LlamaCasty/TASKS/task-03-capture-pipeline.md

# TASK 3 — Capture Pipeline (Scenes/Sources)

> Catalog: [`TASKS.md`](../TASKS.md) — status and requirements live here.


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

### Status: 🔶 In progress — 27 of 30 items done (1 excluded: background removal); items 16, 17, 20 open

1. ✅ **Milestone 1 — webcam** — MediaCapture (WinRT SDK projection) with device enumeration, CPU-first frame source, refcounted `CameraManager`, picker dialog, clip shapes (Traditional + Round) + mirror, 480×270 default placement — schema v2
2. ✅ **Schema v3 (Ship Branch A)** — multi-scene webcam (singleton `Webcam` + per-scene `WebcamSceneConfig`), right-click border/context menu, static OBS-style borders, 50%-per-dimension webcam size cap, device-swap (`ReleaseAllAsync`) — 25 tests passing
3. ✅ **Schema v4** — round→rect restore persisted (`WebcamSceneConfig.RectWidth`/`RectHeight`) + one-time legacy-square 16:9 heal on load
4. ✅ **Screen backdrop (ship task #1, schema v5)** — live desktop/game capture as a permanent, non-deletable bottom layer (`Source.IsBackdrop`), 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
5. ✅ **Schema v6 — backdrop Live-only by policy** — `Scene.HasBackdrop`, 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
6. ✅ **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) — 62 tests passing
7. ✅ **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` — 65 tests passing
8. ✅ **Chat scene webcam size cap** — 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
9. ✅ **"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…"
10. ✅ **Webcam resource validation + first-frame proof** — `MediaCaptureFrameSource` validates post-init (VideoDeviceId match, stream properties ≥1, `reader.StartAsync()` status read + throws on non-Success); subscribes `capture.Failed` + `CameraStreamStateChanged` → `SourceFailed` event on the seam; fallback ladder (VideoPreview → VideoRecord). `CameraManager.AcquireAsync` requires first-frame proof (4s timeout): returns true only after a real frame arrives — silent empty box impossible. `MainViewModel` subscribes `CameraFailed` → red `WebcamError` chip in preview + MessageBox names suspect apps (`CameraConflictProbe`). 19041 SDK projection gaps: `Exclusive`/`DeviceLost` not projected; `CameraStreamState.Failed` compared by `(int)2`. 81 tests passing
11. ✅ **Scenes/sources UI** — add/reorder/rename, image + background overlays with move/resize/opacity/reuse
12. ✅ **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). **Post-test follow-up (2026-08-13, game audio bar branch):** the **game audio bar** (desktop/game, a mirror of the mic bar: meter + mute + volume) is **overlaid at the bottom of the preview window** (bottom-center dark chip — monitoring UI only, never on the live output) and appears only while a **full-screen game is producing sound** in the preview (`IGameAudioDetector` seam + default `GameAudioDetector` polling `IFullScreenDetector` + the live loopback level, floor 0.5%, into a pure `GameAudioHysteresis`: SHOW after ~500ms of fullscreen+sound, HIDE ~1s after leaving fullscreen, **silence never hides an active bar**; the VM polls it on a 250ms `DispatcherTimer`); **capture now runs for the app's lifetime** (mixer started once at startup via `StartMicCaptureAsync`, disposed in `Shutdown` — not go-live) so the meters preview live; the **MIC label became a button with a status dot** (`Models/MicStatus`: green = connected via the source `Started` event, yellow = mic problem, red = no device); picking a mic takes effect immediately (`AudioMixer.RestartMic`, loopback keeps running); fixed a latent `?.Invoke(meter.Push(...))` short-circuit that skipped the meter update when nothing was subscribed. **Round 2 (2026-08-13):** the meters were dead on a flat scale (real speech/game RMS is ~0.01..0.1 linear) — the raw level is now mapped via `AudioLevelMeter.ToDisplay` (−60..0 dBFS spread across 0..1) so typical input reads ~1/3..2/3 of the bar at default volume. 169 tests passing, 0 warnings. **Round 3 (2026-08-13):** the mic bar gained a **mic mute icon** (a microphone glyph in the speaker's 16px style, red + slash when muted) between the meter and the speaker — both mutes adjacent with spacing between them, same `ToggleMicMuteCommand`; and the top-center LIVE badge became an **always-visible REC sign** — dark gray dot + dim "REC" offline, bright red (#e94560) + "REC" + elapsed while live, **darker red (#8f1f1f)** when live with a **private** stream (driven by the dialog's chosen visibility) — `RecDotBrush`/`RecTextBrush`/`RecDotOpacity`/`IsLivePrivate`, pulsing while live. **Queued:** task 22 (voice filters). Voice-filter note: the meter's `ToDisplay` input is the pre-filter mic level; when filters land they must apply BEFORE the meter/encoder mix
13. ✅ 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)
14. ✅ **Social bar v2 (six-slot dialog, sign-in gate, real logos)** — global bar layer (never a Source, no sources-list row), content-sized, centered, GREEN glow when ON, top/bottom snap-drag (default BOTTOM, persisted `SocialBarPosition`; drag clamps to 0/1040, tie→bottom). Footer Social button gets a state dot (green=ON). Dialog "Social Media Site Promotion" (`SocialsDialog` + `ViewModels/SocialsDialogViewModel`, WPF-free + injected `ISocialValidator`/sign-in/sign-out fakes): ON/OFF bar switch (`SocialsConfig.BarEnabled`, schema v8), 6 fixed slots — row 1 always YouTube (signed-in → channel handle; signed-out → sign-in gate → OAuth; delete → confirm sign-out, mirrors `StopStream`), row 2 free, rows 3-6 lock icons on freemium (Premium seam: all six). Validation: `DetectService` (URL domain / fediverse `@user@domain` / bare→Website) → async `ISocialValidator` on confirm/Save; valid snaps to text + real service logo (bundled SVG path data via `LogoDataFor`, Simple Icons CC0 — initials badges gone); invalid → red do-not, stays editable, Save blocked. LCR justify dropped (`BarJustify` unread), per-scene toggle dropped (`Scene.HasSocialBar` back-compat). **Post-test fixes (2026-08-12):** footer label "Socials" (not "Social"); fediverse `@user@domain` validates — the full handle is the identity end-to-end (`DetectService`/`CanonicalUrlFor`/`HttpSocialValidator` build `https://domain/@user`, no domain loss); **Cancel is a hard stop** — `ISocialValidator.LookupAsync` takes a `CancellationToken`, dialog VM owns a CTS, Cancel/X/Save abort in-flight lookups (HTTP request killed, canceled continuations never touch slot state), and `ConfirmEdit` skips re-submitting identical text (LostFocus on dismiss never re-fires a lookup). `HttpSocialValidator` now has real tests (fake `HttpMessageHandler`). 105 tests passing. **Post-test fixes (2026-08-12, round 2):** fediverse `@user@domain` no longer shows a generic chain — it resolves to the instance's actual software via nodeinfo (`/.well-known/nodeinfo` → `software.name`; `SocialService.Fediverse` enum member + `SocialEntry.FediverseSoftware` persisted in a new `SocialEntry.Software` column, schema migration by column-presence) and renders that software's bundled logo (`LogoDataForFediverse`: mastodon/peertube/pixelfed/misskey/lemmy/pleroma/firefish, generic fediverse honeycomb fallback). Dialog row-2 edit/trash icons were too dark — `IconButton` style gains `Foreground=#d0d0d0`; trash overrides `#e94560` (app red). 112 tests passing. **Post-test fixes (2026-08-12, round 3):** a fediverse handle whose identity domain is itself a redirect (e.g. YunoHost default-app subdomains — `@user@llamachile.tube` where the mastodon instance lives at `mastodon.llamachile.tube`) now still resolves its software: nodeinfo on the identity domain is SSO-blocked, so `HttpSocialValidator` follows the bare root `https://domain/` 302 to the real instance host and re-runs the nodeinfo lookup there.
15. ✅ **Window capture** — absorbed into the Screen picker (no separate source type); dedicated window-as-source work is pending
16. ❌ **Scene compositing (D3DImage/MediaElement)** — SUPERSEDED, permanently out (2026-09-01): the software output compositor (TASK 4 step 1) + the XAML preview ARE the design; a D3D11 swap stays a possibility behind the `VideoFrame` seam, not a feature
17. ☐ **Text source** — live text ("Starting soon", "Back in 5", handle, callout)
18. ✅ **Chat box** — YouTube live chat rendered *on* the stream so viewers read along in-video — `ChatBoxRenderer` (WPF FormattedText → VideoFrame), configurable font size/color/badges/timestamps/max-messages via Elements panel, schema v10, persisted across save/load
19. ❌ **Background removal (milestone 2)** — ONNX Runtime + DirectML, MediaPipe Selfie Segmentation — deliberately NOT in this build
20. ☐ **Alerts** — Super Chat / membership / subscribe pop-ins; build after the six; **free and ungated** (the stale "one paid feature" label predates the 2026-08-31 monetization reversal and is corrected 2026-09-01 — the paid swap is the branding flash ONLY; see Monetization in `ai.md`). **v1 IN** per the complete-v1 ruling. **Precursor — reward-event capture (2026-09-01):** Alerts render from the app's canonical `RewardEvent` feed (all 7 `liveChatMessage` reward types, persisted to SQLite + the session report — see TASK 10 → "Related work — monetization awareness"), so it consumes that already-built data rather than re-integrating `liveChatMessages`. That capture is the required prior milestone.
21. ✅ **Show Desktop toggle** — `Source.ShowDesktop` bool persisted in DB (schema migration + LayoutStore read/write). When checked, primary monitor captures regardless of fullscreen game state. Toggling off falls back to running game or releases to static placeholder. `ClearBackdropCaptureAsync` clears `CaptureKey` + `VideoImageSource` so static fallback renders. Toggle on Live backdrop context menu (IsCheckable MenuItem).
22. ✅ **Top bar — status light + avatar + Log In button** — red/green/pulsing ellipse (disconnected/connected/live). Avatar border visible only when connected, loads via `BitmapImage` code-behind. "Log In" button visible when disconnected, calls `StartStreamCommand` → GoLiveWindow. `ShowStartStream` now requires `IsConnected`.
23. ✅ **Chat preview — one-at-a-time mock messages** — `RunMockChatPreviewAsync`: simple async loop, displays `MockChatMessages[n]` via `Take(n+1)`, 1000ms between messages, wraps at end. `ChatPreviewEnabled` property on Source (default true). Stops on real messages, restarts on fade timer clear.
24. ✅ **All backdrops seeded + EnsureDefaultBackdrop** — Live, Chat, Ending backdrops added (ending-backdrop.jpg replaced). `EnsureDefaultBackdrop()` called on every scene switch. `SeedEndingBackdrop` replaces existing (not skip-if-exists). Chat scene no longer skipped.
25. ✅ **SceneCatalog fix** — Chat scene display name corrected to "Chat" (was "YouTube Chat" — that name belongs to the layer/SourceType.ChatBox, not the scene).
26. ✅ **Left panel spacing + context menu reorder** — HR margins matched, Row 4 changed from `*` to `Auto`. Context menu reordered: Border Thickness first, then Opacity, Color, Effect.
21. ✅ **Logo + richer in-app About (2026-08-13, queued → 2026-08-14 SHIPPED)** — the ytLlive wordmark in the top bar opens the About overlay (already wired); the About overlay is now the **creator hub**: the real logo (the "llama fortnite superman logo" from the creator's vault, copied to `Assets/llama-logo.png` — the creator's own art, no third-party license), plus **creator-hub links** — llama chile shop on YouTube (`MainViewModel.ChannelUrl`), Mastodon (`https://mastodon.llamachile.tube/@gramps`), **Buy me a coffee** (`https://buymeacoffee.com/llamachiley` — live), and **Unlock Premium** (greyed "coming soon" — the **billing** product URL is a tabled seam, `PremiumUrl`, until TASK 10 picks the subscription provider). A **Licenses & legal** button flips the About overlay to an in-app scrolling panel that loads the full `THIRD-PARTY-NOTICES.txt` text (`MainViewModel.ShowLicenses` reads the shipped file from the executable directory on first open; graceful "not found" fallback — **never the OS viewer, everything stays in-app**); "← Back to About" returns. The About overlay is also the in-app home of the notices — the top-bar About button that opened the file in the OS viewer was removed on 2026-08-13 for exactly this reason. Integration test (Good Dog Rule — ONE): `AboutHubTests.About_Opens_InApp_Licensing_Loads_Shipped_Notices` drives the real window + VM, asserting the hub opens, the link URLs are real, the licensing panel loads the shipped notices text (contains "Third-Party Notices" + "LGPL"), and back returns to the hub. 174 tests passing, 0 warnings
22. ✅ **Voice filters on the mic channel (2026-08-13 queued → SHIPPED 2026-08-14 inside TASK 9, the audio milestone)** — the standard four applied to the sound input path (before the meter/encoder mix): **bass boost, treble, noise suppression, compressor** (set decided with the creator 2026-08-13). Noise suppression = a **pure-C# noise gate** (creator chose over RNNoise / a second ffmpeg `afftdn` pipe, 2026-08-14 — KISS). Always-on — no UI knobs; the mic stays the creator's single audio control
27. ✅ **Webcam row gates on the app-wide identity (2026-08-24, TASK 26)** — the (+) menu's Webcam item greys out whenever a webcam exists **anywhere** (`CanAddWebcam` = `StagedScene != null && _webcam == null`; renamed from `CanAddWebcamToStagedScene` whose per-scene rule let a second picker run from a scene lacking the config), raised at both `_webcam` mutation sites (create / last-config removal) + scene staging + elements change. Creator's visual pass found it: minis/no-capture-rows/capture-controls all good. ONE integration test `WebcamMenuGateTests.CanAddWebcam_Gates_On_The_AppWide_Webcam_Identity` (real window + temp DB seeded with a webcam in Starting; asserts greyed while Live staged, re-enabled after `RemoveSourceCommand` clears the last config + the `Webcam` DB row). Stale map fixed in the same commit: ai.md's "empty-canvas right-click Show Webcam" claim dropped — that XAML never shipped (`ShowWebcamCommand`/`CanShowWebcamInStagedScene` are wired but unbound dead code, audit item). 224 tests (223 pass; the pre-existing AudioPipelineTests failure is unrelated)
28. ✅ **YouTube Chat layer: one-per-layout gate + legacy label heal (2026-08-24, TASK 27)** — same rule as TASK 26 applied to the chat layer: the (+) menu's YouTube Chat item greys out while any scene carries a ChatBox source (`CanAddYouTubeChat`, raised on staging + elements change; `AddSource` refuses a second), tooltip "One chat layer at a time — it's already in your stream". Plus the creator's label fix: layers added by commit `65641d8` were named "Chat"; LoadLayout now heals exactly that un-renamed default to "YouTube Chat" so the Layers row matches the (+) picklist (creator renames untouched, idempotent). ONE integration test `ChatLayerGateTests.LegacyChatName_Heals_And_CanAddYouTubeChat_Gates_On_The_Existing_Layer` (real window + temp DB with a legacy "Chat" row: healed on load + persisted on save, greyed cross-scene and in-scene, re-enabled after remove). 225 tests (224 pass; pre-existing AudioPipelineTests failure unrelated)
29. ✅ **Broadcast metadata pull-out + launch geometry (2026-08-24)** — creator ask: "a tab-pullout on the right side of the preview pane — white tab, YouTube-red label reading 'Text' — opening a form with all settable liveBroadcast fields; fields that can't be filled before launch greyed out; saving/updating remote content; field data saved and pre-loaded on app run". Shipped as specified with one correction: the API is the inverse of "more fields once live" for contentDetails (those lock in created/ready) — the pull-out carries the always-editable snippet/status set: Title, Description, Tags (csv), Visibility (private/unlisted/public), Made-for-Kids, plus read-only Scheduled Start. **Always visible** (creator revised same day from Live-only gating). White 30px tab, rotated red "Text", right edge vertically centered; click slides a dark 320px drawer left over the preview (200ms CubicEase). Every edit persists to Settings keys (`Broadcast.*`) immediately; **Update Broadcast** button calls the new `YouTubeStreamService.UpdateBroadcast` (PUT `liveBroadcasts?part=snippet,status`, echoes scheduledStartTime because update replaces the whole snippet part). Go Live prefills from the form and captures what was inserted (`CaptureGoLive`). The old un-persisted Default Stream Title/Description fields came OFF the App Settings overlay (replaced by the form); `DefaultStreamTitle/Description` VM properties deleted. **Launch geometry** (same unit): default 1920×1040, MinWidth 1366, MinHeight 768; `WindowStartupLocation=Manual` + window size/position persisted on close via `RestoreBounds` (maximized-safe), restored in ctor clamped to minimums and the primary work area (disconnected-secondary fallback). ONE integration test `BroadcastPullOutTests.Metadata_Persists_WindowRestores_Clamped_And_UpdatePatchesRemote`. 228 tests (227 pass; pre-existing AudioPipelineTests failure unrelated)
30. ✅ **Gear menu cleanup + Default Location for Recordings + single Start button (2026-08-29)** — **KISS: removed** Gear-menu `Save Layout`/`Save Layout As…`/`Open Layout…` (redundant with auto-save; multi-layout = OBS) + dead `SaveLayoutCommand`/`SaveLayoutAsCommand`/`OpenLayoutCommand` + `SaveLayoutAs()`/`OpenLayoutFile()` methods. **App Settings panel:** first real setting — `Default Location for Recordings` (configured folder via `ChooseRecordFolderCommand` + "Use Downloads" reset via `ResetRecordFolderCommand`, resolved path shown). Fallback chain: configured → `%USERPROFILE%\Downloads` → `MyVideos`. `StartRecordFile()` + `ChooseRecordFolder()` `InitialDirectory` updated to use the new fallback. **Single Start button:** `PrimaryButtonText`/`IsStreamingStart` + their `OnPropertyChanged` calls removed; button `Content="Start"` in XAML — pills are the intent surface, button is always just Start. `Choose Record Folder` fast-path kept in the button context menu. Monetization (About links/premium) deferred to a later task. ONE fallback test `DefaultRecordFolder_Falls_Back_To_Downloads`. build 0 warnings, 247 tests (2 known failures, pre-existing).

### 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. **Free and
   ungated** — paid = flash removal only (stale "one paid feature" corrected 2026-09-01). Consumes
   the canonical `RewardEvent` feed (reward-event capture, TASK 10 → related work).

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

### Source memory model (design decision)

1. A scene has resources. Resources can be shared across scenes.
2. A resource exists exactly once in memory, no matter how many scenes use it (a logo in five
   scenes = one loaded bitmap).
3. 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.
4. 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".
5. A webcam in two scenes = one capture session, two catalog entries.
6. Refcount by catalog size: the last usage removed → the resource is disposed and evicted.
7. 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**:
   1. 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)
   2. `MediaCaptureFrameSource` (CPU-first: `MemoryPreference = Cpu`, BGRA8 via `CreateFrameReaderAsync`), `MediaCaptureCameraEnumerator` (`DeviceInformation.FindAllAsync(DeviceClass.VideoCapture)`)
   3. `CameraManager`: refcounted by `DeviceId`, one shared `WriteableBitmap` app-wide, dispatcher-coalesced UI updates (~render rate, latest-frame drop), placeholder/`AppLog` + warning on failure
   4. `CameraPickerDialog` (mirror of `ReuseImageDialog`) — "Searching for cameras…" / list / "No cameras found" states
   5. 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
   6. Default placement 16:9 **480×270**, bottom-right, 32px margin; drag/resize/selection shared with Image sources
   7. **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
   8. **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):
   1. **Preview:** click-drag a source in the center panel to reposition it; resize via handles
   2. **Scenes list:** drag rows to reorder scenes
   3. **Sources list:** drag rows to reorder sources (this *is* the z-order) — implemented