达不到帧率的判据改用实测速率（DSHOW 回读值会说谎），探针加帧率扫描 - What: short_capture_fallacy() 改为以**实测**速率为准（新增 measured_fps 关键字参数），消息改成"it delivers about 15 fps while the config asks for 30 (1920x1080 reported 30, MJPG/DSHOW)"——把驱动自报值降级为"矛盾的一部分"而不是判据；app_window 的 _check_capture_negotiation() 相应改为用 packet 的 capture_fps（实测）判据、实测为 0 时不下结论（等窗口填满）。tools/camera_probe.py 重写：probe() 返回结构体、format_row() 把 reported 与 measured 分列并在达不到 90% 时标 "<-- misses the request"；新增 --samples 与**帧率扫描**（同一格式依次申请 60/30/20/15/10 fps，逐行给实测值与"跟随申请 / 只有申请的 x 倍"的判断，最后给"本次看到的ceiling"）。tests/test_worker_frame_rate.py 的归因测试同步更新，并显式覆盖"驱动自报 30 而实测 15 必须判为不达标"与"没有实测值时不说话"。 - Why: 用户跑探针的结果推翻了我上一轮的判据：MJPG 1920x1080@30 -> MJPG 1920x1080 @ 30.0 measured 15.0。DSHOW 后端下 CAP_PROP_FPS 只是回读你设的值，所以 SDK 的 status.fps 同样不可信 —— 我原来比较"申请 vs 协商"等于拿申请跟自己比，那个提示永远不会出现（用户实际看到的只有轨道上的实测 16.7）。这也解释了为什么这件事必须靠实测：真实速率只能测出来。另外探针显示 1280x720 MJPG 实测也是 15、YUYV 只有 1 fps，说明换分辨率不解决问题，需要区分"摄像头本身的上限"与"我们申请多少就被砍半"。 - Verification: shared 全量 161 passed（含新增/更新的 3 项断言）；studio 91 passed；ui_check 554 项检查 0 失败；探针在本机（无摄像头）仍返回 1 并给出解释，format_row/_decode 单测通过（"reported 30.0 measured 15.0 ... <-- misses the request"）。 - Not in this change: 未改 SDK 采集申请顺序/后端；未做自动降级；frames.csv 仍未记录 process_ms/capture_fps。

shared/src/orisys_app_shared/acquisition/sdk_worker.py

@@ -195,24 +195,33 @@ def capture_status_of(sensor) -> dict:
     }
 
 
-def short_capture_fallacy(status: Mapping[str, Any] | None) -> str:
-    """A one-line description of a capture negotiation that fell short.
+def short_capture_fallacy(
+    status: Mapping[str, Any] | None, *, measured_fps: float = 0.0
+) -> str:
+    """A one-line description of a capture that falls short of the request.
 
-    Empty when the driver gave what was asked for (or when either half is
-    unknown): this exists to be *said*, not to fill a field.
+    The rate to compare against is the **measured** one. OpenCV's DSHOW backend
+    reports ``CAP_PROP_FPS`` back as whatever was set — a camera that advertises
+    30 and delivers 15 says "30.0" — so the reported figure cannot be the evidence
+    (it is included only to show the contradiction).
+
+    Empty when nothing measurable fell short, or when either half is unknown: this
+    exists to be *said*, not to fill a field.
     """
     if not isinstance(status, Mapping):
         return ""
     requested = dict(status.get("requested") or {})
     negotiated = dict(status.get("negotiated") or {})
-    wanted = requested.get("fps")
-    got = negotiated.get("fps")
     try:
-        wanted_value = float(wanted)
-        got_value = float(got)
+        wanted_value = float(requested.get("fps"))
     except (TypeError, ValueError):
         return ""
-    if wanted_value <= 0 or got_value <= 0 or got_value >= wanted_value * 0.9:
+    if wanted_value <= 0:
+        return ""
+    measured = float(measured_fps or 0.0)
+    if measured <= 0.0:
+        return ""
+    if measured >= wanted_value * 0.9:
         return ""
     size = ""
     width, height = negotiated.get("width"), negotiated.get("height")
@@ -220,11 +229,13 @@ def short_capture_fallacy(status: Mapping[str, Any] | None) -> str:
         size = f"{int(width)}x{int(height)} "
     fourcc = str(negotiated.get("fourcc") or "").strip()
     backend = str(negotiated.get("backend") or "").strip()
+    reported = negotiated.get("fps")
     detail = "/".join(part for part in (fourcc, backend) if part)
     return (
-        f"the camera negotiated {size}@{got_value:g} fps "
-        f"(the config asks for {wanted_value:g})"
-        + (f" [{detail}]" if detail else "")
+        f"it delivers about {measured:g} fps while the config asks for "
+        f"{wanted_value:g}"
+        + (f" ({size}reported {float(reported):g}" if reported else f" ({size}")
+        + (f", {detail})" if detail else ")")
     )
 
 

shared/tests/test_worker_frame_rate.py

@@ -312,11 +312,19 @@ def test_a_low_camera_rate_is_recorded_as_a_negotiation(monkeypatch):
         assert status["negotiated"]["fps"] == 16.67, status
         assert status["negotiated"]["fourcc"] == "MJPG"
         assert status["negotiated"]["backend"] == "MSMF"
-        detail = short_capture_fallacy(status)
-        assert "1920x1080" in detail and "16.67" in detail and "30" in detail, detail
-        # A driver that gives what was asked for says nothing at all.
+        # The *measured* rate is the evidence: DSHOW echoes the requested fps back
+        # as the "negotiated" one, so trusting that number would hide a camera
+        # that advertises 30 and delivers 15 (measured on this project's camera).
+        detail = short_capture_fallacy(status, measured_fps=16.67)
+        assert "16.67" in detail and "30" in detail and "1920x1080" in detail, detail
+        assert short_capture_fallacy(status, measured_fps=29.5) == ""
+        # A driver reporting 30 while delivering half of it is the case that
+        # matters, and it must not slip through.
         source.status.fps = 30.0
-        assert short_capture_fallacy(worker.capture_status()) == ""
+        echoing = worker.capture_status()
+        assert short_capture_fallacy(echoing, measured_fps=15.0) != ""
+        # No measured rate yet: nothing to say.
+        assert short_capture_fallacy(echoing) == ""
     finally:
         worker.stop(wait=True)
         _restore(saved)