JSON File Structure

Each JSON file contains array of per-frame annotation data:

• The first element in the array (“zero frame”) contains general metadata, while the rest of the elements contain data for frames 1...N (where N is the last frame).

• The length of the root array is therefore N+1 elements.

Example:

[
{Zero frame object},
{Object for frame 1},
{Object for frame 2},
...
{Object for the last frame}
]

Zero frame object format

Field name	Type	Description
version	string (“1.4”)	The version of the output format
file	string (e.g: “/video/072.mp4”)	Annotated video file name with relative path to its location at the time of annotation
frame_skip	Integer	In case frames were skipped, indicates skipping step
original_frame	Integer	First frame index. In case that target movie was divided to parts, the number of the second part will be the last frame+1
part	Integer	Part Index, in case that target movie was divided into multiple parts. Starting from part 1.
attributes	Map <attrID, value>	Non-interpolated file attribute values
objects	List <ObjectPropertiesFrame()>	Ids and properties of all the annotated objects in the video

Object Properties on frame 0

Field name	Type	Description
nm	string (examples: “0.1”, “0.2”)	Unique object identifier
shape	string	One of the object shapes: bBox poly multiline skeleton bitmap
type	string	Object type id
parent	string	Identifier of the parent object (only present if nested)
attributes	Map<attrId, value>	Non-interpolated object attribute values

Frame object format

Field name	Type	Description
attributes	Map <attrID, value>	Interpolated file attribute values on this frame
objects	List <ObjectPropertiesFrame()>	array of objects appearing on this frame

Object Properties

Field name	Type	Description
nm	string	Id of the object (string) Constructed by 2 or 3 numbers divided by “.”
x1	number	Left edge coordinate in pixel of the containing BB of the object shape
y1	number	Top edge coordinate in pixels of the containing BB of the object shape
x2	number	Right edge coordinate in pixels of the containing BB of the object shape
y2	number	Bottom edge coordinate in pixels of the containing BB of the object shape
path	• List <List<[x: float, y: float]>> **For polygon and multiline in legacy export version) • List <Point>	Shape outline path Bitmaps may have holes and disjoint areas, and therefore bitmap outline is a bit more complicated: it consists of several closed path sections, and points are included in the bitmap according to the “even-odd” rule (This rule determines the "insideness" of a point on the canvas by drawing a ray from that point to infinity in any direction and counting the number of path segments from the given shape that the ray crosses. If this number is odd, the point is inside; if even, the point is outside). **Note that in bitmap paths, points are not objects but arrays containing x coordinate as a 1st element and y coordinate as a 2nd element. *** Bound box shape objects will have their vertexes in the following order (upper left, upper right, bottom right , bottom left) If legacy export option is selected for polygon or multiline : Objects with polygon and multiline shapes will have a single path represented by a collection of {x, y} points.
skeleton	Map <skeletonBoneId, Point>	Map of skeleton points
attributes	Map <attrID, value>	Interpolated object attribute values on this frame
key	Boolean	true if this is a key instance of object shape false if this is interpolated instance of object shape
attr_key	Boolean	true if at least one object attribute has a key value on this frame

Point

Field name	Type	Description
x	Float	point x coordinate
y	Float	point y coordinate