Video Tracking

2D Bounding Box Tracking

In the labeling interface of video tracking, move the slider around to move across frames.

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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.

_images/box2d_tracking_keyframe.gif

Ending object track

For an object that disappears after certain frame, click “End Object Track” or press Ctrl-E (Cmd-E for Mac users) at the frame of its last occurrence. The bounding box labels after this frame will be deleted.

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Track Linking

Sometimes an object reappears in the frame due to occlusion or re-entrance, and track linking enables individual tracks to be linked as a single instance. Select a label, click “Track-Link” or press Ctrl-L (Cmd-L for Mac users), and click on any other tracks that you want to link with this label. The tracks you choose to link appears in dashed lines. Click “Finish Track-Link” or hit Enter to finish this operation.

_images/box2d_tracking_track-link.gif

Track linking for 2D bounding box does not allow the tracks to be linked to have overlapping frames; make sure to end object tracks correctly for all tracks before the linking operation.

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.

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Redrawing a segmentation label

At a different frame, sometimes it is easier to redraw the entire segmentation label than adjusting each existing vertex. Press Ctrl-delete (Cmd-delete for Mac users) to re-draw a segmentation label in the selected object track.

_images/seg2d_tracking_redraw.gif