Added missing typing annotations in datasets/video_utils (#4172)

* style: Fixed last missing typing annotation

* style: Fixed typing

* style: Fixed remaining typing annotations

* style: Fixed typing

* style: Fixed typing

* refactor: Removed unused import

* Update torchvision/datasets/video_utils.py
Co-authored-by: Philip Meier <github.pmeier@posteo.de>
Co-authored-by: Prabhat Roy <prabhatroy@fb.com>

torchvision/datasets/video_utils.py

@@ -2,7 +2,7 @@ import bisect
 import math
 import warnings
 from fractions import Fraction
-from typing import List
+from typing import Any, Dict, List, Optional, Callable, Union, Tuple, TypeVar, cast
 
 import torch
 from torchvision.io import (
@@ -14,8 +14,10 @@ from torchvision.io import (
 
 from .utils import tqdm
 
+T = TypeVar("T")
 
-def pts_convert(pts, timebase_from, timebase_to, round_func=math.floor):
+
+def pts_convert(pts: int, timebase_from: Fraction, timebase_to: Fraction, round_func: Callable = math.floor) -> int:
     """convert pts between different time bases
     Args:
         pts: presentation timestamp, float
@@ -27,7 +29,7 @@ def pts_convert(pts, timebase_from, timebase_to, round_func=math.floor):
     return round_func(new_pts)
 
 
-def unfold(tensor, size, step, dilation=1):
+def unfold(tensor: torch.Tensor, size: int, step: int, dilation: int = 1) -> torch.Tensor:
     """
     similar to tensor.unfold, but with the dilation
     and specialized for 1d tensors
@@ -55,17 +57,17 @@ class _VideoTimestampsDataset:
     pickled when forking.
     """
 
-    def __init__(self, video_paths: List[str]):
+    def __init__(self, video_paths: List[str]) -> None:
         self.video_paths = video_paths
 
-    def __len__(self):
+    def __len__(self) -> int:
         return len(self.video_paths)
 
-    def __getitem__(self, idx):
+    def __getitem__(self, idx: int) -> Tuple[List[int], Optional[float]]:
         return read_video_timestamps(self.video_paths[idx])
 
 
-def _collate_fn(x):
+def _collate_fn(x: T) -> T:
     """
     Dummy collate function to be used with _VideoTimestampsDataset
     """
@@ -100,19 +102,19 @@ class VideoClips:
 
     def __init__(
         self,
-        video_paths,
-        clip_length_in_frames=16,
-        frames_between_clips=1,
-        frame_rate=None,
-        _precomputed_metadata=None,
-        num_workers=0,
-        _video_width=0,
-        _video_height=0,
-        _video_min_dimension=0,
-        _video_max_dimension=0,
-        _audio_samples=0,
-        _audio_channels=0,
-    ):
+        video_paths: List[str],
+        clip_length_in_frames: int = 16,
+        frames_between_clips: int = 1,
+        frame_rate: Optional[int] = None,
+        _precomputed_metadata: Optional[Dict[str, Any]] = None,
+        num_workers: int = 0,
+        _video_width: int = 0,
+        _video_height: int = 0,
+        _video_min_dimension: int = 0,
+        _video_max_dimension: int = 0,
+        _audio_samples: int = 0,
+        _audio_channels: int = 0,
+    ) -> None:
 
         self.video_paths = video_paths
         self.num_workers = num_workers
@@ -131,7 +133,7 @@ class VideoClips:
             self._init_from_metadata(_precomputed_metadata)
         self.compute_clips(clip_length_in_frames, frames_between_clips, frame_rate)
 
-    def _compute_frame_pts(self):
+    def _compute_frame_pts(self) -> None:
         self.video_pts = []
         self.video_fps = []
 
@@ -139,8 +141,8 @@ class VideoClips:
         # so need to create a dummy dataset first
         import torch.utils.data
 
-        dl = torch.utils.data.DataLoader(
-            _VideoTimestampsDataset(self.video_paths),
+        dl: torch.utils.data.DataLoader = torch.utils.data.DataLoader(
+            _VideoTimestampsDataset(self.video_paths),  # type: ignore[arg-type]
             batch_size=16,
             num_workers=self.num_workers,
             collate_fn=_collate_fn,
@@ -157,7 +159,7 @@ class VideoClips:
                 self.video_pts.extend(clips)
                 self.video_fps.extend(fps)
 
-    def _init_from_metadata(self, metadata):
+    def _init_from_metadata(self, metadata: Dict[str, Any]) -> None:
         self.video_paths = metadata["video_paths"]
         assert len(self.video_paths) == len(metadata["video_pts"])
         self.video_pts = metadata["video_pts"]
@@ -165,7 +167,7 @@ class VideoClips:
         self.video_fps = metadata["video_fps"]
 
     @property
-    def metadata(self):
+    def metadata(self) -> Dict[str, Any]:
         _metadata = {
             "video_paths": self.video_paths,
             "video_pts": self.video_pts,
@@ -173,7 +175,7 @@ class VideoClips:
         }
         return _metadata
 
-    def subset(self, indices):
+    def subset(self, indices: List[int]) -> "VideoClips":
         video_paths = [self.video_paths[i] for i in indices]
         video_pts = [self.video_pts[i] for i in indices]
         video_fps = [self.video_fps[i] for i in indices]
@@ -198,7 +200,9 @@ class VideoClips:
         )
 
     @staticmethod
-    def compute_clips_for_video(video_pts, num_frames, step, fps, frame_rate):
+    def compute_clips_for_video(
+        video_pts: torch.Tensor, num_frames: int, step: int, fps: int, frame_rate: Optional[int] = None
+    ) -> Tuple[torch.Tensor, Union[List[slice], torch.Tensor]]:
         if fps is None:
             # if for some reason the video doesn't have fps (because doesn't have a video stream)
             # set the fps to 1. The value doesn't matter, because video_pts is empty anyway
@@ -206,21 +210,22 @@ class VideoClips:
         if frame_rate is None:
             frame_rate = fps
         total_frames = len(video_pts) * (float(frame_rate) / fps)
-        idxs = VideoClips._resample_video_idx(int(math.floor(total_frames)), fps, frame_rate)
-        video_pts = video_pts[idxs]
+        _idxs = VideoClips._resample_video_idx(int(math.floor(total_frames)), fps, frame_rate)
+        video_pts = video_pts[_idxs]
         clips = unfold(video_pts, num_frames, step)
         if not clips.numel():
             warnings.warn(
                 "There aren't enough frames in the current video to get a clip for the given clip length and "
                 "frames between clips. The video (and potentially others) will be skipped."
             )
-        if isinstance(idxs, slice):
-            idxs = [idxs] * len(clips)
+        idxs: Union[List[slice], torch.Tensor]
+        if isinstance(_idxs, slice):
+            idxs = [_idxs] * len(clips)
         else:
-            idxs = unfold(idxs, num_frames, step)
+            idxs = unfold(_idxs, num_frames, step)
         return clips, idxs
 
-    def compute_clips(self, num_frames, step, frame_rate=None):
+    def compute_clips(self, num_frames: int, step: int, frame_rate: Optional[int] = None) -> None:
         """
         Compute all consecutive sequences of clips from video_pts.
         Always returns clips of size `num_frames`, meaning that the
@@ -243,19 +248,19 @@ class VideoClips:
         clip_lengths = torch.as_tensor([len(v) for v in self.clips])
         self.cumulative_sizes = clip_lengths.cumsum(0).tolist()
 
-    def __len__(self):
+    def __len__(self) -> int:
         return self.num_clips()
 
-    def num_videos(self):
+    def num_videos(self) -> int:
         return len(self.video_paths)
 
-    def num_clips(self):
+    def num_clips(self) -> int:
         """
         Number of subclips that are available in the video list.
         """
         return self.cumulative_sizes[-1]
 
-    def get_clip_location(self, idx):
+    def get_clip_location(self, idx: int) -> Tuple[int, int]:
         """
         Converts a flattened representation of the indices into a video_idx, clip_idx
         representation.
@@ -268,7 +273,7 @@ class VideoClips:
         return video_idx, clip_idx
 
     @staticmethod
-    def _resample_video_idx(num_frames, original_fps, new_fps):
+    def _resample_video_idx(num_frames: int, original_fps: int, new_fps: int) -> Union[slice, torch.Tensor]:
         step = float(original_fps) / new_fps
         if step.is_integer():
             # optimization: if step is integer, don't need to perform
@@ -279,7 +284,7 @@ class VideoClips:
         idxs = idxs.floor().to(torch.int64)
         return idxs
 
-    def get_clip(self, idx):
+    def get_clip(self, idx: int) -> Tuple[torch.Tensor, torch.Tensor, Dict[str, Any], int]:
         """
         Gets a subclip from a list of videos.
 
@@ -320,22 +325,22 @@ class VideoClips:
             end_pts = clip_pts[-1].item()
             video, audio, info = read_video(video_path, start_pts, end_pts)
         else:
-            info = _probe_video_from_file(video_path)
-            video_fps = info.video_fps
+            _info = _probe_video_from_file(video_path)
+            video_fps = _info.video_fps
             audio_fps = None
 
-            video_start_pts = clip_pts[0].item()
-            video_end_pts = clip_pts[-1].item()
+            video_start_pts = cast(int, clip_pts[0].item())
+            video_end_pts = cast(int, clip_pts[-1].item())
 
             audio_start_pts, audio_end_pts = 0, -1
             audio_timebase = Fraction(0, 1)
-            video_timebase = Fraction(info.video_timebase.numerator, info.video_timebase.denominator)
-            if info.has_audio:
-                audio_timebase = Fraction(info.audio_timebase.numerator, info.audio_timebase.denominator)
+            video_timebase = Fraction(_info.video_timebase.numerator, _info.video_timebase.denominator)
+            if _info.has_audio:
+                audio_timebase = Fraction(_info.audio_timebase.numerator, _info.audio_timebase.denominator)
                 audio_start_pts = pts_convert(video_start_pts, video_timebase, audio_timebase, math.floor)
                 audio_end_pts = pts_convert(video_end_pts, video_timebase, audio_timebase, math.ceil)
-                audio_fps = info.audio_sample_rate
-            video, audio, info = _read_video_from_file(
+                audio_fps = _info.audio_sample_rate
+            video, audio, _ = _read_video_from_file(
                 video_path,
                 video_width=self._video_width,
                 video_height=self._video_height,
@@ -362,7 +367,7 @@ class VideoClips:
         assert len(video) == self.num_frames, f"{video.shape} x {self.num_frames}"
         return video, audio, info, video_idx
 
-    def __getstate__(self):
+    def __getstate__(self) -> Dict[str, Any]:
         video_pts_sizes = [len(v) for v in self.video_pts]
         # To be back-compatible, we convert data to dtype torch.long as needed
         # because for empty list, in legacy implementation, torch.as_tensor will
@@ -371,10 +376,10 @@ class VideoClips:
         video_pts = [x.to(torch.int64) for x in self.video_pts]
         # video_pts can be an empty list if no frames have been decoded
         if video_pts:
-            video_pts = torch.cat(video_pts)
+            video_pts = torch.cat(video_pts)  # type: ignore[assignment]
             # avoid bug in https://github.com/pytorch/pytorch/issues/32351
             # TODO: Revert it once the bug is fixed.
-            video_pts = video_pts.numpy()
+            video_pts = video_pts.numpy()  # type: ignore[attr-defined]
 
         # make a copy of the fields of self
         d = self.__dict__.copy()
@@ -390,7 +395,7 @@ class VideoClips:
         d["_version"] = 2
         return d
 
-    def __setstate__(self, d):
+    def __setstate__(self, d: Dict[str, Any]) -> None:
         # for backwards-compatibility
         if "_version" not in d:
             self.__dict__ = d