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TASK 21 slice 2b: native-FPS pacing in MediaVideoSource (probe -> delay seam)

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- MediaVideoSource takes optional IFrameRateProbe? + Func<TimeSpan,CancellationToken,Task>? delay
  seams (default Task.Delay); probes FPS once in RunAsync, delays by 1/fps after each
  emitted frame. No probe/unknown fps -> no pacing (ffmpeg pipe backpressure throttles).
- Test: MediaVideoSource_PacesFramesByProbedFps (fake probe returns 1000fps + recording
  delay; one delay per frame ~= 1ms). Media tests 5/5, build 0 warnings.

Derivative reference: per-frame delay pacing of decoded output, standard in media playback.
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Llama Chile Shop
2026-08-31 19:47:38 -07:00
parent 8fa78423e6
commit a2219be198
5 changed files with 68 additions and 12 deletions
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TASKS.md
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@@ -1044,7 +1044,7 @@ The tasks below are ordered by dependency and risk. Each task builds on the prev
4. ✅ `MediaVideoSource` implements `IMediaFrameSource`: FFmpeg raw video decoder → `VideoFrame` pipeline — spawns ffmpeg `-f rawvideo -pix_fmt bgra`, drains the pipe via pure `RawVideoFrameReader` (`Services/RawVideoFrameReader.cs`), raises `FrameAvailable`/`Completed`; lifecycle is `StartAsync`/`StopAsync`; decode process behind `IDecodeProcess`/`FfmpegDecodeProcess` seam (binary-stdout mirror of `IEncoderProcess`). Shipped 2026-08-31; refactored onto `IMediaFrameSource` with this slice.
4b. ✅ Slice 2a — native-FPS probe seam: `FfmpegFrameRateParser` (pure, prefers `avg_frame_rate=` then `r_frame_rate=`, rational N/N/M, unknown→null) + `IFrameRateProbe`/`FfmpegFrameRateProbe` (derives sibling `ffprobe.exe` from the located ffmpeg dir, reuses the `IDecodeProcess` seam; null if ffprobe absent) + `FfmpegLocator.ProbeFileName` now also extracts `ffprobe.exe` from the pinned archive (conditional). Tests: `FfmpegFrameRateParserTests` (6 pure units + 1 probe integration via fake locator/process) + `FfmpegLocatorTests` still green — 15/15.
5. ✅ `IMediaFrameSource` + `MediaVideoSourceManager` (`Services/IMediaFrameSource.cs`, `Services/MediaVideoSourceManager.cs`): app-wide decode-session ownership refcounted by `MediaPath` with a `Func<string, IMediaFrameSource?>` factory seam; `AcquireAsync`/`ReleaseAsync`/`ReleaseAllAsync`/`GetLatestFrame`; coalesces frames onto the UI dispatcher onto a single shared `WriteableBitmap` per file (mirror of `ScreenCaptureManager`); `MediaFailed` + `PreviewBitmapChanged`. Unit tests + one integration test (bitmap share/coalesce) — `MediaVideoSourceManagerTests`, 5/5 pass.
6. 🔶 Native-FPS pacing — frames currently emit as fast as the pipe produces them; ffprobe FPS probe + per-frame pacing seam still open (slice 2).
6. ✅ Native-FPS pacing (slice 2b): `MediaVideoSource` takes optional `IFrameRateProbe?` + `Func<TimeSpan,CancellationToken,Task>? delay` seams, probes FPS once in `RunAsync`, and delays by 1/fps after each emitted frame; unknown/absent probe → no pacing. Test: `MediaVideoSource_PacesFramesByProbedFps` (fake probe + recording delay, one delay per frame ≈ 1ms).
7. ☐ Wire into `FramePump` resolver — `Source { Type: MediaSource }` → latest video frame — **resolver + preview routing + manager wired; session acquisition (start/stop on add/remove) still open (comes with the UI picker)**
8. ☐ Wire into `SceneCompositor` — render media source as an image element at its position/size
9. ☐ Loop control — `IsLooping` property, restart on end