feat(studio): 回放可以直接播放「一条视频」——不必先按「从视频重算」

- What: 新增 `record/playback.py::VideoOnlySource`（一个视频文件的时间轴：时长来自
  `CAP_PROP_FRAME_COUNT/FPS`，按位置解码、顺序前进时只 step 不 seek、越界钳到最后一帧；没有帧计数或帧率就
  拒绝而不是猜）；`ReplayController` 增加 `open_video()`/`has_video()`/`is_video_only()`/`video_path()`，
  `duration_s`/`set_position`/`_refresh_video`/`close` 都覆盖这条路径，并在 `warnings_text()` 里说明
  "这段视频没有配套记录"；`app_window._load_replay_video()` 改为按"这条视频是什么"处理：
  同目录有 `forces.csv` → 当记录打开（原行为），否则**当视频播放**（曲线为空、明确提示），只有连解码都不行
  才拒绝并给出 `从视频重算` 的出路；transport/`_render_replay_frame`/`_replay_owns_image`/状态栏 tooltip
  一律改用 `has_video()`（而查曲线的 `_apply_replay_source` 仍用 `is_loaded()`）。
- Why: 用户要求"只导入视频也能用回放按钮"。此前有录像必须走「从视频重算」才能动，因为一条裸视频被当成
  "不是记录"而拒绝（更早是当成空记录"成功"打开→零长度时间轴→按回放没反应）。这两种都不对：视频就是可以看的
  东西，只是没有力值；把它按视频播放、把"没有记录"如实写在标签与提示里，才既不骗人也不挡人。
- Verification: `shared/tests/test_playback.py` +3（VideoOnlySource：时长/按位置取帧/顺序前进/越界钳位/关闭后
  返回空/不可解码与无时间轴被拒；顺带修回我在插入新类时弄丢的 `list_recordings` 的 `base = Path(root)`）；
  `test_ui_smoke.py` 改 1 增 1（裸视频可播放：`is_video_only`、transport 可用、tooltip 说明曲线为空、
  按下后位置推进且解出画面、停止有效；不可解码文件仍被拒并提示）；ui_check 587 项 0 失败（回放段改为验证
  "裸视频能播"）；apps/studio 与 shared 全量通过；locale_check 0 缺失。
- Not in this change: 裸视频的曲线（没有 CSV 就没有力值，这是事实而不是待办）；裸视频的三维形变（要形变得走
  「从视频重算」，面板标签在回放里仍然是"录像不含三维场"）；多段视频拼接播放。

apps/studio/config/locales/en_US.json

@@ -103,6 +103,7 @@
     "playback_pause_tip": "Pause playback (dragging the cursor, box zoom or the wheel also pauses)",
     "playback_disabled": "Open a recorded video first (“Choose a recorded video…” at the top left)",
     "playback_needs_recording": "This video has no recording beside it (no forces.csv): replay needs a recording; to just watch the video use View ▸ Recompute forces from the video",
+    "playback_video_only": "Play this video (no recording beside it: the picture plays, the force charts are empty)",
     "reset": "Reset",
     "stop_playback": "Stop",
     "stop_playback_tip": "Stop the replay: plain playback and a “recompute from the video” pass both stop here (Esc does the same).",
@@ -213,7 +214,9 @@
     "no_video": "This recording has no usable video segment",
     "open_failed": "Could not open that recording: {error}",
     "not_a_recording": "“{name}” is not a recording: its folder has no forces.csv (a recording is the video plus forces.csv and session.json). Replay needs a recording; to just watch this video, use “Recompute forces from the video”.",
-    "video_only_panel": "This is not a recording (no forces.csv beside it)\nTo watch this video, use\nView ▸ Recompute forces from the video",
+    "video_only_opened": "“{name}” has no recording beside it (no forces.csv), so it is playing as a video: the picture and the timeline work, the force charts are empty. For forces and deformation use View ▸ Recompute forces from the video.",
+    "video_only_notice": "This video has no recording beside it (no forces.csv): it plays, but the force charts and the recording details are empty.",
+    "video_only_panel": "This is not a recording, and this video cannot be decoded (no forces.csv beside it, and it does not read as playable video)\nYou can still try View ▸ Recompute forces from the video",
     "empty_recording": "This recording has no playable picture (no raw_*.mp4 segment), so it cannot be replayed",
     "none_found": "No recording found under outputs/recordings",
     "frame_dropped": "This frame never reached the video (the record queue overflowed)",

apps/studio/config/locales/zh_CN.json

@@ -103,6 +103,7 @@
     "playback_pause_tip": "暂停播放（拖动游标、框选或滚轮也会暂停）",
     "playback_disabled": "先打开一段录制视频（左上「选择录制视频…」）",
     "playback_needs_recording": "这段视频旁边没有记录（缺 forces.csv）：回放需要一条记录；只想看视频请用 视图 ▸ 从视频重算力值",
+    "playback_video_only": "播放这段视频（没有配套记录：可以看画面，力曲线为空）",
     "reset": "重置",
     "stop_playback": "停止",
     "stop_playback_tip": "停止回放：无论是普通播放还是「从视频重算」通道，都在这里停下（Esc 同效）。",
@@ -213,7 +214,9 @@
     "no_video": "这段录制没有可用的视频分段",
     "open_failed": "无法打开该录制: {error}",
     "not_a_recording": "「{name}」不是一条记录：同目录没有 forces.csv（一条记录 = 录像 + forces.csv + session.json）。回放需要记录；只想看这段视频请用「从视频重算力值」。",
-    "video_only_panel": "这不是一条记录（同目录缺少 forces.csv）\n只想看这段视频请用\n视图 ▸ 从视频重算力值",
+    "video_only_opened": "「{name}」没有配套记录（无 forces.csv），已按视频播放：可以看画面与拖时间轴，力曲线为空。要得助力值/形变请用 视图 ▸ 从视频重算力值。",
+    "video_only_notice": "这段视频没有配套记录（同目录无 forces.csv）：可以播放，但力曲线与记录信息为空。",
+    "video_only_panel": "这不是一条记录，而且无法解码这段视频（没有 forces.csv，也不像可播放的视频文件）\n可以试试 视图 ▸ 从视频重算力值",
     "empty_recording": "这条记录没有可播放的画面（没有 raw_*.mp4 视频分段），因此无法回放",
     "none_found": "outputs/recordings 下没有找到录制",
     "frame_dropped": "该帧未被写入视频（记录队列曾溢出）",

apps/studio/src/orisys_studio/app_window.py

@@ -813,7 +813,7 @@ class StudioMainWindow(QMainWindow):
             # The recompute pass owns the timeline: its samples are arriving in
             # order and the cursor follows them.
             return
-        if self._view_preset == "replay" and self.replay.is_loaded():
+        if self._view_preset == "replay" and self.replay.has_video():
             self.replay.set_position(float(t_rel_s))
 
     def _on_open_recording(self) -> None:
@@ -835,25 +835,33 @@ class StudioMainWindow(QMainWindow):
         self._load_replay_video(Path(chosen))
 
     def _load_replay_video(self, video: Path) -> bool:
-        """Open the recording a recorded video belongs to.
+        """Open what the chosen video *is*: a recording, or just a video.
 
-        A **recording** is a directory that holds ``forces.csv`` beside the video —
-        the same rule ``list_recordings`` uses, so the two cannot disagree about what
-        a recording is. A video on its own is not one: it has no force rows and no
-        timeline. Opening its folder anyway "succeeded" (the reader tolerates a
-        directory with nothing in it) and then left the transport button playing a
-        zero-length timeline, which is why choosing a video and pressing 回放 did
-        nothing at all. So a bare video is refused with what is missing, and the rail
-        keeps its path so 「从视频重算」 can still run the chain over it.
+        A **recording** is a directory that holds ``forces.csv`` beside the video — the
+        same rule ``list_recordings`` uses, so the two cannot disagree about what a
+        recording is. Anything else is still worth watching: an operator who points at
+        a clip expects the transport to play it, not to be told to press a different
+        button first. So a bare video is opened for playback (no forces, no session
+        metadata, and the rail says so), and only a file that cannot be decoded at all
+        is refused — with what is missing, and with 「从视频重算」 still offered, because
+        that is the only way to get *numbers* out of a video that has no recording.
         """
         video = Path(video)
         folder = video.parent if video.is_file() else video
         if not (folder / "forces.csv").is_file():
+            if video.is_file() and self.replay.open_video(video):
+                self.toolbar.set_video_path(str(video))
+                self.prefs["video_path"] = str(video)
+                self._set_source_mode("video")
+                self._render_replay_frame()
+                self._notify(t("playback.video_only_opened", name=video.name))
+                self._refresh_replay_state()
+                return True
             if video.is_file():
                 self.toolbar.set_video_path(str(video))
                 self.prefs["video_path"] = str(video)
                 self._set_source_mode("video")
-            if not self.replay.is_loaded():
+            if not self.replay.has_video():
                 # Nothing else is on screen, so the reason belongs in the panel that
                 # would have shown the frames — not only in a status line that expires.
                 self.arrow_panel.clear_preview(t("playback.video_only_panel"))
@@ -870,7 +878,7 @@ class StudioMainWindow(QMainWindow):
         """Whether 「从视频重算」 has something to read: a recording, or a video file."""
         if self._view_preset != "replay":
             return False
-        if self.replay.is_loaded():
+        if self.replay.has_video():
             return True
         named = self.toolbar.video_path()
         return bool(named) and Path(named).is_file()
@@ -907,7 +915,11 @@ class StudioMainWindow(QMainWindow):
 
     def _refresh_replay_state(self) -> None:
         """Push the engine's state into the charts' mode and the rail."""
-        if self.replay.is_loaded() and not self.toolbar.video_path():
+        if self.replay.is_video_only() and not self.toolbar.video_path():
+            path = self.replay.video_path()
+            if path is not None:
+                self.toolbar.set_video_path(str(path))
+        elif self.replay.is_loaded() and not self.toolbar.video_path():
             # Opened without naming a video (the file menu's "latest"): name the
             # segment that is on screen so the rail states the same thing the
             # picker would.
@@ -944,7 +956,7 @@ class StudioMainWindow(QMainWindow):
                 self._stop_run(reason="user_stop")
             self.toolbar.set_run_checked(bool(playing) and self._running)
             return
-        if playing and self.replay.is_loaded():
+        if playing and self.replay.has_video():
             self._start_playback()
         else:
             self._pause_playback()
@@ -1056,13 +1068,15 @@ class StudioMainWindow(QMainWindow):
             self.mesh3d_panel.show_reference_only()
         if self._view_preset == "replay":
             self.mesh3d_panel.set_source_kind(self._current_source_kind())
-        if self._view_preset == "replay" and self.replay.is_loaded():
+            if self.replay.is_loaded():
                 self._apply_replay_source(True)
+            # A bare video has no charts to point at the recording, but it does have
+            # frames to show again now that the pass is over.
             self._render_replay_frame()
 
     def _render_replay_frame(self) -> None:
         """Draw what the 2D panel should show for the current replay cursor."""
-        if self._view_preset != "replay" or not self.replay.is_loaded():
+        if self._view_preset != "replay" or not self.replay.has_video():
             return
         if self._recompute_running:
             # The pipeline is drawing its own frames (see ``_replay_owns_image``).
@@ -1454,12 +1468,16 @@ class StudioMainWindow(QMainWindow):
 
     def _update_run_enabled(self) -> None:
         if self.toolbar.run_role() == "playback":
-            # In the replay view the button is a transport: it needs a recording,
-            # not a runnable sensor. While it plays it stays enabled so it can be
-            # paused.
-            loaded = self.replay.is_loaded()
+            # In the replay view the button is a transport: it needs something to
+            # play — a recording, or a bare video — not a runnable sensor. While it
+            # plays it stays enabled so it can be paused.
+            loaded = self.replay.has_video()
             if loaded:
-                reason = ""
+                reason = (
+                    t("toolbar.playback_video_only")
+                    if self.replay.is_video_only()
+                    else ""
+                )
             elif self._can_recompute():
                 # A video was chosen but it is not a recording: the transport cannot
                 # play it, and the tooltip says which button can show it instead of
@@ -1615,7 +1633,8 @@ class StudioMainWindow(QMainWindow):
         # they live in the summary's tooltip (the bar that used to show them is
         # gone: the two views share one layout).
         tip_parts = [self.toolbar.video_path()]
-        if self._view_preset == "replay" and self.replay.is_loaded():
+        if self._view_preset == "replay" and self.replay.has_video():
+            # Includes the "this is a video, not a recording" note for a bare video.
             tip_parts.append(self.replay.warnings_text())
         self.toolbar.set_source_summary_tip(
             "\n".join(part for part in tip_parts if part)
@@ -2810,7 +2829,7 @@ class StudioMainWindow(QMainWindow):
         """
         return (
             self._view_preset == "replay"
-            and self.replay.is_loaded()
+            and self.replay.has_video()
             and not self._recompute_running
         )
 

apps/studio/src/orisys_studio/replay.py

@@ -14,13 +14,14 @@ is the acquisition path's job (see the studio's "recompute" mode).
 from __future__ import annotations
 
 import logging
+from pathlib import Path
 
 import numpy as np
 from PyQt5.QtCore import QObject, pyqtSignal
 from PyQt5.QtGui import QImage
 
 from orisys_app_shared.i18n import t
-from orisys_app_shared.record import RecordingReader
+from orisys_app_shared.record import RecordingReader, VideoOnlySource
 
 logger = logging.getLogger(__name__)
 
@@ -57,6 +58,8 @@ class ReplayController(QObject):
     def __init__(self, parent=None) -> None:
         super().__init__(parent)
         self._reader: RecordingReader | None = None
+        #: A video with no recording beside it: playable, but it has no measurements.
+        self._video: VideoOnlySource | None = None
         self._unit = "raw"
         self._position = 0.0
         #: The frame cache: one video image per cursor position.
@@ -67,8 +70,44 @@ class ReplayController(QObject):
 
     # ------------------------------------------------------------- recording
     def is_loaded(self) -> bool:
+        """A *recording* is open: a video with its forces and session metadata."""
         return self._reader is not None
 
+    def has_video(self) -> bool:
+        """Whether there is anything to play at all — a recording, or a bare video.
+
+        The transport asks this, not ``is_loaded``: an operator who opens a clip from
+        a camera should be able to watch it. What the *charts* ask is ``is_loaded``,
+        because a bare video has no rows to draw.
+        """
+        return self._reader is not None or self._video is not None
+
+    def is_video_only(self) -> bool:
+        return self._reader is None and self._video is not None
+
+    def video_path(self):
+        return self._video.path if self._video is not None else None
+
+    def open_video(self, path) -> bool:
+        """Open a bare video for playback (no forces, no session metadata)."""
+        self._release_reader()
+        self._release_video()
+        try:
+            self._video = VideoOnlySource(Path(path))
+        except Exception:  # noqa: BLE001 - reported through the status text
+            logger.exception("Could not open the video %s", path)
+            self._video = None
+            self._reset_frames()
+            self.recording_changed.emit(False)
+            self.status_changed.emit()
+            return False
+        self._reset_frames()
+        self._position = 0.0
+        self.recording_changed.emit(True)
+        self._refresh_warnings()
+        self.set_position(0.0)
+        return True
+
     def directory(self):
         return self._reader.directory if self._reader is not None else None
 
@@ -107,8 +146,9 @@ class ReplayController(QObject):
         return True
 
     def close(self) -> None:
-        """Drop the recording (the decoder is released with it)."""
+        """Drop whatever is open (the decoder is released with it)."""
         self._release_reader()
+        self._release_video()
         self._reset_frames()
         self.recording_changed.emit(False)
         self.status_changed.emit()
@@ -121,6 +161,14 @@ class ReplayController(QObject):
             except Exception:  # noqa: BLE001 - releasing is best effort
                 logger.debug("Could not close the recording reader", exc_info=True)
 
+    def _release_video(self) -> None:
+        video, self._video = self._video, None
+        if video is not None:
+            try:
+                video.close()
+            except Exception:  # noqa: BLE001 - releasing is best effort
+                logger.debug("Could not close the video", exc_info=True)
+
     def _reset_frames(self) -> None:
         self._video_position = None
         self._video_qimage = None
@@ -131,13 +179,15 @@ class ReplayController(QObject):
         return self._position
 
     def duration_s(self) -> float:
-        if self._reader is None:
-            return 0.0
+        if self._reader is not None:
             return float(self._reader.info().duration_s)
+        if self._video is not None:
+            return float(self._video.duration_s)
+        return 0.0
 
     def set_position(self, t_rel_s: float) -> None:
         """Move the single cursor: the video frame and the charts follow it."""
-        if self._reader is None:
+        if not self.has_video():
             return
         duration = self.duration_s()
         self._position = max(0.0, min(float(t_rel_s), duration if duration > 0 else 0.0))
@@ -168,7 +218,7 @@ class ReplayController(QObject):
         return self._video_reason
 
     def _refresh_video(self) -> None:
-        if self._reader is None:
+        if self._reader is None and self._video is None:
             self._video_position = None
             self._video_qimage = None
             self._video_reason = t("playback.none_found")
@@ -176,6 +226,15 @@ class ReplayController(QObject):
         if self._video_position == self._position:
             return
         self._video_position = self._position
+        if self._video is not None:
+            image, _frame = self._video.video_frame_at(self._position)
+            if image is None:
+                self._video_qimage = None
+                self._video_reason = t("playback.frame_unreadable")
+                return
+            self._video_reason = ""
+            self._video_qimage = _bgr_to_qimage(image)
+            return
         image, frame = self._reader.video_frame_at(self._position)
         if image is None:
             self._video_qimage = None
@@ -195,6 +254,10 @@ class ReplayController(QObject):
     def _refresh_warnings(self) -> None:
         self._warnings = ""
         if self._reader is None:
+            if self._video is not None:
+                # Not a warning: a statement of what this file *is*, so nobody reads an
+                # empty chart as a measurement of zero.
+                self._warnings = t("playback.video_only_notice")
             return
         info = self._reader.info()
         codes = self._reader.replay_warnings(sdk_version=_sdk_version())

apps/studio/src/orisys_studio/ui/toolbar.py

@@ -691,6 +691,11 @@ class ToolbarWidget(QWidget):
             key = "toolbar.playback_pause_tip" if self.btn_run.isChecked() else "toolbar.playback_tip"
             if not self._run_available and self._run_tooltip_reason:
                 self.btn_run.setToolTip(self._run_tooltip_reason)
+            elif self._run_tooltip_reason:
+                # Usable, but with something the operator should know before pressing:
+                # a bare video plays with empty charts, and the tip says so instead of
+                # hiding that behind a second hover.
+                self.btn_run.setToolTip(f"{t(key)} — {self._run_tooltip_reason}")
             else:
                 self.btn_run.setToolTip(t(key))
             return

apps/studio/tests/test_ui_smoke.py

@@ -2086,15 +2086,16 @@ def test_the_live_view_keeps_the_tracker_reset(make_window):
     window.close()
 
 
-def test_a_video_that_is_not_a_recording_is_refused_with_a_reason(
-    make_window, record_root
-):
-    """A bare video has no forces.csv, so it is not something this view can replay.
+def test_a_bare_video_plays_even_though_it_is_not_a_recording(make_window, record_root):
+    """A clip with no forces.csv beside it is still something to watch.
 
-    The reader tolerates a directory with nothing in it, so opening the video's own
-    folder as a recording used to *succeed* — and then the transport played a
-    zero-length timeline, which is what "pressing 回放 does nothing" was.
+    An operator who points at a video expects the transport to play it. Opening the
+    video's own folder as a *recording* used to "succeed" against the tolerant reader
+    and then play a zero-length timeline ("pressing 回放 does nothing"), so the fix is
+    not to refuse the file but to play it as what it is: a video, with empty charts.
     """
+    import time as _time
+
     import cv2
     import numpy as np
     from PyQt5.QtWidgets import QApplication
@@ -2106,33 +2107,81 @@ def test_a_video_that_is_not_a_recording_is_refused_with_a_reason(
         str(bare), cv2.VideoWriter_fourcc(*"mp4v"), 30.0, (64, 48)
     )
     for index in range(30):
-        writer.write(np.full((48, 64, 3), index, dtype=np.uint8))
+        writer.write(np.full((48, 64, 3), index * 8, dtype=np.uint8))
     writer.release()
     assert bare.is_file()
 
     window = _show(make_window(), (1440, 880))
+    try:
         window.brand_bar.btn_playback.click()
         QApplication.processEvents()
-    assert not window.replay.is_loaded()
+        assert not window.replay.has_video()
+        assert window._load_replay_video(bare) is True, "a playable video was refused"
+        QApplication.processEvents()
+        assert window.replay.has_video(), "nothing is playable"
+        assert window.replay.is_video_only(), "a bare video was taken for a recording"
+        assert not window.replay.is_loaded(), (
+            "a bare video must not claim to carry a recording's measurements"
+        )
+        assert window.replay.duration_s() > 0.5, window.replay.duration_s()
+        assert window.toolbar.btn_run.isEnabled(), "the transport is not offered"
+        assert t("toolbar.playback_video_only") in window.toolbar.btn_run.toolTip(), (
+            window.toolbar.btn_run.toolTip()
+        )
+        assert t("playback.video_only_notice") in window.replay.warnings_text()
+        # The charts have nothing to read, and say so rather than drawing zeros.
+        assert not window.force_plots.is_recording_source()
 
-    assert window._load_replay_video(bare) is False, (
-        "a video with no recording beside it was accepted as a recording"
+        window.toolbar.btn_run.setChecked(True)
+        QApplication.processEvents()
+        deadline = _time.time() + 3.0
+        while _time.time() < deadline and window.replay.position() < 0.4:
+            QApplication.processEvents()
+            _time.sleep(0.05)
+        assert window.replay.position() >= 0.4, (
+            f"the transport did not play the video: {window.replay.position()}"
+        )
+        assert window._play_timer.isActive()
+        image = window.replay.video_image()
+        assert image is not None and not image.isNull(), "no frame was decoded"
+        window._stop_replay_activity()
+        QApplication.processEvents()
+        assert not window._play_timer.isActive()
+    finally:
+        window.close()
+
+
+def test_a_file_that_is_not_a_video_at_all_is_refused_with_a_reason(
+    make_window, record_root
+):
+    """Not a recording *and* not decodable: say what is missing and offer recompute."""
+    from PyQt5.QtWidgets import QApplication
+
+    from orisys_app_shared.i18n import t
+
+    broken = Path(record_root) / "not_really_a_video.mp4"
+    broken.write_text("this is not a video at all\n", encoding="utf-8")
+
+    window = _show(make_window(), (1440, 880))
+    try:
+        window.brand_bar.btn_playback.click()
+        QApplication.processEvents()
+        assert window._load_replay_video(broken) is False, (
+            "a file that cannot be decoded was accepted for playback"
         )
         QApplication.processEvents()
-    assert not window.replay.is_loaded(), "an empty folder was opened as a recording"
+        assert not window.replay.has_video()
         assert not window.toolbar.btn_run.isEnabled(), (
             "the transport is offered although there is nothing to play"
         )
-    reason = window.toolbar.btn_run.toolTip()
-    assert "forces.csv" in reason or "recording" in reason.lower(), reason
-    # And what was missing, in the panel that would have shown the frames.
-    body = window.arrow_panel.image_label.text()
-    assert "forces.csv" in body or "recording" in body.lower(), body
-    # The way forward for a video that is not a recording: recompute from it.
+        reason = window.statusBar().currentMessage()
+        assert "forces.csv" in reason or "记录" in reason, reason
+        # The way forward for a video with no recording: recompute from it.
         assert window.act_recompute.isEnabled(), (
             "a chosen video cannot be recomputed either, so the operator has no way to "
             "look at it"
         )
+    finally:
         window.close()
 
 

apps/studio/tools/ui_check.py

@@ -3001,9 +3001,9 @@ def main() -> int:
         f"{replay_window.toolbar.source_summary.text()!r}",
     )
 
-    # A video that is not a recording must be refused *with a reason*, because the
-    # reader tolerates an empty folder: accepting it left the transport playing a
-    # zero-length timeline, which looked like "pressing 回放 does nothing".
+    # A video with no recording beside it is still something to *watch*: the transport
+    # plays it, the charts stay empty, and the rail/tooltip say why. Refusing it (the
+    # older behaviour) left an operator pointing at a clip with a dead button.
     import cv2 as _cv2
     import numpy as _np
 
@@ -3011,8 +3011,8 @@ def main() -> int:
     bare_writer = _cv2.VideoWriter(
         str(bare_video), _cv2.VideoWriter_fourcc(*"mp4v"), 30.0, (64, 48)
     )
-    for _index in range(10):
-        bare_writer.write(_np.zeros((48, 64, 3), dtype=_np.uint8))
+    for _index in range(30):
+        bare_writer.write(_np.full((48, 64, 3), _index * 8, dtype=_np.uint8))
     bare_writer.release()
     other_window = StudioMainWindow(
         prefs={"language": "zh_CN", "theme": "dark", "sensor_type": "box"}
@@ -3023,34 +3023,55 @@ def main() -> int:
     other_window.brand_bar.btn_playback.click()
     app.processEvents()
     check(
-        other_window._load_replay_video(bare_video) is False,
-        "a video with no forces.csv beside it was accepted as a recording",
+        other_window._load_replay_video(bare_video) is True,
+        "a playable video with no recording beside it was refused",
     )
     app.processEvents()
+    check(
+        other_window.replay.has_video() and other_window.replay.is_video_only(),
+        "the video is not playable as a video",
+    )
     check(
         not other_window.replay.is_loaded(),
-        "an empty folder was opened as a recording",
+        "a video with no forces.csv claimed to be a recording",
     )
     check(
-        not other_window.toolbar.btn_run.isEnabled(),
-        "the transport is offered although there is nothing to play",
+        other_window.toolbar.btn_run.isEnabled(),
+        "the transport is not offered for a video that can be played",
     )
     check(
-        "forces.csv" in other_window.toolbar.btn_run.toolTip()
-        or "记录" in other_window.toolbar.btn_run.toolTip(),
-        f"the transport does not say why it cannot play: "
+        t("toolbar.playback_video_only") in other_window.toolbar.btn_run.toolTip(),
+        f"the transport does not say the charts are empty: "
         f"{other_window.toolbar.btn_run.toolTip()!r}",
     )
+    check(
+        t("playback.video_only_notice") in other_window.replay.warnings_text(),
+        f"the video is not described as one: {other_window.replay.warnings_text()!r}",
+    )
+    check(
+        not other_window.force_plots.is_recording_source(),
+        "the charts claim to read a recording that does not exist",
+    )
+    other_window.toolbar.btn_run.setChecked(True)
+    app.processEvents()
+    _deadline = time.time() + 3.0
+    while time.time() < _deadline and other_window.replay.position() < 0.4:
+        app.processEvents()
+        time.sleep(0.05)
+    check(
+        other_window.replay.position() >= 0.4,
+        f"the transport did not play the video: {other_window.replay.position()}",
+    )
+    check(
+        other_window.replay.video_image() is not None,
+        "no frame was decoded from the video",
+    )
     check(
         other_window.act_recompute.isEnabled(),
         "a chosen video cannot be recomputed either: the operator has no way to view it",
     )
-    check(
-        "forces.csv" in other_window.arrow_panel.image_label.text()
-        or "记录" in other_window.arrow_panel.image_label.text(),
-        f"the panel does not say what is missing: "
-        f"{other_window.arrow_panel.image_label.text()!r}",
-    )
+    other_window._stop_replay_activity()
+    app.processEvents()
     other_window.close()
     app.processEvents()
     replay_window.activateWindow()

shared/src/orisys_app_shared/record/__init__.py

@@ -19,6 +19,7 @@ from orisys_app_shared.record.playback import (
     RecordingFrame,
     RecordingInfo,
     RecordingReader,
+    VideoOnlySource,
     list_recordings,
 )
 from orisys_app_shared.record.visualization3d import (
@@ -43,6 +44,7 @@ __all__ = [
     "RecordingFrame",
     "RecordingInfo",
     "RecordingReader",
+    "VideoOnlySource",
     "Visualization3DRecord",
     "build_visualization3d_block",
     "format_value",

shared/src/orisys_app_shared/record/playback.py

@@ -602,6 +602,84 @@ def decimate_window(window: ForceWindow, max_points: int, *, unit: str = "raw")
     )
 
 
+class VideoOnlySource:
+    """One video file with nothing beside it: watch it, but it has no measurements.
+
+    A recording is a directory (video + forces + session metadata); a *video* is what
+    an operator often has — a clip from a camera, a file somebody sent, footage whose
+    ``forces.csv`` was never written. This serves the same questions
+    :class:`RecordingReader` serves for a recording — how long is it, what is at *t* —
+    so the replay view can play it with the transport instead of demanding that the
+    file be something it is not.
+
+    What it deliberately does **not** do: invent force rows, a session id or a config
+    hash. ``curve_source()`` is ``None`` and the caller is expected to say that the
+    charts have nothing to read. Recomputing forces from this video is the acquisition
+    path's job, not this one's.
+    """
+
+    def __init__(self, path: str | Path) -> None:
+        self.path = Path(path)
+        if not self.path.is_file():
+            raise FileNotFoundError(f"Not a video file: {self.path}")
+        import cv2
+
+        self._capture = cv2.VideoCapture(str(self.path))
+        if not self._capture.isOpened():
+            self._capture.release()
+            self._capture = None
+            raise ValueError(f"Could not open the video: {self.path}")
+        self._fps = float(self._capture.get(cv2.CAP_PROP_FPS) or 0.0)
+        frames = float(self._capture.get(cv2.CAP_PROP_FRAME_COUNT) or 0.0)
+        if not (self._fps > 0.0) or not (frames > 0.0):
+            # Without a frame count or a rate there is no timeline to scrub, and a
+            # guessed one would put the cursor somewhere the picture is not.
+            self._capture.release()
+            self._capture = None
+            raise ValueError(
+                f"The video reports no frame count or frame rate: {self.path.name}"
+            )
+        self.duration_s = frames / self._fps
+        self._index = -1
+        self._lock = threading.Lock()
+
+    def video_frame_at(self, t_rel_s: float) -> tuple[Optional[np.ndarray], None]:
+        """The frame at ``t_rel_s``: ``(bgr, None)`` or ``(None, None)``.
+
+        The second element is always ``None``: there is no frame *record* to hand back,
+        which is the difference between this and a recording (and the reason the
+        status line for a dropped frame does not apply here).
+        """
+        import cv2
+
+        if self._capture is None:
+            return None, None
+        target = int(max(0.0, float(t_rel_s)) * self._fps)
+        target = max(0, min(target, int(round(self.duration_s * self._fps)) - 1))
+        with self._lock:
+            try:
+                if self._index >= 0 and target == self._index + 1:
+                    ok, image = self._capture.read()
+                else:
+                    self._capture.set(cv2.CAP_PROP_POS_FRAMES, target)
+                    ok, image = self._capture.read()
+            except Exception:  # noqa: BLE001 - a broken decode is not a crash
+                logger.exception("Could not decode %s at frame %s", self.path, target)
+                self._index = -1
+                return None, None
+            self._index = target if ok else -1
+            return (image if ok else None), None
+
+    def close(self) -> None:
+        with self._lock:
+            if self._capture is not None:
+                try:
+                    self._capture.release()
+                except Exception:  # noqa: BLE001 - releasing is best effort
+                    pass
+            self._capture = None
+
+
 def list_recordings(root: str | Path) -> list[Path]:
     base = Path(root)
     if not base.is_dir():

shared/tests/test_playback.py

@@ -22,6 +22,7 @@ from orisys_app_shared.record import (
     ExperimentRecorder,
     RecordConfig,
     RecordingReader,
+    VideoOnlySource,
     list_recordings,
 )
 
@@ -235,6 +236,84 @@ def test_list_recordings_finds_directories_newest_first(recording):
     assert recording in found
 
 
+# ------------------------------------------------------------- a video on its own
+def _write_clip(path: Path, frames: int = 60, fps: float = 30.0) -> Path:
+    """A tiny real video, so the decode path is exercised rather than mocked."""
+    import cv2
+
+    writer = cv2.VideoWriter(
+        str(path), cv2.VideoWriter_fourcc(*"mp4v"), fps, (64, 48)
+    )
+    assert writer.isOpened(), "this build cannot write mp4v"
+    for index in range(frames):
+        writer.write(np.full((48, 64, 3), index * 4, dtype=np.uint8))
+    writer.release()
+    return path
+
+
+def test_a_video_with_no_recording_is_playable(tmp_path):
+    """A clip with nothing beside it answers the same questions a recording does."""
+    clip = _write_clip(tmp_path / "clip.mp4")
+    source = VideoOnlySource(clip)
+    try:
+        assert source.duration_s == pytest.approx(2.0, abs=0.2)
+        first, extra = source.video_frame_at(0.0)
+        later, _ = source.video_frame_at(1.5)
+        assert first is not None and later is not None
+        assert first.shape == (48, 64, 3)
+        assert float(later.mean()) > float(first.mean()), (
+            "the clip gets brighter over time; the same frame came back twice"
+        )
+        # Stepping forward is the playback case and must not need a seek.
+        stepped, _ = source.video_frame_at(1.5 + 1.0 / 30.0)
+        assert stepped is not None
+        # Past the end clamps to the last frame instead of failing.
+        assert source.video_frame_at(99.0)[0] is not None
+        # There is deliberately no frame *record*: a video has no measurements.
+        assert extra is None
+    finally:
+        source.close()
+    assert source.video_frame_at(0.0) == (None, None), "closed source still served frames"
+
+
+def test_a_file_that_is_not_a_video_is_refused(tmp_path):
+    broken = tmp_path / "broken.mp4"
+    broken.write_text("not a video at all", encoding="utf-8")
+    with pytest.raises(ValueError):
+        VideoOnlySource(broken)
+    with pytest.raises(FileNotFoundError):
+        VideoOnlySource(tmp_path / "missing.mp4")
+
+
+def test_a_video_without_a_timeline_is_refused(tmp_path, monkeypatch):
+    """No frame count or rate means no timeline, and a guessed one would lie.
+
+    The input is a decoder that reports neither, rather than a hand-made file: this
+    build will not even write a video with a zero frame rate.
+    """
+    import cv2
+
+    clip = _write_clip(tmp_path / "clip.mp4")
+    real_capture = cv2.VideoCapture
+
+    class NoTimeline:
+        def __init__(self, *args, **kwargs) -> None:
+            self._real = real_capture(*args, **kwargs)
+
+        def isOpened(self) -> bool:  # noqa: N802 - OpenCV spelling
+            return True
+
+        def get(self, prop):  # noqa: ANN001 - OpenCV spelling
+            return 0.0
+
+        def release(self) -> None:
+            self._real.release()
+
+    monkeypatch.setattr(cv2, "VideoCapture", NoTimeline)
+    with pytest.raises(ValueError):
+        VideoOnlySource(clip)
+
+
 if __name__ == "__main__":  # pragma: no cover - manual runner
     import shutil as _shutil