feat(extract): 抽帧打印进度日志

ffmpeg 增加 -progress pipe:1 并解析 frame=N：每约 10 个检查点打印
'抽帧进度 X/Y 帧 (Z 帧/s)'，长视频抽帧期间可见实时进度与处理速度。
测试覆盖进度行解析、进度日志输出与失败路径（Popen mock）。

tests/test_ocr_flow.py

@@ -159,6 +159,84 @@ def test_video_duration_unreadable(monkeypatch) -> None:
     assert _video_duration(Path("/tmp/x.mp4"), "ffmpeg") is None
 
 
+class _FakeReader:
+    """模拟 stderr 读取对象。"""
+
+    def __init__(self, content: str = "") -> None:
+        self._content = content
+
+    def read(self) -> str:
+        return self._content
+
+
+class FakePopen:
+    """模拟 ffmpeg 进程：stdout 可迭代 -progress 行，可配置返回码与 stderr。"""
+
+    def __init__(self, lines=(), returncode: int = 0, stderr: str = "") -> None:
+        self.stdout = list(lines)
+        self.stderr = _FakeReader(stderr)
+        self.returncode = returncode
+
+    def wait(self) -> int:
+        return self.returncode
+
+
+def _fake_popen(lines=(), returncode: int = 0, stderr: str = ""):
+    """构造替换 subprocess.Popen 的工厂函数。"""
+    return lambda *a, **k: FakePopen(lines, returncode, stderr)
+
+
+def test_parse_progress_line() -> None:
+    """-progress 行解析：frame=N 返回数值，其他行与非法值返回 None。"""
+    from nodes.frame_extract import _parse_progress_line
+
+    assert _parse_progress_line("frame=25\n") == 25
+    assert _parse_progress_line("progress=continue") is None
+    assert _parse_progress_line("fps=25.0") is None
+    assert _parse_progress_line("frame=abc") is None
+
+
+def test_frame_extract_progress_logging(monkeypatch, tmp_path) -> None:
+    """ffmpeg -progress 的 frame=N 被解析并打印抽帧进度与速度。"""
+    import logging
+
+    monkeypatch.setattr("nodes.frame_extract._video_size", lambda *a, **k: (1280, 720))
+    monkeypatch.setattr("nodes.frame_extract._video_fps", lambda *a, **k: 25.0)
+    monkeypatch.setattr("nodes.frame_extract._video_duration", lambda *a, **k: 10.0)
+    monkeypatch.setattr(
+        "nodes.frame_extract.subprocess.Popen",
+        _fake_popen(lines=["fps=25.0", "frame=20", "progress=continue", "frame=50", "progress=continue"]),
+    )
+    captured: list[str] = []
+
+    class CaptureHandler(logging.Handler):
+        def emit(self, record):
+            captured.append(record.getMessage())
+
+    logger = logging.getLogger("vrsub.frame-extract")
+    logger.addHandler(CaptureHandler())
+    try:
+        response = frame_invoke(_frame_request(tmp_path))
+    finally:
+        logger.removeHandler(logger.handlers[-1])
+    assert response.status == "completed", response.error
+    assert any("抽帧进度" in message and "帧/s" in message for message in captured)
+
+
+def test_frame_extract_ffmpeg_fails(monkeypatch, tmp_path) -> None:
+    """ffmpeg 抽帧失败时透传错误。"""
+    monkeypatch.setattr("nodes.frame_extract._video_size", lambda *a, **k: (1280, 720))
+    monkeypatch.setattr("nodes.frame_extract._video_fps", lambda *a, **k: 25.0)
+    monkeypatch.setattr("nodes.frame_extract._video_duration", lambda *a, **k: 10.0)
+    monkeypatch.setattr(
+        "nodes.frame_extract.subprocess.Popen",
+        _fake_popen(lines=["frame=1", "progress=end"], returncode=1, stderr="boom"),
+    )
+    response = frame_invoke(_frame_request(tmp_path))
+    assert response.status == "failed"
+    assert "boom" in response.error
+
+
 def test_frame_extract_duration_unknown(monkeypatch, tmp_path) -> None:
     """无法读取视频时长时返回失败。"""
     monkeypatch.setattr("nodes.frame_extract._video_size", lambda *a, **k: (1280, 720))