~75 MB zip — earlier "~30 MB" estimate corrected). A dated autobuild tag is immutable; BtbN retention
  keeps the last 14 daily builds + each month-end build for 2 years, so a cold cache after retention
  expiry 404s — a logged, recoverable failure (the seam throws; the encoder step surfaces it). Once
  cached, the URL is never touched again. The pin is a single `const`, bumpable in one place — and must
  always stay on the **shared** variant (never `gpl`, `nonfree`, or static; see ai.md Licensing).
- **Check-then-pull order** — (1) PATH probe (the user's own install wins), (2) cached
  `%APPDATA%\ytLlive\tools\ffmpeg.exe`, (3) download + extract. Extract `ffmpeg.exe` **plus the
  `libav*.dll` family** (the shared build's bin/ folder; Windows resolves the DLLs from the exe's own
  directory) into a staging dir then move into place — a crash never leaves a corrupt or partial cache.
- **Seam** — `IFfmpegLocator.LocateAsync(CancellationToken)`: search dirs, tools dir, and the downloader
  (`Func<string, CancellationToken, Task<byte[]>>`) are constructor-injected with production defaults, so
  tests fake the network (feeding a real in-memory zip) and never touch disk outside a temp dir.

**New files (all in `Services/Encoder/`):**
- `IFfmpegLocator.cs` — the seam.
- `FfmpegLocator.cs` — the impl (PATH probe → cache → pull+extract exe + DLLs), failures logged via `AppLog`.
- `THIRD-PARTY-NOTICES.txt` (repo root) — the LGPL/BSD/MIT notices + source offer, copied to the build
  output and surfaced via the top-bar **About** button (`MainWindow` code-behind, opens the file in the
  OS viewer).

**Test plan:** the hermetic integration test drives the full decision ladder against a temp tools dir and
a fake downloader returning a real in-memory zip (`.../bin/ffmpeg.exe` entry): PATH hit wins without
downloading, cache hit skips the network, cold cache downloads → extracts → `ffmpeg.exe` lands in the
tools dir, and a second call serves the cache (downloader invoked exactly once). Focused unit tests:
**shared-build DLLs extract alongside the exe**, empty zip throws, missing entry throws, empty download
throws, downloader failure propagates, zero-byte cache is refreshed.

**Same-PR housekeeping:** requirement 2's stale binary facts corrected in this plan (~30 MB → ~75 MB zip;
"gyan.dev/BtB N" → BtbN LGPL-shared only, with the why); the "never do" licensing guardrails recorded in
`ai.md` so the reasoning survives.

**Out of scope (later ship steps):** the FFmpeg subprocess encoder (frames in via stdin, stderr health
parsing), RTMP push, WASAPI audio capture, the frame-pipeline wiring, health stats.

**Built (2026-08-10):** `IFfmpegLocator` + `FfmpegLocator` shipped in `Services/Encoder/`, pinned to the
**lgpl-shared** build `autobuild-2026-08-09-13-03` (extracts `ffmpeg.exe` + the `libav*.dll` family via a
staging dir). `THIRD-PARTY-NOTICES.txt` (repo root) ships to the build output and is surfaced by a new
top-bar **About** button; the "never do" licensing guardrails are recorded in `ai.md` — build **0 warnings**.
Tests: the hermetic `FfmpegLocatorTests` integration test (PATH → cache → download decision ladder with a
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**.

---

## TASK 5 — YouTube Live Stream Management

**Goal:** Create/bind broadcasts, monitor YouTube-side stream health — the v3 way.

### Design decisions (v3)

1. **One-click go-live** — `liveBroadcasts.insert` with `enableAutoStart=true`, `enableAutoStop=true`, `enableMonitorStream=false`, `selfDeclaredMadeForKids=false`, `latencyPreference=low`. No `transition(live)` call, no testing stage, no liveStarting polling. Encoder starts → YouTube brings it live by itself.
2. **Variable reusable stream** — `cdn.resolution=variable`, `cdn.frameRate=variable`, `isReusable=true`. Create once per channel, cache ingestion URL + stream name, reuse for every broadcast. Any quality tier works without recreation; auto step-down needs no API calls.
3. **Report-by-exception** — poll `liveStreams.list`; banner only on `healthStatus` warning/error issues (`configurationIssues[]`). Bottom strip = YouTube logo + green/red connection dot (clickable → opens the dialog).
4. **One dialog, three states** — `not connected` (sign-in) / `connected-offline` (all editable) / `live` (title + description + visibility editable; quality + account greyed out). Both entry points (Start Stream button + bottom strip) open it; prefilled from saved session profile.
5. **Live edits** — `liveBroadcasts.update` with part=`snippet,status` for title/description/privacy.
6. **End stream** — stop encoder → `transition(complete)`, with `enableAutoStop` as the safety net.
7. **Broadcast ID == Video ID** — one ID to track status, health, and the auto-created VOD (`recordFromStart` + `enableDvr`).

### Requirements:

1. **Broadcast creation** — title/description/privacy/scheduledStartTime via API, with the v3 flags above
2. **Reusable stream** — create once, cache + reuse; bind to broadcast
3. **Health monitoring** — poll `liveStreams.list` `healthStatus` + `configurationIssues[]`, surface banner only on warning/error
4. **Live chat** — poll `liveChat/messages`, render in right panel, support Super Chat + membership badges
5. **Error handling** — the YouTube error codes: `errorStreamInactive`, `invalidTransition`, `redundantTransition`, `liveStreamDeletionNotAllowed`, `liveStreamModificationNotAllowed`, `liveBroadcastBindingNotAllowed`

### Status: Not started

---

## TASK 6 — Layout Persistence (SQLite)

**Goal:** Scenes, sources, and asset bytes survive restarts; assets are always available.

### Design decisions

1. **SQLite database** (`Microsoft.Data.Sqlite`) at `%APPDATA%\ytLlive\ytLlive.db`; schema versioned
   via `PRAGMA user_version`.
2. **Assets live in the DB, not on disk** — `Asset` table stores image bytes (BLOB) keyed by a
   SHA-256 content hash (unique). Identical image content collapses to one row regardless of file
   name — the 1:M resource memory model, enforced by the database. No file paths; deleting the
   original file never breaks a scene.
3. **File-model save/open** — the active layout file is tracked (default is the AppData DB).
   **Save Layout As… / Open Layout…** switch the active file; auto-save writes to whatever is active.
4. **Auto-save (invisible)** — ~1.5s debounce on scene add/remove/reorder/rename/hide, source
   add/remove/reorder, and any source transform change; flush on window close.
5. **Schema** — `Scene` (Id, Name, IsHidden, IsChatScene, HasBackdrop, SortOrder), `Asset` (Id, Hash, Data,
   PixelWidth, PixelHeight), `Source` (Id, SceneId FK cascade, AssetId FK, Type, Name, IsEnabled,
   X/Y/Width/Height/Opacity, MonitorIndex, DeviceId, ClipShape, IsMirrored, SortOrder) —
   `user_version` **6** (v1 → v2 = `ALTER TABLE` adds the two webcam columns; v3 = singleton
   `Webcam` + per-scene `WebcamSceneConfig`; v4 = `WebcamSceneConfig.RectWidth`/`RectHeight` for the
   round-to-rect restore; v5 = `Source.IsBackdrop` + `Source.CaptureKey` for the live-capture
    backdrop; v6 = `Scene.HasBackdrop` — the backdrop is **Live-only by policy**
    (one-time backfill turns Starting/BRB/Chat/Ending off and drops their backdrop
    sources; `EnforceBackdropPolicy` re-normalizes every load). `WindowHandle` stays in-memory
    (per-session). Save = transactional rewrite; orphaned assets pruned.
6. **Startup** — load the active file; seed the five canonical scenes
   (Starting/Live/BRB/Chat/Ending, `SceneCatalog`) only when the DB is empty. The (+)
   button re-adds a missing canonical scene and is hidden once all five are present;
   adding beyond the five is rejected — work with less, never more.

### Status: ✅ Implemented

---

## Backlog (future versions)

- v0.2 — Recording to local file (recordings carry the branding flash — see TASK 3 / `ai.md` Monetization)
- v0.3 — Stream scheduling
- v0.4 — Multi-destination restreaming
- v0.5 — Stream clipping