Video Labeling Editor
Overview of the Video Labeling Editor in Ango Hub
Ango Hub provides a labeling editor with which video files can be annotated.
Overview
Loading annotations
When opening a video task with saved annotations, you may see Downloading annotations followed by Preparing the timeline. Wait for the loading card to disappear before selecting, editing, or saving annotations; the editor is temporarily locked while they load.
Supported File Types
The video labeling editor supports video assets with the following file extensions:
.mp4
.webm
.mov
.mkv
Supported Labeling Tools
The video labeling editor supports following labeling tools:
Tools
Bounding Box
Rotated Bounding Box
Polygon
Polyline
Segmentation
Point
Circle
Skeleton
Classifications
Radio
Checkbox
Single-Select Dropdown
Multi-Select Dropdown
Single-Select Tree
Multi-Select Tree
Text
Relations
Single Relation
Group Relation
Playback Bar
The back and forward arrows allow you to move backwards and forwards one frame at a time, or to the beginning/end of the video. The Play 
button starts and stops playback. The slider allows you to move between frames by clicking on the playhead and dragging it to find the frame you need.
Turn on Loop from the playback controls to restart the video automatically whenever it reaches the end. You can also press G to turn Loop on or off. The Loop button is highlighted while looping is enabled.
You may also navigate to a specific frame by typing its number and pressing Enter or clicking outside of the text field:
The volume button allows you to change the volume of the audio when playing the file back. The "1x" button allows you to change the playback speed. Playback speed can be set from 0.1x to 10x, in 0.1x increments.
Your playback speed and volume remain selected when you move to another video asset using the navigation arrows, Submit, or Skip.
Video annotation counts
Hover over the Video annotation counts button in the top-right toolbar to open Timeline Statistics for the current video:
Tools shows Total Annotations, Keyframe Annotations, and Unique Objects.
Classifications shows Total Annotations, Keyframe Annotations, and Unique Classifications for frame-specific classifications. Classifications answered once for the whole video are not counted.
Relations shows Total Relations for the task.
For tools and frame-specific classifications, Total Annotations counts every in-view frame in each annotation's range, including keyframes and interpolated frames. Keyframe Annotations counts only the in-view keyframes. The unique counts show how many object or classification tracks are annotated in the video.
The totals update automatically when you add, edit, or remove annotations, change an annotation's frame range, or mark frames as out of view. Out-of-view frames are excluded from the annotation and keyframe totals.
Sections without annotations are hidden. If there is nothing to count, the tooltip shows No annotations yet.
To the right, there is a three-dot menu. Clicking it will make the following options appear:
Annotation length determines the default segment length when creating an annotation on the video.
Jump size lets you customize how many frames to jump backward or forward when using the Shift + Z/C keyboard shortcuts.
Videos with Variable Frame Rate
See Variable Frame Rate (VFR) Video Compatibility for details and recommendations.
In videos with variable frame rate (VFR), the following warning is displayed:
Buffering
Ango Hub does not load the entire video in memory right from the start, as that would be computationally expensive, delay loading, and would use unnecessary memory. Instead, Hub loads it chunk by chunk, buffering it.
You can see how much of the video has been downloaded (buffered) by looking at the playback bar as below:
If your download speed is not sufficiently high to smoothly play the video, a warning will appear:
Timeline
The timeline view allows you to see the annotations throughout the video in a visual way.
When you create a new annotation, a new row will be added to the timeline view. You can click on the row to select its annotation, or click on the annotation to select its row:
Objects belonging to the same class are automatically grouped and collapsed. To see each object, click on the arrow:
Next to each object's class name, the first few characters of its unique Object ID will be visible. Hover over the characters to display and be able to copy to your clipboard the object's ID:
You can change each object row's order in the timeline by dragging and dropping it using its handle:
Managing timeline tracks
Each object row in the timeline has a lock button and a three-dot menu with additional track actions:
The lock button locks or unlocks the object track directly from the timeline row.
In the three-dot menu, Move to top moves the track to the top of its current class group, and Move to bottom moves it to the bottom of its current class group.
Completed marks the track green and moves it to the bottom of the object list, helping annotators keep finished tracks separate from tracks that still need work.
The Track color swatches let you color-code a track. To return to the track's class color, click Reset to default color above the swatches, or click the currently selected swatch again. Locked tracks cannot have their color changed.
Frame-specific classification rows also support move and color actions, but do not show the lock button.
Adding a keyframe
When you move the object, or change the answer in a frame-specific classification, a keyframe is added to the row, indicated by a white rhombus on the line:
You may also add a keyframe without editing the object, by clicking on the segment, to the frame where you would like to add the frame, and then on the "Add Keyframe" button 
.
Removing a keyframe
To remove the keyframe, navigate to the frame where the keyframe is located, and click on the row or the annotation of which you'd like to delete the keyframe. A Remove Keyframe button will appear. Click on it to remove the keyframe:
Marking objects and classifications out of view
Select an object or frame-specific classification in the timeline to mark individual frames or a range of frames as out of view. Out-of-view ranges are shaded on that annotation's timeline row and are preserved when you save and reopen the task.
A single frame
Navigate to the frame you want to change, then click Toggle current frame out of view or press W. Only the current frame is marked out of view; the frames before and after it are unchanged. Use the same action again on that frame to bring it back into view.
You can also use W inside an existing out-of-view range to bring just that frame back into view. To mark a range, use one of the methods below.
Using the start and end actions
Navigate to the first frame where the annotation is out of view, then click Set as start of out of view or press Q.
Navigate to the last frame where the annotation is out of view, then click Set as end of out of view or press E. The annotation is back in view on the following frame:
An out-of-view object is hidden from the video and the Objects list. You can still select it or open its context menu from the timeline, for example to bring it back into view.
Nested classifications for an out-of-view object remain available in its timeline context menu.
Using the interval button
Navigate to the frame where you'd like the out of view segment to start.
Select the object or frame-specific classification in the timeline.
Click on the
icon to start the out of view segment.Navigate to frame where you'd like for your out of view segment to end.
Click again on the same button. All frames in that annotation in the interval will be marked as out of view.
You can also press Alt+Q to start the interval and Alt+E to end it. Starting on an out-of-view frame lets you mark an interval back in view instead.
Frame-specific classifications
On an out-of-view frame, the classification's existing answer stays visible in its panel, but you cannot change or delete it, or add another answer instance. Move to an in-view frame to edit it again.
When exporting with Only Key Frames disabled, the classification has no answer on its out-of-view frames. With Only Key Frames enabled, stored keyframes are included, even if they fall inside an out-of-view range. See Export Options.
Making annotations appear for shorter/longer
There are two ways.
The first way is to click and drag on the handles on the left/right side of the segment to shrink/extend the annotation duration:
The second way is to click on the segment, then to navigate to the frame where you'd like the segment to start or end, and click on the "Set Annotation Start" (or "Set Annotation End") button:
Giving Annotations Names
You may give each annotation its own name by clicking on it and pressing "D" on your keyboard. Alternatively, you may right-click on it, click on the three-dot menu, and click on "Update Description".
Once you update an annotation's description, it will appear on the timeline:
Split and Merge Segments
To split a segment into two separate segments, navigate to the frame where you'd like the segments to split and click on the "Split" button that appears:
To merge two segments, click on the first segment, then Shift + click on the second segment. Then, click on the "Merge" button that appears.
Removing Segment Keyframes over an Interval
When a segment is selected, hovering over the 
icon will cause this dialog to appear:
Pick the frame interval where you would like to remove the keyframes in the selected segment and click on "Remove".
How to Annotate Videos
The following are the labeling tools supported on videos:
Entity (only in Waveform View)
From the Tools panel on the left sidebar, select a supported labeling tool. Then, follow the instructions found on each tool's docs page, linked to above.
If no tools are present in the project, only answer the questions in the Classifications panel.
Labeling Properties Specific to Videos
Frame Interpolation
Between keyframes, objects are automatically linearly interpolated. So for example, if you create a keyframe on frame 1 for an object on the top-left corner of the video, and in frame 100 of the same object being in the bottom-right corner of the video, Ango Hub will automatically fill in the contents of frames between 1-100 with interpolation, having the object smoothly move from one corner to the next.
Frame-Specific Classifications
When creating classifications such as radio, dropdown, and others, project managers may choose to make those classifications general (e.g., one response per video) or frame-specific (e.g. one response per frame.)
If the classification has been marked as "frame-specific", then it will appear in the timeline and it will behave like a tool-based object with keyframes.
Select its timeline row to use the out-of-view actions, including W for a single frame and Q / E for a range. These actions apply to frame-specific classifications, rather than classifications answered once for the whole video.
Annotating Audio Entities in Videos (Waveform View)
You can switch to Waveform View by pressing this button:
In Waveform View, the timeline will be replaced with the video's sound waveform. All tools other than Entity will be disabled. Annotating audio in this view is equal to doing so in the audio labeling editor. Please consult the documentation page on the audio labeling editor for more information.
To split an audio entity, select one segment, move the playhead inside it, and click Split next to Merge. Both halves keep the segment's nested answers and can be edited independently. See Splitting an entity.
For video assets, Waveform View shows the current frame and total frame count under the time display. The frame readout uses the same 1-based frame numbering convention as the video editor's frame box.
You can switch back to the video labeling editor at any time by pressing on the same button again.
If the waveform appears as a flat line, but you were expecting a rich sound wave, please click on the Show Soundwave button.
Keyboard Shortcuts
A full list of keyboard shortcuts is available by clicking on the Keyboard button on the right side of the top bar:
Further reading
Audio Labeling EditorLabeling Editor InterfaceLast updated