# HANDOFF — Session State

## Branch / Commit State

**`main`**, working through TASK 21 (media source). Local commits ahead of
`origin/main` (not yet pushed — user pushes at agreed checkpoints):
- `a1d9751` — docs: ffmpeg decode-contract verification recipe + WSL CLR boundary
- `8f49010` — TASK 21 Increment B: FFmpeg rawvideo video decoder -> VideoFrame
- `f89b9f9` — docs: default-device audio assumption (README + startup log)
- `e8ff4df` — TASK 22: global audio sync offset (positive delay at the mixer out)

Prior milestones pushed through `origin/main`: TASK 31 (`3bf053a..670fe3a`), plus
the full refactor series (Commit F `3107f92`, Commit G `85893ea`).

## What's In Flight

**TASK 21 (media source) — all headless-testable decoder/mechanism slices shipped (slice 1 + 2a + 2b + 3); the remaining UI-picker (acquisition) slice is handed off below — it is a GUI feature to build + verify on native Windows.**

Increment A (the `Source` model: `MediaSourceType`, `SourceType.MediaSource`,
`MediaPath`/`MediaIsLooping`/`MediaVolume`/`MediaPlaybackState` + LayoutStore
persistence) and Increment B (the decoder `MediaVideoSource`) shipped earlier.

This session:
- Refactored `Services/MediaVideoSource.cs` onto the new
  `Services/IMediaFrameSource.cs` (`Key`, `FrameAvailable`, `Completed`,
  `StartAsync`/`StopAsync`; `Start`→`StartAsync`, `FrameReady`→`FrameAvailable`)
  — behavior preserved, `MediaVideoSourceTests` updated and passing.
- Added `Services/MediaVideoSourceManager.cs` — app-wide decode-session
  ownership refcounted by `MediaPath`, `Func<string, IMediaFrameSource?>` factory
  seam, `AcquireAsync`/`ReleaseAsync`/`ReleaseAllAsync`/`GetLatestFrame`, frames
  coalesced onto the UI dispatcher onto one shared `WriteableBitmap` per file,
  `MediaFailed` + `PreviewBitmapChanged`. Structural mirror of `ScreenCaptureManager`.
- Added `ytLive.Tests/MediaVideoSourceManagerTests.cs` (5 unit + 1 integration:
  single shared bitmap, coalesce-to-latest). **Verified: all 10 media tests pass
  (5 manager + 3 reader + 1 decoder integration + 1), build 0 warnings.**

Slice 1 step 4 (wire-in) shipped: `_mediaManager` wired in the core ctor
(`path => new MediaVideoSource(path, 1920, 1080, new FfmpegLocator(), new FfmpegDecodeProcess())`,
dispatched preview), `OnMediaPreviewBitmapChanged` sets `VideoImageSource` on every
`IsMediaSource` with a matching `MediaPath`, a `Source { IsMediaSource, MediaPath }`
case in `ResolveOutputFrame` feeds `_mediaManager.GetLatestFrame`, `Source.DisplaySource`
routes `VideoImageSource` for `MediaSource`, and the manager is disposed on shutdown.
Lives in the new `ViewModels/MainViewModel.Media.cs` partial. **Verified: 14/14
media + DisplaySource tests pass, build 0 warnings.**

Next (slice 1 step 4's remaining open end): no session acquisition yet — nothing
`AcquireAsync`s a media path, so no frames flow until the UI picker (a later slice)
starts a session on add and releases on remove.

Slice 2a shipped: the native-FPS **probe seam** (not yet wired into pacing).
`Services/FfmpegFrameRateParser.cs` (pure — prefers `avg_frame_rate=` then
`r_frame_rate=`, rational `N`/`N/M`, unknown→null), `Services/FrameRateProbe.cs`
(`IFrameRateProbe` + `FfmpegFrameRateProbe` — derives sibling `ffprobe.exe` from
the located ffmpeg dir, reuses the `IDecodeProcess` seam for the ffprobe
subprocess text, null if ffprobe absent), and `FfmpegLocator.ProbeFileName`
(`ffprobe.exe`) + conditional extraction alongside ffmpeg.exe. Tests:
`ytLive.Tests/FfmpegFrameRateParserTests.cs` (6 pure units + 1 probe integration
via fake locator/process); `FfmpegLocatorTests` still green — 15/15 pass, build
0 warnings. Slice 2b shipped too: `MediaVideoSource` now takes optional
`IFrameRateProbe?` + `Func<TimeSpan,CancellationToken,Task>? delay` seams,
probes FPS once in `RunAsync`, and paces each emitted frame by 1/fps (unknown/
absent probe → no pacing). New test `MediaVideoSource_PacesFramesByProbedFps`
(fake probe + recording delay, one delay per frame ≈1ms). Media tests 5/5,
build 0 warnings.

Next (slice 3): loop control — SHIPPED. `MediaVideoSource` takes a
`Func<IDecodeProcess>` process factory (a single `Process` can't be re-`Start()`ed,
so each loop pass creates a fresh decoder) and wraps the decode in a
`do…while (Looping)` restart, keyed on the new `IMediaFrameSource.Looping` flag;
Production wiring in `MainViewModel` (media factory) now passes the factory AND
`FfmpegFrameRateProbe` (closing the slice-2b gap where production had no probe →
no pacing). Loop test `MediaVideoSource_LoopsUntilLoopDisabled` (single frame
re-emits, `Completed` only when loop cleared) — media tests 12/12 (6 source + 6
manager), build 0 warnings. Open: wiring `Source.MediaIsLooping` into
`IMediaFrameSource.Looping` needs a manager-level per-path loop provider — lands
with the UI picker (acquisition) slice.

**Landmine:** a stale `testhost` can lock `ytLive.Tests`'s `ytLive.dll` and break
`dotnet build` of the test project — kill it first (`cmd.exe /c "taskkill /PID N /F"`)
on MSB3027. Full-suite vstest hangs headless (RealAppHost/WASAPI) — only filtered
pure tests run in WSL; user verifies the GUI suites on native Windows PowerShell
(which may also hang if WASAPI startup blocks — pre-existing, not this change).

## Next

1. **(Handed off) UI picker slice** — the last TASK 21 work unit. GUI feature; build + verify natively on Windows.
2. Await user push checkpoint for the pending commits (TASK 22 + TASK 21 slices below).

## UI picker slice — handoff spec (2026-08-31)

Nothing `AcquireAsync`s a media path yet, so **no frames flow in a running app** —
the decoder, manager, pacing, and loop mechanism are all shipped and unit-tested,
but a media Source has no way to start a session. Deliverables, in order:

1. **File picker + add/remove commands** (mirror `MainViewModel.Background.cs`/`Trax.cs`
   `OpenFileDialog` usage — see `MainViewModel.Trax.cs:68`). A "Media" source action
   opens an `OpenFileDialog` filtered to video (mp4/mov/avi); on OK set `Source.MediaPath`,
   add to scene, and **`AcquireAsync(MediaPath)`**; on remove **`ReleaseAllAsync(MediaPath)`**.
   On `StagedScene` layout loads/teardown, call `ReleaseAllAsync` for every media path no
   longer present (and acquire new ones) so sessions track the live scene.
2. **Wire `Source.MediaIsLooping` → `IMediaFrameSource.Looping`** — needs a manager-level
   per-**path** loop provider (see ambiguity: sessions are refcounted per `MediaPath` and
   shared across scenes, but `MediaIsLooping` is per-`Source`; a scene set → the path's
   session `Looping` = any live reference has it on, so one scene turning it on while
   another shares the file is shared behaviour — pick a rule and record it).
3. **Loop toggle + volume slider** in the source context menu / inspector (TASKS 11/10).
4. `MediaVolume`/`MediaPlaybackState` wiring (audio path for media is future work).

**Design notes to preserve:** `ResolveOutputFrame` reads `_mediaManager.GetLatestFrame(MediaPath)`;
`OnMediaPreviewBitmapChanged` adopts the shared `WriteableBitmap` per path; `MediaFailed` →
`OnMediaFailed` (currently `Debug.WriteLine`, surface in UI). Composer scales any frame size.
Tmpl: the real-ffmpeg decode/loop/restart path is only exercised natively on Windows — first
GUI smoke test should add a short mp4, confirm it plays and previews, then crash further.

## The directive (2026-08-31, user)

Rewrite the project into functional components to aid AI retrieval —
`Services/ChatOverlayLayer.cs` / `SceneGraph.cs` style (owner-state extraction),
not line-count chasing. Audio assumption is now an explicit contract (README
"Audio Assumption"): the app uses system defaults, never fights Windows device
locking, and does not debug user audio issues — OS's problem, not ours.