test output_format in video datasets (#7879)

test/datasets_utils.py

@@ -662,27 +662,39 @@ class VideoDatasetTestCase(DatasetTestCase):
     FEATURE_TYPES = (torch.Tensor, torch.Tensor, int)
     REQUIRED_PACKAGES = ("av",)
 
-    DEFAULT_FRAMES_PER_CLIP = 1
+    FRAMES_PER_CLIP = 1
 
     def __init__(self, *args, **kwargs):
         super().__init__(*args, **kwargs)
         self.dataset_args = self._set_default_frames_per_clip(self.dataset_args)
 
-    def _set_default_frames_per_clip(self, inject_fake_data):
+    def _set_default_frames_per_clip(self, dataset_args):
         argspec = inspect.getfullargspec(self.DATASET_CLASS.__init__)
         args_without_default = argspec.args[1 : (-len(argspec.defaults) if argspec.defaults else None)]
         frames_per_clip_last = args_without_default[-1] == "frames_per_clip"
 
-        @functools.wraps(inject_fake_data)
+        @functools.wraps(dataset_args)
         def wrapper(tmpdir, config):
-            args = inject_fake_data(tmpdir, config)
+            args = dataset_args(tmpdir, config)
             if frames_per_clip_last and len(args) == len(args_without_default) - 1:
-                args = (*args, self.DEFAULT_FRAMES_PER_CLIP)
+                args = (*args, self.FRAMES_PER_CLIP)
 
             return args
 
         return wrapper
 
+    def test_output_format(self):
+        for output_format in ["TCHW", "THWC"]:
+            with self.create_dataset(output_format=output_format) as (dataset, _):
+                for video, *_ in dataset:
+                    if output_format == "TCHW":
+                        num_frames, num_channels, *_ = video.shape
+                    else:  # output_format == "THWC":
+                        num_frames, *_, num_channels = video.shape
+
+                assert num_frames == self.FRAMES_PER_CLIP
+                assert num_channels == 3
+
     @test_all_configs
     def test_transforms_v2_wrapper(self, config):
         # `output_format == "THWC"` is not supported by the wrapper. Thus, we skip the `config` if it is set explicitly

torchvision/datasets/video_utils.py

@@ -187,9 +187,9 @@ class VideoClips:
         }
         return type(self)(
             video_paths,
-            self.num_frames,
-            self.step,
-            self.frame_rate,
+            clip_length_in_frames=self.num_frames,
+            frames_between_clips=self.step,
+            frame_rate=self.frame_rate,
             _precomputed_metadata=metadata,
             num_workers=self.num_workers,
             _video_width=self._video_width,