ledgrab/ANDROID-REVIEW/android-missing-functionality.md

# Android (TV) — Missing Functionality Assessment

> Status: review/feasibility document. No code changes. Last updated 2026-06-01.

## Context

LedGrab ships an **experimental on-device Android-TV build**: a Kotlin shell that
embeds the Python FastAPI server via **Chaquopy**, with Kotlin↔Python **bridges**
(`PythonBridge`, `BleBridge`, `UsbSerialBridge`). Several desktop features are
unavailable on this build because their Python backends rely on native libraries
that have no Android/Chaquopy wheels (`mss`, `dxcam`, `sounddevice`/PortAudio,
`opencv`, `nvidia-ml-py`, `winrt`, `dbus-next`), or on OS facilities Android
sandboxes differently.

The README "Feature support by OS" table now carries an Android column reflecting
this. This document assesses **whether each missing feature can be added**, how, and
whether it's worth it.

### The enabling pattern (why most of this is feasible)

Every desktop capability that's "missing" on Android is missing only because of a
*native dependency*, not because the capability is impossible. Android exposes the
same capability through a platform API, and the codebase already has the bridge
shape to plug it in:

> **Bridge pattern:** a Kotlin component captures an event/buffer → pushes it across
> the Chaquopy JNI boundary into a **module-level receiver** in a small Python engine
> → an existing engine/stream consumes it unchanged.

Reference implementation: `server/src/ledgrab/core/capture_engines/mediaprojection_engine.py`
(`configure()` + `push_frame()` + a bounded `queue.Queue`) ↔
`android/app/src/main/java/com/ledgrab/android/ScreenCapture.kt` ↔
`PythonBridge.pushFrame()`. Screen capture already works on Android this exact way.

So for most missing features the work is: **add a Kotlin capture source + a thin
Python receiver engine mirroring that pattern.**

---

## Current Android capability matrix

| Feature | Desktop | Android (TV) today | Missing? |
| ------- | ------- | ------------------ | -------- |
| Screen capture | DXCam/WGC/MSS | ✅ MediaProjection + root `screenrecord` | No |
| LED transports (network/USB-serial/BLE) | ✅ | ✅ (USB via Android driver, BLE via Android bridge) | No |
| System metrics | psutil | ✅ CPU/RAM/battery/thermal via `/proc`, `/sys` (`AndroidMetricsProvider`) | No |
| **Audio capture** | WASAPI / Sounddevice | ❌ no PortAudio | **Yes** |
| Notification capture | WinRT / D-Bus | ✅ NotificationListenerService → `push_notification()` | No (implemented) |
| Webcam capture | OpenCV | ✅ Camera2 + on-demand bridge (`AndroidCameraEngine`) | No (implemented) |
| GPU monitoring | NVML | ❌ no NVIDIA GPU | Marginal |
| Capture from *another* Android phone | scrcpy/ADB | ❌ | Skip (redundant) |
| Automation: window/process conditions | Windows ctypes | ❌ sandboxed | Partial |
| Monitor names / multi-display | WMI / generic | Single built-in display | Low value |

---

## Per-feature feasibility

### 🔊 Audio capture — **FEASIBLE, HIGH VALUE** ⭐ (detailed plan exists)

- **Blocker:** only `sounddevice`/PortAudio is missing — not the capability.
- **Android path:** `AudioPlaybackCapture` (API 29+) captures system playback audio and
  **takes a `MediaProjection` token — which the app already obtains for screen capture.**
  Kotlin `AudioRecord` → push PCM (float32) → a new push-based `AndroidAudioEngine`
  mirroring `mediaprojection_engine.py`, registered in `core/audio/__init__.py`, feeding
  the existing `AudioAnalyzer` unchanged. Mic (`AudioSource.MIC`) is the fallback.
- **Effort:** moderate. **Value:** high — music/sound-reactive lighting is a flagship use
  on a TV box. **No new Python deps.**
- ⚠️ DRM-protected apps (Netflix etc.) opt out of playback capture; works for non-DRM
  media and the device's own audio. Root mode (no MediaProjection) → mic-only.
- 📄 **See `android-audio-capture-plan.md`** for the full implementation plan.

### 🔔 Notification capture — **IMPLEMENTED** ✅ (shipped)

- **Android is the *best* platform for this:** `NotificationListenerService` is the native,
  event-push mechanism (no polling).
- **Path:** a `NotificationListenerService` resolves the posting app's display label and
  pushes it via a module-level `push_notification()` into the existing
  `os_notification_listener.py` pipeline (a new push-based `_AndroidBackend` alongside
  `_WindowsBackend`/`_LinuxBackend`). Existing `NotificationColorStripSource` filters,
  per-app colors/sounds, and the history endpoint all work unchanged. **No new Python deps.**
- **Permission:** user enables "Notification access" in Settings (`ACTION_NOTIFICATION_LISTENER_SETTINGS`);
  no runtime-permission popup.
- **Effort:** moderate. **Value:** high.
- ✅ **Implemented** on branch `feature/android-notification-capture`: a push-based
  `_AndroidBackend` + module-level `push_notification()` in `os_notification_listener.py`,
  a Kotlin `LedGrabNotificationListener` (NLS), and prompt-once permission UX. App-name
  parity — only the resolved app label crosses the JNI boundary, never the notification
  title/body. ⚠️ App labels can differ across OSes (Windows `display_name` / Linux D-Bus
  `app_name` / Android `getApplicationLabel`), so desktop-configured per-app colors/filters
  may need re-matching on Android.

### 📷 Webcam capture — **IMPLEMENTED** ✅ (shipped)

- **Blocker** was `opencv-python-headless` (no Chaquopy cp311 wheel) — but capture doesn't
  *need* OpenCV. Implemented with **Camera2** + `ImageReader` in Kotlin pushing RGB frames
  through the same bridge as MediaProjection into a new `AndroidCameraEngine`.
- **Path:** a Kotlin `CameraBridge` singleton (Camera2) enumerates cameras and **opens the
  camera on demand** (only while a capture source is active — driven Python→Kotlin via the
  `BleBridge`/`UsbSerialBridge` pattern), converts each frame YUV_420_888→RGB, and pushes it
  into a push-based `AndroidCameraEngine` (`core/capture_engines/android_camera_engine.py`)
  that mirrors `mediaprojection_engine.py`. Cameras surface as selectable "displays" exactly
  like the desktop OpenCV `CameraEngine`; the data-driven capture-template UI (engine list +
  `resolution` config + display picker) needs **no changes**. **No new Python deps; no new
  Gradle deps** (Camera2 is in-platform).
- **Permission:** `CAMERA` requested at capture-start, gated on `FEATURE_CAMERA_ANY` so
  camera-less TV boxes never see the prompt; graceful degradation when denied. The service is
  promoted with the `camera` FGS type (+ `FOREGROUND_SERVICE_CAMERA`) **only when CAMERA is
  already granted**, so backgrounded capture keeps working without risking a failed service
  start on camera-less boxes. (Unlike audio playback capture, the camera can't ride the
  MediaProjection token, so it needs its own FGS type to survive backgrounding.)
- **Effort:** moderate. **Value:** low (TVs rarely have cameras), but the implementation reuses
  existing infrastructure end-to-end. **Priority `0`** so it's never auto-selected over
  MediaProjection — chosen explicitly via `engine_type="android_camera"`.
- ⚠️ **MVP scope / limitations:** webcam capture works **while LedGrab capture is running**
  (no camera-only server path on Android); one camera active at a time; `"auto"` picks a
  balanced output size (not the sensor max) to keep per-frame YUV→RGB cheap; USB-UVC webcams
  appear only if the device routes them through Camera2 (varies by box); no frame-rotation
  correction.
- 📄 **See `android-webcam-capture-plan.md`** for the full implementation notes.

### 🎮 GPU monitoring — **MARGINAL, SKIP FOR NOW**

- NVML is desktop-NVIDIA only. Android GPU load lives in **vendor-specific sysfs**
  (Adreno `/sys/class/kgsl/kgsl-3d0/gpubusy`, Mali `/sys/class/devfreq/*.mali/...`),
  inconsistent and often root-only.
- CPU/RAM/battery/thermal are **already** covered by `AndroidMetricsProvider`. A best-effort
  GPU-load reader could be added to that provider, but reliability is poor and value is low.

### 🪟 Automation: window/process conditions — **PARTIAL**

- Android forbids full window/process enumeration (`getRunningTasks` restricted since API 21+).
- **Obtainable:** the *current foreground app package* via `UsageStatsManager` (needs the
  `PACKAGE_USAGE_STATS` special access) or an `AccessibilityService`.
- So "when <app> is in the foreground → scene X" is feasible (mirrors
  `automations/platform_detector.py`, which currently returns empty off-Windows); full
  window-title matching is **not**. **Effort:** moderate. **Value:** moderate (per-app scenes
  on a TV box).

### 📱 Capture from *another* Android phone (scrcpy/ADB) — **SKIP**

- Impractical and redundant: no `adb` binary in Chaquopy, TV boxes can't reliably host an
  adb server, and the device already captures its **own** screen via MediaProjection.

### 🖥️ Monitor names / multi-display — **LOW VALUE**

- `DisplayManager` can report a better display name and enumerate secondary (HDMI) displays,
  but MediaProjection captures the default display; capturing a secondary display is more
  involved and rarely useful on a single-screen box.

---

## Prioritization

| Priority | Feature | Effort | Value | New Python deps | Status |
| -------- | ------- | ------ | ----- | --------------- | ------ |
| 1 | Notification capture | Moderate | High | None | **✅ Implemented** |
| 2 | Audio capture | Moderate | High | None | **✅ Implemented** |
| 4 | Webcam capture (Camera2) | Moderate | Low | None | **✅ Implemented** |
| 3 | Automation: foreground-app condition | Moderate | Moderate | None | Idea (only remaining) |
| — | GPU load (vendor sysfs) | Low–Med | Low | None | Not recommended |
| — | Capture from another phone | — | — | — | Won't do |
| — | Multi-display / monitor names | Low | Low | None | Not recommended |

**Status:** notifications, audio, **and webcam** are all shipped — each reuses existing
infrastructure (bridge pattern, the MediaProjection consent token / process-global
`Python.getInstance()`, the capture/audio/notification pipelines) and adds **zero** Python
dependencies, so none risks the Chaquopy `--no-deps` build constraint documented in
`CLAUDE.md`. The only remaining idea is the **foreground-app automation condition** (moderate
value); GPU load, another-phone capture, and multi-display remain not-recommended / won't-do.

## Cross-cutting notes

- **No `build.gradle.kts` / Chaquopy pip impact** for notifications or audio — both use Android
  platform APIs (Kotlin) + stdlib/`numpy` (already bundled) on the Python side.
- **Per-instance `PythonBridge`:** `PythonBridge` is created per `CaptureService` instance, so
  system-bound services (e.g. a `NotificationListenerService`) call Python via the
  process-global `Python.getInstance()` rather than borrowing that bridge.
- **Permissions are the recurring friction**, not the capture: audio needs `RECORD_AUDIO` +
  (for playback capture) a MediaProjection token; notifications need the "Notification access"
  settings toggle; foreground-app automation needs `PACKAGE_USAGE_STATS`.