MindAttic.Capture

Programmatic video capture and screenshots for MindAttic games and apps: trailer footage, store screenshots, devlog clips and bug-repro video, triggered from code or recorded by hand from the tray.

Why

• Get trailer, store-shot and devlog footage as a by-product of playing, not a separate recording session.
• Catch the moment: a replay saved on "boss-death" includes the seconds before it happened.
• Record any app with no code changes, or wire one line into a WPF app or a Unity game.
• Leave a long run unattended: a shut-off valve stops capture before the disk or memory runs out.
• Keep shipped builds clean: capture stays out of Release builds.

Features

• Rolling lossless (FFV1) or hardware HEVC tape that clips, replays and whole sessions are cut from.
• Screenshots, clips, replays and sessions from code, trigger rules, hotkeys, a localhost API and a JavaScript bridge.
• A system-tray recorder (capture-tray.exe) for hand recording: screens, any open app, or a dragged area.
• The -capture command-line flag, understood by every wired MindAttic GUI app.
• Sidecar JSON per file and a session manifest, with markers written as video chapters.
• Crash recovery: finished segments stay on disk and are exported on the next launch or by capture recover.

 your app / game                     MindAttic.Capture                               R:\MindAttic\Capture\
 ───────────────                     ─────────────────                               ─────────────────────
 Capture.Raise("critical-hit") ──>  trigger rules ──> replay / clip / screenshot ──>  {RepoName}\{RepoName}_{timestamp}.{ext}
 -capture video / screen N     ──>  session tape (1 s segments, lossless FFV1)  ──>    {RepoName}_{start}.mkv + .mp4
 ScreenshotAsync / ClipAsync   ──>  host adapter (desktop, WPF, WebView2, Unity)       *.png  *.mp4  *.json sidecars
                                                                                        session.json manifest

Package	Target	What it does
MindAttic.Capture	netstandard2.1; net10.0	Core: API, -capture parsing, trigger rules, rolling tape, exports, sidecars, session manifest. No third-party dependencies (Unity consumes the netstandard2.1 build).
MindAttic.Capture.Windows	net10.0-windows10.0.19041	Desktop capture: Windows Graphics Capture for windows, Desktop Duplication / GDI for monitors and regions, WASAPI audio, global hotkeys, DI.
MindAttic.Capture.Wpf	net10.0-windows10.0.19041	CaptureWpf.Init(this, e.Args): records the main window at native size, export on exit.
MindAttic.Capture.WebView2	net10.0-windows10.0.19041	window.mindattic.capture JavaScript bridge for any WebView2.
capture.exe (agent)	net10.0-windows10.0.19041	CLI and localhost API: record any app with no code changes, serve browser pages and scripts, finalize and recover sessions.
com.mindattic.capture (Unity)	Unity 6, Windows	Game-view capture via GPU readback, game audio, Play Mode menu; reads -capture from the player command line.

The agent and the tray recorder are installed together (see Install and deploy below). With the agent installed, apps hand their session export to it and exit immediately.

Install and deploy

Run run.ps1 from the repo root. It installs the agent (capture.exe) and tray recorder (capture-tray.exe) only when the source is newer than the installed copy, so it is cheap to run every time.

.\run.ps1               # install if stale
.\run.ps1 -Force        # install even if the installed copy looks current
.\run.ps1 -Launch       # also start the tray recorder

• Binaries stay in %LOCALAPPDATA%\MindAttic\Capture\bin, where DesktopCapture finds the agent for other apps.
• It writes C:\Apps\MindAttic.Capture\run.bat (under %LOCALAPPDATA%\Programs when C:\Apps is missing). The desktop shortcut MindAttic Capture opens that file, which asks first: 1) Deploy & Run reinstalls (-Force -Launch) and starts the tray recorder; 2) Run just starts the installed tray recorder. .\run.ps1 -LauncherOnly rewrites the launcher and shortcut without installing anything.
• tools\install.ps1 is the underlying installer; add -AddToPath to get capture on PATH everywhere. A file in use is renamed to *.old and replaced, so installing is safe while an export runs.

Tray recorder

capture-tray.exe sits in the system tray and records without any code changes. The icon turns red with the elapsed time while recording, and a left-click stops it.

• Record Screen and Screenshot per monitor; Record App and Screenshot App pick any open window and capture it at its own size, filed under the app's name.
• Record Area and Screenshot Area dim every monitor and let you drag a rectangle: grips move and resize it, arrow keys nudge it (Shift for 10 px), aspect-ratio buttons snap it (16:9, 9:16, 1:1, and more), Enter confirms, Esc cancels. A red frame marks the area while it records.
• The selector toolbar chooses video files (lossless + MP4, lossless only, MP4 only, GIF) and image format (PNG, JPG). Areas can be saved as named regions, starting with a 9:16 "YouTube Short".
• Hotkeys: Ctrl+Alt+Shift+R starts and stops recording whatever is armed, Ctrl+Alt+Shift+S takes a screenshot. Both are rebindable in Settings.
• Finished captures are listed with their sizes in a notification; Open Last Capture and Show Last Capture in Folder are in the menu. Exit waits for a recording that is starting or saving.
• Settings (capture folder, default formats, start with Windows, hotkeys) and saved regions live in %LOCALAPPDATA%\MindAttic\Capture\tray.json.

Video is encoded by ffmpeg (choco install ffmpeg, or put ffmpeg.exe next to the app). Hardware encoders (NVENC → QuickSync → AMF) are probed automatically, with a software fallback.

How it works

Everything video comes from one tape: a recorder writing 1-second segments to {root}\.staging\. A recording, clip, replay or session is just a time range cut from the tape. Starting a recording is instant, and SaveReplay(before, after) can include footage from before the event. The tape is lossless FFV1 (TapeQuality.Lossless) or hardware HEVC (HighQuality). Exports produce a .mkv master plus, depending on the preset, an H.264 .mp4 that imports into any editor, WebM, GIF or animated WebP, and a thumbnail.

The -capture flag

Every MindAttic GUI app wired to MindAttic.Capture understands the same flag:

Game.exe -capture video                 # film from start to exit at the app's native resolution
Game.exe -capture screen 5              # a PNG every 5 seconds until exit (also 500ms, 10s, 1m)
Game.exe -capture video screen 5        # both
Game.exe -demo -capture video hq        # hardware HEVC tape (~0.2 GB/min) instead of lossless
Game.exe -capture video 8h              # stop after 8 hours (the shut-off valve can stop it sooner)
Game.exe -capture                       # same as -capture video
Game.exe -capture video -capture-config capture.json   # explicitly opt into settings/rules from a file

Capture is off unless the -capture flag is literally on the command line: there is no environment variable and no project config auto-loaded on launch, so a plain launch is always a plain launch. -capture-config path.json is the one way to bring in settings or trigger rules, and it is opt-in — you have to pass it yourself.

-capture followed by anything that isn't a capture word (for example an app's own -capture <folder>) is left alone. -demo and other flags belong to the app: capture only records what runs.

When the app closes, the session goes to R:\MindAttic\Capture\{RepoName}\{RepoName}_{session start}.mkv and .mp4, alongside every screenshot, clip and replay its events triggered. If capture.exe is installed, the export runs in a detached process so the app exits immediately. If the app crashes, a job object stops ffmpeg, the finished segments stay on disk, and the next launch (or capture recover) exports them as session-recovered.

If R: is missing, output falls back to %USERPROFILE%\Videos\MindAttic with a warning.

The shut-off valve

A long run can't fill the disk or exhaust memory. While capture runs, the engine polls the machine every 5 s. The first limit crossed stops capture and exports everything recorded so far, exactly as if the app had closed. The app keeps running, and nothing is deleted.

Limit (limits in capture.json)	Default	Why
minFreeDiskGB	50	output (and staging) drive nearly full
minFreeMemoryMB	2048	the machine is running out of RAM
maxEncoderMemoryMB	4096	frames are backing up inside ffmpeg (the drive or CPU can't keep up)
maxEncoderLagSeconds	60	the encoder is that far behind real time
maxDuration	off	-capture video 8h, or "maxDuration": "8h"

Set a limit to 0 to turn it off, or "enabled": false to turn off all the resource limits; a duration cap (-capture video 8h or "maxDuration") still applies. Flags on the command line win over the config file. pollEvery changes the interval. Every poll is appended to {RepoName}_{start}.stats.csv. That file records free disk, available RAM, CPU, app and encoder memory, encoder lag, tape time, frames written and dropped, and the drive's write rate. The engine log goes to {RepoName}_{start}.log, with a status line each minute. The session manifest records the lowest and highest values seen, plus stoppedBy when the valve closed.

Quick start

WPF app (one line in App.OnStartup, before showing the main window):

CaptureWpf.Init(this, e.Args);   // -capture video / -capture screen N; capture.json beside the exe for rules

The app's project needs net10.0-windows10.0.19041.0 (or later) and MINDATTIC_CAPTURE in DefineConstants for Capture.Raise hooks. Automata is the worked example.

Unity game: add to Packages/manifest.json "com.mindattic.capture": "file:../../MindAttic.Capture/unity/com.mindattic.capture". Players then honor -capture video / -capture screen 5 and nothing else — there is no project config auto-loaded from StreamingAssets, so a plain launch never has capture silently on or off by surprise; in the editor use MindAttic ▸ Capture to record Play Mode. Game code raises events with CaptureUnity.Raise("battle-complete"); to bring in rules, pass -capture-config path.json explicitly.

Websites: C:\Apps\MindAttic.Browser\MindAttic.Browser.exe <url | site folder> -capture video. Capture always uses this deployed copy of MindAttic.Browser (capture run --url included); deploy or refresh it with that repo's run.ps1. A folder is served at https://<folder>.local/, and its captures are named after the folder (mindattic.com\mindattic.com_<timestamp>.mkv) or, for generic folders like dist or wwwroot, after the repository. A URL's captures are named after its host. Pages (in the browser, any WebView2 with the bridge, or plain browsers with capture serve) call:

mindattic.capture.raise('critical-hit', { damage: 912 });
await mindattic.capture.screenshot('victory');
await mindattic.capture.replay(15, 5, 'boss-death');

Windows app (in-process, any UI framework):

await using var capture = await DesktopCapture.StartAsync(CaptureTarget.CurrentApp, args,
    o => { o.AppName = "GridGame"; o.ReplayArmed = true; });

// anywhere in game/app code (compiled out when MINDATTIC_CAPTURE is not defined):
Capture.Raise("critical-hit", new CaptureData { ["damage"] = 912 });
Capture.Marker("boss-phase-2");
Capture.Screenshot("victory");

// or the instance API:
var shot   = await capture.Engine.ScreenshotAsync("store-shot");
var clip   = await capture.Engine.ClipAsync(TimeSpan.FromSeconds(10), "devlog", new() { Preset = CapturePreset.Devlog });
var replay = await capture.Engine.SaveReplayAsync(TimeSpan.FromSeconds(15), TimeSpan.FromSeconds(5), "boss-death");
capture.Engine.Triggers.On("boss-death").Replay(TimeSpan.FromSeconds(15), TimeSpan.FromSeconds(5)).Cooldown(TimeSpan.FromSeconds(30));

Any app, no code changes (agent):

capture run -- Game.exe -demo                  # record the app's window from launch to exit
capture run --window "Notepad" -- notepad.exe  # launcher stubs: name the real window
capture run --url http://localhost:5173        # record a web app in the deployed MindAttic Browser
capture shot --region 0,0,1920,1080 --format png
capture record --monitor 0 --duration 30s --preset devlog
capture replay --window "GridGame" --length 30s   # Enter or `capture save` saves the last 30 s
capture serve --window "Tutor"                    # localhost API for browser pages and scripts
capture raise critical-hit damage=900              # send an event to `capture serve`
capture recover R:\MindAttic\Capture             # export sessions left by crashed apps

Targets: --monitor N, --region x,y,w,h, --window "title", --hwnd 0x1234, --process name.

capture.json

Placed beside the exe (picked up automatically), or passed with -capture-config / --config:

{
  "enabled": true,
  "outputRoot": "R:\\Recording",
  "fileTemplate": "{app}_{timestamp}",
  "tapeQuality": "Lossless",
  "audio": "App",
  "replay": { "armed": true, "seconds": 30 },
  "rules": [
    { "on": "critical-hit", "action": "replay", "before": "5s", "after": "2s",
      "where": { "damage": ">=500" }, "debounce": "1s", "maxPerSession": 25 },
    { "on": "battle-complete", "action": "screenshot", "tag": "victory", "cooldown": "10s" },
    { "on": "boss-death", "action": "replay", "before": "15s", "after": "5s", "preset": "Trailer" },
    { "on": "battle-*", "action": "marker" }
  ],
  "hotkeys": { "F9": "screenshot", "F10": "toggle-recording", "F11": "save-replay" },
  "diskWarnGB": 500,
  "limits": { "minFreeDiskGB": 50, "minFreeMemoryMB": 2048, "maxEncoderMemoryMB": 4096, "maxEncoderLagSeconds": 60, "maxDuration": "8h" },
  "postCapture": [ { "on": "replay", "run": "pwsh -File notify.ps1 \"{path}\"" } ]
}

• enabled: (default true) false makes every capture call a no-op. Only takes effect via an explicitly-loaded file (-capture-config path.json) — there is no auto-loaded project config and no environment variable, so this never turns capture off behind your back; an explicit -capture ... on the same command line always wins over it anyway.
• Actions: screenshot, replay, clip, marker, start-recording, stop-recording, toggle-recording.
• Rule controls: where, cooldown, debounce, maxPerSession, enabled, preset, format.
• Presets:
  • Trailer: lossless master + high-quality MP4
  • Lossless
  • Devlog: MP4, 1080p max
  • BugReport: 720p30 MP4
  • Session
• Disk usage: nothing is ever deleted automatically. diskWarnGB only warns.

Localhost API (capture serve)

• Endpoint: http://127.0.0.1:47800/.
• Who can call it:
  • Browser pages on localhost/127.0.0.1 origins.
  • Other origins added with --allow-origin.
  • Non-browser clients that send the X-Capture-Token header from %LOCALAPPDATA%\MindAttic\Capture\agent.json.
• Operations: POST /raise {event, data}, /marker, /screenshot, /clip {seconds}, /replay {before, after}, /record/start|stop|pause|resume, GET /status.
• WebSocket: /ws accepts the same operations as {op, ...} messages.
• Commands: the API can never run commands; postCapture only comes from config files.

Output

Everything goes to R:\MindAttic\Capture\{RepoName}\. Each file name starts with the project name, so a file copied elsewhere still says what it shows, followed by ISO 8601 local time with : replaced by . (Windows file names cannot contain :):

R:\MindAttic\Capture\UnitySolarSystem\
  UnitySolarSystem_2026-10-11T14.38.02.625.session.json   session manifest: app, version, events, markers, captures, diagnostics
  UnitySolarSystem_2026-10-11T14.38.02.625.mkv / .mp4 / .thumb.jpg / .mkv.json   the -capture video session (named by its start)
  UnitySolarSystem_2026-10-11T14.38.03.577.png / .png.json   a screenshot and its sidecar
  UnitySolarSystem_2026-10-11T14.39.12.004.mkv / .mp4        a replay, clip or recording

tools\prefix-existing-captures.ps1 renames captures made before the prefix (and fixes the names inside their manifests). It only renames, skips files still in use, and is safe to re-run.

{RepoName} is the git repository the app runs from (an app in bin\Debug, a Unity project, a local site folder), so projects that share a product name (GridGame, GridGame2025, GridGame2026) still get separate folders. Unity players carry it from the build. Outside a repo it falls back to the app name. If R: is missing, output goes to %USERPROFILE%\Videos\MindAttic\Capture with a warning. fileTemplate can change the names (tokens {timestamp} {date} {time} {session} {tag} {index} {kind} {app}).

Each sidecar records:

• kind, the tag (e.g. the tour stop or event name), app, build version and session
• host, timestamp and the trigger that fired
• tape range, with markers as offsets
• your custom key/values

Markers are also written into exported video as chapters.

Production builds

Capture is a development tool and stays out of shipped builds:

• .NET apps: reference the packages only outside Release. Automata is the example:

  <ItemGroup Condition="'$(Configuration)' != 'Release'">
    <PackageReference Include="MindAttic.Capture.Wpf" Version="1.0.0" />
  </ItemGroup>
  

  The packages define MINDATTIC_CAPTURE, so wrap the init call and hooks in #if MINDATTIC_CAPTURE. Release builds then contain no capture code at all. The packages come from the workspace feed C:\LocalNuGet (refresh with dotnet pack src\<project> -c Release -o C:\LocalNuGet).
• Unity:
  • Capture runs in the editor, in development builds, and in players built with MindAttic ▸ Capture ▸ Build Windows Player (Capture Enabled) (adds the MINDATTIC_CAPTURE define, output Builds/Capture/).
  • Normal production players ignore -capture (one log line) and never start ffmpeg.
  • Unity projects reference the package by path (file:../../MindAttic.Capture/unity/com.mindattic.capture), which needs this repo checked out next to them, the same as any sibling-repo dependency here. Once the repo is pushed it can be switched to https://github.com/mindattic/MindAttic.Capture.git?path=/unity/com.mindattic.capture#<tag> if you prefer pinned versions.
  • After changing the core, run tools\update-unity-plugin.ps1.

Limits worth knowing

• Lossless is big. FFV1 is roughly 1–7 GB per minute depending on resolution (a 5120x1440 desktop measured about 7 GB/min). Use -capture=hq for long sessions.
• Window capture size. It uses the window's size when capture starts; later resizes are cropped or padded.
• Windows 10 border. Windows 10 shows a yellow capture border (Windows 11 doesn't).
• H.264 width. Hardware H.264 is limited to 4096 px wide; wider MP4s use x264.
• Audio. "App" audio is currently the whole-system mix (WASAPI loopback). Per-process audio capture is a later step. If the host can't create its audio tracks, the recording is made video-only instead of failing.
• ffmpeg licensing. The common Windows builds are GPL. That's fine as a separate exe for internal use. Public builds that bundle ffmpeg need an LGPL build or GPL compliance.

Development

dotnet build MindAttic.Capture.slnx
dotnet test  MindAttic.Capture.slnx      # engine and desktop tests need ffmpeg and an interactive desktop

Source layout: src\ holds the core, Windows, Wpf, WebView2, Agent and Tray projects; tests\ holds MindAttic.Capture.Tests and MindAttic.Capture.Windows.Tests; unity\ is the Unity package and js\ the JavaScript client. capture recover with no root also scans the fallback output folder.

Documentation

This README is also the home page of the published docs at https://mindattic.github.io/MindAttic.Capture/ (built by .github\workflows\docs.yml through the shared DocFX pipeline).

• User stories
• Agent instructions

License

No license file: all rights reserved.

Part of MindAttic — see more projects at github.com/mindattic.