feat: enhance telemetry metrics with target FPS tracking and logging

app/camera/camera_service.py

@@ -27,12 +27,15 @@ class CameraService(QObject):
         camera_started()          — camera successfully opened and streaming
         camera_stopped()          — camera stopped (clean shutdown)
         camera_error(str)         — camera error description
+        format_changed(float)     — actual FPS after format was applied
+                                    (emitted after camera restarts with new format)
     """
 
     frame_ready = Signal(QVideoFrame)
     camera_started = Signal()
     camera_stopped = Signal()
     camera_error = Signal(str)
+    format_changed = Signal(float)   # actual FPS delivered by camera after format change
 
     def __init__(self, parent: QObject | None = None) -> None:
         super().__init__(parent)
@@ -42,6 +45,11 @@ class CameraService(QObject):
         self._sink = QVideoSink(self)
         self._current_info: CameraInfo | None = None
 
+        # Desired format — applied on next (re)start
+        self._desired_width: int = DEFAULT_WIDTH
+        self._desired_height: int = DEFAULT_HEIGHT
+        self._desired_fps: float = float(DEFAULT_FPS)
+
         self._session.setVideoSink(self._sink)
         self._sink.videoFrameChanged.connect(self._on_frame)
 
@@ -51,7 +59,7 @@ class CameraService(QObject):
 
     def start(self, camera_info: CameraInfo) -> None:
         """Start streaming from the given camera device."""
-        self.stop()
+        self._stop_camera()
 
         self._current_info = camera_info
         self._camera = QCamera(camera_info.device, self)
@@ -59,22 +67,17 @@ class CameraService(QObject):
         self._camera.activeChanged.connect(self._on_active_changed)
 
         self._session.setCamera(self._camera)
-        self._apply_best_format(camera_info)
+        self._apply_format()
         self._camera.start()
         logger.info("Camera start requested: %s", camera_info.name)
 
     def stop(self) -> None:
-        """Stop the current camera."""
-        if self._camera is not None:
-            self._camera.stop()
-            self._camera.errorOccurred.disconnect()
-            self._camera.activeChanged.disconnect()
-            self._camera = None
-            self._current_info = None
-            logger.info("Camera stopped")
+        """Stop the current camera and forget the device."""
+        self._stop_camera()
+        self._current_info = None
 
     def reconnect(self) -> None:
-        """Restart the current camera after an error or disconnect."""
+        """Restart the current camera (e.g. after an error or disconnect)."""
         if self._current_info is not None:
             logger.info("Reconnecting camera: %s", self._current_info.name)
             self.start(self._current_info)
@@ -82,19 +85,29 @@ class CameraService(QObject):
             logger.warning("Reconnect requested but no camera was previously started")
 
     def set_resolution(self, width: int, height: int) -> None:
-        """Request a specific resolution. Effective on next start() if camera is active."""
-        if self._camera is None:
-            return
-        self._set_format(width, height, fps=None)
+        """
+        Request a new resolution.
+
+        The camera is stopped and restarted so the backend reliably applies
+        the new format (QCamera.setCameraFormat on an active camera is often
+        silently ignored by Media Foundation on Windows).
+        """
+        self._desired_width = width
+        self._desired_height = height
+        if self._current_info is not None:
+            logger.info("Resolution change requested: %dx%d — restarting camera", width, height)
+            self.start(self._current_info)
 
     def set_fps(self, fps: float) -> None:
-        """Request a specific frame rate."""
-        if self._camera is None or self._current_info is None:
-            return
-        # Get current resolution from active format
-        fmt = self._camera.cameraFormat()
-        res = fmt.resolution()
-        self._set_format(res.width(), res.height(), fps=fps)
+        """
+        Request a new frame rate.
+
+        Same stop+start strategy as set_resolution().
+        """
+        self._desired_fps = fps
+        if self._current_info is not None:
+            logger.info("FPS change requested: %.1f — restarting camera", fps)
+            self.start(self._current_info)
 
     @property
     def is_active(self) -> bool:
@@ -105,28 +118,37 @@ class CameraService(QObject):
         return self._current_info
 
     # ------------------------------------------------------------------
-    # Video output accessor for direct QVideoWidget connection
+    # Internal video output accessors (kept for future use)
     # ------------------------------------------------------------------
 
     def video_sink(self) -> QVideoSink:
-        """Return the internal QVideoSink (used by VideoRenderer)."""
         return self._sink
 
     def capture_session(self) -> QMediaCaptureSession:
-        """Return the capture session (can be connected to QVideoWidget directly)."""
         return self._session
 
     # ------------------------------------------------------------------
     # Private helpers
     # ------------------------------------------------------------------
 
-    def _apply_best_format(self, info: CameraInfo) -> None:
-        """Pick the best matching format: prefer DEFAULT_WIDTH x DEFAULT_HEIGHT at DEFAULT_FPS."""
-        if not info.formats:
-            return
-        self._set_format(DEFAULT_WIDTH, DEFAULT_HEIGHT, fps=float(DEFAULT_FPS))
+    def _stop_camera(self) -> None:
+        """Stop and destroy the QCamera object without clearing _current_info."""
+        if self._camera is not None:
+            self._camera.stop()
+            self._camera.errorOccurred.disconnect()
+            self._camera.activeChanged.disconnect()
+            self._camera = None
+            logger.debug("Camera stopped (internal)")
 
-    def _set_format(self, width: int, height: int, fps: float | None) -> None:
+    def _apply_format(self) -> None:
+        """
+        Select the best matching QCameraFormat and apply it before start().
+
+        The format is chosen by score:
+          +1000  exact resolution match
+          +100   exact FPS match (within 1 fps)
+          -|Δpixels|  area proximity (tie-breaker)
+        """
         if self._camera is None or self._current_info is None:
             return
 
@@ -138,11 +160,11 @@ class CameraService(QObject):
             w, h = res.width(), res.height()
             f = fmt.maxFrameRate()
 
-            res_match = int(w == width and h == height) * 1000
-            fps_match = int(fps is not None and abs(f - fps) < 1) * 100
-            area_score = -(abs(w * h - width * height))
-
-            score = res_match + fps_match + area_score
+            score = (
+                int(w == self._desired_width and h == self._desired_height) * 1000
+                + int(abs(f - self._desired_fps) < 1) * 100
+                - abs(w * h - self._desired_width * self._desired_height)
+            )
             if score > best_score:
                 best_score = score
                 best = fmt
@@ -151,12 +173,29 @@ class CameraService(QObject):
             self._camera.setCameraFormat(best)
             res = best.resolution()
             logger.info(
-                "Camera format set: %dx%d @ %.1f fps",
-                res.width(),
-                res.height(),
-                best.maxFrameRate(),
+                "Camera format requested: %dx%d @ %.1f fps",
+                res.width(), res.height(), best.maxFrameRate(),
             )
 
+    def _log_actual_format(self) -> None:
+        """Log the format the camera actually started with and emit format_changed."""
+        if self._camera is None:
+            return
+        fmt = self._camera.cameraFormat()
+        res = fmt.resolution()
+        actual_fps = fmt.maxFrameRate()
+        logger.info(
+            "Camera format ACTUAL: %dx%d @ %.1f fps",
+            res.width(), res.height(), actual_fps,
+        )
+        if actual_fps != self._desired_fps:
+            logger.warning(
+                "Requested %.1f fps but camera is delivering %.1f fps "
+                "(camera may not support this combination)",
+                self._desired_fps, actual_fps,
+            )
+        self.format_changed.emit(actual_fps)
+
     def _on_frame(self, frame: QVideoFrame) -> None:
         if frame.isValid():
             self.frame_ready.emit(frame)
@@ -167,7 +206,9 @@ class CameraService(QObject):
 
     def _on_active_changed(self, active: bool) -> None:
         if active:
-            logger.info("Camera active: %s", self._current_info.name if self._current_info else "?")
+            name = self._current_info.name if self._current_info else "?"
+            logger.info("Camera active: %s", name)
+            self._log_actual_format()   # report what the camera actually accepted
             self.camera_started.emit()
         else:
             logger.info("Camera inactive")

app/overlay/telemetry_overlay.py

@@ -24,6 +24,15 @@ class TelemetryOverlay(IOverlayLayer):
         overlay = TelemetryOverlay()
         camera_view.add_overlay_layer(overlay)
         telemetry_collector.metrics_updated.connect(overlay.on_metrics_updated)
+
+    Display format:
+        FPS req   60.0          ← what was requested from camera
+        FPS got   30.2          ← what camera actually delivered
+        Frame     33.1 ms
+        Drop         0
+        CPU sys   14.8 %        ← normalised by cpu_count (matches Task Manager)
+        CPU core 118.4 %        ← per single core (can exceed 100%)
+        Mem        68 MB
     """
 
     def __init__(self) -> None:
@@ -60,7 +69,6 @@ class TelemetryOverlay(IOverlayLayer):
         box_w = max_width + OVERLAY_PADDING * 2
         box_h = line_height * len(lines) + OVERLAY_PADDING * 2
 
-        # Position relative to the actual video area, not the full widget
         x = video_rect.left() + OVERLAY_MARGIN
         y = video_rect.top() + OVERLAY_MARGIN
 
@@ -83,12 +91,19 @@ class TelemetryOverlay(IOverlayLayer):
 
     @staticmethod
     def _format_lines(snap: TelemetrySnapshot) -> list[str]:
-        lines = [
-            f"FPS    {snap.fps:>6.1f}",
-            f"Frame  {snap.frame_time_ms:>6.1f} ms",
-            f"Drop   {snap.dropped_frames:>6d}",
-            f"CPU    {snap.cpu_percent:>5.1f} %",
-        ]
+        lines: list[str] = []
+
+        # FPS — show target if known, then actual
+        if snap.target_fps is not None:
+            lines.append(f"FPS req  {snap.target_fps:>6.1f}")
+        lines.append(f"FPS got  {snap.fps:>6.1f}")
+
+        lines.append(f"Frame    {snap.frame_time_ms:>6.1f} ms")
+        lines.append(f"Drop     {snap.dropped_frames:>6d}")
+        lines.append(f"CPU sys  {snap.cpu_percent_sys:>5.1f} %")
+        lines.append(f"CPU core {snap.cpu_percent_core:>5.1f} %")
+
         if snap.memory_mb is not None:
-            lines.append(f"Mem    {snap.memory_mb:>5.0f} MB")
+            lines.append(f"Mem      {snap.memory_mb:>5.0f} MB")
+
         return lines

app/telemetry/telemetry_collector.py

@@ -17,10 +17,13 @@ from app.config import TELEMETRY_UPDATE_INTERVAL_MS
 class TelemetrySnapshot:
     """Immutable snapshot of current performance metrics."""
 
-    fps: float
+    fps: float                    # actual frames received in the last second
+    target_fps: float | None      # FPS requested from the camera (None = unknown)
     frame_time_ms: float          # average inter-frame time in ms
     dropped_frames: int           # cumulative dropped frames detected
-    cpu_percent: float            # this process CPU usage (0–100, all cores)
+    cpu_percent_sys: float        # process CPU as % of total system capacity
+                                  # (divided by cpu_count) — matches Task Manager
+    cpu_percent_core: float       # process CPU per single core — can exceed 100%
     memory_mb: float | None       # process private working set in MB
     timestamp: float              # time.perf_counter() when snapshot was taken
 
@@ -32,6 +35,9 @@ class TelemetryCollector(QObject):
     Connect to FrameDispatcher:
         dispatcher.subscribe(collector.on_frame, drop_if_busy=False)
 
+    Receive target FPS updates from CameraService:
+        camera_service.format_changed.connect(collector.set_target_fps)
+
     Listen to metrics updates:
         collector.metrics_updated.connect(my_slot)
     """
@@ -46,6 +52,7 @@ class TelemetryCollector(QObject):
         super().__init__(parent)
 
         self._update_interval_ms = update_interval_ms
+        self._target_fps: float | None = None
 
         # frame timing ring-buffer (last 120 samples)
         self._frame_times: deque[float] = deque(maxlen=120)
@@ -54,12 +61,13 @@ class TelemetryCollector(QObject):
         self._dropped_frames: int = 0
 
         # FPS window — count frames in the last second
-        self._fps_window: deque[float] = deque()  # timestamps of recent frames
+        self._fps_window: deque[float] = deque()
         self._fps_window_size_s: float = 1.0
 
-        # psutil process reference — call cpu_percent once to initialise the baseline
+        # psutil — initialise baseline so first real reading is non-zero
         self._process = psutil.Process()
-        self._process.cpu_percent()  # first call always returns 0.0; discard it
+        self._process.cpu_percent()  # first call always returns 0.0; discard
+        self._cpu_count: int = max(psutil.cpu_count(logical=True) or 1, 1)
 
         # periodic snapshot timer
         self._timer = QTimer(self)
@@ -67,9 +75,16 @@ class TelemetryCollector(QObject):
         self._timer.timeout.connect(self._emit_snapshot)
         self._timer.start()
 
-        # latest snapshot (available synchronously)
         self._latest: TelemetrySnapshot = self._make_empty_snapshot()
 
+    # ------------------------------------------------------------------
+    # Configuration
+    # ------------------------------------------------------------------
+
+    def set_target_fps(self, fps: float | None) -> None:
+        """Record the FPS that was requested from the camera."""
+        self._target_fps = fps
+
     # ------------------------------------------------------------------
     # Frame subscriber callback
     # ------------------------------------------------------------------
@@ -78,12 +93,11 @@ class TelemetryCollector(QObject):
         """Called by FrameDispatcher for every frame. Must be fast."""
         now = time.perf_counter()
 
-        # inter-frame time
         if self._last_frame_time > 0:
             delta = now - self._last_frame_time
             self._frame_times.append(delta)
 
-            # drop detection: if delta > 2.5× the rolling average, count as drop
+            # drop detection: gap > 2.5× rolling average
             if len(self._frame_times) >= 5:
                 avg = sum(self._frame_times) / len(self._frame_times)
                 if delta > avg * 2.5:
@@ -92,9 +106,7 @@ class TelemetryCollector(QObject):
         self._last_frame_time = now
         self._total_frames += 1
 
-        # FPS window
         self._fps_window.append(now)
-        # prune old entries
         cutoff = now - self._fps_window_size_s
         while self._fps_window and self._fps_window[0] < cutoff:
             self._fps_window.popleft()
@@ -104,7 +116,6 @@ class TelemetryCollector(QObject):
     # ------------------------------------------------------------------
 
     def latest_snapshot(self) -> TelemetrySnapshot:
-        """Return the most recently computed snapshot."""
         return self._latest
 
     def reset_counters(self) -> None:
@@ -131,46 +142,49 @@ class TelemetryCollector(QObject):
         cutoff = now - self._fps_window_size_s
         while self._fps_window and self._fps_window[0] < cutoff:
             self._fps_window.popleft()
-        fps = float(len(self._fps_window))  # frames in the last second
+        fps = float(len(self._fps_window))
 
         # average frame time
-        if self._frame_times:
-            avg_frame_time_ms = (sum(self._frame_times) / len(self._frame_times)) * 1000.0
-        else:
-            avg_frame_time_ms = 0.0
+        avg_frame_time_ms = (
+            (sum(self._frame_times) / len(self._frame_times)) * 1000.0
+            if self._frame_times
+            else 0.0
+        )
 
-        # CPU — this process only, cumulative since last call (non-blocking)
+        # CPU — per-core reading, then derive system-normalised value
         try:
-            cpu = self._process.cpu_percent()
+            cpu_core = self._process.cpu_percent()
         except Exception:
-            cpu = 0.0
+            cpu_core = 0.0
+        cpu_sys = cpu_core / self._cpu_count
 
         # Memory — private working set (Windows) or RSS (macOS/Linux)
-        # This excludes shared DLLs/frameworks and matches Task Manager "Private"
         try:
             mem_info = self._process.memory_info()
-            # wset = Windows Working Set (private); rss on macOS/Linux
             mem_bytes = getattr(mem_info, "wset", None) or mem_info.rss
-            mem_mb = mem_bytes / (1024 * 1024)
+            mem_mb: float | None = mem_bytes / (1024 * 1024)
         except Exception:
             mem_mb = None
 
         return TelemetrySnapshot(
             fps=round(fps, 1),
+            target_fps=self._target_fps,
             frame_time_ms=round(avg_frame_time_ms, 2),
             dropped_frames=self._dropped_frames,
-            cpu_percent=round(cpu, 1),
+            cpu_percent_sys=round(cpu_sys, 1),
+            cpu_percent_core=round(cpu_core, 1),
             memory_mb=round(mem_mb, 1) if mem_mb is not None else None,
             timestamp=now,
         )
 
-    @staticmethod
-    def _make_empty_snapshot() -> TelemetrySnapshot:
+    def _make_empty_snapshot(self) -> TelemetrySnapshot:
         return TelemetrySnapshot(
             fps=0.0,
+            target_fps=self._target_fps,
             frame_time_ms=0.0,
             dropped_frames=0,
-            cpu_percent=0.0,
+            cpu_percent_sys=0.0,
+            cpu_percent_core=0.0,
             memory_mb=None,
             timestamp=time.perf_counter(),
         )

app/ui/main_window.py

@@ -120,6 +120,9 @@ class MainWindow(QMainWindow):
         # TelemetryCollector → TelemetryOverlay (data only, no repaint trigger here)
         self._telemetry.metrics_updated.connect(self._telemetry_overlay.on_metrics_updated)
 
+        # CameraService → TelemetryCollector: keep target FPS in sync
+        self._camera_service.format_changed.connect(self._telemetry.set_target_fps)
+
         # CameraService status
         self._camera_service.camera_started.connect(self._on_camera_started)
         self._camera_service.camera_stopped.connect(self._on_camera_stopped)

notes/02-mvp-app.md

@@ -0,0 +1,194 @@
+# Stan aplikacji — MVP Camera Preview
+
+Data: 2026-05-12
+Środowisko dev: Windows 11, Python 3.12.10, PySide6 6.11.0
+Środowisko docelowe: Mac Mini (Intel i7, macOS Ventura), kamera ELP USB
+
+---
+
+## Zaimplementowane moduły
+
+### Struktura projektu
+
+```
+duck-preview2/
+├── app/
+│   ├── config.py                        # stałe i domyślne ustawienia
+│   ├── main.py                          # entry point (python -m app.main)
+│   ├── camera/
+│   │   ├── camera_enumerator.py         # wykrywanie kamer przez QMediaDevices
+│   │   └── camera_service.py            # zarządzanie QCamera + QMediaCaptureSession
+│   ├── pipeline/
+│   │   └── frame_dispatcher.py          # pub/sub dystrybucja QVideoFrame
+│   ├── telemetry/
+│   │   └── telemetry_collector.py       # pomiar FPS, frame time, CPU, pamięci
+│   ├── overlay/
+│   │   ├── overlay_layer.py             # interfejs IOverlayLayer (ABC)
+│   │   └── telemetry_overlay.py         # implementacja — box z metrykami
+│   └── ui/
+│       ├── camera_view.py               # CameraView — render + kompozycja overlayów
+│       ├── main_window.py               # główne okno, wiring komponentów
+│       └── menu_bar.py                  # menu: Camera / Video / Debug
+├── tests/
+│   ├── test_frame_dispatcher.py         # 8 testów jednostkowych
+│   └── test_telemetry_collector.py      # 7 testów jednostkowych
+├── pyproject.toml                       # konfiguracja pytest + ruff
+├── requirements.txt                     # PySide6, psutil
+└── requirements-dev.txt                 # + pytest, ruff
+```
+
+### Opis komponentów
+
+#### CameraEnumerator (`app/camera/camera_enumerator.py`)
+- Wykrywa dostępne kamery przez `QMediaDevices.videoInputs()`
+- Zwraca listę `CameraInfo` z nazwą, id i listą obsługiwanych formatów (rozdzielczość × FPS)
+- Formaty deduplikowane i posortowane (największa rozdzielczość pierwsza)
+- Obsługa braku kamer bez crasha
+
+#### CameraService (`app/camera/camera_service.py`)
+- Opakowuje `QCamera` + `QMediaCaptureSession` + `QVideoSink`
+- API: `start(CameraInfo)`, `stop()`, `reconnect()`, `set_resolution()`, `set_fps()`
+- Algorytm doboru formatu: score-based (priorytet: dopasowanie rozdzielczości, potem FPS)
+- Sygnały: `frame_ready(QVideoFrame)`, `camera_started`, `camera_stopped`, `camera_error`
+
+#### FrameDispatcher (`app/pipeline/frame_dispatcher.py`)
+- Pub/sub: `subscribe(callback, drop_if_busy=True)` / `unsubscribe(callback)`
+- `drop_if_busy=True` — klatka pomijana jeśli subskrybent jest zajęty (render)
+- `drop_if_busy=False` — każda klatka dociera (telemetria)
+- Odporny na wyjątki w subskrybentach (jeden nie blokuje pozostałych)
+
+#### TelemetryCollector (`app/telemetry/telemetry_collector.py`)
+- Subskrybuje każdą klatkę (`drop_if_busy=False`)
+- Mierzy: FPS (okno 1 s), średni frame time (ring-buffer 120 próbek), dropped frames (heurystyka 2.5× avg)
+- CPU: `psutil.Process.cpu_percent()` — tylko nasz proces, inicjalizowany w `__init__` (warmup)
+- RAM: `memory_info().wset` (Windows private working set) lub `rss` (macOS/Linux)
+- Emituje `metrics_updated(TelemetrySnapshot)` co 500 ms przez `QTimer`
+
+#### IOverlayLayer (`app/overlay/overlay_layer.py`)
+- Abstrakcja (ABC) dla pluggable overlayów
+- Interface: `paint(painter: QPainter, video_rect: QRect)`, `visible: bool`, `name: str`
+- Nowe overlaye nie wymagają modyfikacji żadnego istniejącego kodu
+
+#### TelemetryOverlay (`app/overlay/telemetry_overlay.py`)
+- Implementacja `IOverlayLayer`
+- Rysuje semi-przezroczysty box z metrykami w lewym górnym rogu video
+- Slot `on_metrics_updated(TelemetrySnapshot)` — odbiera dane z TelemetryCollector
+- Format: FPS, Frame time, Drop count, CPU %, Mem MB
+
+#### CameraView (`app/ui/camera_view.py`)
+- Zwykły `QWidget` (nie `QVideoWidget`) — render przez `QPainter` w `paintEvent`
+- Odbiera `QVideoFrame` przez slot `on_frame()`, konwertuje do `QImage.Format_RGB32`
+- Letterboxing z zachowaniem aspect ratio
+- Rejestr overlayów: `add_overlay_layer()`, `remove_overlay_layer()`, `set_all_overlays_visible()`
+- W `paintEvent`: rysuje klatkę → iteruje po warstwach, każda dostaje `painter.save()/restore()`
+
+#### MainWindow (`app/ui/main_window.py`)
+- Wires together wszystkie komponenty
+- Minimalny status bar (nazwa kamery, błędy)
+- `closeEvent` → `CameraService.stop()`
+
+#### AppMenuBar (`app/ui/menu_bar.py`)
+- Menu **Camera**: lista wykrytych kamer (radio), Reconnect
+- Menu **Video**: Resolution submenu, FPS submenu (pobierane z `QCameraDevice.videoFormats()`)
+- Menu **Debug**: Show Overlay (toggle), Console Logging (toggle poziom logowania)
+
+---
+
+## Co działało na Windows 11 (dev)
+
+- Wykrycie wbudowanej kamery laptopa
+- Podgląd w czasie rzeczywistym
+- Przełączanie rozdzielczości i FPS z menu
+- Overlay z metrykami widoczny i aktualizowany
+- Toggle overlay przez Debug menu
+- Logowanie do konsoli przez Debug menu
+- Reconnect po zmianie kamery
+- Letterboxing przy resize okna
+
+---
+
+## Co próbowaliśmy i nie wyszło
+
+### QVideoWidget jako renderer (porzucone)
+
+**Podejście:** Użycie `QVideoWidget` jako centralnego widgetu + nałożenie `OverlayWidget` (child lub sibling).
+
+**Problem:** Na Windows `QVideoWidget` tworzy natywne okno HWND z powierzchnią D3D (Media Foundation backend). Natywna powierzchnia jest rysowana poza hierarchią Qt i zawsze przykrywa wszystkie `QWidget` — niezależnie od:
+- kolejności z-order (`raise_()`)
+- rodzica (child/sibling)
+- flag okna
+- `WA_TranslucentBackground` / `WA_NoSystemBackground`
+
+Żaden `QWidget` nie może się wyświetlić nad `QVideoWidget` na Windows.
+
+**Próby ratowania:**
+1. `OverlayWidget` jako child `QVideoWidget` — zasłonięty przez natywną powierzchnię
+2. Kontener `QWidget` z `QVideoWidget` i `OverlayWidget` jako rodzeństwo — nadal zasłonięty
+3. `setWindowFlags(FramelessWindowHint)` na child widget — odrywa widget od rodzica, tworzy osobne (niewidoczne) okno top-level
+
+**Rozwiązanie:** Porzucenie `QVideoWidget`. Własny `CameraView(QWidget)` odbiera klatki przez `QVideoSink`, konwertuje do `QImage` i rysuje przez `QPainter`. Overlay w tym samym `paintEvent` — brak konfliktu z natywnym renderowaniem.
+
+### OverlayWidget jako osobny QWidget (porzucone)
+
+**Podejście:** `OverlayWidget` z `WA_TransparentForMouseEvents` i `WA_TranslucentBackground` nałożony na video.
+
+**Problem:** Poza konfliktem z `QVideoWidget`, `WA_TranslucentBackground` na child widget działa tylko gdy rodzic też jest transparentny — Qt nie komponuje dziecka z tłem rodzica innym niż własne. W praktyce overlay był niewidoczny lub zasłaniał video czarnym prostokątem.
+
+---
+
+## Znane ograniczenia i uwagi
+
+### Pomiar CPU
+
+`psutil.Process.cpu_percent()` zwraca procent **względem jednego rdzenia** (np. 50% = pół rdzenia). Na wielordzeniowym procesorze 15% w Task Managerze (uśrednione po rdzeniach) może odpowiadać 50% na jednym rdzeniu. To nie jest błąd — to różna metodologia. Task Manager pokazuje `total_cpu / num_cores`, psutil pokazuje `cpu_time / wall_time`.
+
+Jeśli potrzebny jest widok "jak Task Manager": `process.cpu_percent() / psutil.cpu_count()`.
+
+### Pomiar RAM
+
+`memory_info().wset` (Windows) = Private Working Set = to co Task Manager pokazuje w kolumnie "Pamięć". RSS zawiera też współdzielone biblioteki (Qt DLLs ~40 MB) i dlatego było zawyżone. Na macOS używane jest `rss` (tam `wset` nie istnieje).
+
+### Wydajność konwersji klatek
+
+`QVideoFrame.toImage()` + `convertToFormat(RGB32)` wykonuje się na CPU. Przy 1080p60 to koszt ~1-3 ms/klatkę. Dla MVP akceptowalny. Przy przyszłej integracji YOLO warto rozważyć bezpośredni dostęp do danych przez `QVideoFrame.map()` i przekazywanie raw bufora do GPU.
+
+### Brak testów integracyjnych
+
+Testy jednostkowe pokrywają `FrameDispatcher` i `TelemetryCollector` w izolacji (bez Qt event loop). Brak testów `CameraView`, `CameraService` i `MainWindow` — wymagałyby `QApplication` i mockowania urządzeń.
+
+---
+
+## Stan zgodności z PRD (01-mvp-preview.md)
+
+| Wymaganie | Status |
+|---|---|
+| Realtime camera preview | Zaimplementowane |
+| Camera switching | Zaimplementowane |
+| Resolution selection | Zaimplementowane |
+| FPS selection | Zaimplementowane |
+| Reconnect/restart | Zaimplementowane |
+| Realtime FPS metric | Zaimplementowane |
+| Frame time metric | Zaimplementowane |
+| Dropped frames detection | Zaimplementowane (heurystyka) |
+| CPU usage metric | Zaimplementowane |
+| Memory usage metric | Zaimplementowane |
+| Overlay system | Zaimplementowane (IOverlayLayer) |
+| Performance metrics display | Zaimplementowane (TelemetryOverlay) |
+| Minimal GUI | Zaimplementowane |
+| Camera menu | Zaimplementowane |
+| Resolution/FPS menu | Zaimplementowane |
+| Debug/telemetry options | Zaimplementowane |
+| Architecture ready for AI subscribers | Zaimplementowane (IOverlayLayer + FrameDispatcher) |
+| Low latency preview | Zaimplementowane (drop-if-busy w dispatcher) |
+| Non-blocking GUI thread | Zaimplementowane |
+
+---
+
+## Następne kroki (poza MVP)
+
+- Walidacja na Mac Mini z kamerą ELP (AVFoundation backend, macOS Ventura)
+- Snapshot / recording
+- Integracja YOLO: `YoloBboxOverlay(IOverlayLayer)` + worker w osobnym procesie
+- Integracja OCR
+- Optymalizacja konwersji klatek (QVideoFrame.map() → numpy → GPU)
+- Testy integracyjne z QApplication + mock camera

tests/test_telemetry_collector.py

@@ -10,7 +10,7 @@ from unittest.mock import MagicMock, patch
 class TestTelemetryCollector:
     """Test telemetry calculations in isolation (no Qt event loop required)."""
 
-    def _make_collector(self):
+    def _make_collector(self, cpu_count: int = 8):
         """Construct a TelemetryCollector bypassing Qt machinery."""
         from app.telemetry.telemetry_collector import TelemetryCollector
 
@@ -23,8 +23,11 @@ class TestTelemetryCollector:
         col._dropped_frames = 0
         col._fps_window = deque()
         col._fps_window_size_s = 1.0
+        col._target_fps = None
+        col._cpu_count = cpu_count
+
         col._process = MagicMock()
-        # Simulate Windows: wset is present and takes priority over rss
+        # Simulate Windows: wset takes priority over rss
         mem_info = MagicMock()
         mem_info.wset = 50 * 1024 * 1024   # 50 MB private working set
         mem_info.rss = 70 * 1024 * 1024    # RSS (larger, includes shared)
@@ -40,7 +43,6 @@ class TestTelemetryCollector:
     def test_fps_counts_frames_in_window(self):
         col = self._make_collector()
         now = time.perf_counter()
-        # Simulate 30 frames within the last second
         for i in range(30):
             col._fps_window.append(now - 0.9 + i * 0.03)
         snap = col._compute_snapshot()
@@ -60,7 +62,6 @@ class TestTelemetryCollector:
 
     def test_frame_time_average(self):
         col = self._make_collector()
-        # 10 frames at 33.3 ms each
         interval = 0.0333
         for _ in range(10):
             col._frame_times.append(interval)
@@ -69,7 +70,6 @@ class TestTelemetryCollector:
 
     def test_drop_detection(self):
         col = self._make_collector()
-        # Seed with 10 normal frames at ~16 ms
         normal_interval = 0.016
         now = time.perf_counter()
         col._last_frame_time = now - normal_interval * 10
@@ -77,15 +77,11 @@ class TestTelemetryCollector:
             col._last_frame_time += normal_interval
             col._frame_times.append(normal_interval)
 
-        # Simulate a big gap (3× normal) — should trigger drop detection
-        col._last_frame_time = now - normal_interval * 10  # reset base
-        # Manually call on_frame-like logic
+        col._last_frame_time = now
         with patch("app.telemetry.telemetry_collector.time") as mock_time:
-            # Set last_frame_time to something reasonable
             col._last_frame_time = now
             big_delta = normal_interval * 5  # 5× average → drop
             mock_time.perf_counter.return_value = now + big_delta
-            # Replicate the drop detection logic
             delta = big_delta
             col._frame_times.append(delta)
             avg = sum(col._frame_times) / len(col._frame_times)
@@ -110,3 +106,34 @@ class TestTelemetryCollector:
         col = self._make_collector()
         snap = col._compute_snapshot()
         assert snap.memory_mb == 50.0
+
+    def test_cpu_sys_is_core_divided_by_cpu_count(self):
+        col = self._make_collector(cpu_count=8)
+        col._process.cpu_percent.return_value = 80.0  # 80% of one core
+        snap = col._compute_snapshot()
+        assert snap.cpu_percent_core == 80.0
+        assert snap.cpu_percent_sys == round(80.0 / 8, 1)
+
+    def test_cpu_sys_never_exceeds_100_on_single_core_machine(self):
+        col = self._make_collector(cpu_count=1)
+        col._process.cpu_percent.return_value = 95.0
+        snap = col._compute_snapshot()
+        assert snap.cpu_percent_sys == snap.cpu_percent_core == 95.0
+
+    def test_cpu_sys_le_cpu_core(self):
+        """cpu_percent_sys must always be <= cpu_percent_core."""
+        col = self._make_collector(cpu_count=4)
+        col._process.cpu_percent.return_value = 150.0
+        snap = col._compute_snapshot()
+        assert snap.cpu_percent_sys <= snap.cpu_percent_core
+
+    def test_target_fps_none_by_default(self):
+        col = self._make_collector()
+        snap = col._compute_snapshot()
+        assert snap.target_fps is None
+
+    def test_set_target_fps_reflected_in_snapshot(self):
+        col = self._make_collector()
+        col.set_target_fps(60.0)
+        snap = col._compute_snapshot()
+        assert snap.target_fps == 60.0