iptvnator/docs/architecture/embedded-mpv-native.md

Embedded MPV Native Integration

This document explains how IPTVnator embeds MPV inside the Electron app, which files are source versus generated build output, and what must be true before the feature is safe to expose to users.

What To Commit

Source files for the embedded MPV integration:

• apps/electron-backend/build-embedded-mpv.js builds the native addon for the current Electron runtime.
• apps/electron-backend/native/binding.gyp defines the native addon build.
• apps/electron-backend/native/src/embedded_mpv.mm owns the macOS libmpv render integration.
• apps/electron-backend/src/app/services/embedded-mpv-native.service.ts owns Electron main-process session lifecycle and support detection.
• apps/electron-backend/src/app/events/embedded-mpv.events.ts registers the IPC contract.
• apps/electron-backend/src/app/api/main.preload.ts exposes the preload bridge to the renderer.
• libs/shared/interfaces/src/lib/embedded-mpv-session.interface.ts defines the shared session and audio-track contract.
• libs/ui/playback/src/lib/embedded-mpv-player/ owns the Angular UI and controls.

Generated native-addon build output:

• apps/electron-backend/native/build/

The build directory contains files such as Makefile, binding.Makefile, config.gypi, embedded_mpv.target.mk, gyp-mac-tool, embedded_mpv.node, .o, and .d files. These are generated by node-gyp and must not be committed. The repo .gitignore ignores this directory.

How It Is Embedded

The embedded player does not spawn the normal mpv application and does not use --wid window reparenting. IPTVnator loads libmpv through a native Node addon and renders MPV frames into an app-owned native macOS view.

The flow is:

1. Angular receives a ResolvedPortalPlayback payload and renders EmbeddedMpvPlayerComponent.
2. The component paints a loading state before requesting native startup work.
3. If available, the preload API asks the main process to prepare the embedded MPV addon. This loads embedded_mpv.node and its dylibs, but does not create a native view or MPV playback session.
4. The component asks the preload API to create an embedded MPV session with the current viewport bounds and initial volume.
5. The Electron preload forwards calls through IPC to the main process.
6. EmbeddedMpvNativeService owns sessions, polls snapshots, and emits session updates to the renderer.
7. The native addon creates an mpv_handle, configures vo=libmpv, disables MPV's own OSC/input handling, and creates an app-owned NSOpenGLView inside the Electron window content view.
8. The addon creates a mpv_render_context and uses MPV's render API to draw frames into the OpenGL surface.
9. Resize, scroll, and fullscreen changes are measured in Angular and sent back to the addon as native bounds so the NSView stays aligned with the Angular layout.
10. Playback controls remain IPTVnator-owned Angular UI. MPV receives commands only through the controlled IPC surface.

The renderer never gets direct native-module access. It can only call the preload contract:

• prepare native addon
• create session
• load playback
• set bounds
• play/pause
• seek
• set volume
• set audio track
• dispose session
• subscribe to session updates

Settings uses the preload support API only as a lightweight availability check. That check verifies platform, experiment gating, addon presence, and bundled libmpv.2.dylib presence without require()-loading embedded_mpv.node. This avoids blocking Settings navigation on macOS dlopen and code-signing work.

When embedded-mpv is the saved player, the settings store schedules an idle prepareEmbeddedMpv() call. This intentionally moves the first native addon load away from the click-to-play path. It can still block the Electron main process briefly because Node native addon loading is synchronous, but doing it during idle is less visible than doing it when the user clicks a video. Actual MPV session creation still happens on playback because it needs the current Electron window handle and viewport bounds.

The MPV video surface is a native AppKit/OpenGL view, not a normal DOM element. Do not place critical Angular overlays on top of the video viewport and expect CSS z-index to win. The embedded MPV controls use a compositor-safe control dock below the native viewport instead of a true overlay on top of the OpenGL surface.

The dock has a stable reserved height while embedded controls are enabled. Controls fade in and out inside that fixed dock, so normal show/hide behavior does not resize the native MPV viewport or make the video jump. Volume and audio-track panels replace the default transport controls inside the same dock and provide a back button to return to the default controls. Popovers and menus must stay inside that dock unless the native layering strategy changes. The native MPV view deliberately ignores hit testing so mouse movement passes through to Chromium and can reveal Angular controls even when the pointer moves quickly across the video area.

Resume And Track Handling

ResolvedPortalPlayback.startTime is treated as a media offset in seconds for VOD and episodes. The native addon passes it as the start option in one MPV loadfile options map together with title, user agent, referrer, and HTTP headers.

Live catchup is different: the catchup URL already encodes the archive window, so live catchup playback must not pass an absolute Unix timestamp as startTime.

Audio tracks are discovered from MPV's track-list property. The selected track is controlled through MPV's aid property. Switching tracks must not reload the stream.

Subtitle tracks mirror the audio-track contract: same track-list source, same parsing pipeline, but selected through MPV's sid property. A trackId of -1 from the renderer is interpreted as "disable subtitles" and translated to sid=no at the addon boundary. Playback speed is observed and set through MPV's speed property, clamped at the addon to [0.25, 4.0]. Aspect override uses MPV's video-aspect-override property as a passthrough string ("no", "16:9", "4:3", "21:9", "2.35:1"). All four properties (sid, speed, video-aspect-override, plus aid) are observed at session init so renderer state stays in sync with the native side without needing extra round-trips.

The renderer learns which features the loaded addon binary supports through the EmbeddedMpvSupport.capabilities field returned from getEmbeddedMpvSupport(). The service probes typeof addon.<method> === 'function' for each optional native export. Older addon binaries with the original audio-only surface return capabilities: { subtitles: false, playbackSpeed: false, aspectOverride: false, screenshot: false }, and the renderer hides the corresponding controls instead of throwing at runtime. After a native rebuild, the new buttons light up automatically without renderer changes.

Renderer Architecture And Reactivity

The Angular side of the embedded MPV player is intentionally split so the player component stays a view-only orchestrator. The renderer files live under libs/ui/playback/src/lib/embedded-mpv-player/:

• embedded-mpv-format.utils.ts — pure helpers (formatTime, audioTrackLabel, subtitleTrackLabel, speedLabel, aspectLabel, volumeIcon, volumeLabel, readStoredVolume, persistVolume, measureBounds) and preset constants (SPEED_PRESETS, ASPECT_PRESETS, HIDDEN_BOUNDS, MENU_OPEN_BOTTOM_CUTOUT_PX).
• embedded-mpv-shortcuts.ts — EmbeddedMpvShortcuts class with attach(handlers) / detach(). Owns the document keydown listener and routes through a callback interface; the component supplies the callbacks. Listens for Space/K (toggle), F (fullscreen), arrow keys (seek/volume), M (mute), Escape (close popovers).
• embedded-mpv-overlay-visibility.service.ts — singleton service that exposes overlayActive: signal<boolean>. Tracks MatDialog.afterOpened/afterAllClosed for dialog-shaped overlays and falls back to a MutationObserver on the CDK overlay container for any remaining backdrop-bearing CDK overlays. The MPV NSView is hidden off-screen while a modal is open so DOM dialogs can paint above it.
• embedded-mpv-ui-state.ts — EmbeddedMpvMenuState (single-open popover state machine with volumeOpen, audioOpen, subtitleOpen, speedOpen, aspectOpen signals plus anyOpen computed; toggle/open/close/closeAll helpers) and EmbeddedMpvFeedback (transient overlay that auto-clears after a configurable delay; used for keypress feedback).
• embedded-mpv-session-controller.ts — component-scoped Injectable service that owns the support, session, sessionId, stalled, and retryToken signals. Subscribes to onEmbeddedMpvSessionUpdate, runs the polling-driven stalled timer, owns bounds-sync (resize, scroll, overlay state), and exposes the imperative IPC surface (startSession, togglePaused, seekBy/seekTo, applyVolume, setAudioTrack, setSubtitleTrack, setSpeed, setAspect, retry).
• embedded-mpv-player.component.ts — view-only shell. Holds view children, derived computed signals, DOM event listeners (pointermove, pointerdown, fullscreenchange, dblclick), and three effect()s.

Bounds compositing strategy

The native NSView paints over the WebContents layer, so any DOM region it covers cannot receive pointer events and any CSS z-index competition is unwinnable. The component compensates with a single boundsProvider(host) closure on the controller that returns one of three bound shapes, evaluated each time the active bounds-sync runs:

• Modal overlay open (any MatDialog, including the command palette) → HIDDEN_BOUNDS. The MPV view moves off-screen so the dialog has the full window.
• Control popover open (any of the menu states above) → host bounds with MENU_OPEN_BOTTOM_CUTOUT_PX (300 px) removed from the bottom. The popover region becomes DOM-receiving while video keeps playing in the upper region.
• Idle → full host bounds.

The viewport DOM element also reserves --embedded-mpv-controls-height (64 px) at the bottom when controls are enabled, so the controls strip itself is always DOM and always reachable for hover-to-reveal even before the popover-cutout takes effect.

Reactivity rules (signals and effects)

A signal read inside an effect() becomes a tracked dependency and re-runs the entire effect on change. The cleanup-then-rebuild pattern that lives in effect((onCleanup) => { ... }) is catastrophic for stateful resources like MPV sessions — every dependency change disposes the active session and creates a new one, restarting playback.

Defensive practice for this component:

Any signal read inside an effect that is used as input to a one-shot side effect (write a value, emit an event, schedule a timer, pass an initial argument) must be wrapped in untracked(). Only signals whose change is supposed to trigger a re-run go in the tracked block.

Concrete bugs from the audit, recorded so they don't get reintroduced:

• Infinite session-create loop. EmbeddedMpvSessionController.startSession once wrote this.support.set(prepared) after the prepareEmbeddedMpv round-trip. The component's session-creation effect tracks this.support(), so the write fired the effect → cleanup disposed the session → new session was created → prepare ran again → support was set again. Symptom: endless "Loading stream…" spinner. Fix: do not write support inside startSession; the constructor's loadSupport() already populates it including capabilities.
• Stream restart on volume change. The session-creation effect once read this.volume() directly to pass to startSession's initialVolume. Each volume tick re-ran the effect, disposing and recreating the session — for VOD/series this restarted playback from the beginning. Fix: read it via untracked(() => this.volume()). Subsequent volume changes flow through controller.applyVolume(), never through the effect graph.
• Spurious timeUpdate re-emits and volume.set calls. The session-fan-out effect calls scheduleControlsHide(), which reads isPlaying, menus.anyOpen, statusLabel, and controlsVisible. Those reads became tracked deps, so opening any popover, pausing, or hovering re-ran the body. No loop in isolation, but a parent that wires timeUpdate back into playback.startTime would have hit the volume-restart bug class. Fix: wrap the side-effect block in untracked() so the effect listens only to session changes.
• 2 Hz no-op stalled-tracker re-runs. The controller's stalled effect tracked the full session signal, which updates on every position-poll snapshot. handleStalledTracking is a no-op for non-loading status, so the re-runs cost nothing useful. Fix: track a sessionStatus = computed(() => this.session()?.status ?? null) instead so the effect fires only on real status transitions.

When adding a new effect, audit it the same way: list every tracked signal read explicitly, justify each one as a re-trigger source, and wrap everything else in untracked(). When extending an existing helper that is called from inside an effect, treat the helper's signal reads as if they were inline in the effect.

IPC safety

Renderer-side IPC methods on the controller use the canonical sessionId() signal as the gate, not session()?.id. The session payload during the loading window carries a placeholder id (embedded-mpv-starting) set by createLoadingSession(); pushing that placeholder to the addon would hit getSessionOrThrow for a session that does not exist. The native side throws Napi::Error rather than std::runtime_error so that misuse surfaces as a JS exception rather than a process abort, but the renderer should still gate properly so the addon never sees the placeholder.

Every IPC call goes through a guardIpc helper that swallows addon-side throws — sessions can be torn down while a call is in flight, and snapshot polling will resync state on the next tick.

Power management

The Electron main process holds an electron.powerSaveBlocker of type prevent-display-sleep whenever any embedded MPV session has status playing. Released on pause, dispose, or shutdown. Necessary because libmpv-rendered video does not own the windowing surface, so MPV's own screensaver inhibition does not apply. See EmbeddedMpvNativeService.updatePowerBlocker() for the implementation.

Packaging State

Current development behavior:

• The addon build is macOS-only.
• The build script first looks for a staged runtime at vendor/embedded-mpv/darwin-<arch>/.
• The staged runtime must contain include/mpv/client.h, lib/*.dylib, and runtime-manifest.json.
• The compiled .node addon is copied into dist/apps/electron-backend/native/embedded_mpv.node.
• Bundled runtime files are copied into dist/apps/electron-backend/native/lib/. Most are .dylib files, but some Homebrew-linked runtimes expose non-.dylib Mach-O files such as a framework Python binary.
• macOS afterPack copies dist/apps/electron-backend/native/ into app.asar.unpacked/electron-backend/native/ so the addon, manifest, dylibs, and non-.dylib Mach-O runtime files are filesystem-addressable.
• Linux and Windows packaging do not include the Embedded MPV native directory.

Current release caveat:

• Release packaging requires a vendored-lgpl runtime manifest.
• Release packaging rejects embedded MPV binaries linked to /opt/homebrew or /usr/local.
• Local development can opt into Homebrew libmpv only by setting IPTVNATOR_EMBEDDED_MPV_ALLOW_HOMEBREW=1; packaged release validation rejects that runtime origin.

Before public release, packaging must:

• stage an LGPL-compatible libmpv and required dylibs for darwin-arm64 and darwin-x64
• collect indirect dependencies expressed as absolute paths, @loader_path, or @rpath
• rewrite install names and dependency paths to app-relative paths such as @loader_path
• code-sign and notarize the full dependency set
• publish the corresponding FFmpeg/libmpv source and build metadata

Users do not need the MPV GUI application for this architecture. IPTVnator bundles libmpv for release builds. If the bundled runtime is missing or fails to load, embedded MPV is hidden/unsupported and the existing inline/external players remain available.

Runtime Staging

Runtime staging tooling lives in:

• /Users/4gray/Code/iptvnator/tools/embedded-mpv/
• /Users/4gray/Code/iptvnator/vendor/embedded-mpv/

Release runtime policy:

• FFmpeg must be built without --enable-gpl and without --enable-nonfree.
• mpv must be built with -Dlibmpv=true and -Dgpl=false.
• The runtime must be dynamically linked and shipped with license/source-distribution notices.

After building an LGPL-compatible prefix for an architecture:

node tools/embedded-mpv/stage-macos-runtime.mjs arm64 /path/to/lgpl-prefix
node tools/embedded-mpv/stage-macos-runtime.mjs x64 /path/to/lgpl-prefix

Tagged macOS release CI builds that prefix from pinned source archives first. The workflow can temporarily run the same path for macOS PR artifacts while the bundled runtime is being tested:

pnpm embedded-mpv:build-runtime -- arm64 /tmp/embedded-mpv-prefix
pnpm embedded-mpv:stage-runtime -- arm64 /tmp/embedded-mpv-prefix

The CI builder pins FFmpeg 8.1, mpv 0.41.0, libplacebo 7.360.1, libass 0.17.3, FreeType 2.13.3, FriBidi 1.0.16, and HarfBuzz 8.5.0. FFmpeg disables autodetected external libraries so Homebrew libraries cannot silently enter the runtime. Libplacebo is checked out from git with the submodules required by its Meson build because the generated GitHub archive does not include submodule contents. Even with Vulkan disabled, libplacebo still compiles Vulkan stubs and needs 3rdparty/Vulkan-Headers. The generated manifest records source URLs, archive SHA-256 values where applicable, libplacebo git commit/submodule metadata, FFmpeg configure flags, and mpv Meson flags. The staging step normalizes that manifest to origin: vendored-lgpl, which release package validation requires.

The Electron backend build consumes the staged runtime, copies Mach-O runtime files into the native build output, and rewrites Mach-O paths so embedded_mpv.node loads @loader_path/lib/libmpv.2.dylib instead of a machine-local Homebrew path. After install_name_tool rewrites any addon or runtime binary, the build re-signs that binary with an ad-hoc signature for local development. Release packaging still performs the normal app signing and notarization later.

For local development before the vendored runtime exists, Homebrew can be used explicitly:

pnpm run serve:backend:embedded-mpv

That script first runs the local native build with IPTVNATOR_EMBEDDED_MPV_ALLOW_HOMEBREW=1, then starts Electron with IPTVNATOR_ENABLE_EMBEDDED_MPV_EXPERIMENT=1. This path is intentionally development-only. Packaged macOS builds reject homebrew-dev manifests and any /opt/homebrew or /usr/local embedded MPV links.

If the settings page does not show Embedded MPV (Experimental, macOS) after starting with those flags, check the native build output:

ls apps/electron-backend/native/build/Release/embedded_mpv.node

If only embedded-mpv-unavailable.txt exists, the dev app started from a build where no runtime was available. Stop the Electron dev process and rerun pnpm run serve:backend:embedded-mpv so the native target is rebuilt before Electron starts. The native MPV build target is intentionally uncached because it depends on local runtime files and environment variables such as IPTVNATOR_EMBEDDED_MPV_ALLOW_HOMEBREW and IPTVNATOR_EMBEDDED_MPV_ARCH.

If opening Settings hard-crashes Electron on macOS and the crash report says Code Signature Invalid, one of the copied runtime binaries was modified by install_name_tool without being re-signed. Rebuild the native target and verify the copied addon/runtime files:

IPTVNATOR_EMBEDDED_MPV_ALLOW_HOMEBREW=1 node apps/electron-backend/build-embedded-mpv.js
codesign --verify --verbose=2 apps/electron-backend/native/build/Release/embedded_mpv.node
codesign --verify --verbose=2 apps/electron-backend/native/build/Release/lib/libmpv.2.dylib

If support detection reports a missing @rpath/... dependency, the dependency collector missed an indirect runtime file. The packaging helper must copy that file into native/lib/, rewrite the dependency to @loader_path/<name>, and include non-.dylib Mach-O files in the asset copy glob.

Same-Version macOS Release Gate

The normal release tag can produce Linux, Windows, and macOS artifacts from the same source version while only macOS carries the bundled Embedded MPV runtime.

For tagged macOS builds, CI must:

• build the pinned LGPL-compatible runtime for the matrix architecture
• stage it into vendor/embedded-mpv/darwin-${arch} before pnpm run build:backend
• set IPTVNATOR_EMBEDDED_MPV_ARCH=${arch} for backend build and packaging
• set IPTVNATOR_REQUIRE_EMBEDDED_MPV=1 for packaging and package-layout verification

During the temporary macOS artifact tests, CI also sets IPTVNATOR_REQUIRE_EMBEDDED_MPV=1 for macOS PR and master push backend build, packaging, and package-layout verification. After the artifacts are manually validated, remove the workflow's temporary pull_request and refs/heads/master conditions so PR, development, Linux, and Windows packaging leave IPTVNATOR_REQUIRE_EMBEDDED_MPV unset or 0. In that normal mode the package validators still reject a present but invalid Embedded MPV runtime, but they do not require the addon to exist. This keeps the native feature in-tree without making non-macOS or non-release builds depend on macOS runtime artifacts.

Release Safety

The feature is still experimental. The largest risks are native-process risks, not normal Angular UI risks:

• a bad native addon or libmpv crash can crash the Electron main process
• packaging can fail if libmpv or one of its dylib dependencies is missing, unsigned, or linked to the wrong runtime path
• macOS graphics behavior can vary across Intel, Apple Silicon, external displays, fullscreen transitions, and hardware decoding paths
• Homebrew libmpv builds can target a newer macOS version than IPTVnator's declared deployment target

It is reasonable to ship the code in-tree behind the current experiment flag. It is not yet safe to make it the default player. It can be exposed as macOS-only experimental if support detection is strict, the UI clearly labels it experimental, and fallback to Video.js or external MPV/VLC stays available.

If an embedded session fails to initialize, the app should keep the user in control by preserving the normal player setting choices. If a native crash occurs, normal settings fallback cannot intercept that crash, so broader macOS smoke testing and packaged-app testing are required before broad release.

Suggested Release Gate

Do not expose embedded MPV broadly until these pass on both Apple Silicon and Intel macOS:

• packaged .app starts without Homebrew installed
• bundled libmpv and dependent dylibs pass code signing and notarization
• VOD resume starts near the saved offset
• live HLS, MPEG-TS, MP4/VOD, headers, referrer, volume, seek, fullscreen, route changes, and cleanup work
• audio-track switching works on a stream with multiple audio tracks
• fallback behavior is clear when the addon or native dependencies are unavailable