Safer video loading from SLP

sleap_io/io/main.py

@@ -7,16 +7,19 @@
 from pathlib import Path
 
 
-def load_slp(filename: str) -> Labels:
+def load_slp(filename: str, open_videos: bool = True) -> Labels:
     """Load a SLEAP dataset.
 
     Args:
         filename: Path to a SLEAP labels file (`.slp`).
+        open_videos: If `True` (the default), attempt to open the video backend for
+            I/O. If `False`, the backend will not be opened (useful for reading metadata
+            when the video files are not available).
 
     Returns:
         The dataset as a `Labels` object.
     """
-    return slp.read_labels(filename)
+    return slp.read_labels(filename, open_videos=open_videos)
 
 
 def save_slp(

sleap_io/io/slp.py

@@ -44,7 +44,10 @@ class InstanceType(IntEnum):
 
 
 def make_video(
-    labels_path: str, video_json: dict, video_ind: int | None = None
+    labels_path: str,
+    video_json: dict,
+    video_ind: int | None = None,
+    open_backend: bool = True,
 ) -> Video:
     """Create a `Video` object from a JSON dictionary.
 
@@ -53,6 +56,9 @@ def make_video(
         video_json: A dictionary containing the video metadata.
         video_ind: The index of the video in the labels file. This is used to try to
             recover the source video for embedded videos. This is skipped if `None`.
+        open_backend: If `True` (the default), attempt to open the video backend for
+            I/O. If `False`, the backend will not be opened (useful for reading metadata
+            when the video files are not available).
     """
     backend_metadata = video_json["backend"]
     video_path = backend_metadata["filename"]
@@ -67,22 +73,6 @@ def make_video(
     # Basic path resolution.
     video_path = Path(Path(video_path).as_posix().replace("\\", "/"))
 
-    try:
-        if not video_path.exists():
-            # Check for the same filename in the same directory as the labels file.
-            video_path_ = Path(labels_path).parent / video_path.name
-            if video_path_.exists():
-                video_path = video_path_
-            else:
-                # TODO (TP): Expand capabilities of path resolution to support more
-                # complex path finding strategies.
-                pass
-    except OSError:
-        pass
-
-    # Convert video path to string.
-    video_path = video_path.as_posix()
-
     if is_embedded:
         # Try to recover the source video.
         with h5py.File(labels_path, "r") as f:
@@ -91,23 +81,44 @@ def make_video(
                     f[f"video{video_ind}/source_video"].attrs["json"]
                 )
                 source_video = make_video(
-                    labels_path, source_video_json, video_ind=None
+                    labels_path,
+                    source_video_json,
+                    video_ind=None,
+                    open_backend=open_backend,
                 )
 
-    if "filenames" in backend_metadata:
-        # This is an ImageVideo.
-        # TODO: Path resolution.
-        video_path = backend_metadata["filenames"]
-
-    try:
-        backend = VideoBackend.from_filename(
-            video_path,
-            dataset=backend_metadata.get("dataset", None),
-            grayscale=backend_metadata.get("grayscale", None),
-            input_format=backend_metadata.get("input_format", None),
-        )
-    except ValueError:
-        backend = None
+    backend = None
+    if open_backend:
+        try:
+            if not video_path.exists():
+                # Check for the same filename in the same directory as the labels file.
+                video_path_ = Path(labels_path).parent / video_path.name
+                if video_path_.exists() and video_path.stat():
+                    video_path = video_path_
+                else:
+                    # TODO (TP): Expand capabilities of path resolution to support more
+                    # complex path finding strategies.
+                    pass
+        except (OSError, PermissionError, FileNotFoundError):
+            pass
+
+        # Convert video path to string.
+        video_path = video_path.as_posix()
+
+        if "filenames" in backend_metadata:
+            # This is an ImageVideo.
+            # TODO: Path resolution.
+            video_path = backend_metadata["filenames"]
+
+        try:
+            backend = VideoBackend.from_filename(
+                video_path,
+                dataset=backend_metadata.get("dataset", None),
+                grayscale=backend_metadata.get("grayscale", None),
+                input_format=backend_metadata.get("input_format", None),
+            )
+        except:
+            backend = None
 
     return Video(
         filename=video_path,
@@ -117,11 +128,14 @@ def make_video(
     )
 
 
-def read_videos(labels_path: str) -> list[Video]:
+def read_videos(labels_path: str, open_backend: bool = False) -> list[Video]:
     """Read `Video` dataset in a SLEAP labels file.
 
     Args:
         labels_path: A string path to the SLEAP labels file.
+        open_backend: If `True` (the default), attempt to open the video backend for
+            I/O. If `False`, the backend will not be opened (useful for reading metadata
+            when the video files are not available).
 
     Returns:
         A list of `Video` objects.
@@ -131,7 +145,9 @@ def read_videos(labels_path: str) -> list[Video]:
         read_hdf5_dataset(labels_path, "videos_json")
     ):
         video_json = json.loads(video_data)
-        video = make_video(labels_path, video_json, video_ind=video_ind)
+        video = make_video(
+            labels_path, video_json, video_ind=video_ind, open_backend=open_backend
+        )
         videos.append(video)
     return videos
 
@@ -1003,17 +1019,20 @@ def write_lfs(labels_path: str, labels: Labels):
         )
 
 
-def read_labels(labels_path: str) -> Labels:
+def read_labels(labels_path: str, open_videos: bool = True) -> Labels:
     """Read a SLEAP labels file.
 
     Args:
         labels_path: A string path to the SLEAP labels file.
+        open_videos: If `True` (the default), attempt to open the video backend for
+            I/O. If `False`, the backend will not be opened (useful for reading metadata
+            when the video files are not available).
 
     Returns:
         The processed `Labels` object.
     """
     tracks = read_tracks(labels_path)
-    videos = read_videos(labels_path)
+    videos = read_videos(labels_path, open_backend=open_videos)
     skeletons = read_skeletons(labels_path)
     points = read_points(labels_path)
     pred_points = read_pred_points(labels_path)