Tracking is similar to image annotation, but each object can appear in multiple images. We can use bounding boxes or polygons to track the instances across the frames. The labels of the same instance in the exported label file will have the same label id.
2D Bounding Box Tracking¶
In the labeling interface of video tracking, move the slider around to move across frames.
Bounding box interpolation¶
Create a bounding box at the first frame it appears, and adjust the bounding boxes in the subsequent frames. For a given bounding box track, the frames in which the box is edited are considered a keyframe. The frames between keyframes are automatically interpolated using the interpolation method selected during project creation.
Ending object track¶
For an object that disappears after certain frame, click “End Object Track” or
Cmd-E for Mac users) at the frame of its last occurrence.
The bounding box labels after this frame will be deleted.
Instance Segmentation Tracking¶
Track labeling for instance segmentation is similar with that for bounding box. A key difference is that for instance segmentation, overlapping frames is allowed when linking different tracks.
Moving a segmentation label¶
After labeling a segmentation label in a keyframe, adjusting each vertex in a
subsequent frame can be laborious. Press
m and drag a selected label to move
the entire label around.
Redrawing a segmentation label¶
At a different frame, sometimes it is easier to redraw the entire segmentation
label than adjusting each existing vertex. Press
for Mac users) to re-draw a segmentation label in the selected object track.