Video Annotation

Detailed guide on how to quickly annotate videos using automatic interpolation.

All tools available for Image annotation are also available in video annotation. You can use Bounding box, Polygon, Polyline, Keypoint and Cuboid tools to label your objects. You can also create issues, navigate between frames, or switch between Object Detection, Classification and Attribute annotation modes.

Video Annotation basics

The video bar appears at the bottom of the screen in video annotation tasks

Skip step

This is the number of frames that the skip forward or skip backward buttons on either side of the play button, will skip. So if you have 20 set as the skip step, when you press the skip forward button, you will move 20 frames forward. To move a single frame backward or forward use the navigation buttons at the top.

Track Objects

This switch allows you track an object across the video. In a track, labels on different frames are marked as belonging to the same object moving through the video. When the switch is turned on, any object you label will be labeled in track mode.

In this mode, the object sidebar shows a slightly different object card, as can be seen in the image above. You can move between different frames that the object track is in, using buttons in this card.

A track object card

Ending a track

When the track is finished (object goes out of view), mark the track's end by clicking on the End track (first button in the object card in the right sidebar) button. This will stop propagating the labels in subsequent frames.

Skipping occluded frames

If an object is not visible in a frame but re-appears again a few frames later, you can mark it occluded from the object card as shown in the image above. Occluded objects are displayed with a broken line box, and are not included when exporting the annotations.

Automatic Interpolation

When the track mode is turned on, automatic interpolation is automatically started as soon as you label at-least 2 frames in a track.

Interpolation can be used in two labeling flows:

Labeling flow 1 (Intermediate interpolation)

1. Label the first frame in which an object appears.

2. Adjust its position/size in the next frame.

3. Automatic interpolation will now adjust the bounding box in all subsequent frames.

4. If you adjustments in any of the subsequent frames, other frames will also be automatically adjusted.

Labeling flow 2 (Forward interpolation)

1. Label the first frame in which an object appears.

2. Skip a few frames.

3. Adjust the bounding box after a few frames.

4. All frames in between will be automatically adjusted.

5. Any subsequent frames will also be adjusted automatically.