Bugfix when end_frame is zero (#1541)

<!-- Contributing guide:
https://github.com/openvinotoolkit/datumaro/blob/develop/CONTRIBUTING.md
-->

### Summary
Ticket Number: 144505
When video end_frame is zero, it was saved as None, not 0.
Due to this, end_frame information was lost when exporting it.


### How to test
1. Make a video media with start_frame=0 and end_frame=0
    ```
item = dm.DatasetItem(..., media=Video('video.mp4', start_frame=0,
end_frame=0), ...)
    ```
2. export the dataset as datumaro format
3. check it the end_frame is described in the output json file
ex. 
    ```
    {
        "id": "video",
        ...,
        "video": {
            "path": "video.mp4",
            "step": 1,
            "start_frame": 0,
            "end_frame": 0
        }
    },
    ```
### Checklist
<!-- Put an 'x' in all the boxes that apply -->
- [x] I have added unit tests to cover my changes.​
- [ ] I have added integration tests to cover my changes.​
- [x] I have added the description of my changes into
[CHANGELOG](https://github.com/openvinotoolkit/datumaro/blob/develop/CHANGELOG.md).​
- [ ] I have updated the
[documentation](https://github.com/openvinotoolkit/datumaro/tree/develop/docs)
accordingly

### License

- [x] I submit _my code changes_ under the same [MIT
License](https://github.com/openvinotoolkit/datumaro/blob/develop/LICENSE)
that covers the project.
  Feel free to contact the maintainers if that's a concern.
- [ ] I have updated the license header for each file (see an example
below).

```python
# Copyright (C) 2024 Intel Corporation
#
# SPDX-License-Identifier: MIT
```

CHANGELOG.md

@@ -18,6 +18,10 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0
 - Pass Keyword Argument to TabularDataBase
   (<https://github.com/openvinotoolkit/datumaro/pull/1522>)
 
+### Bug fixes
+- Preserve end_frame information of a video when it is zero.
+  (<https://github.com/openvinotoolkit/datumaro/pull/1541>)
+
 ## Q2 2024 Release 1.7.0
 ### New features
 - Support 'Video' media type in datumaro format

src/datumaro/components/media.py

@@ -612,14 +612,14 @@ def __init__(
         self._path = path
 
         assert 0 <= start_frame
-        if end_frame:
+        if end_frame is not None:
             assert start_frame <= end_frame
             # we can't know the video length here,
             # so we cannot validate if the end_frame is valid.
         assert 0 < step
         self._step = step
         self._start_frame = start_frame
-        self._end_frame = end_frame or None
+        self._end_frame = end_frame
 
         self._reader = None
         self._iterator: Optional[_VideoFrameIterator] = None

tests/integration/cli/test_video.py

@@ -163,14 +163,14 @@ def _make_sample_video_dataset(test_dir: str, media_type=None) -> Dataset:
                 ),
                 DatasetItem(
                     "1",
-                    media=Video(video_path, step=1, start_frame=0, end_frame=1),
+                    media=Video(video_path, step=1, start_frame=0, end_frame=0),
                     annotations=[
                         Label(0),
                     ],
                 ),
                 DatasetItem(
                     "2",
-                    media=Video(video_path, step=1, start_frame=2, end_frame=2),
+                    media=Video(video_path, step=1, start_frame=1, end_frame=2),
                     annotations=[
                         Label(1),
                     ],
@@ -206,6 +206,7 @@ def test_can_export_video_dataset(self):
 
             dataset_dir = osp.join(test_dir, "test_video")
             expected.save(dataset_dir, save_media=True)
+
             run(self, "project", "import", "-p", project_dir, "-f", "datumaro", dataset_dir)
 
             result_dir = osp.join(test_dir, "test_video_result")

tests/unit/test_video.py

@@ -172,6 +172,13 @@ def test_can_compare(self, test_dir):
         assert video1 != Video(video_path3)
         assert Video(video_path3, end_frame=3) == video1
 
+    @mark_requirement(Requirements.DATUM_GENERAL_REQ)
+    @scoped
+    def test_can_preserve_zero_end_frame(self):
+        video = Video("video.avi", start_frame=0, end_frame=0)
+
+        assert video._end_frame != None
+
 
 class VideoExtractorTest:
     @mark_requirement(Requirements.DATUM_GENERAL_REQ)

tests/utils/test_utils.py

@@ -199,16 +199,16 @@ def compare_datasets(
             test.assertEqual(item_a.attributes, item_b.attributes, item_a.id)
 
         if require_media and item_a.media and item_b.media:
-            if isinstance(item_a.media, Image):
+            if isinstance(item_a.media, VideoFrame):
+                test.assertEqual(item_a.media, item_b.media, item_a.id)
+                test.assertEqual(item_a.media.index, item_b.media.index, item_a.id)
+            elif isinstance(item_a.media, Image):
                 test.assertEqual(item_a.media, item_b.media, item_a.id)
             elif isinstance(item_a.media, PointCloud):
                 test.assertEqual(item_a.media.data, item_b.media.data, item_a.id)
                 test.assertEqual(item_a.media.extra_images, item_b.media.extra_images, item_a.id)
             elif isinstance(item_a.media, Video):
                 test.assertEqual(item_a.media, item_b.media, item_a.id)
-            elif isinstance(item_a.media, VideoFrame):
-                test.assertEqual(item_a.media, item_b.media, item_a.id)
-                test.assertEqual(item_a.index, item_b.index, item_a.id)
             elif isinstance(item_a.media, MultiframeImage):
                 test.assertEqual(item_a.media.data, item_b.media.data, item_a.id)
         test.assertEqual(len(item_a.annotations), len(item_b.annotations), item_a.id)