Error check in get_frames_at, adjust indices in get_frames_in_range

Author: Dan-Flores

src/torchcodec/decoders/_video_decoder.py

@@ -220,9 +220,14 @@ def get_frames_at(self, indices: list[int]) -> FrameBatch:
         Returns:
             FrameBatch: The frames at the given indices.
         """
-        indices = [
-            index if index >= 0 else index + self._num_frames for index in indices
-        ]
+        for i, index in enumerate(indices):
+            index = index if index >= 0 else index + self._num_frames
+            if not 0 <= index < self._num_frames:
+                raise IndexError(
+                    f"Index {index} is out of bounds; must be in the range [0, {self._num_frames})."
+                )
+            else:
+                indices[i] = index
 
         data, pts_seconds, duration_seconds = core.get_frames_at_indices(
             self._decoder, frame_indices=indices
@@ -247,6 +252,8 @@ def get_frames_in_range(self, start: int, stop: int, step: int = 1) -> FrameBatc
         Returns:
             FrameBatch: The frames within the specified range.
         """
+        start = start if start >= 0 else start + self._num_frames
+        stop = min(stop if stop >= 0 else stop + self._num_frames, self._num_frames)
         if not 0 <= start < self._num_frames:
             raise IndexError(
                 f"Start index {start} is out of bounds; must be in the range [0, {self._num_frames})."