The annotation timeline populates as users annotate their videos. It gives annotators a complete view of the objects and keypoints in their annotation set, and allows them to alter the annotations as needed. Aside from annotation operations, the timeline includes functions to control video playback and time scale.
Play and pause the video being annotated with these buttons near the upper left of the timline, or use Space.
Use these buttons to move one frame forward or backward in the video. Annotators can also use Left and Right.
Use these buttons to navigate directly to the first or last frame of the current video. Annotators can also use Home and End, or Fn + Left and Fn + Right on mac.
Click the volume icon to the left of the seekbar to adjust or mute the current video's volume.
The seek bar shows annotators their position in the current segment of video, and displays the timestamp and frame number to its left. Click and drag the purple indicator along the seek bar to move around the video segment.
Keypoints and Extrapolated Annotations
As users manually annotate a frame, a keypoint (an individual dot) appears on the timeline. That keypoint can be extended through multiple frames using the context menu, creating a horizontal line on the timeline. As the annotator edits those extrapolated values or makes new ones, each manual annotation places another keypoint on the timeline. Deleting a keypoint or extrapolated annotation will delete everything from that frame until the next keypoint.
The purple cursor on the timeline represents the current frame being displayed. Click and drag the head of the cursor to change frames. As you hover over the top of the timeline, a gray cursor will move along with your mouse to help show which annotations are present in any single frame.
Using either of the buttons above, or by clicking and dragging the purple indicator in between them, users can change the time scale of the timeline to view the annotations at higher or lower time resolution.
Timeline Context Menu
Just like on the annotation canvas, annotators can access a context menu on the annotation timeline by right clicking it. See below for the options provided to annotators from the timeline context menu.
Extend to Cursor
This option extends the most recent annotation of the selected object to the selected frame. After extending an annotation, users can edit frames along the new range, and the edits will propagate throughout the rest of the extended range.
Trim to Here
This option allows annotators to trim the first or last frame of an annotation range to the current frame.
This option allows annotators to delete the selected instance altogether.
Interpolate to Next/Previous
This option is only available for object detection tasks on video, and allows the user to generate linearly interpolated (both size and position) bounding boxes between two keypoints.
The 'track' button next to the video controls allows annotators to propagate their annotations through many frames in a video. The button is enabled once an annotation is selected, and reads 'stop' once tracking begins. Once clicked, annotators can watch the tracker leverage the initial annotation to draw masks or bounding boxes that capture the same object in subsequent frames.
Annotators can manually save work if they need to leave the canvas without submitting or flagging their annotation set. To do so, simply click the save icon in the annotation timeline, which turns green when there are unsaved changes. Saving is not available when editing existing annotations.
Annotators can go undo and redo annotation operations using these buttons, or by using the hotkeys Ctrl + z and Ctrl + y.
Annotators can reset the canvas using this icon. Resetting the canvas cannot be undone, so annotators will first receive a prompt before the annotations are cleared.
Adding a New Instance
This icon is only available for instance segmentation and object detection tasks. Clicking this icon allows users to explicitly add a new instance of the selected class, rather than adding to an existing instance of that class.
This icon appears in the annotation list next to each object mask that has been drawn on the canvas. Clicking it will delete the corresponding object mask.