ANNOTATION_FORMAT.md

Annotation Format

The object masks are provided in JSON files as RLE encoded strings. We use pycocotools to encode/decode these masks.

The JSON file contains a dictionary which is organized as follows:

sequences:
    - width: <int>  # image_dims
      height: <int>
      id: <int>
      seq_name: <str>
      dataset: <str>  # LaSOT, BDD, ArgoVerse, HACS, ...
      fps: <int>
      all_image_paths:
        - <str>
        ...
      annotated_image_paths:
        - <str>
        ...
      neg_category_ids: 
        - <int>
        ...
      not_exhaustive_category_ids:
        - <int>
        ...
      track_category_ids:
        ...  # see below for details
      segmentations:
        ...  # see below for details
categories:
    - id: <int>
      name: <str>
      synset: <str>
      def: <str>
      synonyms: 
        - <str>
        ...
    ...
    ...
split: <str>  # train/val/test

• categories: List of all object categories in the dataset. We use the same category IDs as the LVIS dataset.
• sequences: List of all video sequences in the datasets. Each list entry is a dictionary with basic attributes e.g. image size, video ID, etc, and also the mask annotations for the object tracks in this video.
• split: which split (train/val/test) the annotations belong to.

Mask Annotations and Category IDs Per Sequence

The track_category_ids is a dict which conveys the category ID for each object track in that sequence:

track_category_ids:
    track_id: category_id
    ...

The segmentations field is a list with one entry per annotated video frame. Each list element is a dict with track IDs as keys and encoded masks and other attributes as values. In the example below, '1' and '2' are the track IDs

segmentations: 
    - 1:                    # first frame
        rle: <str>
        is_gt: <bool>
        score: <float>
        bbox:               # only present in `first_frame_annotations` file
          - x coord <int>
          - y coord <int>
          - width <int>
          - height <int>
        point:              # only present in `first_frame_annotations` file
          - x coord <int>
          - y coord <int>
      2:
    - 1: ...                # second frame
      2: ...
    - 1: ...                # third frame
      2: ...

For the training set, we adopted a semi-automated workflow for annotating temporally dense object masks. The is_gt field conveys whether the given mask was annotated automatically or by a human annotator. The score field conveys the confidence for an automatically annotated mask.

• For the val and test sets, all annotations were done by humans, so the is_gt and score fields can be ignored.

• For the first_frame_annotations files (useful for exemplar-guided tasks), there are two additional fields bbox and point which convey the bounding box and a random point on the object for the first frame in which it occurs.

• In the segmentations and track_category_ids fields, track IDs are encoded as strings (the JSON file format enforces that dict keys must be strings). Remember to cast them as int when parsing the annotations.

Format for Evaluation Code

For evaluating your predicted results, the code expects a single JSON file with the same format as the ground-truth format explained above. For the exemplar-guided and open-world tasks, the track_category_ids field is still required for parsing the prediction file, but the value is irrelevant i.e. you can assign any class ID to the tracks.