帧率读数改为"采集时刻"的到达率，并在旁边显示每帧耗时 - What: sdk_worker 的采集循环里把帧率与时间戳的取样点从"算完之后"(t1) 改成"取到这一帧的时刻"(t0)——frame_times、SIGPkt.mono_t（实时分支）与 last_frame_mono（断线判定）都用 t0，所以 16.7 FPS 现在明确表示"帧是以这个速率到达的"，而不是把流水线耗时当成帧率；process_ms 的终点从 process_chain 之后改到 read_forces_from_sensor 之后（t_done），因此它终于涵盖这一帧的**全部**开销（此前漏掉力值读取）；last_frame_at 仍取 t1（compute chain 结束）作为节拍相位参考，行为不变（帧率测试仍然通过）。app_window 在 视图▸显示帧率 打开时把每帧耗时一起显示在轨道摘要里："16.7 FPS · 58 ms"，并新增 _latest_process_ms（随会话/回放清空）。tests/test_ui_smoke.py 增加一项断言：轨道同时给出速率与耗时，且没有耗时数据时仍只显示速率。 - Why: 用户看到 Studio 上方显示 16.67 fps 而不是 30，问是不是显示错了。查证结论：这个数字来自 packet.fps，是采集循环真实的"到达率"，记录里的行数也是它——不是界面 bug；但它有两个缺陷让这个数字**无法单独判读**：(1) 取样点在算完之后，于是它把本机流水线耗时混进了"设备帧率"；(2) 旁边没有每帧耗时，而"16.7 FPS"既可能是摄像头只给 16.7，也可能是流水线跟不上 30（实测：每帧 ≤30 ms 时循环仍能跑满 29.3 fps；40/50/60/70 ms 分别掉到 24.7/19.8/16.5/14.1 fps——16.67 恰好对应每帧约 60 ms）。本机 app 配置（365x365 拼接、dis_mode=3）在 480p 素材上 process_chain+力值读取只要 ~10 ms（上限约 100 fps），因此本次报的 16.67 不可能是这台机器上这个配置的流水线瓶颈；两种可能必须靠耗时数据区分。 - Verification: pytest shared/tests/test_worker_frame_rate.py 4 项全过（30 fps 设备仍被消费在 29.3 fps）；studio 全量 90 passed（新增 1 项）；ui_check 554 项检查 0 失败；真实 SDK 复测：文件源 55.4 fps 到达率、每帧 18.2 ms（含力值读取）。 - Not in this change: frames.csv 仍未记录 process_ms（下次改记录格式、加未滤波 17 列时一并加，避免连做两次版本升级）；未动节拍逻辑本身。

apps/studio/src/orisys_studio/app_window.py

@@ -197,6 +197,9 @@ class StudioMainWindow(QMainWindow):
         #: Was the most recent readout valid? ``None`` before the first sample.
         self._last_sample_valid: bool | None = None
         self._latest_fps: float | None = None
+        #: What the last frame cost to acquire and process, in milliseconds — the
+        #: other half of the frame-rate reading.
+        self._latest_process_ms: float | None = None
         #: Last coefficients file written by the calibration panel (not applied).
         self._last_calibration_export = ""
         self._depth_range_value: tuple[float, float] | None = None
@@ -1357,6 +1360,11 @@ class StudioMainWindow(QMainWindow):
                 detail = t("status.rail_video_name", name=Path(path).name)
         if self._show_fps and self._latest_fps is not None:
             fps = f"{self._latest_fps:.1f} FPS"
+            # The cost goes next to the rate because one without the other cannot
+            # be read: "16.7 FPS" is either a slow camera or a pipeline that
+            # cannot keep up, and only this number tells the two apart.
+            if self._latest_process_ms:
+                fps = f"{fps} · {self._latest_process_ms:.0f} ms"
             detail = f"{detail} · {fps}" if detail else fps
         self.toolbar.set_source_summary(detail)
         # The full path and the replay's notes do not fit on a 30 px rail, so
@@ -2111,6 +2119,7 @@ class StudioMainWindow(QMainWindow):
         self._last_display_available = None
         self._last_sample_valid = None
         self._latest_fps = None
+        self._latest_process_ms = None
         self._depth_range_value = None
         self._last_depth_frame = None
         # The new session's store is cleared *before* the charts are attached to
@@ -2197,6 +2206,7 @@ class StudioMainWindow(QMainWindow):
         if not keep_frame:
             self.arrow_panel.clear_preview(t("panels.arrow_empty"))
         self._latest_fps = None
+        self._latest_process_ms = None
         self._last_sample_valid = None
         self._last_display_fallback = None
         self._last_display_available = None
@@ -2365,6 +2375,7 @@ class StudioMainWindow(QMainWindow):
             self._render_run_image(packet)
         if is_new:
             self._latest_fps = getattr(packet, "fps", None)
+            self._latest_process_ms = getattr(packet, "process_ms", None)
         # The rail carries the live telemetry (fps, validity, calibration) and
         # the record strip its own numbers. Both compare before repainting, so
         # this is safe on a 16 ms timer.

apps/studio/tests/test_ui_smoke.py

@@ -2105,6 +2105,29 @@ def test_the_status_bar_is_a_notice_line_not_a_state_line(make_window):
     _finish(window, stuck)
 
 
+def test_the_rail_reads_the_rate_and_what_it_cost(qt_app, make_window):
+    """A frame rate alone cannot say whether we or the camera are the slow part.
+
+    ``packet.process_ms`` is the whole per-frame cost, so the rail shows it next
+    to the rate: "16.7 FPS · 58 ms" means the loop cannot keep up, while
+    "16.7 FPS · 6 ms" means the camera is only delivering 16.7.
+    """
+    window = make_window()
+    window._show_fps = True
+    window._latest_fps = 16.67
+    window._latest_process_ms = 58.4
+    window._refresh_status_rail()
+    text = window.toolbar.source_summary.text()
+    assert "16.7 FPS" in text, text
+    assert "58 ms" in text, text
+
+    # Without a measured cost the rate is still shown, on its own.
+    window._latest_process_ms = None
+    window._refresh_status_rail()
+    assert window.toolbar.source_summary.text().strip().endswith("FPS")
+    window.close()
+
+
 # ------------------------------------------------------- plot settings dialog
 def test_the_chart_gear_opens_the_settings_dialog(qt_app, make_window):
     """The gear is the one place the filters can be changed from the UI."""