update sensor bench

src/sensor_bench/camera_discovery.py

@@ -0,0 +1,138 @@
+"""Discover USB cameras for Sensor Bench (Windows DSHOW/MSMF, Linux V4L2)."""
+
+from __future__ import annotations
+
+import contextlib
+import os
+import sys
+from dataclasses import dataclass
+
+import cv2
+
+DEFAULT_MAX_CAMERA_INDEX = 10
+
+
+@dataclass(frozen=True)
+class CameraInfo:
+    index: int
+    backend_name: str
+    backend_api: int
+    width: int
+    height: int
+
+    @property
+    def source(self) -> str:
+        return str(self.index)
+
+    def label(self) -> str:
+        return f"{self.index} ({self.width}x{self.height}) [{self.backend_name}]"
+
+
+@contextlib.contextmanager
+def _suppress_opencv_noise():
+    """Hide OpenCV VideoCapture probe warnings (stderr + OpenCV log)."""
+    prev_level = None
+    set_level = None
+    try:
+        logging = getattr(getattr(cv2, "utils", None), "logging", None)
+        if logging is not None:
+            set_level = getattr(logging, "setLogLevel", None)
+            get_level = getattr(logging, "getLogLevel", None)
+            silent = getattr(logging, "LOG_LEVEL_SILENT", 0)
+            if set_level is not None:
+                if get_level is not None:
+                    prev_level = get_level()
+                set_level(silent)
+    except Exception:
+        prev_level = None
+
+    devnull = open(os.devnull, "w")
+    try:
+        with contextlib.redirect_stderr(devnull):
+            stderr_fd = sys.stderr.fileno()
+            saved_fd = os.dup(stderr_fd)
+            try:
+                os.dup2(devnull.fileno(), stderr_fd)
+                yield
+            finally:
+                os.dup2(saved_fd, stderr_fd)
+                os.close(saved_fd)
+    finally:
+        devnull.close()
+        if set_level is not None and prev_level is not None:
+            try:
+                set_level(prev_level)
+            except Exception:
+                pass
+
+
+def _backend_candidates() -> list[tuple[str, int]]:
+    candidates: list[tuple[str, int]] = []
+    if sys.platform == "win32":
+        if hasattr(cv2, "CAP_DSHOW"):
+            candidates.append(("DSHOW", cv2.CAP_DSHOW))
+        if hasattr(cv2, "CAP_MSMF"):
+            candidates.append(("MSMF", cv2.CAP_MSMF))
+    elif sys.platform.startswith("linux"):
+        if hasattr(cv2, "CAP_V4L2"):
+            candidates.append(("V4L2", cv2.CAP_V4L2))
+    if not candidates:
+        candidates.append(("ANY", cv2.CAP_ANY))
+    return candidates
+
+
+def _try_open(index: int, backend_name: str, backend_api: int) -> CameraInfo | None:
+    cap = cv2.VideoCapture(index, backend_api)
+    if not cap.isOpened():
+        cap.release()
+        return None
+    ok, frame = cap.read()
+    width = int(cap.get(cv2.CAP_PROP_FRAME_WIDTH) or 0)
+    height = int(cap.get(cv2.CAP_PROP_FRAME_HEIGHT) or 0)
+    if not ok or frame is None:
+        if width <= 0 or height <= 0:
+            cap.release()
+            return None
+    else:
+        h, w = frame.shape[:2]
+        width = width or int(w)
+        height = height or int(h)
+    cap.release()
+    return CameraInfo(
+        index=index,
+        backend_name=backend_name,
+        backend_api=backend_api,
+        width=width,
+        height=height,
+    )
+
+
+def list_cameras(max_index: int = DEFAULT_MAX_CAMERA_INDEX) -> list[CameraInfo]:
+    """Probe indices ``0 .. max_index`` and return working cameras."""
+    found: list[CameraInfo] = []
+    seen_indices: set[int] = set()
+    backends = _backend_candidates()
+
+    with _suppress_opencv_noise():
+        for index in range(0, max_index + 1):
+            for backend_name, backend_api in backends:
+                info = _try_open(index, backend_name, backend_api)
+                if info is None:
+                    continue
+                if index in seen_indices:
+                    break
+                found.append(info)
+                seen_indices.add(index)
+                break
+    return found
+
+
+def pick_default_camera(cameras: list[CameraInfo], preferred: str | None = None) -> str | None:
+    if not cameras:
+        return None
+    preferred = (preferred or "").strip()
+    if preferred:
+        for cam in cameras:
+            if cam.source == preferred:
+                return cam.source
+    return cameras[0].source